Refactored Andriod project to use MVVM structure (Need to apply this so sales too after merge)

- Used MVVM structure so fragments are not doing all the operation from views to data and calls
- organized the structure of our proejct

android/app/src/main/java/com/example/petstoremobile/activities/MainActivity.java

@@ -14,20 +14,17 @@ import androidx.appcompat.app.AppCompatActivity;
 import androidx.core.graphics.Insets;
 import androidx.core.view.ViewCompat;
 import androidx.core.view.WindowInsetsCompat;
+import androidx.lifecycle.ViewModelProvider;
 
 import com.example.petstoremobile.R;
-import com.example.petstoremobile.api.auth.AuthApi;
 import com.example.petstoremobile.api.auth.TokenManager;
-import com.example.petstoremobile.dtos.AuthDTO;
+import com.example.petstoremobile.viewmodels.AuthViewModel;
-import com.example.petstoremobile.dtos.UserDTO;
+import com.example.petstoremobile.utils.Resource;
 
 import javax.inject.Inject;
 import javax.inject.Named;
 
 import dagger.hilt.android.AndroidEntryPoint;
-import retrofit2.Call;
-import retrofit2.Callback;
-import retrofit2.Response;
 
 //The login screen activity
 @AndroidEntryPoint
@@ -37,12 +34,11 @@ public class MainActivity extends AppCompatActivity {
     private EditText etPassword;
     private Button btnLogin;
     private TextView tvLoginStatus;
+    private AuthViewModel viewModel;
 
-    @Inject AuthApi authApi;
     @Inject TokenManager tokenManager;
     @Inject @Named("baseUrl") String baseUrl;
 
-
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         EdgeToEdge.enable(this);
@@ -54,8 +50,7 @@ public class MainActivity extends AppCompatActivity {
                 // If a customer somehow remained logged in, clear them out
                 tokenManager.clearLoginData();
             } else {
-                Intent intent = new Intent(this, HomeActivity.class);
+                startActivity(new Intent(this, HomeActivity.class));
-                startActivity(intent);
                 finish();
                 return;
             }
@@ -99,92 +94,51 @@ public class MainActivity extends AppCompatActivity {
                 return;
             }
 
-            //Call login from api and get response
+            performLogin(username, password);
-            authApi.login(new AuthDTO.LoginRequest(username,password)).enqueue(new Callback<AuthDTO.LoginResponse>() {
+        });
-                @Override
+    }
-                public void onResponse(Call<AuthDTO.LoginResponse> call, Response<AuthDTO.LoginResponse> response) {
-                    if (response.isSuccessful() && response.body() != null) {
-                        String role = response.body().getRole();
 
-                        // Check if the user is a CUSTOMER and deny login if so
+    private void performLogin(String username, String password) {
+        viewModel.login(username, password).observe(this, resource -> {
+            if (resource == null) return;
+
+            switch (resource.status) {
+                case LOADING:
+                    btnLogin.setEnabled(false);
+                    tvLoginStatus.setText("Logging in...");
+                    break;
+                case SUCCESS:
+                    if (resource.data != null) {
+                        String role = resource.data.getRole();
                         if ("CUSTOMER".equalsIgnoreCase(role)) {
-                            Toast.makeText(MainActivity.this, "Access denied: Customers are not allowed to log in.", Toast.LENGTH_LONG).show();
+                            btnLogin.setEnabled(true);
                             tvLoginStatus.setText("Customers are not allowed to log in");
-                            return;
+                            Toast.makeText(this, "Access denied: Customers are not allowed to log in.", Toast.LENGTH_LONG).show();
+                        } else {
+                            tokenManager.saveLoginData(resource.data.getToken(), resource.data.getUsername(), role);
+                            fetchUserIdAndNavigate();
                         }
-
-                        //save login data in shared preferences
-                        tokenManager.saveLoginData(
-                                response.body().getToken(),
-                                response.body().getUsername(),
-                                role
-                        );
-
-                        //fetch user id from api then login to home activity
-                        authApi.getMe()
-                                .enqueue(new Callback<UserDTO>() {
-                                    @Override
-                                    public void onResponse(Call<UserDTO> call,
-                                                           Response<UserDTO> response) {
-                                        if (response.isSuccessful() && response.body() != null) {
-                                            tokenManager.saveUserId(response.body().getId());
                     }
-
+                    break;
-                                        Toast.makeText(MainActivity.this, "Login successful", Toast.LENGTH_SHORT).show();
+                case ERROR:
-                                        startActivity(new Intent(MainActivity.this, HomeActivity.class));
+                    btnLogin.setEnabled(true);
-                                        finish();
+                    tvLoginStatus.setText(resource.message);
-                                    }
+                    Toast.makeText(this, resource.message, Toast.LENGTH_LONG).show();
-
+                    break;
-                                    @Override
-                                    public void onFailure(Call<UserDTO> call,
-                                                          Throwable t) {
-                                        Log.e("MainActivity", "Failed to fetch userId", t);
-
-                                        Toast.makeText(MainActivity.this, "Login successful", Toast.LENGTH_SHORT).show();
-                                        startActivity(new Intent(MainActivity.this, HomeActivity.class));
-                                        finish();
             }
         });
-                    } else {
-                        String errorMessage;
-                        switch (response.code()) {
-                            case 401:
-                                errorMessage = "Invalid username or password";
-                                break;
-                            case 500:
-                                errorMessage = "Server error. Please try again later.";
-                                break;
-                            case 503:
-                                errorMessage = "Service unavailable. Backend may be starting up.";
-                                break;
-                            default:
-                                errorMessage = "Login failed (Error " + response.code() + ")";
-                        }
-                        Toast.makeText(MainActivity.this, errorMessage, Toast.LENGTH_LONG).show();
-                        tvLoginStatus.setText(errorMessage);
-                    }
     }
 
-                @Override
+    private void fetchUserIdAndNavigate() {
-                public void onFailure(Call<AuthDTO.LoginResponse> call, Throwable t) {
+        viewModel.getMe().observe(this, resource -> {
-                    Log.e("MainActivity", "Login request failed", t);
+            if (resource != null && resource.status != Resource.Status.LOADING) {
-
+                if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
-                    String errorMessage;
+                    tokenManager.saveUserId(resource.data.getId());
-                    if (t instanceof java.net.ConnectException ||
-                        t instanceof java.net.SocketTimeoutException ||
-                        t instanceof java.net.UnknownHostException) {
-                        errorMessage = "Cannot connect to server at " + baseUrl +
-                                ". Please check if the backend is running.";
-                    } else if (t instanceof java.io.IOException) {
-                        errorMessage = "Network error. Please check your connection.";
-                    } else {
-                        errorMessage = "Login failed: " + t.getMessage();
                 }
-
+                Toast.makeText(this, "Login successful", Toast.LENGTH_SHORT).show();
-                    Toast.makeText(MainActivity.this, errorMessage, Toast.LENGTH_LONG).show();
+                startActivity(new Intent(this, HomeActivity.class));
-                    tvLoginStatus.setText(errorMessage);
+                finish();
             }
         });
-        });
     }
 }

android/app/src/main/java/com/example/petstoremobile/fragments/listfragments/AdoptionFragment.java

@@ -7,17 +7,19 @@ import android.util.Log;
 import android.view.*;
 import android.widget.*;
 import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import androidx.fragment.app.Fragment;
+import androidx.lifecycle.ViewModelProvider;
 import androidx.navigation.fragment.NavHostFragment;
 import androidx.recyclerview.widget.LinearLayoutManager;
 import androidx.recyclerview.widget.RecyclerView;
 import androidx.swiperefreshlayout.widget.SwipeRefreshLayout;
 import com.example.petstoremobile.R;
 import com.example.petstoremobile.adapters.AdoptionAdapter;
-import com.example.petstoremobile.api.AdoptionApi;
 import com.example.petstoremobile.dtos.AdoptionDTO;
-import com.example.petstoremobile.dtos.PageResponse;
 import com.example.petstoremobile.fragments.ListFragment;
+import com.example.petstoremobile.viewmodels.AdoptionViewModel;
+import com.example.petstoremobile.utils.Resource;
 import com.example.petstoremobile.utils.EventDecorator;
 import com.google.android.material.floatingactionbutton.FloatingActionButton;
 import com.prolificinteractive.materialcalendarview.CalendarDay;
@@ -28,10 +30,7 @@ import java.text.ParseException;
 import java.text.SimpleDateFormat;
 import java.util.*;
 
-import javax.inject.Inject;
-
 import dagger.hilt.android.AndroidEntryPoint;
-import retrofit2.*;
 
 @AndroidEntryPoint
 public class AdoptionFragment extends Fragment implements AdoptionAdapter.OnAdoptionClickListener {
@@ -39,7 +38,7 @@ public class AdoptionFragment extends Fragment implements AdoptionAdapter.OnAdop
     private List<AdoptionDTO> adoptionList = new ArrayList<>();
     private List<AdoptionDTO> filteredList = new ArrayList<>();
     private AdoptionAdapter adapter;
-    @Inject AdoptionApi api;
+    private AdoptionViewModel viewModel;
     private SwipeRefreshLayout swipeRefresh;
     private EditText etSearch;
     private ImageButton hamburger;
@@ -50,7 +49,13 @@ public class AdoptionFragment extends Fragment implements AdoptionAdapter.OnAdop
     private final SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd", Locale.getDefault());
 
     @Override
-    public View onCreateView(LayoutInflater inflater, ViewGroup container,
+    public void onCreate(@Nullable Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        viewModel = new ViewModelProvider(this).get(AdoptionViewModel.class);
+    }
+
+    @Override
+    public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container,
                              Bundle savedInstanceState) {
         View view = inflater.inflate(R.layout.fragment_adoption, container, false);
 
@@ -177,26 +182,34 @@ public class AdoptionFragment extends Fragment implements AdoptionAdapter.OnAdop
         adapter.notifyDataSetChanged();
     }
 
+    // Helper function to get a list of all adoptions from the backend
     private void loadAdoptions() {
+        //Load all adoptions from the backend using viewModel
+        viewModel.getAllAdoptions(0, 500).observe(getViewLifecycleOwner(), resource -> {
+            if (resource == null) return;
+
+            // Check the status to see if the resource is loaded and display the data
+            switch (resource.status) {
+                case LOADING:
+                    // Show loading indicator
                     if (swipeRefresh != null) swipeRefresh.setRefreshing(true);
-        api.getAllAdoptions(0, 500).enqueue(new Callback<PageResponse<AdoptionDTO>>() {
+                    break;
-            public void onResponse(Call<PageResponse<AdoptionDTO>> c,
+                case SUCCESS:
-                                   Response<PageResponse<AdoptionDTO>> r) {
+                    // Hide loading indicator and display data
                     if (swipeRefresh != null) swipeRefresh.setRefreshing(false);
-                if (r.isSuccessful() && r.body() != null) {
+                    if (resource.data != null) {
                         adoptionList.clear();
-                    adoptionList.addAll(r.body().getContent());
+                        adoptionList.addAll(resource.data.getContent());
                         updateCalendarDecorators();
                         filter(etSearch != null ? etSearch.getText().toString() : "");
-                } else {
-                    Toast.makeText(getContext(), "Failed to load adoptions", Toast.LENGTH_SHORT).show();
-                    Log.e("AdoptionFragment", "Error: " + r.message());
                     }
-            }
+                    break;
-            public void onFailure(Call<PageResponse<AdoptionDTO>> c, Throwable t) {
+                case ERROR:
+                    // Hide loading indicator and toast error message
                     if (swipeRefresh != null) swipeRefresh.setRefreshing(false);
-                Toast.makeText(getContext(), "Network error", Toast.LENGTH_SHORT).show();
+                    Toast.makeText(getContext(), "Failed to load adoptions: " + resource.message, Toast.LENGTH_SHORT).show();
-                Log.e("AdoptionFragment", t.getMessage());
+                    Log.e("AdoptionFragment", "Error loading adoptions: " + resource.message);
+                    break;
             }
         });
     }

android/app/src/main/java/com/example/petstoremobile/fragments/listfragments/AppointmentFragment.java

@@ -4,7 +4,9 @@ import android.graphics.Color;
 import android.os.Bundle;
 
 import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import androidx.fragment.app.Fragment;
+import androidx.lifecycle.ViewModelProvider;
 import androidx.navigation.fragment.NavHostFragment;
 import androidx.recyclerview.widget.LinearLayoutManager;
 import androidx.recyclerview.widget.RecyclerView;
@@ -21,14 +23,14 @@ import android.widget.Toast;
 
 import com.example.petstoremobile.R;
 import com.example.petstoremobile.adapters.AppointmentAdapter;
-import com.example.petstoremobile.api.AppointmentApi;
-import com.example.petstoremobile.api.PetApi;
-import com.example.petstoremobile.api.ServiceApi;
 import com.example.petstoremobile.dtos.AppointmentDTO;
 import com.example.petstoremobile.dtos.ServiceDTO;
-import com.example.petstoremobile.dtos.PageResponse;
 import com.example.petstoremobile.dtos.PetDTO;
 import com.example.petstoremobile.fragments.ListFragment;
+import com.example.petstoremobile.viewmodels.AppointmentViewModel;
+import com.example.petstoremobile.viewmodels.PetViewModel;
+import com.example.petstoremobile.viewmodels.ServiceViewModel;
+import com.example.petstoremobile.utils.Resource;
 import com.example.petstoremobile.utils.EventDecorator;
 import com.google.android.material.floatingactionbutton.FloatingActionButton;
 import com.prolificinteractive.materialcalendarview.CalendarDay;
@@ -45,12 +47,7 @@ import java.util.HashSet;
 import java.util.List;
 import java.util.Locale;
 
-import javax.inject.Inject;
-
 import dagger.hilt.android.AndroidEntryPoint;
-import retrofit2.Call;
-import retrofit2.Callback;
-import retrofit2.Response;
 
 @AndroidEntryPoint
 public class AppointmentFragment extends Fragment implements AppointmentAdapter.OnAppointmentClickListener {
@@ -61,9 +58,9 @@ public class AppointmentFragment extends Fragment implements AppointmentAdapter.
     private List<ServiceDTO> serviceList = new ArrayList<>();
 
     private AppointmentAdapter adapter;
-    @Inject AppointmentApi api;
+    private AppointmentViewModel appointmentViewModel;
-    @Inject PetApi petApi;
+    private PetViewModel petViewModel;
-    @Inject ServiceApi serviceApi;
+    private ServiceViewModel serviceViewModel;
 
     private SwipeRefreshLayout swipeRefreshLayout;
     private EditText etSearch;
@@ -75,7 +72,15 @@ public class AppointmentFragment extends Fragment implements AppointmentAdapter.
     private final SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd", Locale.getDefault());
 
     @Override
-    public View onCreateView(LayoutInflater inflater, ViewGroup container,
+    public void onCreate(@Nullable Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        appointmentViewModel = new ViewModelProvider(this).get(AppointmentViewModel.class);
+        petViewModel = new ViewModelProvider(this).get(PetViewModel.class);
+        serviceViewModel = new ViewModelProvider(this).get(ServiceViewModel.class);
+    }
+
+    @Override
+    public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container,
                              Bundle savedInstanceState) {
         View view = inflater.inflate(R.layout.fragment_appointment, container, false);
 
@@ -91,7 +96,6 @@ public class AppointmentFragment extends Fragment implements AppointmentAdapter.
         loadPets();
         loadServices();
 
-
         FloatingActionButton fabAdd = view.findViewById(R.id.fabAddAppointment);
         fabAdd.setOnClickListener(v -> openAppointmentDetails(-1));
 
@@ -239,76 +243,54 @@ public class AppointmentFragment extends Fragment implements AppointmentAdapter.
         openAppointmentDetails(position);
     }
 
+    // Helper function to get a list of all appointments from the backend
     private void loadAppointmentData() {
-        if (swipeRefreshLayout != null)
+        //Load all appointments from the backend using viewModel
-            swipeRefreshLayout.setRefreshing(true);
+        appointmentViewModel.getAllAppointments(0, 500).observe(getViewLifecycleOwner(), resource -> {
-        api.getAllAppointments(0, 500).enqueue(new Callback<PageResponse<AppointmentDTO>>() {
+            if (resource == null) return;
-            @Override
+
-            public void onResponse(Call<PageResponse<AppointmentDTO>> call,
+            // Check the status to see if the resource is loaded and display the data
-                                   Response<PageResponse<AppointmentDTO>> response) {
+            switch (resource.status) {
-                if (swipeRefreshLayout != null)
+                case LOADING:
-                    swipeRefreshLayout.setRefreshing(false);
+                    // Show loading indicator
-                if (response.isSuccessful() && response.body() != null) {
+                    if (swipeRefreshLayout != null) swipeRefreshLayout.setRefreshing(true);
+                    break;
+                case SUCCESS:
+                    // Hide loading indicator and display data
+                    if (swipeRefreshLayout != null) swipeRefreshLayout.setRefreshing(false);
+                    if (resource.data != null) {
                         appointmentList.clear();
-                    appointmentList.addAll(response.body().getContent());
+                        appointmentList.addAll(resource.data.getContent());
                         updateCalendarDecorators();
                         filterAppointments(etSearch != null ? etSearch.getText().toString() : "");
-                } else {
-                    Log.e("AppointmentFragment", "Error: " + response.message());
-                    Toast.makeText(getContext(), "Failed to load appointments", Toast.LENGTH_SHORT).show();
                     }
-            }
+                    break;
-
+                case ERROR:
-            @Override
+                    // Hide loading indicator and toast error message
-            public void onFailure(Call<PageResponse<AppointmentDTO>> call, Throwable t) {
+                    if (swipeRefreshLayout != null) swipeRefreshLayout.setRefreshing(false);
-                if (swipeRefreshLayout != null)
+                    Toast.makeText(getContext(), "Failed to load appointments: " + resource.message, Toast.LENGTH_SHORT).show();
-                    swipeRefreshLayout.setRefreshing(false);
+                    Log.e("AppointmentFragment", "Error loading appointments: " + resource.message);
-                Toast.makeText(getContext(), "Network error: " + t.getMessage(), Toast.LENGTH_SHORT).show();
+                    break;
-                Log.e("AppointmentFragment", t.getMessage());
             }
         });
     }
 
-
-
     // Load Pets
     private void loadPets() {
-        petApi.getAllPets(0,100).enqueue(new Callback<PageResponse<PetDTO>>() {
+        petViewModel.getAllPets(0, 100).observe(getViewLifecycleOwner(), resource -> {
-
+            if (resource != null && resource.status == Resource.Status.SUCCESS && resource.data != null) {
-            @Override
-            public void onResponse(Call<PageResponse<PetDTO>> call, Response<PageResponse<PetDTO>> response) {
-                if (response.isSuccessful() && response.body() !=null) {
                 petList.clear();
-                    petList.addAll(response.body().getContent());
+                petList.addAll(resource.data.getContent());
-                }
-            }
-
-            @Override
-            public void onFailure(Call<PageResponse<PetDTO>> call, Throwable t) {
-
-                Log.e("AppointmentFragment", "Pet load error:" + t.getMessage());
-
             }
         });
     }
 
     // Load Services
-
     private void loadServices() {
-        serviceApi.getAllServices(0,100).enqueue(new Callback<PageResponse<ServiceDTO>>() {
+        serviceViewModel.getAllServices(0, 100).observe(getViewLifecycleOwner(), resource -> {
-            @Override
+            if (resource != null && resource.status == Resource.Status.SUCCESS && resource.data != null) {
-            public void onResponse(Call<PageResponse<ServiceDTO>> call, Response<PageResponse<ServiceDTO>> response) {
-                if (response.isSuccessful() && response.body() != null) {
                 serviceList.clear();
-                    serviceList.addAll(response.body().getContent());
+                serviceList.addAll(resource.data.getContent());
-
-                }
-            }
-
-            @Override
-            public void onFailure(Call<PageResponse<ServiceDTO>> call, Throwable t) {
-                Log.e("AppointmentFragmnet", "Service load error: " + t.getMessage());
-
             }
         });
     }

android/app/src/main/java/com/example/petstoremobile/fragments/listfragments/InventoryFragment.java

@@ -20,6 +20,7 @@ import android.widget.Toast;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.fragment.app.Fragment;
+import androidx.lifecycle.ViewModelProvider;
 import androidx.navigation.fragment.NavHostFragment;
 import androidx.recyclerview.widget.LinearLayoutManager;
 import androidx.recyclerview.widget.RecyclerView;
@@ -28,23 +29,16 @@ import androidx.swiperefreshlayout.widget.SwipeRefreshLayout;
 import com.example.petstoremobile.R;
 import com.example.petstoremobile.adapters.BlackTextArrayAdapter;
 import com.example.petstoremobile.adapters.InventoryAdapter;
-import com.example.petstoremobile.api.CategoryApi;
-import com.example.petstoremobile.api.InventoryApi;
-import com.example.petstoremobile.dtos.BulkDeleteRequest;
 import com.example.petstoremobile.dtos.CategoryDTO;
 import com.example.petstoremobile.dtos.InventoryDTO;
-import com.example.petstoremobile.dtos.PageResponse;
 import com.example.petstoremobile.fragments.ListFragment;
+import com.example.petstoremobile.viewmodels.InventoryViewModel;
+import com.example.petstoremobile.utils.Resource;
 
 import java.util.ArrayList;
 import java.util.List;
 
-import javax.inject.Inject;
-
 import dagger.hilt.android.AndroidEntryPoint;
-import retrofit2.Call;
-import retrofit2.Callback;
-import retrofit2.Response;
 
 @AndroidEntryPoint
 public class InventoryFragment extends Fragment implements InventoryAdapter.OnInventoryClickListener {
@@ -55,8 +49,7 @@ public class InventoryFragment extends Fragment implements InventoryAdapter.OnIn
     private final List<InventoryDTO> inventoryList = new ArrayList<>();
     private final List<CategoryDTO> categoryList = new ArrayList<>();
     private InventoryAdapter adapter;
-    @Inject InventoryApi inventoryApi;
+    private InventoryViewModel viewModel;
-    @Inject CategoryApi categoryApi;
 
     private SwipeRefreshLayout swipeRefreshLayout;
     private EditText etSearch;
@@ -82,7 +75,13 @@ public class InventoryFragment extends Fragment implements InventoryAdapter.OnIn
     private boolean spinnerReady = false;
 
     @Override
-    public View onCreateView(LayoutInflater inflater, ViewGroup container,
+    public void onCreate(@Nullable Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        viewModel = new ViewModelProvider(this).get(InventoryViewModel.class);
+    }
+
+    @Override
+    public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container,
                              Bundle savedInstanceState) {
         View view = inflater.inflate(R.layout.fragment_inventory, container, false);
 
@@ -117,21 +116,13 @@ public class InventoryFragment extends Fragment implements InventoryAdapter.OnIn
 
     // Categories
     private void loadCategories() {
-        categoryApi.getAllCategories(0, 100).enqueue(new Callback<PageResponse<CategoryDTO>>() {
+        viewModel.getAllCategories(0, 100).observe(getViewLifecycleOwner(), resource -> {
-            @Override
+            if (resource != null && resource.status == Resource.Status.SUCCESS && resource.data != null) {
-            public void onResponse(Call<PageResponse<CategoryDTO>> call,
-                                   Response<PageResponse<CategoryDTO>> response) {
-                if (response.isSuccessful() && response.body() != null) {
                 categoryList.clear();
-                    categoryList.addAll(response.body().getContent());
+                categoryList.addAll(resource.data.getContent());
                 setupCategorySpinner();
-                }
+            } else if (resource != null && resource.status == Resource.Status.ERROR) {
-            }
+                Log.e(TAG, "Failed to load categories: " + resource.message);
-
-            @Override
-            public void onFailure(Call<PageResponse<CategoryDTO>> call, Throwable t) {
-                Log.e(TAG, "Failed to load categories", t);
-                // Still setup spinner with just "All"
                 setupCategorySpinner();
             }
         });
@@ -145,6 +136,7 @@ public class InventoryFragment extends Fragment implements InventoryAdapter.OnIn
             categoryNames.add(c.getCategoryName());
         }
 
+        if (getContext() != null) {
             BlackTextArrayAdapter<String> spinnerAdapter = new BlackTextArrayAdapter<>(
                     requireContext(),
                     android.R.layout.simple_spinner_item,
@@ -173,6 +165,7 @@ public class InventoryFragment extends Fragment implements InventoryAdapter.OnIn
                 }
             });
         }
+    }
 
     // Search
 
@@ -209,7 +202,7 @@ public class InventoryFragment extends Fragment implements InventoryAdapter.OnIn
 
         rv.addOnScrollListener(new RecyclerView.OnScrollListener() {
             @Override
-            public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
+            public void onScrolled(@NonNull RecyclerView recyclerView, int dx, int dy) {
                 if (dy <= 0)
                     return;
                 LinearLayoutManager lm = (LinearLayoutManager) rv.getLayoutManager();
@@ -230,11 +223,10 @@ public class InventoryFragment extends Fragment implements InventoryAdapter.OnIn
         swipeRefreshLayout.setOnRefreshListener(() -> loadInventory(true));
     }
 
-    // Load inventory
+    // Helper function to get a list of all inventory items from the backend
     private void loadInventory(boolean reset) {
         if (isLoading)
             return;
-        isLoading = true;
 
         if (reset) {
             currentPage = 0;
@@ -244,37 +236,36 @@ public class InventoryFragment extends Fragment implements InventoryAdapter.OnIn
         // Build query: combine search text + selected category
         String q = buildQuery();
 
-        inventoryApi.getAllInventory(q, currentPage, PAGE_SIZE, "inventoryId,asc")
+        //Load all inventory items from the backend using viewModel
-                .enqueue(new Callback<PageResponse<InventoryDTO>>() {
+        viewModel.getAllInventory(q, currentPage, PAGE_SIZE, "inventoryId,asc").observe(getViewLifecycleOwner(), resource -> {
-                    @Override
+            if (resource == null) return;
-                    public void onResponse(Call<PageResponse<InventoryDTO>> call,
-                                           Response<PageResponse<InventoryDTO>> response) {
-                        isLoading = false;
-                        if (swipeRefreshLayout != null)
-                            swipeRefreshLayout.setRefreshing(false);
 
-                        if (response.isSuccessful() && response.body() != null) {
+            // Check the status to see if the resource is loaded and display the data
-                            PageResponse<InventoryDTO> page = response.body();
+            switch (resource.status) {
-                            if (reset)
+                case LOADING:
-                                inventoryList.clear();
+                    // Show loading indicator
-                            inventoryList.addAll(page.getContent());
+                    isLoading = true;
+                    if (swipeRefreshLayout != null) swipeRefreshLayout.setRefreshing(true);
+                    break;
+                case SUCCESS:
+                    // Hide loading indicator and display data
+                    isLoading = false;
+                    if (swipeRefreshLayout != null) swipeRefreshLayout.setRefreshing(false);
+                    if (resource.data != null) {
+                        if (reset) inventoryList.clear();
+                        inventoryList.addAll(resource.data.getContent());
                         adapter.notifyDataSetChanged();
-                            isLastPage = page.isLast();
+                        isLastPage = resource.data.isLast();
-                            if (!isLastPage)
+                        if (!isLastPage) currentPage++;
-                                currentPage++;
-                        } else {
-                            Log.e(TAG, "Error " + response.code());
-                            Toast.makeText(getContext(), "Failed to load inventory", Toast.LENGTH_SHORT).show();
                     }
-                    }
+                    break;
-
+                case ERROR:
-                    @Override
+                    // Hide loading indicator and toast error message
-                    public void onFailure(Call<PageResponse<InventoryDTO>> call, Throwable t) {
                     isLoading = false;
-                        if (swipeRefreshLayout != null)
+                    if (swipeRefreshLayout != null) swipeRefreshLayout.setRefreshing(false);
-                            swipeRefreshLayout.setRefreshing(false);
+                    Log.e(TAG, "Error: " + resource.message);
-                        Log.e(TAG, "Network error", t);
+                    Toast.makeText(getContext(), "Failed to load inventory: " + resource.message, Toast.LENGTH_SHORT).show();
-                        Toast.makeText(getContext(), "Network error: " + t.getMessage(), Toast.LENGTH_SHORT).show();
+                    break;
             }
         });
     }
@@ -308,24 +299,17 @@ public class InventoryFragment extends Fragment implements InventoryAdapter.OnIn
     }
 
     private void bulkDelete(List<Long> ids) {
-        inventoryApi.bulkDeleteInventory(new BulkDeleteRequest(ids))
+        viewModel.bulkDeleteInventory(ids).observe(getViewLifecycleOwner(), resource -> {
-                .enqueue(new Callback<Void>() {
+            if (resource != null && resource.status != Resource.Status.LOADING) {
-                    @Override
+                if (resource.status == Resource.Status.SUCCESS) {
-                    public void onResponse(Call<Void> call, Response<Void> response) {
-                        if (response.isSuccessful()) {
                     adapter.clearSelection();
                     hideBulkDeleteBar();
                     loadInventory(true);
                     Toast.makeText(getContext(), ids.size() + " item(s) deleted", Toast.LENGTH_SHORT).show();
                 } else {
-                            Toast.makeText(getContext(), "Delete failed", Toast.LENGTH_SHORT).show();
+                    Toast.makeText(getContext(), "Delete failed: " + resource.message, Toast.LENGTH_SHORT).show();
                 }
             }
-
-                    @Override
-                    public void onFailure(Call<Void> call, Throwable t) {
-                        Toast.makeText(getContext(), "Network error", Toast.LENGTH_SHORT).show();
-                    }
         });
     }
 

android/app/src/main/java/com/example/petstoremobile/fragments/listfragments/PetFragment.java

@@ -5,6 +5,7 @@ import android.os.Bundle;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.fragment.app.Fragment;
+import androidx.lifecycle.ViewModelProvider;
 import androidx.navigation.fragment.NavHostFragment;
 import androidx.recyclerview.widget.LinearLayoutManager;
 import androidx.recyclerview.widget.RecyclerView;
@@ -25,10 +26,10 @@ import android.widget.Toast;
 import com.example.petstoremobile.R;
 import com.example.petstoremobile.adapters.BlackTextArrayAdapter;
 import com.example.petstoremobile.adapters.PetAdapter;
-import com.example.petstoremobile.api.PetApi;
-import com.example.petstoremobile.dtos.PageResponse;
 import com.example.petstoremobile.dtos.PetDTO;
 import com.example.petstoremobile.fragments.ListFragment;
+import com.example.petstoremobile.viewmodels.PetViewModel;
+import com.example.petstoremobile.utils.Resource;
 import com.google.android.material.floatingactionbutton.FloatingActionButton;
 
 import java.util.ArrayList;
@@ -38,9 +39,6 @@ import javax.inject.Inject;
 import javax.inject.Named;
 
 import dagger.hilt.android.AndroidEntryPoint;
-import retrofit2.Call;
-import retrofit2.Callback;
-import retrofit2.Response;
 
 @AndroidEntryPoint
 public class PetFragment extends Fragment implements PetAdapter.OnPetClickListener {
@@ -48,13 +46,19 @@ public class PetFragment extends Fragment implements PetAdapter.OnPetClickListen
     private List<PetDTO> filteredList = new ArrayList<>();
     private ImageButton hamburger;
     private PetAdapter adapter;
-    @Inject PetApi api;
+    private PetViewModel viewModel;
+    
     @Inject @Named("baseUrl") String baseUrl;
     private SwipeRefreshLayout swipeRefreshLayout;
     private EditText etSearch;
     private Spinner spinnerStatus;
 
-    //load pet view
+    @Override
+    public void onCreate(@Nullable Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        viewModel = new ViewModelProvider(this).get(PetViewModel.class);
+    }
+
     @Override
     public View onCreateView(LayoutInflater inflater, ViewGroup container,
                              Bundle savedInstanceState) {
@@ -67,12 +71,9 @@ public class PetFragment extends Fragment implements PetAdapter.OnPetClickListen
         setupStatusFilter(view);
         setupSwipeRefresh(view);
 
-
-        //Add button to opens the add dialog
         FloatingActionButton fabAddPet = view.findViewById(R.id.fabAddPet);
         fabAddPet.setOnClickListener(v -> openPetDetails(-1));
 
-        //Make the hamburger button open the drawer from listFragment
         hamburger.setOnClickListener(v -> {
             Fragment parent = getParentFragment();
             if (parent != null) {
@@ -103,7 +104,6 @@ public class PetFragment extends Fragment implements PetAdapter.OnPetClickListen
         });
     }
 
-    //Setup the status filter spinner
     private void setupStatusFilter(View view) {
         spinnerStatus = view.findViewById(R.id.spinnerStatus);
         String[] statuses = {"All Statuses", "Available", "Adopted"};
@@ -122,7 +122,6 @@ public class PetFragment extends Fragment implements PetAdapter.OnPetClickListen
         });
     }
 
-    // Helper function to filter pets based on search and status filter
     private void filterPets() {
         String query = etSearch.getText().toString().toLowerCase();
         String selectedStatus = spinnerStatus.getSelectedItem().toString();
@@ -146,14 +145,10 @@ public class PetFragment extends Fragment implements PetAdapter.OnPetClickListen
 
     private void setupSwipeRefresh(View view) {
         swipeRefreshLayout = view.findViewById(R.id.swipeRefreshPet);
-        swipeRefreshLayout.setOnRefreshListener(() -> {
+        swipeRefreshLayout.setOnRefreshListener(this::loadPetData);
-            loadPetData();
-        });
     }
 
-    //Open pet profile
     private void openPetProfile(int position) {
-        //Make a bundle to pass data to the profile fragment
         Bundle args = new Bundle();
         PetDTO pet = filteredList.get(position);
         args.putInt("petId", pet.getPetId().intValue());
@@ -172,12 +167,10 @@ public class PetFragment extends Fragment implements PetAdapter.OnPetClickListen
         NavHostFragment.findNavController(this).navigate(R.id.nav_pet_profile, args);
     }
 
-    //Open the pet detail view for adding
     private void openPetDetails(int position) {
         NavHostFragment.findNavController(this).navigate(R.id.nav_pet_detail);
     }
 
-    // Called by PetAdapter when a row is clicked to open the details view
     @Override
     public void onPetClick(int position) {
         openPetProfile(position);
@@ -185,38 +178,35 @@ public class PetFragment extends Fragment implements PetAdapter.OnPetClickListen
 
     // Helper function to get a list of all pets from the backend
     private void loadPetData() {
-        if (swipeRefreshLayout != null) {
+        //Load all pets from the backend using viewModel
-            swipeRefreshLayout.setRefreshing(true);
+        viewModel.getAllPets(0, 100).observe(getViewLifecycleOwner(), resource -> {
-        }
+            if (resource == null) return;
-        api.getAllPets(0, 100).enqueue(new Callback<PageResponse<PetDTO>>() {
+            
-            @Override
+            // Check the status to see if the resource is loaded and display the data
-            public void onResponse(Call<PageResponse<PetDTO>> call, Response<PageResponse<PetDTO>> response) {
+            switch (resource.status) {
-                if (swipeRefreshLayout != null) {
+                case LOADING:
-                    swipeRefreshLayout.setRefreshing(false);
+                    // Show loading indicator
-                }
+                    if (swipeRefreshLayout != null) swipeRefreshLayout.setRefreshing(true);
-                if (response.isSuccessful() && response.body() != null) {
+                    break;
+                case SUCCESS:
+                    // Hide loading indicator and display data
+                    if (swipeRefreshLayout != null) swipeRefreshLayout.setRefreshing(false);
+                    if (resource.data != null) {
                         petList.clear();
-                    petList.addAll(response.body().getContent());
+                        petList.addAll(resource.data.getContent());
                         filterPets();
-
-                } else {
-                    Log.e("onResponse: ", response.message());
                     }
-            }
+                    break;
-
+                case ERROR:
-            @Override
+                    // Hide loading indicator and toast error message
-            public void onFailure(Call<PageResponse<PetDTO>> call, Throwable t) {
+                    if (swipeRefreshLayout != null) swipeRefreshLayout.setRefreshing(false);
-                if (swipeRefreshLayout != null) {
+                    Toast.makeText(getContext(), "Failed to load pets: " + resource.message, Toast.LENGTH_SHORT).show();
-                    swipeRefreshLayout.setRefreshing(false);
+                    Log.e("PetFragment", "Error loading pets: " + resource.message);
-                }
+                    break;
-                Toast.makeText(getContext(),
-                        "Failed to load pets", Toast.LENGTH_SHORT).show();
-                Log.e("onFailure: ", t.getMessage());
             }
         });
     }
 
-    //set up the recyclerview and adapter
     private void setupRecyclerView(View view) {
         RecyclerView recyclerView = view.findViewById(R.id.recyclerViewPets);
         adapter = new PetAdapter(filteredList, this);

android/app/src/main/java/com/example/petstoremobile/fragments/listfragments/ProductFragment.java

@@ -5,18 +5,21 @@ import android.text.*;
 import android.util.Log;
 import android.view.*;
 import android.widget.*;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import androidx.fragment.app.Fragment;
+import androidx.lifecycle.ViewModelProvider;
 import androidx.navigation.fragment.NavHostFragment;
 import androidx.recyclerview.widget.LinearLayoutManager;
 import androidx.recyclerview.widget.RecyclerView;
 import androidx.swiperefreshlayout.widget.SwipeRefreshLayout;
 import com.example.petstoremobile.R;
 import com.example.petstoremobile.adapters.ProductAdapter;
-import com.example.petstoremobile.api.ProductApi;
 import com.example.petstoremobile.api.auth.TokenManager;
-import com.example.petstoremobile.dtos.PageResponse;
 import com.example.petstoremobile.dtos.ProductDTO;
 import com.example.petstoremobile.fragments.ListFragment;
+import com.example.petstoremobile.viewmodels.ProductViewModel;
+import com.example.petstoremobile.utils.Resource;
 import com.google.android.material.floatingactionbutton.FloatingActionButton;
 import java.util.*;
 
@@ -24,7 +27,6 @@ import javax.inject.Inject;
 import javax.inject.Named;
 
 import dagger.hilt.android.AndroidEntryPoint;
-import retrofit2.*;
 
 @AndroidEntryPoint
 public class ProductFragment extends Fragment implements ProductAdapter.OnProductClickListener {
@@ -34,13 +36,19 @@ public class ProductFragment extends Fragment implements ProductAdapter.OnProduc
     private ProductAdapter adapter;
     private SwipeRefreshLayout swipeRefresh;
     private EditText etSearch;
+    private ProductViewModel viewModel;
 
-    @Inject ProductApi api;
     @Inject @Named("baseUrl") String baseUrl;
     @Inject TokenManager tokenManager;
 
     @Override
-    public View onCreateView(LayoutInflater inflater, ViewGroup container,
+    public void onCreate(@Nullable Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        viewModel = new ViewModelProvider(this).get(ProductViewModel.class);
+    }
+
+    @Override
+    public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container,
                              Bundle savedInstanceState) {
         View view = inflater.inflate(R.layout.fragment_product, container, false);
 
@@ -109,25 +117,33 @@ public class ProductFragment extends Fragment implements ProductAdapter.OnProduc
         adapter.notifyDataSetChanged();
     }
 
+    // Helper function to get a list of all products from the backend
     private void loadProducts() {
+        //Load all products from the backend using viewModel
+        viewModel.getAllProducts(null, 0, 100).observe(getViewLifecycleOwner(), resource -> {
+            if (resource == null) return;
+
+            // Check the status to see if the resource is loaded and display the data
+            switch (resource.status) {
+                case LOADING:
+                    // Show loading indicator
                     if (swipeRefresh != null) swipeRefresh.setRefreshing(true);
-        api.getAllProducts(null, 0, 100)
+                    break;
-                .enqueue(new Callback<PageResponse<ProductDTO>>() {
+                case SUCCESS:
-                    public void onResponse(Call<PageResponse<ProductDTO>> c,
+                    // Hide loading indicator and display data
-                                           Response<PageResponse<ProductDTO>> r) {
                     if (swipeRefresh != null) swipeRefresh.setRefreshing(false);
-                        if (r.isSuccessful() && r.body() != null) {
+                    if (resource.data != null) {
                         productList.clear();
-                            productList.addAll(r.body().getContent());
+                        productList.addAll(resource.data.getContent());
                         filter();
-                        } else {
-                            Toast.makeText(getContext(), "Failed to load products",
-                                    Toast.LENGTH_SHORT).show();
                     }
-                    }
+                    break;
-                    public void onFailure(Call<PageResponse<ProductDTO>> c, Throwable t) {
+                case ERROR:
+                    // Hide loading indicator and toast error message
                     if (swipeRefresh != null) swipeRefresh.setRefreshing(false);
-                        Log.e("ProductFragment", t.getMessage());
+                    Toast.makeText(getContext(), "Failed to load products: " + resource.message, Toast.LENGTH_SHORT).show();
+                    Log.e("ProductFragment", "Error loading products: " + resource.message);
+                    break;
             }
         });
     }

android/app/src/main/java/com/example/petstoremobile/fragments/listfragments/ProductSupplierFragment.java

@@ -5,25 +5,24 @@ import android.text.*;
 import android.util.Log;
 import android.view.*;
 import android.widget.*;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import androidx.fragment.app.Fragment;
+import androidx.lifecycle.ViewModelProvider;
 import androidx.navigation.fragment.NavHostFragment;
 import androidx.recyclerview.widget.LinearLayoutManager;
 import androidx.recyclerview.widget.RecyclerView;
 import androidx.swiperefreshlayout.widget.SwipeRefreshLayout;
 import com.example.petstoremobile.R;
 import com.example.petstoremobile.adapters.ProductSupplierAdapter;
-import com.example.petstoremobile.api.ProductSupplierApi;
-import com.example.petstoremobile.dtos.PageResponse;
 import com.example.petstoremobile.dtos.ProductSupplierDTO;
 import com.example.petstoremobile.fragments.ListFragment;
-import com.example.petstoremobile.fragments.listfragments.detailfragments.ProductSupplierDetailFragment;
+import com.example.petstoremobile.viewmodels.ProductSupplierViewModel;
+import com.example.petstoremobile.utils.Resource;
 import com.google.android.material.floatingactionbutton.FloatingActionButton;
 import java.util.*;
 
-import javax.inject.Inject;
-
 import dagger.hilt.android.AndroidEntryPoint;
-import retrofit2.*;
 
 @AndroidEntryPoint
 public class ProductSupplierFragment extends Fragment
@@ -34,11 +33,16 @@ public class ProductSupplierFragment extends Fragment
     private ProductSupplierAdapter adapter;
     private SwipeRefreshLayout swipeRefresh;
     private EditText etSearch;
-
+    private ProductSupplierViewModel viewModel;
-    @Inject ProductSupplierApi api;
 
     @Override
-    public View onCreateView(LayoutInflater inflater, ViewGroup container,
+    public void onCreate(@Nullable Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        viewModel = new ViewModelProvider(this).get(ProductSupplierViewModel.class);
+    }
+
+    @Override
+    public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container,
                              Bundle savedInstanceState) {
         View view = inflater.inflate(R.layout.fragment_product_supplier, container, false);
 
@@ -103,25 +107,33 @@ public class ProductSupplierFragment extends Fragment
         adapter.notifyDataSetChanged();
     }
 
+    // Helper function to get a list of all product suppliers from the backend
     private void loadData() {
+        //Load all product suppliers from the backend using viewModel
+        viewModel.getAllProductSuppliers(0, 100).observe(getViewLifecycleOwner(), resource -> {
+            if (resource == null) return;
+
+            // Check the status to see if the resource is loaded and display the data
+            switch (resource.status) {
+                case LOADING:
+                    // Show loading indicator
                     if (swipeRefresh != null) swipeRefresh.setRefreshing(true);
-        api.getAllProductSuppliers(0, 100)
+                    break;
-                .enqueue(new Callback<PageResponse<ProductSupplierDTO>>() {
+                case SUCCESS:
-                    public void onResponse(Call<PageResponse<ProductSupplierDTO>> c,
+                    // Hide loading indicator and display data
-                                           Response<PageResponse<ProductSupplierDTO>> r) {
                     if (swipeRefresh != null) swipeRefresh.setRefreshing(false);
-                        if (r.isSuccessful() && r.body() != null) {
+                    if (resource.data != null) {
                         psList.clear();
-                            psList.addAll(r.body().getContent());
+                        psList.addAll(resource.data.getContent());
                         filter(etSearch != null ? etSearch.getText().toString() : "");
-                        } else {
-                            Toast.makeText(getContext(), "Failed to load",
-                                    Toast.LENGTH_SHORT).show();
                     }
-                    }
+                    break;
-                    public void onFailure(Call<PageResponse<ProductSupplierDTO>> c, Throwable t) {
+                case ERROR:
+                    // Hide loading indicator and toast error message
                     if (swipeRefresh != null) swipeRefresh.setRefreshing(false);
-                        Log.e("PSFragment", t.getMessage());
+                    Toast.makeText(getContext(), "Failed to load: " + resource.message, Toast.LENGTH_SHORT).show();
+                    Log.e("PSFragment", "Error loading: " + resource.message);
+                    break;
             }
         });
     }

android/app/src/main/java/com/example/petstoremobile/fragments/listfragments/PurchaseOrderFragment.java

@@ -5,23 +5,23 @@ import android.text.*;
 import android.util.Log;
 import android.view.*;
 import android.widget.*;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import androidx.fragment.app.Fragment;
+import androidx.lifecycle.ViewModelProvider;
 import androidx.navigation.fragment.NavHostFragment;
 import androidx.recyclerview.widget.LinearLayoutManager;
 import androidx.recyclerview.widget.RecyclerView;
 import androidx.swiperefreshlayout.widget.SwipeRefreshLayout;
 import com.example.petstoremobile.R;
 import com.example.petstoremobile.adapters.PurchaseOrderAdapter;
-import com.example.petstoremobile.api.PurchaseOrderApi;
-import com.example.petstoremobile.dtos.PageResponse;
 import com.example.petstoremobile.dtos.PurchaseOrderDTO;
 import com.example.petstoremobile.fragments.ListFragment;
+import com.example.petstoremobile.viewmodels.PurchaseOrderViewModel;
+import com.example.petstoremobile.utils.Resource;
 import java.util.*;
 
-import javax.inject.Inject;
-
 import dagger.hilt.android.AndroidEntryPoint;
-import retrofit2.*;
 
 @AndroidEntryPoint
 public class PurchaseOrderFragment extends Fragment
@@ -32,8 +32,13 @@ public class PurchaseOrderFragment extends Fragment
     private PurchaseOrderAdapter adapter;
     private SwipeRefreshLayout swipeRefresh;
     private EditText etSearch;
+    private PurchaseOrderViewModel viewModel;
 
-    @Inject PurchaseOrderApi api;
+    @Override
+    public void onCreate(@Nullable Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        viewModel = new ViewModelProvider(this).get(PurchaseOrderViewModel.class);
+    }
 
     @Override
     public View onCreateView(LayoutInflater inflater, ViewGroup container,
@@ -75,7 +80,7 @@ public class PurchaseOrderFragment extends Fragment
             public void afterTextChanged(Editable s) {
             }
 
-            public void onTextChanged(CharSequence s, int a, int b, int c) {
+            public void onTextChanged(CharSequence s, int start, int before, int count) {
                 filter(s.toString());
             }
         });
@@ -102,29 +107,33 @@ public class PurchaseOrderFragment extends Fragment
         adapter.notifyDataSetChanged();
     }
 
+    // Helper function to get a list of all purchase orders from the backend
     private void loadData() {
-        if (swipeRefresh != null)
+        //Load all purchase orders from the backend using viewModel
-            swipeRefresh.setRefreshing(true);
+        viewModel.getAllPurchaseOrders(0, 100).observe(getViewLifecycleOwner(), resource -> {
-        api.getAllPurchaseOrders(0, 100)
+            if (resource == null) return;
-                .enqueue(new Callback<PageResponse<PurchaseOrderDTO>>() {
-                    public void onResponse(Call<PageResponse<PurchaseOrderDTO>> c,
-                                           Response<PageResponse<PurchaseOrderDTO>> r) {
-                        if (swipeRefresh != null)
-                            swipeRefresh.setRefreshing(false);
-                        if (r.isSuccessful() && r.body() != null) {
-                            poList.clear();
-                            poList.addAll(r.body().getContent());
-                            filter(etSearch != null ? etSearch.getText().toString() : "");
-                        } else {
-                            Toast.makeText(getContext(), "Failed to load purchase orders",
-                                    Toast.LENGTH_SHORT).show();
-                        }
-                    }
 
-                    public void onFailure(Call<PageResponse<PurchaseOrderDTO>> c, Throwable t) {
+            // Check the status to see if the resource is loaded and display the data
-                        if (swipeRefresh != null)
+            switch (resource.status) {
-                            swipeRefresh.setRefreshing(false);
+                case LOADING:
-                        Log.e("POFragment", t.getMessage());
+                    // Show loading indicator
+                    if (swipeRefresh != null) swipeRefresh.setRefreshing(true);
+                    break;
+                case SUCCESS:
+                    // Hide loading indicator and display data
+                    if (swipeRefresh != null) swipeRefresh.setRefreshing(false);
+                    if (resource.data != null) {
+                        poList.clear();
+                        poList.addAll(resource.data.getContent());
+                        filter(etSearch != null ? etSearch.getText().toString() : "");
+                    }
+                    break;
+                case ERROR:
+                    // Hide loading indicator and toast error message
+                    if (swipeRefresh != null) swipeRefresh.setRefreshing(false);
+                    Toast.makeText(getContext(), "Failed to load purchase orders: " + resource.message, Toast.LENGTH_SHORT).show();
+                    Log.e("POFragment", "Error loading purchase orders: " + resource.message);
+                    break;
             }
         });
     }

android/app/src/main/java/com/example/petstoremobile/fragments/listfragments/SaleFragment.java

@@ -1,6 +1,8 @@
 package com.example.petstoremobile.fragments.listfragments;
 
 import android.os.Bundle;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import androidx.fragment.app.Fragment;
 import androidx.navigation.fragment.NavHostFragment;
 import androidx.recyclerview.widget.LinearLayoutManager;

android/app/src/main/java/com/example/petstoremobile/fragments/listfragments/ServiceFragment.java

@@ -5,6 +5,7 @@ import android.os.Bundle;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.fragment.app.Fragment;
+import androidx.lifecycle.ViewModelProvider;
 import androidx.navigation.fragment.NavHostFragment;
 import androidx.recyclerview.widget.LinearLayoutManager;
 import androidx.recyclerview.widget.RecyclerView;
@@ -22,21 +23,16 @@ import android.widget.Toast;
 
 import com.example.petstoremobile.R;
 import com.example.petstoremobile.adapters.ServiceAdapter;
-import com.example.petstoremobile.api.ServiceApi;
-import com.example.petstoremobile.dtos.PageResponse;
 import com.example.petstoremobile.dtos.ServiceDTO;
 import com.example.petstoremobile.fragments.ListFragment;
+import com.example.petstoremobile.viewmodels.ServiceViewModel;
+import com.example.petstoremobile.utils.Resource;
 import com.google.android.material.floatingactionbutton.FloatingActionButton;
 
 import java.util.ArrayList;
 import java.util.List;
 
-import javax.inject.Inject;
-
 import dagger.hilt.android.AndroidEntryPoint;
-import retrofit2.Call;
-import retrofit2.Callback;
-import retrofit2.Response;
 
 @AndroidEntryPoint
 public class ServiceFragment extends Fragment implements ServiceAdapter.OnServiceClickListener {
@@ -45,13 +41,19 @@ public class ServiceFragment extends Fragment implements ServiceAdapter.OnServic
     private List<ServiceDTO> filteredList = new ArrayList<>();
     private ServiceAdapter adapter;
     private ImageButton hamburger;
-    @Inject ServiceApi api;
+    private ServiceViewModel viewModel;
     private SwipeRefreshLayout swipeRefreshLayout;
     private EditText etSearch;
 
+    @Override
+    public void onCreate(@Nullable Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        viewModel = new ViewModelProvider(this).get(ServiceViewModel.class);
+    }
+
     //load service view
     @Override
-    public View onCreateView(LayoutInflater inflater, ViewGroup container,
+    public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container,
                              Bundle savedInstanceState) {
         View view = inflater.inflate(R.layout.fragment_service, container, false);
 
@@ -98,8 +100,8 @@ public class ServiceFragment extends Fragment implements ServiceAdapter.OnServic
         } else {
             String lower = query.toLowerCase();
             for (ServiceDTO s : serviceList) {
-                if (s.getServiceName().toLowerCase().contains(lower)
+                if ((s.getServiceName() != null && s.getServiceName().toLowerCase().contains(lower))
-                        || s.getServiceDesc().toLowerCase().contains(lower)) {
+                        || (s.getServiceDesc() != null && s.getServiceDesc().toLowerCase().contains(lower))) {
                     filteredList.add(s);
                 }
             }
@@ -109,9 +111,7 @@ public class ServiceFragment extends Fragment implements ServiceAdapter.OnServic
 
     private void setupSwipeRefresh(View view) {
         swipeRefreshLayout = view.findViewById(R.id.swipeRefreshService);
-        swipeRefreshLayout.setOnRefreshListener(() -> {
+        swipeRefreshLayout.setOnRefreshListener(this::loadServiceData);
-            loadServiceData();
-        });
     }
 
     //Open the service detail view depending on the mode
@@ -141,35 +141,33 @@ public class ServiceFragment extends Fragment implements ServiceAdapter.OnServic
 
     // Helper function to get a list of all services from the backend
     private void loadServiceData() {
-        if (swipeRefreshLayout != null) {
+        //Load all services from the backend using viewModel
-            swipeRefreshLayout.setRefreshing(true);
+        viewModel.getAllServices(0, 100).observe(getViewLifecycleOwner(), resource -> {
-        }
+            if (resource == null) return;
-        api.getAllServices(0, 100).enqueue(new Callback<PageResponse<ServiceDTO>>() {
+
-            @Override
+            // Check the status to see if the resource is loaded and display the data
-            public void onResponse(Call<PageResponse<ServiceDTO>> call, Response<PageResponse<ServiceDTO>> response) {
+            switch (resource.status) {
-                if (swipeRefreshLayout != null) {
+                case LOADING:
-                    swipeRefreshLayout.setRefreshing(false);
+                    // Show loading indicator
-                }
+                    if (swipeRefreshLayout != null) swipeRefreshLayout.setRefreshing(true);
-                if (response.isSuccessful() && response.body() != null) {
+                    break;
+                case SUCCESS:
+                    // Hide loading indicator and display data
+                    if (swipeRefreshLayout != null) swipeRefreshLayout.setRefreshing(false);
+                    if (resource.data != null) {
                         serviceList.clear();
-                    serviceList.addAll(response.body().getContent());
+                        serviceList.addAll(resource.data.getContent());
-                    filterServices(etSearch.getText().toString());
+                        filterServices(etSearch != null ? etSearch.getText().toString() : "");
-
-                } else {
-                    Log.e("onResponse: ", response.message());
-                }
-            }
-
-            @Override
-            public void onFailure(Call<PageResponse<ServiceDTO>> call, Throwable t) {
-                if (swipeRefreshLayout != null) {
-                    swipeRefreshLayout.setRefreshing(false);
                     }
+                    break;
+                case ERROR:
+                    // Hide loading indicator and toast error message
+                    if (swipeRefreshLayout != null) swipeRefreshLayout.setRefreshing(false);
                     if (getContext() != null) {
-                    Toast.makeText(getContext(),
+                        Toast.makeText(getContext(), "Failed to load services: " + resource.message, Toast.LENGTH_SHORT).show();
-                            "Failed to load services", Toast.LENGTH_SHORT).show();
                     }
-                Log.e("onFailure: ", t.getMessage());
+                    Log.e("ServiceFragment", "Error loading services: " + resource.message);
+                    break;
             }
         });
     }

android/app/src/main/java/com/example/petstoremobile/fragments/listfragments/SupplierFragment.java

@@ -5,6 +5,7 @@ import android.os.Bundle;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.fragment.app.Fragment;
+import androidx.lifecycle.ViewModelProvider;
 import androidx.navigation.fragment.NavHostFragment;
 import androidx.recyclerview.widget.LinearLayoutManager;
 import androidx.recyclerview.widget.RecyclerView;
@@ -22,21 +23,16 @@ import android.widget.Toast;
 
 import com.example.petstoremobile.R;
 import com.example.petstoremobile.adapters.SupplierAdapter;
-import com.example.petstoremobile.api.SupplierApi;
-import com.example.petstoremobile.dtos.PageResponse;
 import com.example.petstoremobile.dtos.SupplierDTO;
 import com.example.petstoremobile.fragments.ListFragment;
+import com.example.petstoremobile.viewmodels.SupplierViewModel;
+import com.example.petstoremobile.utils.Resource;
 import com.google.android.material.floatingactionbutton.FloatingActionButton;
 
 import java.util.ArrayList;
 import java.util.List;
 
-import javax.inject.Inject;
-
 import dagger.hilt.android.AndroidEntryPoint;
-import retrofit2.Call;
-import retrofit2.Callback;
-import retrofit2.Response;
 
 @AndroidEntryPoint
 public class SupplierFragment extends Fragment implements SupplierAdapter.OnSupplierClickListener {
@@ -45,13 +41,19 @@ public class SupplierFragment extends Fragment implements SupplierAdapter.OnSupp
     private List<SupplierDTO> filteredList = new ArrayList<>();
     private SupplierAdapter adapter;
     private ImageButton hamburger;
-    @Inject SupplierApi api;
+    private SupplierViewModel viewModel;
     private SwipeRefreshLayout swipeRefreshLayout;
     private EditText etSearch;
 
+    @Override
+    public void onCreate(@Nullable Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        viewModel = new ViewModelProvider(this).get(SupplierViewModel.class);
+    }
+
     //load supplier view
     @Override
-    public View onCreateView(LayoutInflater inflater, ViewGroup container,
+    public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container,
                              Bundle savedInstanceState) {
         View view = inflater.inflate(R.layout.fragment_supplier, container, false);
 
@@ -98,9 +100,9 @@ public class SupplierFragment extends Fragment implements SupplierAdapter.OnSupp
         } else {
             String lower = query.toLowerCase();
             for (SupplierDTO s : supplierList) {
-                if (s.getSupCompany().toLowerCase().contains(lower)
+                if ((s.getSupCompany() != null && s.getSupCompany().toLowerCase().contains(lower))
-                        || s.getSupContactFirstName().toLowerCase().contains(lower)
+                        || (s.getSupContactFirstName() != null && s.getSupContactFirstName().toLowerCase().contains(lower))
-                        || s.getSupContactLastName().toLowerCase().contains(lower)) {
+                        || (s.getSupContactLastName() != null && s.getSupContactLastName().toLowerCase().contains(lower))) {
                     filteredList.add(s);
                 }
             }
@@ -110,9 +112,7 @@ public class SupplierFragment extends Fragment implements SupplierAdapter.OnSupp
 
     private void setupSwipeRefresh(View view) {
         swipeRefreshLayout = view.findViewById(R.id.swipeRefreshSupplier);
-        swipeRefreshLayout.setOnRefreshListener(() -> {
+        swipeRefreshLayout.setOnRefreshListener(this::loadSupplierData);
-            loadSupplierData();
-        });
     }
 
     //Open the supplier detail view depending on the mode
@@ -144,35 +144,33 @@ public class SupplierFragment extends Fragment implements SupplierAdapter.OnSupp
 
     // Helper function to get a list of all suppliers from the backend
     private void loadSupplierData() {
-        if (swipeRefreshLayout != null) {
+        //Load all suppliers from the backend using viewModel
-            swipeRefreshLayout.setRefreshing(true);
+        viewModel.getAllSuppliers(0, 100).observe(getViewLifecycleOwner(), resource -> {
-        }
+            if (resource == null) return;
-        api.getAllSuppliers(0, 100).enqueue(new Callback<PageResponse<SupplierDTO>>() {
+
-            @Override
+            // Check the status to see if the resource is loaded and display the data
-            public void onResponse(Call<PageResponse<SupplierDTO>> call, Response<PageResponse<SupplierDTO>> response) {
+            switch (resource.status) {
-                if (swipeRefreshLayout != null) {
+                case LOADING:
-                    swipeRefreshLayout.setRefreshing(false);
+                    // Show loading indicator
-                }
+                    if (swipeRefreshLayout != null) swipeRefreshLayout.setRefreshing(true);
-                if (response.isSuccessful() && response.body() != null) {
+                    break;
+                case SUCCESS:
+                    // Hide loading indicator and display data
+                    if (swipeRefreshLayout != null) swipeRefreshLayout.setRefreshing(false);
+                    if (resource.data != null) {
                         supplierList.clear();
-                    supplierList.addAll(response.body().getContent());
+                        supplierList.addAll(resource.data.getContent());
                         filterSuppliers(etSearch.getText().toString());
-
-                } else {
-                    Log.e("onResponse: ", response.message());
-                }
-            }
-
-            @Override
-            public void onFailure(Call<PageResponse<SupplierDTO>> call, Throwable t) {
-                if (swipeRefreshLayout != null) {
-                    swipeRefreshLayout.setRefreshing(false);
                     }
+                    break;
+                case ERROR:
+                    // Hide loading indicator and toast error message
+                    if (swipeRefreshLayout != null) swipeRefreshLayout.setRefreshing(false);
                     if (getContext() != null) {
-                    Toast.makeText(getContext(),
+                        Toast.makeText(getContext(), "Failed to load suppliers: " + resource.message, Toast.LENGTH_SHORT).show();
-                            "Failed to load suppliers", Toast.LENGTH_SHORT).show();
                     }
-                Log.e("onFailure: ", t.getMessage());
+                    Log.e("SupplierFragment", "Error loading suppliers: " + resource.message);
+                    break;
             }
         });
     }

android/app/src/main/java/com/example/petstoremobile/fragments/listfragments/detailfragments/ProductDetailFragment.java

@@ -13,10 +13,12 @@ import android.widget.*;
 import androidx.activity.result.ActivityResultLauncher;
 import androidx.activity.result.contract.ActivityResultContracts;
 import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import androidx.appcompat.app.AlertDialog;
 import androidx.core.content.ContextCompat;
 import androidx.core.content.FileProvider;
 import androidx.fragment.app.Fragment;
+import androidx.lifecycle.ViewModelProvider;
 import androidx.navigation.fragment.NavHostFragment;
 
 import com.bumptech.glide.Glide;
@@ -28,9 +30,11 @@ import com.example.petstoremobile.adapters.BlackTextArrayAdapter;
 import com.example.petstoremobile.api.*;
 import com.example.petstoremobile.api.auth.TokenManager;
 import com.example.petstoremobile.dtos.*;
+import com.example.petstoremobile.viewmodels.ProductViewModel;
+import com.example.petstoremobile.utils.Resource;
+import com.example.petstoremobile.utils.FileUtils;
+
 import java.io.File;
-import java.io.FileOutputStream;
-import java.io.InputStream;
 import java.math.BigDecimal;
 import java.util.*;
 
@@ -41,7 +45,6 @@ import dagger.hilt.android.AndroidEntryPoint;
 import okhttp3.MediaType;
 import okhttp3.MultipartBody;
 import okhttp3.RequestBody;
-import retrofit2.*;
 
 @AndroidEntryPoint
 public class ProductDetailFragment extends Fragment {
@@ -61,9 +64,8 @@ public class ProductDetailFragment extends Fragment {
 
     private List<CategoryDTO> categoryList = new ArrayList<>();
     private Uri photoUri;
+    private ProductViewModel viewModel;
 
-    @Inject ProductApi productApi;
-    @Inject CategoryApi categoryApi;
     @Inject @Named("baseUrl") String baseUrl;
     @Inject TokenManager tokenManager;
 
@@ -74,12 +76,13 @@ public class ProductDetailFragment extends Fragment {
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
+        viewModel = new ViewModelProvider(this).get(ProductViewModel.class);
+
         galleryLauncher = registerForActivityResult(
                 new ActivityResultContracts.StartActivityForResult(),
                 result -> {
                     if (result.getResultCode() == Activity.RESULT_OK && result.getData() != null) {
                         Uri selectedImage = result.getData().getData();
-                        // Update image view locally
                         Glide.with(this).load(selectedImage).into(ivProductImage);
                         photoUri = selectedImage;
                         hasImage = true;
@@ -92,7 +95,6 @@ public class ProductDetailFragment extends Fragment {
                 new ActivityResultContracts.TakePicture(),
                 success -> {
                     if (success) {
-                        // Update image view locally
                         Glide.with(this).load(photoUri).into(ivProductImage);
                         hasImage = true;
                         isImageChanged = true;
@@ -185,18 +187,11 @@ public class ProductDetailFragment extends Fragment {
 
     // Helper function to load categories from the backend for the spinner
     private void loadCategories() {
-        categoryApi.getAllCategories(0, 100)
+        viewModel.getAllCategories(0, 100).observe(getViewLifecycleOwner(), resource -> {
-                .enqueue(new Callback<PageResponse<CategoryDTO>>() {
+            if (resource != null && resource.status == Resource.Status.SUCCESS && resource.data != null) {
-                    public void onResponse(Call<PageResponse<CategoryDTO>> c,
+                categoryList = resource.data.getContent();
-                                           Response<PageResponse<CategoryDTO>> r) {
-                        if (r.isSuccessful() && r.body() != null) {
-                            categoryList = r.body().getContent();
                 populateCategorySpinner();
             }
-                    }
-                    public void onFailure(Call<PageResponse<CategoryDTO>> c, Throwable t) {
-                        Log.e("ProductDetail", "Category load failed: " + t.getMessage());
-                    }
         });
     }
 
@@ -265,24 +260,19 @@ public class ProductDetailFragment extends Fragment {
     // updating/adding photo, removing photo or no change
     private void performPendingImageActions(String successMsg) {
         if (isImageRemoved) {
-            //if the image is removed then delete the image
+            viewModel.deleteProductImage(prodId).observe(getViewLifecycleOwner(), resource -> {
-            productApi.deleteProductImage(prodId).enqueue(new Callback<Void>() {
+                if (resource != null && resource.status != Resource.Status.LOADING) {
-                @Override
+                    if (resource.status == Resource.Status.SUCCESS) {
-                public void onResponse(Call<Void> call, Response<Void> response) {
                         Toast.makeText(getContext(), successMsg, Toast.LENGTH_SHORT).show();
-                    navigateBack();
+                    } else {
-                }
-                @Override
-                public void onFailure(Call<Void> call, Throwable t) {
                         Toast.makeText(getContext(), successMsg + " (but image removal failed)", Toast.LENGTH_SHORT).show();
+                    }
                     navigateBack();
                 }
             });
         } else if (isImageChanged && photoUri != null) {
-            //if the image is changed then upload it
             uploadProductImageAndNavigate(photoUri, successMsg);
         } else {
-            //if no changes then navigate back
             Toast.makeText(getContext(), successMsg, Toast.LENGTH_SHORT).show();
             navigateBack();
         }
@@ -291,8 +281,7 @@ public class ProductDetailFragment extends Fragment {
     // Helper function to upload the product image by calling the backend
     // and then navigate back to the previous screen
     private void uploadProductImageAndNavigate(Uri uri, String successMsg) {
-        try {
+        File file = FileUtils.getFileFromUri(requireContext(), uri);
-            File file = getFileFromUri(uri);
         if (file == null) {
             Toast.makeText(getContext(), successMsg, Toast.LENGTH_SHORT).show();
             navigateBack();
@@ -302,50 +291,18 @@ public class ProductDetailFragment extends Fragment {
         RequestBody requestFile = RequestBody.create(file, MediaType.parse(requireContext().getContentResolver().getType(uri)));
         MultipartBody.Part body = MultipartBody.Part.createFormData("image", file.getName(), requestFile);
 
-            productApi.uploadProductImage(prodId, body)
+        viewModel.uploadProductImage(prodId, body).observe(getViewLifecycleOwner(), resource -> {
-                    .enqueue(new Callback<Void>() {
+            if (resource != null && resource.status != Resource.Status.LOADING) {
-                        @Override
+                if (resource.status == Resource.Status.SUCCESS) {
-                        public void onResponse(Call<Void> call, Response<Void> response) {
-                            if (response.isSuccessful()) {
                     Toast.makeText(getContext(), successMsg, Toast.LENGTH_SHORT).show();
                 } else {
                     Toast.makeText(getContext(), successMsg + " (but image upload failed)", Toast.LENGTH_SHORT).show();
                 }
                 navigateBack();
             }
-                        @Override
-                        public void onFailure(Call<Void> call, Throwable t) {
-                            Toast.makeText(getContext(), successMsg + " (network error during upload)", Toast.LENGTH_SHORT).show();
-                            navigateBack();
-                        }
         });
-        } catch (Exception e) {
-            Log.e("ProductDetail", "Error uploading image", e);
-            Toast.makeText(getContext(), successMsg, Toast.LENGTH_SHORT).show();
-            navigateBack();
-        }
     }
 
-    // Helper function to get the File from the Uri
-    private File getFileFromUri(Uri uri) {
-        try {
-            InputStream inputStream = requireContext().getContentResolver().openInputStream(uri);
-            File tempFile = new File(requireContext().getCacheDir(), "upload_product_image.jpg");
-            FileOutputStream outputStream = new FileOutputStream(tempFile);
-            byte[] buffer = new byte[1024];
-            int length;
-            while ((length = inputStream.read(buffer)) > 0) {
-                outputStream.write(buffer, 0, length);
-            }
-            outputStream.close();
-            inputStream.close();
-            return tempFile;
-        } catch (Exception e) {
-            return null;
-        }
-    }
-
-    // Function to save the product to the server
     private void saveProduct() {
         String name = etProductName.getText().toString().trim();
         String desc = etProductDesc.getText().toString().trim();
@@ -372,35 +329,25 @@ public class ProductDetailFragment extends Fragment {
         ProductDTO dto = new ProductDTO(name, category.getCategoryId(), desc, price);
 
         if (isEditing) {
-            productApi.updateProduct(prodId, dto).enqueue(new Callback<ProductDTO>() {
+            viewModel.updateProduct(prodId, dto).observe(getViewLifecycleOwner(), resource -> {
-                @Override
+                if (resource != null && resource.status != Resource.Status.LOADING) {
-                public void onResponse(Call<ProductDTO> call, Response<ProductDTO> response) {
+                    if (resource.status == Resource.Status.SUCCESS) {
-                    if (response.isSuccessful()) {
                         performPendingImageActions("Updated");
                     } else {
-                        Toast.makeText(getContext(), "Error " + response.code(), Toast.LENGTH_SHORT).show();
+                        Toast.makeText(getContext(), "Error: " + resource.message, Toast.LENGTH_SHORT).show();
                     }
                 }
-                @Override
-                public void onFailure(Call<ProductDTO> call, Throwable t) {
-                    Toast.makeText(getContext(), "Network error", Toast.LENGTH_SHORT).show();
-                }
             });
         } else {
-            productApi.createProduct(dto).enqueue(new Callback<ProductDTO>() {
+            viewModel.createProduct(dto).observe(getViewLifecycleOwner(), resource -> {
-                @Override
+                if (resource != null && resource.status != Resource.Status.LOADING) {
-                public void onResponse(Call<ProductDTO> call, Response<ProductDTO> response) {
+                    if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
-                    if (response.isSuccessful() && response.body() != null) {
+                        prodId = resource.data.getProdId();
-                        prodId = response.body().getProdId();
                         performPendingImageActions("Saved");
                     } else {
-                        Toast.makeText(getContext(), "Error saving", Toast.LENGTH_SHORT).show();
+                        Toast.makeText(getContext(), "Error saving: " + resource.message, Toast.LENGTH_SHORT).show();
                     }
                 }
-                @Override
-                public void onFailure(Call<ProductDTO> call, Throwable t) {
-                    Toast.makeText(getContext(), "Network error", Toast.LENGTH_SHORT).show();
-                }
             });
         }
     }
@@ -410,14 +357,11 @@ public class ProductDetailFragment extends Fragment {
         new AlertDialog.Builder(requireContext())
                 .setTitle("Delete Product?")
                 .setPositiveButton("Yes", (d, w) ->
-                        productApi.deleteProduct(prodId)
+                        viewModel.deleteProduct(prodId).observe(getViewLifecycleOwner(), resource -> {
-                                .enqueue(new Callback<Void>() {
+                            if (resource != null && resource.status == Resource.Status.SUCCESS) {
-                                    public void onResponse(Call<Void> c, Response<Void> r) {
                                 navigateBack();
-                                    }
+                            } else if (resource != null && resource.status == Resource.Status.ERROR) {
-                                    public void onFailure(Call<Void> c, Throwable t) {
+                                Toast.makeText(getContext(), "Delete failed: " + resource.message, Toast.LENGTH_SHORT).show();
-                                        Toast.makeText(getContext(), "Delete failed",
-                                                Toast.LENGTH_SHORT).show();
                             }
                         }))
                 .setNegativeButton("No", null).show();

android/app/src/main/java/com/example/petstoremobile/models/Adoption.java

@@ -1,79 +0,0 @@
-package com.example.petstoremobile.models;
-
-public class Adoption {
-    private int adoptionId;
-    private String adopterName;
-    private String adopterEmail;
-    private String adopterPhone;
-    private String petName;
-    private String adoptionDate;
-    private String status;
-
-    // Constructor
-    public Adoption(int adoptionId, String adopterName, String adopterEmail, String adopterPhone, String petName, String adoptionDate, String status) {
-        this.adoptionId = adoptionId;
-        this.adopterName = adopterName;
-        this.adopterEmail = adopterEmail;
-        this.adopterPhone = adopterPhone;
-        this.petName = petName;
-        this.adoptionDate = adoptionDate;
-        this.status = status;
-    }
-
-    // Getters and setters
-    public int getAdoptionId() {
-        return adoptionId;
-    }
-
-    public void setAdoptionId(int adoptionId) {
-        this.adoptionId = adoptionId;
-    }
-
-    public String getAdopterName() {
-        return adopterName;
-    }
-
-    public void setAdopterName(String adopterName) {
-        this.adopterName = adopterName;
-    }
-
-    public String getAdopterEmail() {
-        return adopterEmail;
-    }
-
-    public void setAdopterEmail(String adopterEmail) {
-        this.adopterEmail = adopterEmail;
-    }
-
-    public String getAdopterPhone() {
-        return adopterPhone;
-    }
-
-    public void setAdopterPhone(String adopterPhone) {
-        this.adopterPhone = adopterPhone;
-    }
-
-    public String getPetName() {
-        return petName;
-    }
-
-    public void setPetName(String petName) {
-        this.petName = petName;
-    }
-
-    public String getAdoptionDate() {
-        return adoptionDate;
-    }
-
-    public void setAdoptionDate(String adoptionDate) {
-        this.adoptionDate = adoptionDate;
-    }
-
-    public String getStatus() {
-        return status;
-    }
-
-    public void setStatus(String status) {
-        this.status = status;
-    }
-}

android/app/src/main/java/com/example/petstoremobile/models/Appointment.java

@@ -1,76 +0,0 @@
-package com.example.petstoremobile.models;
-
-
-public class Appointment {
-    private int appointmentId;
-    private String customerName;
-    private String petName;
-    private String serviceType;
-    private String appointmentDate;
-    private String appointmentTime;
-    private String status;
-
-    // Constructor
-    public Appointment(int appointmentId, String customerName, String petName, String serviceType, String appointmentDate, String appointmentTime, String status) {
-        this.appointmentId = appointmentId;
-        this.customerName = customerName;
-        this.petName = petName;
-        this.serviceType = serviceType;
-        this.appointmentDate = appointmentDate;
-        this.appointmentTime = appointmentTime;
-        this.status = status;
-    }
-
-    // Getters and setters
-    public int getAppointmentId() {
-        return appointmentId;
-    }
-
-    public String getCustomerName() {
-        return customerName;
-    }
-
-    public void setCustomerName(String customerName) {
-        this.customerName = customerName;
-    }
-
-    public String getPetName() {
-        return petName;
-    }
-
-    public void setPetName(String petName) {
-        this.petName = petName;
-    }
-
-    public String getServiceType() {
-        return serviceType;
-    }
-
-    public void setServiceType(String serviceType) {
-        this.serviceType = serviceType;
-    }
-
-    public String getAppointmentDate() {
-        return appointmentDate;
-    }
-
-    public void setAppointmentDate(String appointmentDate) {
-        this.appointmentDate = appointmentDate;
-    }
-
-    public String getAppointmentTime() {
-        return appointmentTime;
-    }
-
-    public void setAppointmentTime(String appointmentTime) {
-        this.appointmentTime = appointmentTime;
-    }
-
-    public String getStatus() {
-        return status;
-    }
-
-    public void setStatus(String status) {
-        this.status = status;
-    }
-}

android/app/src/main/java/com/example/petstoremobile/models/Inventory.java

@@ -1,66 +0,0 @@
-package com.example.petstoremobile.models;
-
-
-public class Inventory {
-    private int inventoryId;
-    private String itemName;
-    private String category;
-    private int quantity;
-    private double unitPrice;
-    private String supplier;
-
-    // Constructor
-    public Inventory(int inventoryId, String itemName, String category, int quantity, double unitPrice, String supplier) {
-        this.inventoryId = inventoryId;
-        this.itemName = itemName;
-        this.category = category;
-        this.quantity = quantity;
-        this.unitPrice = unitPrice;
-        this.supplier = supplier;
-    }
-
-    // Getters and setters
-    public int getInventoryId() {
-        return inventoryId;
-    }
-
-    public String getItemName() {
-        return itemName;
-    }
-
-    public void setItemName(String itemName) {
-        this.itemName = itemName;
-    }
-
-    public String getCategory() {
-        return category;
-    }
-
-    public void setCategory(String category) {
-        this.category = category;
-    }
-
-    public int getQuantity() {
-        return quantity;
-    }
-
-    public void setQuantity(int quantity) {
-        this.quantity = quantity;
-    }
-
-    public double getUnitPrice() {
-        return unitPrice;
-    }
-
-    public void setUnitPrice(double unitPrice) {
-        this.unitPrice = unitPrice;
-    }
-
-    public String getSupplier() {
-        return supplier;
-    }
-
-    public void setSupplier(String supplier) {
-        this.supplier = supplier;
-    }
-}

android/app/src/main/java/com/example/petstoremobile/models/Product.java

@@ -1,66 +0,0 @@
-package com.example.petstoremobile.models;
-
-
-public class Product {
-    private int productId;
-    private String productName;
-    private String productDesc;
-    private String category;
-    private double productPrice;
-    private int stockQuantity;
-
-    // Constructor
-    public Product(int productId, String productName, String productDesc, String category, double productPrice, int stockQuantity) {
-        this.productId = productId;
-        this.productName = productName;
-        this.productDesc = productDesc;
-        this.category = category;
-        this.productPrice = productPrice;
-        this.stockQuantity = stockQuantity;
-    }
-
-    // Getters and setters
-    public int getProductId() {
-        return productId;
-    }
-
-    public String getProductName() {
-        return productName;
-    }
-
-    public void setProductName(String productName) {
-        this.productName = productName;
-    }
-
-    public String getProductDesc() {
-        return productDesc;
-    }
-
-    public void setProductDesc(String productDesc) {
-        this.productDesc = productDesc;
-    }
-
-    public String getCategory() {
-        return category;
-    }
-
-    public void setCategory(String category) {
-        this.category = category;
-    }
-
-    public double getProductPrice() {
-        return productPrice;
-    }
-
-    public void setProductPrice(double productPrice) {
-        this.productPrice = productPrice;
-    }
-
-    public int getStockQuantity() {
-        return stockQuantity;
-    }
-
-    public void setStockQuantity(int stockQuantity) {
-        this.stockQuantity = stockQuantity;
-    }
-}

android/app/src/main/java/com/example/petstoremobile/models/ProductSupplier.java

@@ -1,49 +0,0 @@
-package com.example.petstoremobile.models;
-
-public class ProductSupplier {
-    private int supId;
-    private int prodId;
-    private String supCompany;
-    private String prodName;
-    private double cost;
-
-    public ProductSupplier(int supId, int prodId, String supCompany, String prodName, double cost) {
-        this.supId = supId;
-        this.prodId = prodId;
-        this.supCompany = supCompany;
-        this.prodName = prodName;
-        this.cost = cost;
-    }
-
-    public int getSupId() {
-        return supId;
-    }
-
-    public int getProdId() {
-        return prodId;
-    }
-
-    public String getSupCompany() {
-        return supCompany;
-    }
-
-    public String getProdName() {
-        return prodName;
-    }
-
-    public double getCost() {
-        return cost;
-    }
-
-    public void setSupCompany(String supCompany) {
-        this.supCompany = supCompany;
-    }
-
-    public void setProdName(String prodName) {
-        this.prodName = prodName;
-    }
-
-    public void setCost(double cost) {
-        this.cost = cost;
-    }
-}

android/app/src/main/java/com/example/petstoremobile/models/PurchaseOrder.java

@@ -1,31 +0,0 @@
-package com.example.petstoremobile.models;
-
-public class PurchaseOrder {
-    private int purchaseOrderId;
-    private String supplierName;
-    private String orderDate;
-    private String status;
-
-    public PurchaseOrder(int purchaseOrderId, String supplierName, String orderDate, String status) {
-        this.purchaseOrderId = purchaseOrderId;
-        this.supplierName = supplierName;
-        this.orderDate = orderDate;
-        this.status = status;
-    }
-
-    public int getPurchaseOrderId() {
-        return purchaseOrderId;
-    }
-
-    public String getSupplierName() {
-        return supplierName;
-    }
-
-    public String getOrderDate() {
-        return orderDate;
-    }
-
-    public String getStatus() {
-        return status;
-    }
-}

android/app/src/main/java/com/example/petstoremobile/repositories/AdoptionRepository.java

@@ -0,0 +1,156 @@
+package com.example.petstoremobile.repositories;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+
+import com.example.petstoremobile.api.AdoptionApi;
+import com.example.petstoremobile.dtos.AdoptionDTO;
+import com.example.petstoremobile.dtos.PageResponse;
+import com.example.petstoremobile.utils.Resource;
+
+import javax.inject.Inject;
+import javax.inject.Singleton;
+
+import retrofit2.Call;
+import retrofit2.Callback;
+import retrofit2.Response;
+
+@Singleton
+public class AdoptionRepository {
+    private final AdoptionApi adoptionApi;
+
+    @Inject
+    public AdoptionRepository(AdoptionApi adoptionApi) {
+        this.adoptionApi = adoptionApi;
+    }
+
+    /**
+     * Retrieves a paginated list of all adoptions from the API.
+     */
+    public LiveData<Resource<PageResponse<AdoptionDTO>>> getAllAdoptions(int page, int size) {
+        MutableLiveData<Resource<PageResponse<AdoptionDTO>>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        adoptionApi.getAllAdoptions(page, size).enqueue(new Callback<PageResponse<AdoptionDTO>>() {
+            @Override
+            public void onResponse(Call<PageResponse<AdoptionDTO>> call, Response<PageResponse<AdoptionDTO>> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<PageResponse<AdoptionDTO>> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Retrieves a specific adoption record by its ID from the API.
+     */
+    public LiveData<Resource<AdoptionDTO>> getAdoptionById(Long id) {
+        MutableLiveData<Resource<AdoptionDTO>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        adoptionApi.getAdoptionById(id).enqueue(new Callback<AdoptionDTO>() {
+            @Override
+            public void onResponse(Call<AdoptionDTO> call, Response<AdoptionDTO> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<AdoptionDTO> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Sends a request to the API to create a new adoption record.
+     */
+    public LiveData<Resource<AdoptionDTO>> createAdoption(AdoptionDTO adoption) {
+        MutableLiveData<Resource<AdoptionDTO>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        adoptionApi.createAdoption(adoption).enqueue(new Callback<AdoptionDTO>() {
+            @Override
+            public void onResponse(Call<AdoptionDTO> call, Response<AdoptionDTO> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<AdoptionDTO> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Sends a request to the API to update an existing adoption record by ID.
+     */
+    public LiveData<Resource<AdoptionDTO>> updateAdoption(Long id, AdoptionDTO adoption) {
+        MutableLiveData<Resource<AdoptionDTO>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        adoptionApi.updateAdoption(id, adoption).enqueue(new Callback<AdoptionDTO>() {
+            @Override
+            public void onResponse(Call<AdoptionDTO> call, Response<AdoptionDTO> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<AdoptionDTO> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Sends a request to the API to delete a specific adoption record.
+     */
+    public LiveData<Resource<Void>> deleteAdoption(Long id) {
+        MutableLiveData<Resource<Void>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        adoptionApi.deleteAdoption(id).enqueue(new Callback<Void>() {
+            @Override
+            public void onResponse(Call<Void> call, Response<Void> response) {
+                if (response.isSuccessful()) {
+                    data.setValue(Resource.success(null));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<Void> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+}

android/app/src/main/java/com/example/petstoremobile/repositories/AppointmentRepository.java

@@ -0,0 +1,156 @@
+package com.example.petstoremobile.repositories;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+
+import com.example.petstoremobile.api.AppointmentApi;
+import com.example.petstoremobile.dtos.AppointmentDTO;
+import com.example.petstoremobile.dtos.PageResponse;
+import com.example.petstoremobile.utils.Resource;
+
+import javax.inject.Inject;
+import javax.inject.Singleton;
+
+import retrofit2.Call;
+import retrofit2.Callback;
+import retrofit2.Response;
+
+@Singleton
+public class AppointmentRepository {
+    private final AppointmentApi appointmentApi;
+
+    @Inject
+    public AppointmentRepository(AppointmentApi appointmentApi) {
+        this.appointmentApi = appointmentApi;
+    }
+
+    /**
+     * Retrieves a paginated list of all appointments from the API.
+     */
+    public LiveData<Resource<PageResponse<AppointmentDTO>>> getAllAppointments(int page, int size) {
+        MutableLiveData<Resource<PageResponse<AppointmentDTO>>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        appointmentApi.getAllAppointments(page, size).enqueue(new Callback<PageResponse<AppointmentDTO>>() {
+            @Override
+            public void onResponse(Call<PageResponse<AppointmentDTO>> call, Response<PageResponse<AppointmentDTO>> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<PageResponse<AppointmentDTO>> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Retrieves a specific appointment by its ID from the API.
+     */
+    public LiveData<Resource<AppointmentDTO>> getAppointmentById(Long id) {
+        MutableLiveData<Resource<AppointmentDTO>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        appointmentApi.getAppointmentById(id).enqueue(new Callback<AppointmentDTO>() {
+            @Override
+            public void onResponse(Call<AppointmentDTO> call, Response<AppointmentDTO> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<AppointmentDTO> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Sends a request to the API to create a new appointment record.
+     */
+    public LiveData<Resource<AppointmentDTO>> createAppointment(AppointmentDTO appointment) {
+        MutableLiveData<Resource<AppointmentDTO>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        appointmentApi.createAppointment(appointment).enqueue(new Callback<AppointmentDTO>() {
+            @Override
+            public void onResponse(Call<AppointmentDTO> call, Response<AppointmentDTO> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<AppointmentDTO> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Sends a request to the API to update an existing appointment record by ID.
+     */
+    public LiveData<Resource<AppointmentDTO>> updateAppointment(Long id, AppointmentDTO appointment) {
+        MutableLiveData<Resource<AppointmentDTO>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        appointmentApi.updateAppointment(id, appointment).enqueue(new Callback<AppointmentDTO>() {
+            @Override
+            public void onResponse(Call<AppointmentDTO> call, Response<AppointmentDTO> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<AppointmentDTO> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Sends a request to the API to delete a specific appointment record.
+     */
+    public LiveData<Resource<Void>> deleteAppointment(Long id) {
+        MutableLiveData<Resource<Void>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        appointmentApi.deleteAppointment(id).enqueue(new Callback<Void>() {
+            @Override
+            public void onResponse(Call<Void> call, Response<Void> response) {
+                if (response.isSuccessful()) {
+                    data.setValue(Resource.success(null));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<Void> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+}

android/app/src/main/java/com/example/petstoremobile/repositories/AuthRepository.java

@@ -0,0 +1,174 @@
+package com.example.petstoremobile.repositories;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+
+import com.example.petstoremobile.api.auth.AuthApi;
+import com.example.petstoremobile.api.auth.TokenManager;
+import com.example.petstoremobile.dtos.AuthDTO;
+import com.example.petstoremobile.dtos.UserDTO;
+import com.example.petstoremobile.utils.Resource;
+
+import java.util.Map;
+
+import javax.inject.Inject;
+import javax.inject.Singleton;
+
+import okhttp3.MultipartBody;
+import retrofit2.Call;
+import retrofit2.Callback;
+import retrofit2.Response;
+
+@Singleton
+public class AuthRepository {
+    private final AuthApi authApi;
+    private final TokenManager tokenManager;
+
+    @Inject
+    public AuthRepository(AuthApi authApi, TokenManager tokenManager) {
+        this.authApi = authApi;
+        this.tokenManager = tokenManager;
+    }
+
+    /**
+     * Authenticates the user and saves login data (token, username, role) upon success.
+     */
+    public LiveData<Resource<AuthDTO.LoginResponse>> login(AuthDTO.LoginRequest loginRequest) {
+        MutableLiveData<Resource<AuthDTO.LoginResponse>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        authApi.login(loginRequest).enqueue(new Callback<AuthDTO.LoginResponse>() {
+            @Override
+            public void onResponse(Call<AuthDTO.LoginResponse> call, Response<AuthDTO.LoginResponse> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    tokenManager.saveLoginData(
+                            response.body().getToken(),
+                            response.body().getUsername(),
+                            response.body().getRole()
+                    );
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Login failed: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<AuthDTO.LoginResponse> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Retrieves the current user's profile information from the API.
+     */
+    public LiveData<Resource<UserDTO>> getMe() {
+        MutableLiveData<Resource<UserDTO>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        authApi.getMe().enqueue(new Callback<UserDTO>() {
+            @Override
+            public void onResponse(Call<UserDTO> call, Response<UserDTO> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<UserDTO> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Updates the current user's profile details.
+     */
+    public LiveData<Resource<UserDTO>> updateMe(Map<String, String> updates) {
+        MutableLiveData<Resource<UserDTO>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        authApi.updateMe(updates).enqueue(new Callback<UserDTO>() {
+            @Override
+            public void onResponse(Call<UserDTO> call, Response<UserDTO> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<UserDTO> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Uploads a multipart image to be used as the current user's avatar.
+     */
+    public LiveData<Resource<UserDTO>> uploadAvatar(MultipartBody.Part avatar) {
+        MutableLiveData<Resource<UserDTO>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        authApi.uploadAvatar(avatar).enqueue(new Callback<UserDTO>() {
+            @Override
+            public void onResponse(Call<UserDTO> call, Response<UserDTO> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<UserDTO> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Sends a request to the API to remove the current user's avatar.
+     */
+    public LiveData<Resource<Void>> deleteAvatar() {
+        MutableLiveData<Resource<Void>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        authApi.deleteAvatar().enqueue(new Callback<Void>() {
+            @Override
+            public void onResponse(Call<Void> call, Response<Void> response) {
+                if (response.isSuccessful()) {
+                    data.setValue(Resource.success(null));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<Void> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Clears all authentication and login data from storage.
+     */
+    public void logout() {
+        tokenManager.clearLoginData();
+    }
+}

android/app/src/main/java/com/example/petstoremobile/repositories/CategoryRepository.java

@@ -0,0 +1,52 @@
+package com.example.petstoremobile.repositories;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+
+import com.example.petstoremobile.api.CategoryApi;
+import com.example.petstoremobile.dtos.CategoryDTO;
+import com.example.petstoremobile.dtos.PageResponse;
+import com.example.petstoremobile.utils.Resource;
+
+import javax.inject.Inject;
+import javax.inject.Singleton;
+
+import retrofit2.Call;
+import retrofit2.Callback;
+import retrofit2.Response;
+
+@Singleton
+public class CategoryRepository {
+    private final CategoryApi categoryApi;
+
+    @Inject
+    public CategoryRepository(CategoryApi categoryApi) {
+        this.categoryApi = categoryApi;
+    }
+
+    /**
+     * Retrieves a paginated list of all product categories from the API.
+     */
+    public LiveData<Resource<PageResponse<CategoryDTO>>> getAllCategories(int page, int size) {
+        MutableLiveData<Resource<PageResponse<CategoryDTO>>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        categoryApi.getAllCategories(page, size).enqueue(new Callback<PageResponse<CategoryDTO>>() {
+            @Override
+            public void onResponse(Call<PageResponse<CategoryDTO>> call, Response<PageResponse<CategoryDTO>> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<PageResponse<CategoryDTO>> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+}

android/app/src/main/java/com/example/petstoremobile/repositories/InventoryRepository.java

@@ -0,0 +1,184 @@
+package com.example.petstoremobile.repositories;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+
+import com.example.petstoremobile.api.InventoryApi;
+import com.example.petstoremobile.dtos.BulkDeleteRequest;
+import com.example.petstoremobile.dtos.InventoryDTO;
+import com.example.petstoremobile.dtos.InventoryRequest;
+import com.example.petstoremobile.dtos.PageResponse;
+import com.example.petstoremobile.utils.Resource;
+
+import javax.inject.Inject;
+import javax.inject.Singleton;
+
+import retrofit2.Call;
+import retrofit2.Callback;
+import retrofit2.Response;
+
+@Singleton
+public class InventoryRepository {
+    private final InventoryApi inventoryApi;
+
+    @Inject
+    public InventoryRepository(InventoryApi inventoryApi) {
+        this.inventoryApi = inventoryApi;
+    }
+
+    /**
+     * Retrieves a paginated list of inventory items from the API with optional search and sort.
+     */
+    public LiveData<Resource<PageResponse<InventoryDTO>>> getAllInventory(String query, int page, int size, String sort) {
+        MutableLiveData<Resource<PageResponse<InventoryDTO>>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        inventoryApi.getAllInventory(query, page, size, sort).enqueue(new Callback<PageResponse<InventoryDTO>>() {
+            @Override
+            public void onResponse(Call<PageResponse<InventoryDTO>> call, Response<PageResponse<InventoryDTO>> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<PageResponse<InventoryDTO>> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Retrieves a specific inventory item by its ID from the API.
+     */
+    public LiveData<Resource<InventoryDTO>> getInventoryById(Long id) {
+        MutableLiveData<Resource<InventoryDTO>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        inventoryApi.getInventoryById(id).enqueue(new Callback<InventoryDTO>() {
+            @Override
+            public void onResponse(Call<InventoryDTO> call, Response<InventoryDTO> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<InventoryDTO> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Sends a request to the API to create a new inventory record.
+     */
+    public LiveData<Resource<InventoryDTO>> createInventory(InventoryRequest request) {
+        MutableLiveData<Resource<InventoryDTO>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        inventoryApi.createInventory(request).enqueue(new Callback<InventoryDTO>() {
+            @Override
+            public void onResponse(Call<InventoryDTO> call, Response<InventoryDTO> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<InventoryDTO> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Sends a request to the API to update an existing inventory record.
+     */
+    public LiveData<Resource<InventoryDTO>> updateInventory(Long id, InventoryRequest request) {
+        MutableLiveData<Resource<InventoryDTO>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        inventoryApi.updateInventory(id, request).enqueue(new Callback<InventoryDTO>() {
+            @Override
+            public void onResponse(Call<InventoryDTO> call, Response<InventoryDTO> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<InventoryDTO> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Sends a request to the API to delete a specific inventory record.
+     */
+    public LiveData<Resource<Void>> deleteInventory(Long id) {
+        MutableLiveData<Resource<Void>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        inventoryApi.deleteInventory(id).enqueue(new Callback<Void>() {
+            @Override
+            public void onResponse(Call<Void> call, Response<Void> response) {
+                if (response.isSuccessful()) {
+                    data.setValue(Resource.success(null));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<Void> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Sends a request to the API to delete multiple inventory records at once.
+     */
+    public LiveData<Resource<Void>> bulkDeleteInventory(BulkDeleteRequest request) {
+        MutableLiveData<Resource<Void>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        inventoryApi.bulkDeleteInventory(request).enqueue(new Callback<Void>() {
+            @Override
+            public void onResponse(Call<Void> call, Response<Void> response) {
+                if (response.isSuccessful()) {
+                    data.setValue(Resource.success(null));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<Void> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+}

android/app/src/main/java/com/example/petstoremobile/repositories/PetRepository.java

@@ -0,0 +1,208 @@
+package com.example.petstoremobile.repositories;
+
+import com.example.petstoremobile.api.PetApi;
+import com.example.petstoremobile.dtos.PageResponse;
+import com.example.petstoremobile.dtos.PetDTO;
+import com.example.petstoremobile.utils.Resource;
+
+import javax.inject.Inject;
+import javax.inject.Singleton;
+
+import okhttp3.MultipartBody;
+import retrofit2.Call;
+import retrofit2.Callback;
+import retrofit2.Response;
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+
+@Singleton
+public class PetRepository {
+    private final PetApi petApi;
+
+    @Inject
+    public PetRepository(PetApi petApi) {
+        this.petApi = petApi;
+    }
+
+    /**
+     * Retrieves a paginated list of all pets from the API.
+     */
+    public LiveData<Resource<PageResponse<PetDTO>>> getAllPets(int page, int size) {
+        MutableLiveData<Resource<PageResponse<PetDTO>>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        petApi.getAllPets(page, size).enqueue(new Callback<PageResponse<PetDTO>>() {
+            @Override
+            public void onResponse(Call<PageResponse<PetDTO>> call, Response<PageResponse<PetDTO>> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<PageResponse<PetDTO>> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Retrieves a specific pet by its ID from the API.
+     */
+    public LiveData<Resource<PetDTO>> getPetById(Long id) {
+        MutableLiveData<Resource<PetDTO>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        petApi.getPetById(id).enqueue(new Callback<PetDTO>() {
+            @Override
+            public void onResponse(Call<PetDTO> call, Response<PetDTO> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<PetDTO> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Sends a request to the API to create a new pet record.
+     */
+    public LiveData<Resource<PetDTO>> createPet(PetDTO pet) {
+        MutableLiveData<Resource<PetDTO>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        petApi.createPet(pet).enqueue(new Callback<PetDTO>() {
+            @Override
+            public void onResponse(Call<PetDTO> call, Response<PetDTO> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<PetDTO> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Sends a request to the API to update an existing pet record.
+     */
+    public LiveData<Resource<PetDTO>> updatePet(Long id, PetDTO pet) {
+        MutableLiveData<Resource<PetDTO>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        petApi.updatePet(id, pet).enqueue(new Callback<PetDTO>() {
+            @Override
+            public void onResponse(Call<PetDTO> call, Response<PetDTO> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<PetDTO> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Sends a request to the API to delete a specific pet record.
+     */
+    public LiveData<Resource<Void>> deletePet(Long id) {
+        MutableLiveData<Resource<Void>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        petApi.deletePet(id).enqueue(new Callback<Void>() {
+            @Override
+            public void onResponse(Call<Void> call, Response<Void> response) {
+                if (response.isSuccessful()) {
+                    data.setValue(Resource.success(null));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<Void> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Uploads an image file for a specific pet via the API.
+     */
+    public LiveData<Resource<Void>> uploadPetImage(Long id, MultipartBody.Part image) {
+        MutableLiveData<Resource<Void>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        petApi.uploadPetImage(id, image).enqueue(new Callback<Void>() {
+            @Override
+            public void onResponse(Call<Void> call, Response<Void> response) {
+                if (response.isSuccessful()) {
+                    data.setValue(Resource.success(null));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<Void> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Sends a request to the API to delete the image of a specific pet.
+     */
+    public LiveData<Resource<Void>> deletePetImage(Long id) {
+        MutableLiveData<Resource<Void>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        petApi.deletePetImage(id).enqueue(new Callback<Void>() {
+            @Override
+            public void onResponse(Call<Void> call, Response<Void> response) {
+                if (response.isSuccessful()) {
+                    data.setValue(Resource.success(null));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<Void> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+}

android/app/src/main/java/com/example/petstoremobile/repositories/ProductRepository.java

@@ -0,0 +1,209 @@
+package com.example.petstoremobile.repositories;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+
+import com.example.petstoremobile.api.ProductApi;
+import com.example.petstoremobile.dtos.PageResponse;
+import com.example.petstoremobile.dtos.ProductDTO;
+import com.example.petstoremobile.utils.Resource;
+
+import javax.inject.Inject;
+import javax.inject.Singleton;
+
+import okhttp3.MultipartBody;
+import retrofit2.Call;
+import retrofit2.Callback;
+import retrofit2.Response;
+
+@Singleton
+public class ProductRepository {
+    private final ProductApi productApi;
+
+    @Inject
+    public ProductRepository(ProductApi productApi) {
+        this.productApi = productApi;
+    }
+
+    /**
+     * Retrieves a paginated list of products from the API, filtered by an optional query.
+     */
+    public LiveData<Resource<PageResponse<ProductDTO>>> getAllProducts(String query, int page, int size) {
+        MutableLiveData<Resource<PageResponse<ProductDTO>>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        productApi.getAllProducts(query, page, size).enqueue(new Callback<PageResponse<ProductDTO>>() {
+            @Override
+            public void onResponse(Call<PageResponse<ProductDTO>> call, Response<PageResponse<ProductDTO>> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<PageResponse<ProductDTO>> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Retrieves a specific product by its ID from the API.
+     */
+    public LiveData<Resource<ProductDTO>> getProductById(Long id) {
+        MutableLiveData<Resource<ProductDTO>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        productApi.getProductById(id).enqueue(new Callback<ProductDTO>() {
+            @Override
+            public void onResponse(Call<ProductDTO> call, Response<ProductDTO> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<ProductDTO> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Sends a request to the API to create a new product.
+     */
+    public LiveData<Resource<ProductDTO>> createProduct(ProductDTO product) {
+        MutableLiveData<Resource<ProductDTO>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        productApi.createProduct(product).enqueue(new Callback<ProductDTO>() {
+            @Override
+            public void onResponse(Call<ProductDTO> call, Response<ProductDTO> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<ProductDTO> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Sends a request to the API to update an existing product by ID.
+     */
+    public LiveData<Resource<ProductDTO>> updateProduct(Long id, ProductDTO product) {
+        MutableLiveData<Resource<ProductDTO>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        productApi.updateProduct(id, product).enqueue(new Callback<ProductDTO>() {
+            @Override
+            public void onResponse(Call<ProductDTO> call, Response<ProductDTO> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<ProductDTO> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Sends a request to the API to delete a specific product.
+     */
+    public LiveData<Resource<Void>> deleteProduct(Long id) {
+        MutableLiveData<Resource<Void>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        productApi.deleteProduct(id).enqueue(new Callback<Void>() {
+            @Override
+            public void onResponse(Call<Void> call, Response<Void> response) {
+                if (response.isSuccessful()) {
+                    data.setValue(Resource.success(null));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<Void> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Uploads an image file for a specific product via the API.
+     */
+    public LiveData<Resource<Void>> uploadProductImage(Long id, MultipartBody.Part image) {
+        MutableLiveData<Resource<Void>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        productApi.uploadProductImage(id, image).enqueue(new Callback<Void>() {
+            @Override
+            public void onResponse(Call<Void> call, Response<Void> response) {
+                if (response.isSuccessful()) {
+                    data.setValue(Resource.success(null));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<Void> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Sends a request to the API to delete the image of a specific product.
+     */
+    public LiveData<Resource<Void>> deleteProductImage(Long id) {
+        MutableLiveData<Resource<Void>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        productApi.deleteProductImage(id).enqueue(new Callback<Void>() {
+            @Override
+            public void onResponse(Call<Void> call, Response<Void> response) {
+                if (response.isSuccessful()) {
+                    data.setValue(Resource.success(null));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<Void> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+}

android/app/src/main/java/com/example/petstoremobile/repositories/ProductSupplierRepository.java

@@ -0,0 +1,130 @@
+package com.example.petstoremobile.repositories;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+
+import com.example.petstoremobile.api.ProductSupplierApi;
+import com.example.petstoremobile.dtos.PageResponse;
+import com.example.petstoremobile.dtos.ProductSupplierDTO;
+import com.example.petstoremobile.utils.Resource;
+
+import javax.inject.Inject;
+import javax.inject.Singleton;
+
+import retrofit2.Call;
+import retrofit2.Callback;
+import retrofit2.Response;
+
+@Singleton
+public class ProductSupplierRepository {
+    private final ProductSupplierApi api;
+
+    @Inject
+    public ProductSupplierRepository(ProductSupplierApi api) {
+        this.api = api;
+    }
+
+    /**
+     * Retrieves a paginated list of all product-supplier relationships from the API.
+     */
+    public LiveData<Resource<PageResponse<ProductSupplierDTO>>> getAllProductSuppliers(int page, int size) {
+        MutableLiveData<Resource<PageResponse<ProductSupplierDTO>>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        api.getAllProductSuppliers(page, size).enqueue(new Callback<PageResponse<ProductSupplierDTO>>() {
+            @Override
+            public void onResponse(Call<PageResponse<ProductSupplierDTO>> call, Response<PageResponse<ProductSupplierDTO>> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<PageResponse<ProductSupplierDTO>> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Sends a request to the API to create a new product-supplier relationship.
+     */
+    public LiveData<Resource<ProductSupplierDTO>> createProductSupplier(ProductSupplierDTO dto) {
+        MutableLiveData<Resource<ProductSupplierDTO>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        api.createProductSupplier(dto).enqueue(new Callback<ProductSupplierDTO>() {
+            @Override
+            public void onResponse(Call<ProductSupplierDTO> call, Response<ProductSupplierDTO> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<ProductSupplierDTO> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Sends a request to the API to update an existing product-supplier relationship.
+     */
+    public LiveData<Resource<ProductSupplierDTO>> updateProductSupplier(Long productId, Long supplierId, ProductSupplierDTO dto) {
+        MutableLiveData<Resource<ProductSupplierDTO>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        api.updateProductSupplier(productId, supplierId, dto).enqueue(new Callback<ProductSupplierDTO>() {
+            @Override
+            public void onResponse(Call<ProductSupplierDTO> call, Response<ProductSupplierDTO> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<ProductSupplierDTO> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Sends a request to the API to delete a specific product-supplier relationship.
+     */
+    public LiveData<Resource<Void>> deleteProductSupplier(Long productId, Long supplierId) {
+        MutableLiveData<Resource<Void>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        api.deleteProductSupplier(productId, supplierId).enqueue(new Callback<Void>() {
+            @Override
+            public void onResponse(Call<Void> call, Response<Void> response) {
+                if (response.isSuccessful()) {
+                    data.setValue(Resource.success(null));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<Void> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+}

android/app/src/main/java/com/example/petstoremobile/repositories/PurchaseOrderRepository.java

@@ -0,0 +1,78 @@
+package com.example.petstoremobile.repositories;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+
+import com.example.petstoremobile.api.PurchaseOrderApi;
+import com.example.petstoremobile.dtos.PageResponse;
+import com.example.petstoremobile.dtos.PurchaseOrderDTO;
+import com.example.petstoremobile.utils.Resource;
+
+import javax.inject.Inject;
+import javax.inject.Singleton;
+
+import retrofit2.Call;
+import retrofit2.Callback;
+import retrofit2.Response;
+
+@Singleton
+public class PurchaseOrderRepository {
+    private final PurchaseOrderApi api;
+
+    @Inject
+    public PurchaseOrderRepository(PurchaseOrderApi api) {
+        this.api = api;
+    }
+
+    /**
+     * Retrieves a paginated list of all purchase orders from the API.
+     */
+    public LiveData<Resource<PageResponse<PurchaseOrderDTO>>> getAllPurchaseOrders(int page, int size) {
+        MutableLiveData<Resource<PageResponse<PurchaseOrderDTO>>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        api.getAllPurchaseOrders(page, size).enqueue(new Callback<PageResponse<PurchaseOrderDTO>>() {
+            @Override
+            public void onResponse(Call<PageResponse<PurchaseOrderDTO>> call, Response<PageResponse<PurchaseOrderDTO>> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<PageResponse<PurchaseOrderDTO>> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Retrieves a specific purchase order by its ID from the API.
+     */
+    public LiveData<Resource<PurchaseOrderDTO>> getPurchaseOrderById(Long id) {
+        MutableLiveData<Resource<PurchaseOrderDTO>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        api.getPurchaseOrderById(id).enqueue(new Callback<PurchaseOrderDTO>() {
+            @Override
+            public void onResponse(Call<PurchaseOrderDTO> call, Response<PurchaseOrderDTO> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<PurchaseOrderDTO> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+}

android/app/src/main/java/com/example/petstoremobile/repositories/ServiceRepository.java

@@ -0,0 +1,156 @@
+package com.example.petstoremobile.repositories;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+
+import com.example.petstoremobile.api.ServiceApi;
+import com.example.petstoremobile.dtos.PageResponse;
+import com.example.petstoremobile.dtos.ServiceDTO;
+import com.example.petstoremobile.utils.Resource;
+
+import javax.inject.Inject;
+import javax.inject.Singleton;
+
+import retrofit2.Call;
+import retrofit2.Callback;
+import retrofit2.Response;
+
+@Singleton
+public class ServiceRepository {
+    private final ServiceApi serviceApi;
+
+    @Inject
+    public ServiceRepository(ServiceApi serviceApi) {
+        this.serviceApi = serviceApi;
+    }
+
+    /**
+     * Retrieves a paginated list of all services from the API.
+     */
+    public LiveData<Resource<PageResponse<ServiceDTO>>> getAllServices(int page, int size) {
+        MutableLiveData<Resource<PageResponse<ServiceDTO>>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        serviceApi.getAllServices(page, size).enqueue(new Callback<PageResponse<ServiceDTO>>() {
+            @Override
+            public void onResponse(Call<PageResponse<ServiceDTO>> call, Response<PageResponse<ServiceDTO>> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<PageResponse<ServiceDTO>> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Retrieves a specific service by its ID from the API.
+     */
+    public LiveData<Resource<ServiceDTO>> getServiceById(Long id) {
+        MutableLiveData<Resource<ServiceDTO>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        serviceApi.getServiceById(id).enqueue(new Callback<ServiceDTO>() {
+            @Override
+            public void onResponse(Call<ServiceDTO> call, Response<ServiceDTO> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<ServiceDTO> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Sends a request to the API to create a new service.
+     */
+    public LiveData<Resource<ServiceDTO>> createService(ServiceDTO service) {
+        MutableLiveData<Resource<ServiceDTO>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        serviceApi.createService(service).enqueue(new Callback<ServiceDTO>() {
+            @Override
+            public void onResponse(Call<ServiceDTO> call, Response<ServiceDTO> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<ServiceDTO> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Sends a request to the API to update an existing service by ID.
+     */
+    public LiveData<Resource<ServiceDTO>> updateService(Long id, ServiceDTO service) {
+        MutableLiveData<Resource<ServiceDTO>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        serviceApi.updateService(id, service).enqueue(new Callback<ServiceDTO>() {
+            @Override
+            public void onResponse(Call<ServiceDTO> call, Response<ServiceDTO> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<ServiceDTO> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Sends a request to the API to delete a specific service.
+     */
+    public LiveData<Resource<Void>> deleteService(Long id) {
+        MutableLiveData<Resource<Void>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        serviceApi.deleteService(id).enqueue(new Callback<Void>() {
+            @Override
+            public void onResponse(Call<Void> call, Response<Void> response) {
+                if (response.isSuccessful()) {
+                    data.setValue(Resource.success(null));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<Void> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+}

android/app/src/main/java/com/example/petstoremobile/repositories/SupplierRepository.java

@@ -0,0 +1,156 @@
+package com.example.petstoremobile.repositories;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+
+import com.example.petstoremobile.api.SupplierApi;
+import com.example.petstoremobile.dtos.PageResponse;
+import com.example.petstoremobile.dtos.SupplierDTO;
+import com.example.petstoremobile.utils.Resource;
+
+import javax.inject.Inject;
+import javax.inject.Singleton;
+
+import retrofit2.Call;
+import retrofit2.Callback;
+import retrofit2.Response;
+
+@Singleton
+public class SupplierRepository {
+    private final SupplierApi supplierApi;
+
+    @Inject
+    public SupplierRepository(SupplierApi supplierApi) {
+        this.supplierApi = supplierApi;
+    }
+
+    /**
+     * Retrieves a paginated list of all suppliers from the API.
+     */
+    public LiveData<Resource<PageResponse<SupplierDTO>>> getAllSuppliers(int page, int size) {
+        MutableLiveData<Resource<PageResponse<SupplierDTO>>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        supplierApi.getAllSuppliers(page, size).enqueue(new Callback<PageResponse<SupplierDTO>>() {
+            @Override
+            public void onResponse(Call<PageResponse<SupplierDTO>> call, Response<PageResponse<SupplierDTO>> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<PageResponse<SupplierDTO>> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Retrieves a specific supplier by its ID from the API.
+     */
+    public LiveData<Resource<SupplierDTO>> getSupplierById(Long id) {
+        MutableLiveData<Resource<SupplierDTO>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        supplierApi.getSupplierById(id).enqueue(new Callback<SupplierDTO>() {
+            @Override
+            public void onResponse(Call<SupplierDTO> call, Response<SupplierDTO> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<SupplierDTO> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Sends a request to the API to create a new supplier record.
+     */
+    public LiveData<Resource<SupplierDTO>> createSupplier(SupplierDTO supplier) {
+        MutableLiveData<Resource<SupplierDTO>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        supplierApi.createSupplier(supplier).enqueue(new Callback<SupplierDTO>() {
+            @Override
+            public void onResponse(Call<SupplierDTO> call, Response<SupplierDTO> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<SupplierDTO> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Sends a request to the API to update an existing supplier record by ID.
+     */
+    public LiveData<Resource<SupplierDTO>> updateSupplier(Long id, SupplierDTO supplier) {
+        MutableLiveData<Resource<SupplierDTO>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        supplierApi.updateSupplier(id, supplier).enqueue(new Callback<SupplierDTO>() {
+            @Override
+            public void onResponse(Call<SupplierDTO> call, Response<SupplierDTO> response) {
+                if (response.isSuccessful() && response.body() != null) {
+                    data.setValue(Resource.success(response.body()));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<SupplierDTO> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+
+    /**
+     * Sends a request to the API to delete a specific supplier record.
+     */
+    public LiveData<Resource<Void>> deleteSupplier(Long id) {
+        MutableLiveData<Resource<Void>> data = new MutableLiveData<>();
+        data.setValue(Resource.loading(null));
+
+        supplierApi.deleteSupplier(id).enqueue(new Callback<Void>() {
+            @Override
+            public void onResponse(Call<Void> call, Response<Void> response) {
+                if (response.isSuccessful()) {
+                    data.setValue(Resource.success(null));
+                } else {
+                    data.setValue(Resource.error("Error: " + response.message(), null));
+                }
+            }
+
+            @Override
+            public void onFailure(Call<Void> call, Throwable t) {
+                data.setValue(Resource.error(t.getMessage(), null));
+            }
+        });
+
+        return data;
+    }
+}

android/app/src/main/java/com/example/petstoremobile/utils/FileUtils.java

@@ -0,0 +1,27 @@
+package com.example.petstoremobile.utils;
+
+import android.content.Context;
+import android.net.Uri;
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.InputStream;
+
+public class FileUtils {
+    public static File getFileFromUri(Context context, Uri uri) {
+        try {
+            InputStream inputStream = context.getContentResolver().openInputStream(uri);
+            File tempFile = new File(context.getCacheDir(), "upload_image_" + System.currentTimeMillis() + ".jpg");
+            FileOutputStream outputStream = new FileOutputStream(tempFile);
+            byte[] buffer = new byte[1024];
+            int length;
+            while ((length = inputStream.read(buffer)) > 0) {
+                outputStream.write(buffer, 0, length);
+            }
+            outputStream.close();
+            inputStream.close();
+            return tempFile;
+        } catch (Exception e) {
+            return null;
+        }
+    }
+}

android/app/src/main/java/com/example/petstoremobile/utils/Resource.java

@@ -0,0 +1,30 @@
+package com.example.petstoremobile.utils;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
+public class Resource<T> {
+    public enum Status { SUCCESS, ERROR, LOADING }
+
+    public final Status status;
+    public final T data;
+    public final String message;
+
+    private Resource(Status status, @Nullable T data, @Nullable String message) {
+        this.status = status;
+        this.data = data;
+        this.message = message;
+    }
+
+    public static <T> Resource<T> success(@Nullable T data) {
+        return new Resource<>(Status.SUCCESS, data, null);
+    }
+
+    public static <T> Resource<T> error(String msg, @Nullable T data) {
+        return new Resource<>(Status.ERROR, data, msg);
+    }
+
+    public static <T> Resource<T> loading(@Nullable T data) {
+        return new Resource<>(Status.LOADING, data, null);
+    }
+}

android/app/src/main/java/com/example/petstoremobile/viewmodels/AdoptionViewModel.java

@@ -0,0 +1,58 @@
+package com.example.petstoremobile.viewmodels;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.ViewModel;
+
+import com.example.petstoremobile.dtos.AdoptionDTO;
+import com.example.petstoremobile.dtos.PageResponse;
+import com.example.petstoremobile.repositories.AdoptionRepository;
+import com.example.petstoremobile.utils.Resource;
+
+import javax.inject.Inject;
+
+import dagger.hilt.android.lifecycle.HiltViewModel;
+
+@HiltViewModel
+public class AdoptionViewModel extends ViewModel {
+    private final AdoptionRepository repository;
+
+    @Inject
+    public AdoptionViewModel(AdoptionRepository repository) {
+        this.repository = repository;
+    }
+
+    /**
+     * Fetches a paginated list of all adoptions.
+     */
+    public LiveData<Resource<PageResponse<AdoptionDTO>>> getAllAdoptions(int page, int size) {
+        return repository.getAllAdoptions(page, size);
+    }
+
+    /**
+     * Retrieves a single adoption by its ID.
+     */
+    public LiveData<Resource<AdoptionDTO>> getAdoptionById(Long id) {
+        return repository.getAdoptionById(id);
+    }
+
+    /**
+     * Creates a new adoption record.
+     */
+    public LiveData<Resource<AdoptionDTO>> createAdoption(AdoptionDTO adoption) {
+        return repository.createAdoption(adoption);
+    }
+
+    /**
+     * Updates an existing adoption record by ID.
+     */
+    public LiveData<Resource<AdoptionDTO>> updateAdoption(Long id, AdoptionDTO adoption) {
+        return repository.updateAdoption(id, adoption);
+    }
+
+    /**
+     * Deletes an adoption record by ID.
+     */
+    public LiveData<Resource<Void>> deleteAdoption(Long id) {
+        return repository.deleteAdoption(id);
+    }
+}

android/app/src/main/java/com/example/petstoremobile/viewmodels/AppointmentViewModel.java

@@ -0,0 +1,58 @@
+package com.example.petstoremobile.viewmodels;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.ViewModel;
+
+import com.example.petstoremobile.dtos.AppointmentDTO;
+import com.example.petstoremobile.dtos.PageResponse;
+import com.example.petstoremobile.repositories.AppointmentRepository;
+import com.example.petstoremobile.utils.Resource;
+
+import javax.inject.Inject;
+
+import dagger.hilt.android.lifecycle.HiltViewModel;
+
+@HiltViewModel
+public class AppointmentViewModel extends ViewModel {
+    private final AppointmentRepository repository;
+
+    @Inject
+    public AppointmentViewModel(AppointmentRepository repository) {
+        this.repository = repository;
+    }
+
+    /**
+     * Fetches a paginated list of all appointments.
+     */
+    public LiveData<Resource<PageResponse<AppointmentDTO>>> getAllAppointments(int page, int size) {
+        return repository.getAllAppointments(page, size);
+    }
+
+    /**
+     * Retrieves a single appointment by its ID.
+     */
+    public LiveData<Resource<AppointmentDTO>> getAppointmentById(Long id) {
+        return repository.getAppointmentById(id);
+    }
+
+    /**
+     * Creates a new appointment.
+     */
+    public LiveData<Resource<AppointmentDTO>> createAppointment(AppointmentDTO appointment) {
+        return repository.createAppointment(appointment);
+    }
+
+    /**
+     * Updates an existing appointment record by ID.
+     */
+    public LiveData<Resource<AppointmentDTO>> updateAppointment(Long id, AppointmentDTO appointment) {
+        return repository.updateAppointment(id, appointment);
+    }
+
+    /**
+     * Deletes an appointment record by ID.
+     */
+    public LiveData<Resource<Void>> deleteAppointment(Long id) {
+        return repository.deleteAppointment(id);
+    }
+}

android/app/src/main/java/com/example/petstoremobile/viewmodels/AuthViewModel.java

@@ -0,0 +1,68 @@
+package com.example.petstoremobile.viewmodels;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.ViewModel;
+
+import com.example.petstoremobile.dtos.AuthDTO;
+import com.example.petstoremobile.dtos.UserDTO;
+import com.example.petstoremobile.repositories.AuthRepository;
+import com.example.petstoremobile.utils.Resource;
+
+import java.util.Map;
+
+import javax.inject.Inject;
+
+import dagger.hilt.android.lifecycle.HiltViewModel;
+import okhttp3.MultipartBody;
+
+@HiltViewModel
+public class AuthViewModel extends ViewModel {
+    private final AuthRepository repository;
+
+    @Inject
+    public AuthViewModel(AuthRepository repository) {
+        this.repository = repository;
+    }
+
+    /**
+     * Authenticates a user with username and password.
+     */
+    public LiveData<Resource<AuthDTO.LoginResponse>> login(String username, String password) {
+        return repository.login(new AuthDTO.LoginRequest(username, password));
+    }
+
+    /**
+     * Retrieves the profile information of the currently authenticated user.
+     */
+    public LiveData<Resource<UserDTO>> getMe() {
+        return repository.getMe();
+    }
+
+    /**
+     * Updates the profile information of the current user.
+     */
+    public LiveData<Resource<UserDTO>> updateMe(Map<String, String> updates) {
+        return repository.updateMe(updates);
+    }
+
+    /**
+     * Uploads a new avatar image for the current user.
+     */
+    public LiveData<Resource<UserDTO>> uploadAvatar(MultipartBody.Part avatar) {
+        return repository.uploadAvatar(avatar);
+    }
+
+    /**
+     * Deletes the avatar image of the current user.
+     */
+    public LiveData<Resource<Void>> deleteAvatar() {
+        return repository.deleteAvatar();
+    }
+
+    /**
+     * Logs out the current user by clearing stored credentials.
+     */
+    public void logout() {
+        repository.logout();
+    }
+}

android/app/src/main/java/com/example/petstoremobile/viewmodels/InventoryViewModel.java

@@ -0,0 +1,80 @@
+package com.example.petstoremobile.viewmodels;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.ViewModel;
+
+import com.example.petstoremobile.dtos.BulkDeleteRequest;
+import com.example.petstoremobile.dtos.CategoryDTO;
+import com.example.petstoremobile.dtos.InventoryDTO;
+import com.example.petstoremobile.dtos.InventoryRequest;
+import com.example.petstoremobile.dtos.PageResponse;
+import com.example.petstoremobile.repositories.CategoryRepository;
+import com.example.petstoremobile.repositories.InventoryRepository;
+import com.example.petstoremobile.utils.Resource;
+
+import java.util.List;
+
+import javax.inject.Inject;
+
+import dagger.hilt.android.lifecycle.HiltViewModel;
+
+@HiltViewModel
+public class InventoryViewModel extends ViewModel {
+    private final InventoryRepository inventoryRepository;
+    private final CategoryRepository categoryRepository;
+
+    @Inject
+    public InventoryViewModel(InventoryRepository inventoryRepository, CategoryRepository categoryRepository) {
+        this.inventoryRepository = inventoryRepository;
+        this.categoryRepository = categoryRepository;
+    }
+
+    /**
+     * Retrieves a paginated list of inventory items, with optional filtering and sorting.
+     */
+    public LiveData<Resource<PageResponse<InventoryDTO>>> getAllInventory(String query, int page, int size, String sort) {
+        return inventoryRepository.getAllInventory(query, page, size, sort);
+    }
+
+    /**
+     * Retrieves a single inventory item by its ID.
+     */
+    public LiveData<Resource<InventoryDTO>> getInventoryById(Long id) {
+        return inventoryRepository.getInventoryById(id);
+    }
+
+    /**
+     * Creates a new inventory record.
+     */
+    public LiveData<Resource<InventoryDTO>> createInventory(InventoryRequest request) {
+        return inventoryRepository.createInventory(request);
+    }
+
+    /**
+     * Updates an existing inventory record by ID.
+     */
+    public LiveData<Resource<InventoryDTO>> updateInventory(Long id, InventoryRequest request) {
+        return inventoryRepository.updateInventory(id, request);
+    }
+
+    /**
+     * Deletes an inventory record by ID.
+     */
+    public LiveData<Resource<Void>> deleteInventory(Long id) {
+        return inventoryRepository.deleteInventory(id);
+    }
+
+    /**
+     * Deletes multiple inventory records in a single request.
+     */
+    public LiveData<Resource<Void>> bulkDeleteInventory(List<Long> ids) {
+        return inventoryRepository.bulkDeleteInventory(new BulkDeleteRequest(ids));
+    }
+
+    /**
+     * Retrieves a paginated list of categories.
+     */
+    public LiveData<Resource<PageResponse<CategoryDTO>>> getAllCategories(int page, int size) {
+        return categoryRepository.getAllCategories(page, size);
+    }
+}

android/app/src/main/java/com/example/petstoremobile/viewmodels/PetViewModel.java

@@ -0,0 +1,75 @@
+package com.example.petstoremobile.viewmodels;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+import androidx.lifecycle.ViewModel;
+
+import com.example.petstoremobile.dtos.PageResponse;
+import com.example.petstoremobile.dtos.PetDTO;
+import com.example.petstoremobile.repositories.PetRepository;
+import com.example.petstoremobile.utils.Resource;
+
+import javax.inject.Inject;
+
+import dagger.hilt.android.lifecycle.HiltViewModel;
+import okhttp3.MultipartBody;
+
+@HiltViewModel
+public class PetViewModel extends ViewModel {
+    private final PetRepository repository;
+    private final MutableLiveData<Long> _petId = new MutableLiveData<>();
+
+    @Inject
+    public PetViewModel(PetRepository repository) {
+        this.repository = repository;
+    }
+
+    /**
+     * Fetches a paginated list of all pets.
+     */
+    public LiveData<Resource<PageResponse<PetDTO>>> getAllPets(int page, int size) {
+        return repository.getAllPets(page, size);
+    }
+
+    /**
+     * Retrieves a single pet by its ID.
+     */
+    public LiveData<Resource<PetDTO>> getPetById(Long id) {
+        return repository.getPetById(id);
+    }
+
+    /**
+     * Creates a new pet record.
+     */
+    public LiveData<Resource<PetDTO>> createPet(PetDTO pet) {
+        return repository.createPet(pet);
+    }
+
+    /**
+     * Updates an existing pet record by ID.
+     */
+    public LiveData<Resource<PetDTO>> updatePet(Long id, PetDTO pet) {
+        return repository.updatePet(id, pet);
+    }
+
+    /**
+     * Deletes a pet record by ID.
+     */
+    public LiveData<Resource<Void>> deletePet(Long id) {
+        return repository.deletePet(id);
+    }
+
+    /**
+     * Uploads an image for a specific pet.
+     */
+    public LiveData<Resource<Void>> uploadPetImage(Long id, MultipartBody.Part image) {
+        return repository.uploadPetImage(id, image);
+    }
+
+    /**
+     * Deletes the image associated with a specific pet.
+     */
+    public LiveData<Resource<Void>> deletePetImage(Long id) {
+        return repository.deletePetImage(id);
+    }
+}

android/app/src/main/java/com/example/petstoremobile/viewmodels/ProductSupplierViewModel.java

@@ -0,0 +1,51 @@
+package com.example.petstoremobile.viewmodels;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.ViewModel;
+
+import com.example.petstoremobile.dtos.PageResponse;
+import com.example.petstoremobile.dtos.ProductSupplierDTO;
+import com.example.petstoremobile.repositories.ProductSupplierRepository;
+import com.example.petstoremobile.utils.Resource;
+
+import javax.inject.Inject;
+
+import dagger.hilt.android.lifecycle.HiltViewModel;
+
+@HiltViewModel
+public class ProductSupplierViewModel extends ViewModel {
+    private final ProductSupplierRepository repository;
+
+    @Inject
+    public ProductSupplierViewModel(ProductSupplierRepository repository) {
+        this.repository = repository;
+    }
+
+    /**
+     * Fetches a paginated list of all product-supplier relationships.
+     */
+    public LiveData<Resource<PageResponse<ProductSupplierDTO>>> getAllProductSuppliers(int page, int size) {
+        return repository.getAllProductSuppliers(page, size);
+    }
+
+    /**
+     * Creates a new product-supplier relationship.
+     */
+    public LiveData<Resource<ProductSupplierDTO>> createProductSupplier(ProductSupplierDTO dto) {
+        return repository.createProductSupplier(dto);
+    }
+
+    /**
+     * Updates an existing product-supplier relationship.
+     */
+    public LiveData<Resource<ProductSupplierDTO>> updateProductSupplier(Long productId, Long supplierId, ProductSupplierDTO dto) {
+        return repository.updateProductSupplier(productId, supplierId, dto);
+    }
+
+    /**
+     * Deletes a product-supplier relationship by product and supplier IDs.
+     */
+    public LiveData<Resource<Void>> deleteProductSupplier(Long productId, Long supplierId) {
+        return repository.deleteProductSupplier(productId, supplierId);
+    }
+}

android/app/src/main/java/com/example/petstoremobile/viewmodels/ProductViewModel.java

@@ -0,0 +1,84 @@
+package com.example.petstoremobile.viewmodels;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.ViewModel;
+
+import com.example.petstoremobile.dtos.CategoryDTO;
+import com.example.petstoremobile.dtos.PageResponse;
+import com.example.petstoremobile.dtos.ProductDTO;
+import com.example.petstoremobile.repositories.CategoryRepository;
+import com.example.petstoremobile.repositories.ProductRepository;
+import com.example.petstoremobile.utils.Resource;
+
+import javax.inject.Inject;
+
+import dagger.hilt.android.lifecycle.HiltViewModel;
+import okhttp3.MultipartBody;
+
+@HiltViewModel
+public class ProductViewModel extends ViewModel {
+    private final ProductRepository productRepository;
+    private final CategoryRepository categoryRepository;
+
+    @Inject
+    public ProductViewModel(ProductRepository productRepository, CategoryRepository categoryRepository) {
+        this.productRepository = productRepository;
+        this.categoryRepository = categoryRepository;
+    }
+
+    /**
+     * Retrieves a paginated list of products, optionally filtered by a query string.
+     */
+    public LiveData<Resource<PageResponse<ProductDTO>>> getAllProducts(String query, int page, int size) {
+        return productRepository.getAllProducts(query, page, size);
+    }
+
+    /**
+     * Retrieves a single product by its ID.
+     */
+    public LiveData<Resource<ProductDTO>> getProductById(Long id) {
+        return productRepository.getProductById(id);
+    }
+
+    /**
+     * Creates a new product.
+     */
+    public LiveData<Resource<ProductDTO>> createProduct(ProductDTO product) {
+        return productRepository.createProduct(product);
+    }
+
+    /**
+     * Updates an existing product by ID.
+     */
+    public LiveData<Resource<ProductDTO>> updateProduct(Long id, ProductDTO product) {
+        return productRepository.updateProduct(id, product);
+    }
+
+    /**
+     * Deletes a product by its ID.
+     */
+    public LiveData<Resource<Void>> deleteProduct(Long id) {
+        return productRepository.deleteProduct(id);
+    }
+
+    /**
+     * Uploads an image for a specific product.
+     */
+    public LiveData<Resource<Void>> uploadProductImage(Long id, MultipartBody.Part image) {
+        return productRepository.uploadProductImage(id, image);
+    }
+
+    /**
+     * Deletes the image associated with a specific product.
+     */
+    public LiveData<Resource<Void>> deleteProductImage(Long id) {
+        return productRepository.deleteProductImage(id);
+    }
+
+    /**
+     * Retrieves a paginated list of all product categories.
+     */
+    public LiveData<Resource<PageResponse<CategoryDTO>>> getAllCategories(int page, int size) {
+        return categoryRepository.getAllCategories(page, size);
+    }
+}

android/app/src/main/java/com/example/petstoremobile/viewmodels/PurchaseOrderViewModel.java

@@ -0,0 +1,37 @@
+package com.example.petstoremobile.viewmodels;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.ViewModel;
+
+import com.example.petstoremobile.dtos.PageResponse;
+import com.example.petstoremobile.dtos.PurchaseOrderDTO;
+import com.example.petstoremobile.repositories.PurchaseOrderRepository;
+import com.example.petstoremobile.utils.Resource;
+
+import javax.inject.Inject;
+
+import dagger.hilt.android.lifecycle.HiltViewModel;
+
+@HiltViewModel
+public class PurchaseOrderViewModel extends ViewModel {
+    private final PurchaseOrderRepository repository;
+
+    @Inject
+    public PurchaseOrderViewModel(PurchaseOrderRepository repository) {
+        this.repository = repository;
+    }
+
+    /**
+     * Fetches a paginated list of all purchase orders.
+     */
+    public LiveData<Resource<PageResponse<PurchaseOrderDTO>>> getAllPurchaseOrders(int page, int size) {
+        return repository.getAllPurchaseOrders(page, size);
+    }
+
+    /**
+     * Retrieves a single purchase order by its ID.
+     */
+    public LiveData<Resource<PurchaseOrderDTO>> getPurchaseOrderById(Long id) {
+        return repository.getPurchaseOrderById(id);
+    }
+}

android/app/src/main/java/com/example/petstoremobile/viewmodels/ServiceViewModel.java

@@ -0,0 +1,58 @@
+package com.example.petstoremobile.viewmodels;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.ViewModel;
+
+import com.example.petstoremobile.dtos.PageResponse;
+import com.example.petstoremobile.dtos.ServiceDTO;
+import com.example.petstoremobile.repositories.ServiceRepository;
+import com.example.petstoremobile.utils.Resource;
+
+import javax.inject.Inject;
+
+import dagger.hilt.android.lifecycle.HiltViewModel;
+
+@HiltViewModel
+public class ServiceViewModel extends ViewModel {
+    private final ServiceRepository repository;
+
+    @Inject
+    public ServiceViewModel(ServiceRepository repository) {
+        this.repository = repository;
+    }
+
+    /**
+     * Fetches a paginated list of all services.
+     */
+    public LiveData<Resource<PageResponse<ServiceDTO>>> getAllServices(int page, int size) {
+        return repository.getAllServices(page, size);
+    }
+
+    /**
+     * Retrieves a single service by its ID.
+     */
+    public LiveData<Resource<ServiceDTO>> getServiceById(Long id) {
+        return repository.getServiceById(id);
+    }
+
+    /**
+     * Creates a new service.
+     */
+    public LiveData<Resource<ServiceDTO>> createService(ServiceDTO service) {
+        return repository.createService(service);
+    }
+
+    /**
+     * Updates an existing service by ID.
+     */
+    public LiveData<Resource<ServiceDTO>> updateService(Long id, ServiceDTO service) {
+        return repository.updateService(id, service);
+    }
+
+    /**
+     * Deletes a service by ID.
+     */
+    public LiveData<Resource<Void>> deleteService(Long id) {
+        return repository.deleteService(id);
+    }
+}

android/app/src/main/java/com/example/petstoremobile/viewmodels/SupplierViewModel.java

@@ -0,0 +1,58 @@
+package com.example.petstoremobile.viewmodels;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.ViewModel;
+
+import com.example.petstoremobile.dtos.PageResponse;
+import com.example.petstoremobile.dtos.SupplierDTO;
+import com.example.petstoremobile.repositories.SupplierRepository;
+import com.example.petstoremobile.utils.Resource;
+
+import javax.inject.Inject;
+
+import dagger.hilt.android.lifecycle.HiltViewModel;
+
+@HiltViewModel
+public class SupplierViewModel extends ViewModel {
+    private final SupplierRepository repository;
+
+    @Inject
+    public SupplierViewModel(SupplierRepository repository) {
+        this.repository = repository;
+    }
+
+    /**
+     * Fetches a paginated list of all suppliers.
+     */
+    public LiveData<Resource<PageResponse<SupplierDTO>>> getAllSuppliers(int page, int size) {
+        return repository.getAllSuppliers(page, size);
+    }
+
+    /**
+     * Retrieves a single supplier by its ID.
+     */
+    public LiveData<Resource<SupplierDTO>> getSupplierById(Long id) {
+        return repository.getSupplierById(id);
+    }
+
+    /**
+     * Creates a new supplier record.
+     */
+    public LiveData<Resource<SupplierDTO>> createSupplier(SupplierDTO supplier) {
+        return repository.createSupplier(supplier);
+    }
+
+    /**
+     * Updates an existing supplier record by ID.
+     */
+    public LiveData<Resource<SupplierDTO>> updateSupplier(Long id, SupplierDTO supplier) {
+        return repository.updateSupplier(id, supplier);
+    }
+
+    /**
+     * Deletes a supplier record by ID.
+     */
+    public LiveData<Resource<Void>> deleteSupplier(Long id) {
+        return repository.deleteSupplier(id);
+    }
+}