created viewmodels for detailFragments

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

@@ -16,11 +16,7 @@ import com.example.petstoremobile.utils.DialogUtils;
 import com.example.petstoremobile.utils.Resource;
 import com.example.petstoremobile.utils.SpinnerUtils;
 import com.example.petstoremobile.utils.UIUtils;
-import com.example.petstoremobile.viewmodels.AdoptionViewModel;
+import com.example.petstoremobile.viewmodels.AdoptionDetailViewModel;
-import com.example.petstoremobile.viewmodels.CustomerViewModel;
-import com.example.petstoremobile.viewmodels.PetViewModel;
-import com.example.petstoremobile.viewmodels.StoreViewModel;
-import com.example.petstoremobile.viewmodels.UserViewModel;
 
 import java.math.BigDecimal;
 import java.util.*;
@@ -34,35 +30,19 @@ import dagger.hilt.android.AndroidEntryPoint;
 public class AdoptionDetailFragment extends Fragment {
 
     private FragmentAdoptionDetailBinding binding;
+    private AdoptionDetailViewModel viewModel;
 
-    private long adoptionId = -1;
-    private boolean isEditing = false;
     private long preselectedPetId = -1;
     private long preselectedCustomerId = -1;
     private long preselectedStoreId = -1;
     private long preselectedEmployeeId = -1;
 
-    private List<DropdownDTO> petList = new ArrayList<>();
-    private List<DropdownDTO> customerList = new ArrayList<>();
-    private List<DropdownDTO> storeList = new ArrayList<>();
-    private List<DropdownDTO> employeeList = new ArrayList<>();
-
     private final String[] STATUSES = {"Pending", "Completed", "Cancelled"};
 
-    private AdoptionViewModel adoptionViewModel;
-    private PetViewModel petViewModel;
-    private CustomerViewModel customerViewModel;
-    private StoreViewModel storeViewModel;
-    private UserViewModel userViewModel;
-
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
-        adoptionViewModel = new ViewModelProvider(this).get(AdoptionViewModel.class);
+        viewModel = new ViewModelProvider(this).get(AdoptionDetailViewModel.class);
-        petViewModel = new ViewModelProvider(this).get(PetViewModel.class);
-        customerViewModel = new ViewModelProvider(this).get(CustomerViewModel.class);
-        storeViewModel = new ViewModelProvider(this).get(StoreViewModel.class);
-        userViewModel = new ViewModelProvider(this).get(UserViewModel.class);
     }
 
     @Override
@@ -77,6 +57,7 @@ public class AdoptionDetailFragment extends Fragment {
         super.onViewCreated(view, savedInstanceState);
         setupSpinners();
         setupDatePicker();
+        observeViewModel();
         loadSpinnersData();
         handleArguments();
 
@@ -85,29 +66,31 @@ public class AdoptionDetailFragment extends Fragment {
         binding.btnDeleteAdoption.setOnClickListener(v -> confirmDelete());
     }
 
+    private void observeViewModel() {
+        viewModel.getPetList().observe(getViewLifecycleOwner(), list -> refreshPetSpinner());
+        viewModel.getCustomerList().observe(getViewLifecycleOwner(), list -> refreshCustomerSpinner());
+        viewModel.getStoreList().observe(getViewLifecycleOwner(), list -> refreshStoreSpinner());
+        viewModel.getEmployeeList().observe(getViewLifecycleOwner(), list -> refreshEmployeeSpinner());
+    }
+
     @Override
     public void onDestroyView() {
         super.onDestroyView();
         binding = null;
     }
 
-    /**
-     * Configures the spinner for adoption status.
-     */
     private void setupSpinners() {
         SpinnerUtils.setupStringSpinner(requireContext(), binding.spinnerAdoptionStatus, STATUSES);
 
-        // Pet spinner disabled by default until customer is selected
         UIUtils.setViewsEnabled(false, binding.spinnerAdoptionPet);
 
-        // Listener to enable pet spinner based on customer selection
         binding.spinnerAdoptionCustomer.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
             @Override
             public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
                 if (position > 0) {
                     UIUtils.setViewsEnabled(true, binding.spinnerAdoptionPet);
                 } else {
-                    if (!isEditing) {
+                    if (!viewModel.isEditing()) {
                         binding.spinnerAdoptionPet.setSelection(0);
                         UIUtils.setViewsEnabled(false, binding.spinnerAdoptionPet);
                     }
@@ -117,27 +100,21 @@ public class AdoptionDetailFragment extends Fragment {
             public void onNothingSelected(AdapterView<?> parent) {}
         });
 
-        // Listener to load employees based on selected store
         binding.spinnerAdoptionStore.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
             @Override
             public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
-                if (position > 0 && position <= storeList.size()) {
+                if (position > 0 && viewModel.getStoreList().getValue() != null && position <= viewModel.getStoreList().getValue().size()) {
-                    DropdownDTO selectedStore = storeList.get(position - 1);
+                    DropdownDTO selectedStore = viewModel.getStoreList().getValue().get(position - 1);
                     loadEmployees(selectedStore.getId());
                 } else {
-                    employeeList.clear();
+                    viewModel.setEmployeeList(new ArrayList<>());
-                    refreshEmployeeSpinner();
                 }
             }
-
             @Override
             public void onNothingSelected(AdapterView<?> parent) {}
         });
     }
 
-    /**
-     * Configures the date picker dialog for the adoption date field.
-     */
     private void setupDatePicker() {
         binding.etAdoptionDate.setOnClickListener(v -> {
             Calendar c = Calendar.getInstance();
@@ -150,129 +127,77 @@ public class AdoptionDetailFragment extends Fragment {
         });
     }
 
-    /**
-     * Fetches required data for spinners from the backend.
-     */
     private void loadSpinnersData() {
-        loadPets();
+        viewModel.loadPets().observe(getViewLifecycleOwner(), resource -> {
-        loadCustomers();
-        loadStores();
-    }
-
-    /**
-     * Loads the list of pets from the API.
-     */
-    private void loadPets() {
-        petViewModel.getAdoptionPets().observe(getViewLifecycleOwner(), resource -> {
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
-                petList = resource.data;
+                viewModel.setPetList(resource.data);
-                refreshPetSpinner();
+            }
+        });
+        viewModel.loadCustomers().observe(getViewLifecycleOwner(), resource -> {
+            if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
+                viewModel.setCustomerList(resource.data);
+            }
+        });
+        viewModel.loadStores().observe(getViewLifecycleOwner(), resource -> {
+            if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
+                viewModel.setStoreList(resource.data);
             }
         });
     }
 
-    /**
-     * Populates the pet selection spinner with data.
-     */
     private void refreshPetSpinner() {
-        SpinnerUtils.populateSpinner(requireContext(), binding.spinnerAdoptionPet, petList,
+        SpinnerUtils.populateSpinner(requireContext(), binding.spinnerAdoptionPet, viewModel.getPetList().getValue(),
                 DropdownDTO::getLabel, "-- Select Pet --",
                 preselectedPetId, DropdownDTO::getId);
     }
 
-    /**
-     * Loads the list of customers from the API.
-     */
-    private void loadCustomers() {
-        customerViewModel.getCustomerDropdowns().observe(getViewLifecycleOwner(), resource -> {
-            if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
-                customerList = resource.data;
-                refreshCustomerSpinner();
-            }
-        });
-    }
-
-    /**
-     * Populates the customer selection spinner with data.
-     */
     private void refreshCustomerSpinner() {
-        SpinnerUtils.populateSpinner(requireContext(), binding.spinnerAdoptionCustomer, customerList,
+        SpinnerUtils.populateSpinner(requireContext(), binding.spinnerAdoptionCustomer, viewModel.getCustomerList().getValue(),
-                DropdownDTO::getLabel,
+                DropdownDTO::getLabel, "-- Select Customer --",
-                "-- Select Customer --",
                 preselectedCustomerId, DropdownDTO::getId);
     }
 
-    /**
-     * Loads the list of stores from the API.
-     */
-    private void loadStores() {
-        storeViewModel.getStoreDropdowns().observe(getViewLifecycleOwner(), resource -> {
-            if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
-                storeList = resource.data;
-                refreshStoreSpinner();
-            }
-        });
-    }
-
-    /**
-     * Populates the store selection spinner with data.
-     */
     private void refreshStoreSpinner() {
-        SpinnerUtils.populateSpinner(requireContext(), binding.spinnerAdoptionStore, storeList,
+        SpinnerUtils.populateSpinner(requireContext(), binding.spinnerAdoptionStore, viewModel.getStoreList().getValue(),
                 DropdownDTO::getLabel, "-- Select Store --",
                 preselectedStoreId, DropdownDTO::getId);
     }
 
-    /**
-     * Loads the list of employees for a specific store.
-     */
     private void loadEmployees(Long storeId) {
-        storeViewModel.getStoreEmployees(storeId).observe(getViewLifecycleOwner(), resource -> {
+        viewModel.loadEmployees(storeId).observe(getViewLifecycleOwner(), resource -> {
             if (resource != null && resource.status == Resource.Status.SUCCESS && resource.data != null) {
-                employeeList = resource.data;
+                viewModel.setEmployeeList(resource.data);
-                refreshEmployeeSpinner();
             }
         });
     }
 
-    /**
-     * Populates the employee selection spinner with data.
-     */
     private void refreshEmployeeSpinner() {
-        SpinnerUtils.populateSpinner(requireContext(), binding.spinnerAdoptionEmployee, employeeList,
+        SpinnerUtils.populateSpinner(requireContext(), binding.spinnerAdoptionEmployee, viewModel.getEmployeeList().getValue(),
                 DropdownDTO::getLabel, "-- Select Staff --",
                 preselectedEmployeeId, DropdownDTO::getId);
     }
 
-    /**
-     * Handles arguments to determine if the fragment is in edit or add mode.
-     */
     private void handleArguments() {
         Bundle a = getArguments();
         if (a != null && a.containsKey("adoptionId")) {
-            isEditing = true;
+            long adoptionId = a.getLong("adoptionId");
-            adoptionId = a.getLong("adoptionId");
+            viewModel.setAdoptionId(adoptionId);
             binding.tvAdoptionMode.setText("Edit Adoption");
             binding.tvAdoptionId.setText("ID: " + adoptionId);
             binding.tvAdoptionId.setVisibility(View.VISIBLE);
             binding.btnDeleteAdoption.setVisibility(View.VISIBLE);
             loadAdoptionData();
         } else {
-            isEditing = false;
+            viewModel.setAdoptionId(-1);
             binding.tvAdoptionMode.setText("Add Adoption");
             binding.btnDeleteAdoption.setVisibility(View.GONE);
             binding.tvAdoptionId.setVisibility(View.GONE);
-            
-            // Explicitly disable in add mode
             UIUtils.setViewsEnabled(false, binding.spinnerAdoptionPet);
         }
     }
 
-    /**
-     * Fetches specific adoption details from the backend using the ID.
-     */
     private void loadAdoptionData() {
-        adoptionViewModel.getAdoptionById(adoptionId).observe(getViewLifecycleOwner(), resource -> {
+        viewModel.loadAdoption().observe(getViewLifecycleOwner(), resource -> {
             if (resource == null) return;
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 AdoptionDTO a = resource.data;
@@ -289,7 +214,6 @@ public class AdoptionDetailFragment extends Fragment {
                 refreshCustomerSpinner();
                 refreshStoreSpinner();
                 
-                // In edit mode, if a customer is already set, ensure pet spinner is enabled
                 if (preselectedCustomerId != -1) {
                     UIUtils.setViewsEnabled(true, binding.spinnerAdoptionPet);
                 }
@@ -299,9 +223,6 @@ public class AdoptionDetailFragment extends Fragment {
         });
     }
 
-    /**
-     * Validates input and saves the adoption request to the backend.
-     */
     private void saveAdoption() {
         if (binding.spinnerAdoptionCustomer.getSelectedItemPosition() == 0) {
             Toast.makeText(getContext(), "Select a customer", Toast.LENGTH_SHORT).show(); return;
@@ -328,13 +249,13 @@ public class AdoptionDetailFragment extends Fragment {
             }
         }
 
-        DropdownDTO customer = customerList.get(binding.spinnerAdoptionCustomer.getSelectedItemPosition() - 1);
+        DropdownDTO customer = viewModel.getCustomerList().getValue().get(binding.spinnerAdoptionCustomer.getSelectedItemPosition() - 1);
-        DropdownDTO pet      = petList.get(binding.spinnerAdoptionPet.getSelectedItemPosition() - 1);
+        DropdownDTO pet      = viewModel.getPetList().getValue().get(binding.spinnerAdoptionPet.getSelectedItemPosition() - 1);
-        DropdownDTO store    = storeList.get(binding.spinnerAdoptionStore.getSelectedItemPosition() - 1);
+        DropdownDTO store    = viewModel.getStoreList().getValue().get(binding.spinnerAdoptionStore.getSelectedItemPosition() - 1);
         
         Long employeeId = null;
         if (binding.spinnerAdoptionEmployee.getSelectedItemPosition() > 0) {
-            employeeId = employeeList.get(binding.spinnerAdoptionEmployee.getSelectedItemPosition() - 1).getId();
+            employeeId = viewModel.getEmployeeList().getValue().get(binding.spinnerAdoptionEmployee.getSelectedItemPosition() - 1).getId();
         }
         
         String status        = STATUSES[binding.spinnerAdoptionStatus.getSelectedItemPosition()];
@@ -349,33 +270,19 @@ public class AdoptionDetailFragment extends Fragment {
                 fee
         );
 
-        if (isEditing) {
+        viewModel.saveAdoption(dto).observe(getViewLifecycleOwner(), resource -> {
-            adoptionViewModel.updateAdoption(adoptionId, dto).observe(getViewLifecycleOwner(), resource -> {
             if (resource.status == Resource.Status.SUCCESS) {
-                    Toast.makeText(getContext(), "Updated", Toast.LENGTH_SHORT).show();
+                Toast.makeText(getContext(), viewModel.isEditing() ? "Updated" : "Saved", Toast.LENGTH_SHORT).show();
                 navigateBack();
             } else if (resource.status == Resource.Status.ERROR) {
                 Toast.makeText(getContext(), "Error: " + resource.message, Toast.LENGTH_SHORT).show();
             }
         });
-        } else {
-            adoptionViewModel.createAdoption(dto).observe(getViewLifecycleOwner(), resource -> {
-                if (resource.status == Resource.Status.SUCCESS) {
-                    Toast.makeText(getContext(), "Saved", Toast.LENGTH_SHORT).show();
-                    navigateBack();
-                } else if (resource.status == Resource.Status.ERROR) {
-                    Toast.makeText(getContext(), "Error: " + resource.message, Toast.LENGTH_SHORT).show();
-                }
-            });
-        }
     }
 
-    /**
-     * Shows a confirmation dialog before deleting an adoption request.
-     */
     private void confirmDelete() {
         DialogUtils.showDeleteConfirmDialog(requireContext(), "Adoption", () ->
-                adoptionViewModel.deleteAdoption(adoptionId).observe(getViewLifecycleOwner(), resource -> {
+                viewModel.deleteAdoption().observe(getViewLifecycleOwner(), resource -> {
                     if (resource.status == Resource.Status.SUCCESS) {
                         Toast.makeText(getContext(), "Deleted", Toast.LENGTH_SHORT).show();
                         navigateBack();
@@ -385,9 +292,6 @@ public class AdoptionDetailFragment extends Fragment {
                 }));
     }
 
-    /**
-     * Navigates back to the previous fragment.
-     */
     private void navigateBack() {
         NavHostFragment.findNavController(this).popBackStack();
     }

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

@@ -43,37 +43,28 @@ public class AppointmentDetailFragment extends Fragment {
     private final Integer[] HOURS = {9, 10, 11, 12, 13, 14, 15, 16, 17};
     private final Integer[] MINUTES = {0, 15, 30, 45};
 
-    private AppointmentDetailViewModel appointmentViewModel;
+    private AppointmentDetailViewModel viewModel;
     private boolean isUpdatingUI = false;
 
-    /**
-     * Called when the fragment is first created.
-     */
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
-        appointmentViewModel = new ViewModelProvider(this).get(AppointmentDetailViewModel.class);
+        viewModel = new ViewModelProvider(this).get(AppointmentDetailViewModel.class);
     }
 
-    /**
-     * Creates and returns the view hierarchy with the fragment.
-     */
     @Override
     public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
         binding = FragmentAppointmentDetailBinding.inflate(inflater, container, false);
         return binding.getRoot();
     }
 
-    /**
-     * Called immediately after onCreateView has returned.
-     */
     @Override
     public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
         super.onViewCreated(view, savedInstanceState);
         setupSpinners();
         setupDatePicker();
         observeViewModel();
-        appointmentViewModel.loadInitialFormData();
+        viewModel.loadInitialFormData();
         handleArguments();
 
         binding.btnApptBack.setOnClickListener(v -> navigateBack());
@@ -81,110 +72,83 @@ public class AppointmentDetailFragment extends Fragment {
         binding.btnDeleteAppointment.setOnClickListener(v -> confirmDelete());
     }
 
-    /**
-     * Called when the view previously created by onCreateView has been detached.
-     */
     @Override
     public void onDestroyView() {
         super.onDestroyView();
         binding = null;
     }
 
-    /**
-     * Configures the adapters and listeners for all spinners.
-     */
     private void setupSpinners() {
-        //Status Spinner is empty by default the date determines whats in here
         SpinnerUtils.setupStringSpinner(requireContext(), binding.spinnerAppointmentStatus, new String[]{});
 
-        // Set up hour and minute spinners
         String[] hours = new String[HOURS.length];
         for (int i = 0; i < HOURS.length; i++)
             hours[i] = DateTimeUtils.formatTime(HOURS[i], 0);
         SpinnerUtils.setupStringSpinner(requireContext(), binding.spinnerHour, hours);
         SpinnerUtils.setupStringSpinner(requireContext(), binding.spinnerMinute, new String[]{"00", "15", "30", "45"});
 
-        // Pet and Staff spinners disabled by until parent selection
         UIUtils.setViewsEnabled(false, binding.spinnerPet, binding.spinnerStaff);
 
-        // Listener to notify ViewModel of customer selection
         binding.spinnerCustomer.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
             @Override
             public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
-                appointmentViewModel.onCustomerSelected(position);
+                viewModel.onCustomerSelected(position);
             }
             @Override
             public void onNothingSelected(AdapterView<?> parent) {}
         });
 
-        // Listener to notify ViewModel of store selection
         binding.spinnerStore.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
             @Override
             public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
-                appointmentViewModel.onStoreSelected(position);
+                viewModel.onStoreSelected(position);
             }
             @Override
             public void onNothingSelected(AdapterView<?> parent) {}
         });
 
-        // Listeners for other selections
+        SpinnerUtils.setOnIndexSelectedListener(binding.spinnerService, p -> viewModel.onServiceSelected(p));
-        SpinnerUtils.setOnIndexSelectedListener(binding.spinnerService, p -> appointmentViewModel.onServiceSelected(p));
+        SpinnerUtils.setOnIndexSelectedListener(binding.spinnerPet, p -> viewModel.onPetSelected(p));
-        SpinnerUtils.setOnIndexSelectedListener(binding.spinnerPet, p -> appointmentViewModel.onPetSelected(p));
+        SpinnerUtils.setOnIndexSelectedListener(binding.spinnerStaff, p -> viewModel.onStaffSelected(p));
-        SpinnerUtils.setOnIndexSelectedListener(binding.spinnerStaff, p -> appointmentViewModel.onStaffSelected(p));
 
-        // Listeners for time changes
         SpinnerUtils.setOnIndexSelectedListener(binding.spinnerHour, p -> notifyDateTimeStatusChange());
         SpinnerUtils.setOnIndexSelectedListener(binding.spinnerMinute, p -> notifyDateTimeStatusChange());
-
-        // Listener to notify ViewModel of status selection
         SpinnerUtils.setOnIndexSelectedListener(binding.spinnerAppointmentStatus, p -> notifyDateTimeStatusChange());
     }
 
-    /**
-     * Configures the date picker dialog for the appointment date field.
-     */
     private void setupDatePicker() {
         binding.etAppointmentDate.setOnClickListener(v -> 
                 UIUtils.showDatePicker(requireContext(), binding.etAppointmentDate, this::notifyDateTimeStatusChange));
     }
 
-    /**
-     * Observes the ViewModel for UI state and list updates.
-     */
     private void observeViewModel() {
-        appointmentViewModel.getViewState().observe(getViewLifecycleOwner(), this::applyViewState);
+        viewModel.getViewState().observe(getViewLifecycleOwner(), this::applyViewState);
         
-        // Populate spinners when data arrives
+        viewModel.getCustomers().observe(getViewLifecycleOwner(), list ->
-        appointmentViewModel.getCustomers().observe(getViewLifecycleOwner(), list ->
             SpinnerUtils.populateSpinner(requireContext(), binding.spinnerCustomer, list, DropdownDTO::getLabel, "-- Select Customer --", preselectedCustomerId, DropdownDTO::getId));
         
-        appointmentViewModel.getStores().observe(getViewLifecycleOwner(), list ->
+        viewModel.getStores().observe(getViewLifecycleOwner(), list ->
             SpinnerUtils.populateSpinner(requireContext(), binding.spinnerStore, list, DropdownDTO::getLabel, "-- Select Store --", preselectedStoreId, DropdownDTO::getId));
         
-        appointmentViewModel.getServices().observe(getViewLifecycleOwner(), list ->
+        viewModel.getServices().observe(getViewLifecycleOwner(), list ->
             SpinnerUtils.populateSpinner(requireContext(), binding.spinnerService, list, ServiceDTO::getServiceName, "-- Select Service --", preselectedServiceId, ServiceDTO::getServiceId));
 
-        appointmentViewModel.getCustomerPets().observe(getViewLifecycleOwner(), list ->
+        viewModel.getCustomerPets().observe(getViewLifecycleOwner(), list ->
             SpinnerUtils.populateSpinner(requireContext(), binding.spinnerPet, list, DropdownDTO::getLabel, "-- Select Pet --", preselectedPetId, DropdownDTO::getId));
 
-        appointmentViewModel.getStoreEmployees().observe(getViewLifecycleOwner(), list ->
+        viewModel.getStoreEmployees().observe(getViewLifecycleOwner(), list ->
             SpinnerUtils.populateSpinner(requireContext(), binding.spinnerStaff, list, DropdownDTO::getLabel, "-- Select Staff --", preselectedStaffId, DropdownDTO::getId));
     }
 
-    /**
-     * Applies the ViewState provided by the ViewModel to the UI components.
-     */
     private void applyViewState(AppointmentDetailViewModel.ViewState state) {
         isUpdatingUI = true;
 
-        // Mode specific UI
         binding.tvApptMode.setText(state.isEditing ? "Edit Appointment" : "Add Appointment");
-        binding.tvAppointmentId.setText(DateTimeUtils.formatId(appointmentViewModel.getAppointmentId()));
+        binding.tvAppointmentId.setText(DateTimeUtils.formatId(viewModel.getAppointmentId()));
         binding.tvAppointmentId.setVisibility(state.isEditing ? View.VISIBLE : View.GONE);
         binding.btnDeleteAppointment.setVisibility(state.isDeleteVisible ? View.VISIBLE : View.GONE);
         binding.btnSaveAppointment.setVisibility(state.isSaveVisible ? View.VISIBLE : View.GONE);
         
-        // Enabling/Disabling Views and Labels
         UIUtils.setFieldEnabled(state.isCustomerEnabled, binding.spinnerCustomer, binding.tvLabelCustomer);
         UIUtils.setFieldEnabled(state.isStoreEnabled, binding.spinnerStore, binding.tvLabelStore);
         UIUtils.setFieldEnabled(state.isPetEnabled, binding.spinnerPet, binding.tvLabelPet);
@@ -195,7 +159,6 @@ public class AppointmentDetailFragment extends Fragment {
         UIUtils.setViewsEnabled(state.isTimeEnabled, binding.spinnerMinute);
         UIUtils.setViewsEnabled(state.isStatusEnabled, binding.spinnerAppointmentStatus);
 
-        // Update status options
         Object selected = binding.spinnerAppointmentStatus.getSelectedItem();
         String current = selected != null ? selected.toString() : "";
         SpinnerUtils.setupStringSpinner(requireContext(), binding.spinnerAppointmentStatus, state.availableStatuses);
@@ -204,9 +167,6 @@ public class AppointmentDetailFragment extends Fragment {
         isUpdatingUI = false;
     }
 
-    /**
-     * Notifies the ViewModel that the date, time, or status has changed.
-     */
     private void notifyDateTimeStatusChange() {
         if (isUpdatingUI) return;
 
@@ -214,27 +174,21 @@ public class AppointmentDetailFragment extends Fragment {
         String time = buildTimeString();
         Object selected = binding.spinnerAppointmentStatus.getSelectedItem();
         String status = selected != null ? selected.toString() : "";
-        appointmentViewModel.onDateOrTimeChanged(date, time, status);
+        viewModel.onDateOrTimeChanged(date, time, status);
     }
 
-    /**
-     * Handles arguments to determine if the fragment is in edit or add mode.
-     */
     private void handleArguments() {
         Bundle a = getArguments();
         if (a != null && a.containsKey("appointmentId")) {
-            appointmentViewModel.setAppointmentId(a.getLong("appointmentId"));
+            viewModel.setAppointmentId(a.getLong("appointmentId"));
             loadAppointmentData();
         } else {
-            appointmentViewModel.setAppointmentId(-1);
+            viewModel.setAppointmentId(-1);
         }
     }
 
-    /**
-     * Fetches specific appointment details from the backend using the ID.
-     */
     private void loadAppointmentData() {
-        appointmentViewModel.loadAppointment().observe(getViewLifecycleOwner(), resource -> {
+        viewModel.loadAppointment().observe(getViewLifecycleOwner(), resource -> {
             if (resource == null || resource.status != Resource.Status.SUCCESS || resource.data == null) return;
             AppointmentDTO a = resource.data;
             preselectedPetId = a.getPetId() != null ? a.getPetId() : -1;
@@ -254,9 +208,6 @@ public class AppointmentDetailFragment extends Fragment {
         });
     }
 
-    /**
-     * Validates input and saves the appointment to the backend.
-     */
     private void saveAppointment() {
         if (!validateRequiredFields()) return;
 
@@ -264,14 +215,14 @@ public class AppointmentDetailFragment extends Fragment {
         String time = buildTimeString();
         String status = binding.spinnerAppointmentStatus.getSelectedItem().toString().toUpperCase();
 
-        if (!appointmentViewModel.isValidFutureBooking(status, date, time)) {
+        if (!viewModel.isValidFutureBooking(status, date, time)) {
             DialogUtils.showInfoDialog(requireContext(), "Invalid Time", "Booked appointments must be in the future.");
             return;
         }
 
-        appointmentViewModel.saveAppointment(date, time, status).observe(getViewLifecycleOwner(), resource -> {
+        viewModel.saveAppointment(date, time, status).observe(getViewLifecycleOwner(), resource -> {
             if (resource.status == Resource.Status.SUCCESS) {
-                AppointmentDetailViewModel.ViewState state = appointmentViewModel.getViewState().getValue();
+                AppointmentDetailViewModel.ViewState state = viewModel.getViewState().getValue();
                 String message = (state != null && state.isEditing) ? "Updated" : "Saved";
                 Toast.makeText(getContext(), message, Toast.LENGTH_SHORT).show();
                 navigateBack();
@@ -281,9 +232,6 @@ public class AppointmentDetailFragment extends Fragment {
         });
     }
 
-    /**
-     * Validates that all required fields are selected.
-     */
     private boolean validateRequiredFields() {
         if (binding.spinnerCustomer.getSelectedItemPosition() == 0) return UIUtils.showToast(getContext(), "Select a customer");
         if (binding.spinnerStore.getSelectedItemPosition() == 0) return UIUtils.showToast(getContext(), "Select a store");
@@ -293,24 +241,15 @@ public class AppointmentDetailFragment extends Fragment {
         return true;
     }
 
-    /**
-     * Builds a time string from the hour and minute spinners.
-     */
     private String buildTimeString() {
         return DateTimeUtils.formatTime(HOURS[binding.spinnerHour.getSelectedItemPosition()], MINUTES[binding.spinnerMinute.getSelectedItemPosition()]);
     }
 
-    /**
-     * Handles errors that occur during the saving process.
-     */
     private void handleSaveError(String errorMessage) {
         if (errorMessage != null && errorMessage.toLowerCase().contains("not available")) showNoAvailabilityDialog();
         else Toast.makeText(getContext(), errorMessage != null ? errorMessage : "Error saving", Toast.LENGTH_SHORT).show();
     }
 
-    /**
-     * Shows a specialized dialog when a time slot is not available.
-     */
     private void showNoAvailabilityDialog() {
         new androidx.appcompat.app.AlertDialog.Builder(requireContext())
                 .setTitle("No Availability")
@@ -319,26 +258,17 @@ public class AppointmentDetailFragment extends Fragment {
                 .setNegativeButton("Cancel Booking", (d, w) -> navigateBack()).show();
     }
 
-    /**
-     * Shows a confirmation dialog and handles the deletion of an appointment.
-     */
     private void confirmDelete() {
         DialogUtils.showDeleteConfirmDialog(requireContext(), "Appointment", () ->
-                appointmentViewModel.deleteAppointment().observe(getViewLifecycleOwner(), resource -> {
+                viewModel.deleteAppointment().observe(getViewLifecycleOwner(), resource -> {
                     if (resource.status == Resource.Status.SUCCESS) navigateBack();
                 }));
     }
 
-    /**
-     * Navigates back to the previous screen.
-     */
     private void navigateBack() {
         NavHostFragment.findNavController(this).popBackStack();
     }
 
-    /**
-     * Parses a time string and sets the hour and minute spinners.
-     */
     private void parseAndSetTimeSpinners(String time) {
         int[] parsedTime = DateTimeUtils.parseTimeString(time);
         if (parsedTime == null) return;

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

@@ -17,16 +17,10 @@ import com.example.petstoremobile.databinding.FragmentInventoryDetailBinding;
 import com.example.petstoremobile.dtos.DropdownDTO;
 import com.example.petstoremobile.dtos.InventoryDTO;
 import com.example.petstoremobile.dtos.ProductDTO;
-import com.example.petstoremobile.dtos.StoreDTO;
 import com.example.petstoremobile.utils.InputValidator;
 import com.example.petstoremobile.utils.Resource;
 import com.example.petstoremobile.utils.SpinnerUtils;
-import com.example.petstoremobile.viewmodels.InventoryViewModel;
+import com.example.petstoremobile.viewmodels.InventoryDetailViewModel;
-import com.example.petstoremobile.viewmodels.ProductViewModel;
-import com.example.petstoremobile.viewmodels.StoreViewModel;
-
-import java.util.ArrayList;
-import java.util.List;
 
 import dagger.hilt.android.AndroidEntryPoint;
 
@@ -37,33 +31,17 @@ import dagger.hilt.android.AndroidEntryPoint;
 public class InventoryDetailFragment extends Fragment {
 
     private FragmentInventoryDetailBinding binding;
+    private InventoryDetailViewModel viewModel;
 
-    private InventoryViewModel inventoryViewModel;
-    private ProductViewModel productViewModel;
-    private StoreViewModel storeViewModel;
-
-    private boolean isEditing = false;
-    private long inventoryId = -1;
     private long preselectedStoreId = -1;
     private long preselectedProductId = -1;
 
-    private List<DropdownDTO> storeList = new ArrayList<>();
-    private List<ProductDTO> productList = new ArrayList<>();
-
-    /**
-     * Initializes the view models.
-     */
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
-        inventoryViewModel = new ViewModelProvider(this).get(InventoryViewModel.class);
+        viewModel = new ViewModelProvider(this).get(InventoryDetailViewModel.class);
-        productViewModel = new ViewModelProvider(this).get(ProductViewModel.class);
-        storeViewModel = new ViewModelProvider(this).get(StoreViewModel.class);
     }
 
-    /**
-     * Inflates the layout.
-     */
     @Override
     public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container,
                              Bundle savedInstanceState) {
@@ -71,13 +49,11 @@ public class InventoryDetailFragment extends Fragment {
         return binding.getRoot();
     }
 
-    /**
-     * Sets up UI components after the view is created.
-     */
     @Override
     public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
         super.onViewCreated(view, savedInstanceState);
 
+        observeViewModel();
         loadSpinnersData();
         handleArguments();
 
@@ -86,64 +62,47 @@ public class InventoryDetailFragment extends Fragment {
         binding.btnDeleteInventory.setOnClickListener(v -> confirmDelete());
     }
 
+    private void observeViewModel() {
+        viewModel.getStoreList().observe(getViewLifecycleOwner(), list -> refreshStoreSpinner());
+        viewModel.getProductList().observe(getViewLifecycleOwner(), list -> refreshProductSpinner());
+    }
+
     @Override
     public void onDestroyView() {
         super.onDestroyView();
         binding = null;
     }
 
-    /**
-     * Fetches required data for spinners from the backend.
-     */
     private void loadSpinnersData() {
-        loadStores();
+        viewModel.loadStores().observe(getViewLifecycleOwner(), resource -> {
-        loadProducts();
-    }
-
-    /**
-     * Loads the list of stores for the spinner.
-     */
-    private void loadStores() {
-        storeViewModel.getStoreDropdowns().observe(getViewLifecycleOwner(), resource -> {
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
-                storeList = resource.data;
+                viewModel.setStoreList(resource.data);
-                refreshStoreSpinner();
+            }
+        });
+        viewModel.loadProducts().observe(getViewLifecycleOwner(), resource -> {
+            if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
+                viewModel.setProductList(resource.data.getContent());
             }
         });
     }
 
     private void refreshStoreSpinner() {
-        SpinnerUtils.populateSpinner(requireContext(), binding.spinnerInventoryStore, storeList,
+        SpinnerUtils.populateSpinner(requireContext(), binding.spinnerInventoryStore, viewModel.getStoreList().getValue(),
                 DropdownDTO::getLabel, "-- Select Store --",
                 preselectedStoreId, DropdownDTO::getId);
     }
 
-    /**
-     * Loads the list of products for the spinner.
-     */
-    private void loadProducts() {
-        productViewModel.getAllProducts(null, null, 0, 500, "prodName").observe(getViewLifecycleOwner(), resource -> {
-            if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
-                productList = resource.data.getContent();
-                refreshProductSpinner();
-            }
-        });
-    }
-
     private void refreshProductSpinner() {
-        SpinnerUtils.populateSpinner(requireContext(), binding.spinnerInventoryProduct, productList,
+        SpinnerUtils.populateSpinner(requireContext(), binding.spinnerInventoryProduct, viewModel.getProductList().getValue(),
                 ProductDTO::getProdName, "-- Select Product --",
                 preselectedProductId, ProductDTO::getProdId);
     }
 
-    /**
-     * Handles fragment arguments to determine if we are in edit or add mode.
-     */
     private void handleArguments() {
         Bundle args = getArguments();
         if (args != null && args.containsKey("inventoryId")) {
-            isEditing = true;
+            long inventoryId = args.getLong("inventoryId");
-            inventoryId = args.getLong("inventoryId");
+            viewModel.setInventoryId(inventoryId);
 
             binding.tvInventoryMode.setText("Edit Inventory");
             binding.tvInventoryId.setText("Inventory ID: " + inventoryId);
@@ -153,7 +112,7 @@ public class InventoryDetailFragment extends Fragment {
 
             loadInventoryData();
         } else {
-            isEditing = false;
+            viewModel.setInventoryId(-1);
             binding.tvInventoryMode.setText("Add Inventory");
             binding.tvInventoryId.setVisibility(View.GONE);
             binding.btnDeleteInventory.setVisibility(View.GONE);
@@ -161,11 +120,8 @@ public class InventoryDetailFragment extends Fragment {
         }
     }
 
-    /**
-     * Loads existing inventory data from the backend.
-     */
     private void loadInventoryData() {
-        inventoryViewModel.getInventoryById(inventoryId).observe(getViewLifecycleOwner(), resource -> {
+        viewModel.loadInventory().observe(getViewLifecycleOwner(), resource -> {
             if (resource == null) return;
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 InventoryDTO inv = resource.data;
@@ -181,9 +137,6 @@ public class InventoryDetailFragment extends Fragment {
         });
     }
 
-    /**
-     * Validates input and saves the current inventory item details to the backend.
-     */
     private void saveInventory() {
         if (binding.spinnerInventoryStore.getSelectedItemPosition() == 0) {
             Toast.makeText(getContext(), "Please select a store", Toast.LENGTH_SHORT).show();
@@ -200,38 +153,23 @@ public class InventoryDetailFragment extends Fragment {
         }
 
         int quantity = Integer.parseInt(binding.etQuantity.getText().toString().trim());
-        DropdownDTO store = storeList.get(binding.spinnerInventoryStore.getSelectedItemPosition() - 1);
+        DropdownDTO store = viewModel.getStoreList().getValue().get(binding.spinnerInventoryStore.getSelectedItemPosition() - 1);
-        ProductDTO product = productList.get(binding.spinnerInventoryProduct.getSelectedItemPosition() - 1);
+        ProductDTO product = viewModel.getProductList().getValue().get(binding.spinnerInventoryProduct.getSelectedItemPosition() - 1);
 
         InventoryDTO request = new InventoryDTO(product.getProdId(), store.getId(), quantity);
         setButtonsEnabled(false);
 
-        if (isEditing) {
+        viewModel.saveInventory(request).observe(getViewLifecycleOwner(), resource -> {
-            inventoryViewModel.updateInventory(inventoryId, request).observe(getViewLifecycleOwner(), resource -> {
             setButtonsEnabled(true);
             if (resource.status == Resource.Status.SUCCESS) {
-                    Toast.makeText(getContext(), "Inventory updated", Toast.LENGTH_SHORT).show();
+                Toast.makeText(getContext(), viewModel.isEditing() ? "Inventory updated" : "Inventory created", Toast.LENGTH_SHORT).show();
                 navigateBack();
             } else if (resource.status == Resource.Status.ERROR) {
                 Toast.makeText(getContext(), "Error: " + resource.message, Toast.LENGTH_SHORT).show();
             }
         });
-        } else {
-            inventoryViewModel.createInventory(request).observe(getViewLifecycleOwner(), resource -> {
-                setButtonsEnabled(true);
-                if (resource.status == Resource.Status.SUCCESS) {
-                    Toast.makeText(getContext(), "Inventory created", Toast.LENGTH_SHORT).show();
-                    navigateBack();
-                } else if (resource.status == Resource.Status.ERROR) {
-                    Toast.makeText(getContext(), "Error: " + resource.message, Toast.LENGTH_SHORT).show();
-                }
-            });
-        }
     }
 
-    /**
-     * Shows a confirmation dialog before deleting an inventory item.
-     */
     private void confirmDelete() {
         new AlertDialog.Builder(requireContext())
                 .setTitle("Delete inventory item?")
@@ -241,12 +179,9 @@ public class InventoryDetailFragment extends Fragment {
                 .show();
     }
 
-    /**
-     * Sends a request to the API to delete the inventory item.
-     */
     private void deleteInventory() {
         setButtonsEnabled(false);
-        inventoryViewModel.deleteInventory(inventoryId).observe(getViewLifecycleOwner(), resource -> {
+        viewModel.deleteInventory().observe(getViewLifecycleOwner(), resource -> {
             setButtonsEnabled(true);
             if (resource.status == Resource.Status.SUCCESS) {
                 Toast.makeText(getContext(), "Inventory deleted", Toast.LENGTH_SHORT).show();
@@ -257,16 +192,10 @@ public class InventoryDetailFragment extends Fragment {
         });
     }
 
-    /**
-     * Navigates back to the previous fragment.
-     */
     private void navigateBack() {
         NavHostFragment.findNavController(this).popBackStack();
     }
 
-    /**
-     * Enables or disables action buttons.
-     */
     private void setButtonsEnabled(boolean enabled) {
         binding.btnSaveInventory.setEnabled(enabled);
         binding.btnDeleteInventory.setEnabled(enabled);

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

@@ -26,12 +26,8 @@ import com.example.petstoremobile.utils.InputValidator;
 import com.example.petstoremobile.utils.Resource;
 import com.example.petstoremobile.utils.SpinnerUtils;
 import com.example.petstoremobile.utils.UIUtils;
-import com.example.petstoremobile.viewmodels.CustomerViewModel;
+import com.example.petstoremobile.viewmodels.PetDetailViewModel;
-import com.example.petstoremobile.viewmodels.PetViewModel;
-import com.example.petstoremobile.viewmodels.StoreViewModel;
 
-import java.util.ArrayList;
-import java.util.List;
 import java.util.Locale;
 
 import dagger.hilt.android.AndroidEntryPoint;
@@ -43,23 +39,15 @@ import dagger.hilt.android.AndroidEntryPoint;
 public class PetDetailFragment extends Fragment {
 
     private FragmentPetDetailBinding binding;
-    private long petId;
+    private PetDetailViewModel viewModel;
-    private boolean isEditing = false;
     
-    private PetViewModel viewModel;
-    private CustomerViewModel customerViewModel;
-    private StoreViewModel storeViewModel;
-    private List<DropdownDTO> customerList = new ArrayList<>();
-    private List<DropdownDTO> storeList = new ArrayList<>();
     private Long selectedCustomerId = null;
     private Long selectedStoreId = null;
 
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
-        viewModel = new ViewModelProvider(this).get(PetViewModel.class);
+        viewModel = new ViewModelProvider(this).get(PetDetailViewModel.class);
-        customerViewModel = new ViewModelProvider(this).get(CustomerViewModel.class);
-        storeViewModel = new ViewModelProvider(this).get(StoreViewModel.class);
     }
 
     @Override
@@ -74,8 +62,7 @@ public class PetDetailFragment extends Fragment {
         super.onViewCreated(view, savedInstanceState);
 
         setupSpinner();
-        loadCustomers();
+        observeViewModel();
-        loadStores();
         handleArguments();
 
         //set button click listeners
@@ -84,6 +71,23 @@ public class PetDetailFragment extends Fragment {
         binding.btnDeletePet.setOnClickListener(v -> deletePet());
     }
 
+    private void observeViewModel() {
+        viewModel.getCustomerList().observe(getViewLifecycleOwner(), list -> updateCustomerSpinnerSelection());
+        viewModel.getStoreList().observe(getViewLifecycleOwner(), list -> updateStoreSpinnerSelection());
+        
+        viewModel.loadCustomers().observe(getViewLifecycleOwner(), resource -> {
+            if (resource != null && resource.status == Resource.Status.SUCCESS && resource.data != null) {
+                viewModel.setCustomerList(resource.data);
+            }
+        });
+
+        viewModel.loadStores().observe(getViewLifecycleOwner(), resource -> {
+            if (resource != null && resource.status == Resource.Status.SUCCESS && resource.data != null) {
+                viewModel.setStoreList(resource.data);
+            }
+        });
+    }
+
     @Override
     public void onDestroyView() {
         super.onDestroyView();
@@ -113,14 +117,14 @@ public class PetDetailFragment extends Fragment {
         Long customerId = null;
         int customerPos = binding.spinnerCustomer.getSelectedItemPosition();
         if (customerPos > 0) { // 0 means no customer for pet
-            customerId = customerList.get(customerPos - 1).getId();
+            customerId = viewModel.getCustomerList().getValue().get(customerPos - 1).getId();
         }
 
         // Get selected store
         Long storeId = null;
         int storePos = binding.spinnerStore.getSelectedItemPosition();
         if (storePos > 0) {
-            storeId = storeList.get(storePos - 1).getId();
+            storeId = viewModel.getStoreList().getValue().get(storePos - 1).getId();
         }
 
         // Validation: If status is Available, a store must be selected
@@ -150,41 +154,30 @@ public class PetDetailFragment extends Fragment {
         petDTO.setCustomerId(customerId);
         petDTO.setStoreId(storeId);
 
-        //check if the pet is being edited or added
+        viewModel.savePet(petDTO).observe(getViewLifecycleOwner(), resource -> {
-        if (isEditing) {
-            // Update existing pet
-            petDTO.setPetId(petId);
-            viewModel.updatePet(petId, petDTO).observe(getViewLifecycleOwner(), resource -> {
             if (resource.status == Resource.Status.SUCCESS) {
-                    ActivityLogger.logChange(requireContext(), "Pet", "UPDATED", (int) petId);
+                if (viewModel.isEditing()) {
+                    ActivityLogger.logChange(requireContext(), "Pet", "UPDATED", (int) viewModel.getPetId());
                     Toast.makeText(getContext(), "Pet updated successfully!", Toast.LENGTH_SHORT).show();
-                    navigateToPetList();
-                } else if (resource.status == Resource.Status.ERROR) {
-                    Toast.makeText(getContext(), "Error: " + resource.message, Toast.LENGTH_SHORT).show();
-                }
-            });
                 } else {
-            // Add new pet
-            viewModel.createPet(petDTO).observe(getViewLifecycleOwner(), resource -> {
-                if (resource.status == Resource.Status.SUCCESS) {
                     ActivityLogger.log(requireContext(), "Added new Pet: " + name);
                     Toast.makeText(getContext(), "Pet added successfully!", Toast.LENGTH_SHORT).show();
+                }
                 navigateToPetList();
             } else if (resource.status == Resource.Status.ERROR) {
                 Toast.makeText(getContext(), "Error: " + resource.message, Toast.LENGTH_SHORT).show();
             }
         });
     }
-    }
 
     /**
      * Displays a confirmation dialog and handles the deletion of a pet.
      */
     private void deletePet() {
         DialogUtils.showDeleteConfirmDialog(requireContext(), "Pet", () -> 
-                viewModel.deletePet(petId).observe(getViewLifecycleOwner(), resource -> {
+                viewModel.deletePet().observe(getViewLifecycleOwner(), resource -> {
                     if (resource.status == Resource.Status.SUCCESS) {
-                        ActivityLogger.logChange(requireContext(), "Pet", "DELETED", (int) petId);
+                        ActivityLogger.logChange(requireContext(), "Pet", "DELETED", (int) viewModel.getPetId());
                         Toast.makeText(getContext(), "Pet deleted successfully!", Toast.LENGTH_SHORT).show();
                         navigateToPetList();
                     } else if (resource.status == Resource.Status.ERROR) {
@@ -211,30 +204,23 @@ public class PetDetailFragment extends Fragment {
      * Handles arguments passed to the fragment to determine if it's in edit or add mode.
      */
     private void handleArguments() {
-        // Pet is being edited if the bundle contains a petId
         if (getArguments() != null && getArguments().containsKey("petId")) {
-            // Get pet data from arguments and populate fields
+            long petId = getArguments().getLong("petId");
-            isEditing = true;
+            viewModel.setPetId(petId);
-            petId = getArguments().getLong("petId");
             binding.tvMode.setText("Edit Pet");
             binding.tvPetId.setText("ID: " + petId);
             binding.tvPetId.setVisibility(View.VISIBLE);
             binding.btnDeletePet.setVisibility(View.VISIBLE);
             
-            // Disable species and breed fields in edit mode
             UIUtils.setViewsEnabled(false, binding.etPetSpecies, binding.etPetBreed);
-            
             loadPetData();
         } else {
-            // Pet is being added
+            viewModel.setPetId(-1);
-            // Set default values for add a new pet
-            isEditing = false;
             binding.tvMode.setText("Add Pet");
             binding.tvPetId.setVisibility(View.GONE);
             binding.btnDeletePet.setVisibility(View.GONE);
             binding.btnSavePet.setText("Add");
             
-            // Enable species and breed fields in edit mode
             UIUtils.setViewsEnabled(true, binding.etPetSpecies, binding.etPetBreed);
         }
     }
@@ -243,7 +229,7 @@ public class PetDetailFragment extends Fragment {
      * Fetches specific pet details from the backend using the ID.
      */
     private void loadPetData() {
-        viewModel.getPetById(petId).observe(getViewLifecycleOwner(), resource -> {
+        viewModel.loadPet().observe(getViewLifecycleOwner(), resource -> {
             if (resource == null) return;
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 PetDTO p = resource.data;
@@ -267,30 +253,6 @@ public class PetDetailFragment extends Fragment {
         });
     }
 
-    /**
-     * Fetches the list of customers and populates the spinner.
-     */
-    private void loadCustomers() {
-        customerViewModel.getCustomerDropdowns().observe(getViewLifecycleOwner(), resource -> {
-            if (resource != null && resource.status == Resource.Status.SUCCESS && resource.data != null) {
-                customerList = resource.data;
-                updateCustomerSpinnerSelection();
-            }
-        });
-    }
-
-    /**
-     * Fetches the list of stores and populates the spinner.
-     */
-    private void loadStores() {
-        storeViewModel.getStoreDropdowns().observe(getViewLifecycleOwner(), resource -> {
-            if (resource != null && resource.status == Resource.Status.SUCCESS && resource.data != null) {
-                storeList = resource.data;
-                updateStoreSpinnerSelection();
-            }
-        });
-    }
-
     /**
      * Updates the customer spinner with the current list and sets the selection if needed.
      */
@@ -298,7 +260,7 @@ public class PetDetailFragment extends Fragment {
         SpinnerUtils.populateSpinner(
                 requireContext(),
                 binding.spinnerCustomer,
-                customerList,
+                viewModel.getCustomerList().getValue(),
                 DropdownDTO::getLabel,
                 "No Owner",
                 selectedCustomerId,
@@ -313,7 +275,7 @@ public class PetDetailFragment extends Fragment {
         SpinnerUtils.populateSpinner(
                 requireContext(),
                 binding.spinnerStore,
-                storeList,
+                viewModel.getStoreList().getValue(),
                 DropdownDTO::getLabel,
                 "None",
                 selectedStoreId,
@@ -333,11 +295,9 @@ public class PetDetailFragment extends Fragment {
             public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
                 String status = parent.getItemAtPosition(position).toString();
 
-                // Clear any existing error icons when status changes
                 clearSpinnerError(binding.spinnerCustomer);
                 clearSpinnerError(binding.spinnerStore);
 
-                //Disable the customer spinner if the status is "Available"
                 if ("Available".equalsIgnoreCase(status)) {
                     binding.spinnerCustomer.setSelection(0);
                     UIUtils.setViewsEnabled(false, binding.spinnerCustomer);
@@ -345,7 +305,6 @@ public class PetDetailFragment extends Fragment {
                     UIUtils.setViewsEnabled(true, binding.spinnerCustomer);
                 }
 
-                //Disable the store spinner if the status is "Owned"
                 if ("Owned".equalsIgnoreCase(status)) {
                     binding.spinnerStore.setSelection(0);
                     UIUtils.setViewsEnabled(false, binding.spinnerStore);
@@ -360,9 +319,6 @@ public class PetDetailFragment extends Fragment {
         });
     }
 
-    /**
-     * Clears error messages from a Spinner's selected view.
-     */
     private void clearSpinnerError(Spinner spinner) {
         View selectedView = spinner.getSelectedView();
         if (selectedView instanceof TextView) {

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

@@ -17,7 +17,7 @@ import com.example.petstoremobile.api.*;
 import com.example.petstoremobile.api.auth.TokenManager;
 import com.example.petstoremobile.databinding.FragmentProductDetailBinding;
 import com.example.petstoremobile.dtos.*;
-import com.example.petstoremobile.viewmodels.ProductViewModel;
+import com.example.petstoremobile.viewmodels.ProductDetailViewModel;
 import com.example.petstoremobile.utils.DialogUtils;
 import com.example.petstoremobile.utils.FileUtils;
 import com.example.petstoremobile.utils.GlideUtils;
@@ -31,7 +31,6 @@ import java.math.BigDecimal;
 import java.util.*;
 
 import javax.inject.Inject;
-
 import javax.inject.Named;
 
 import dagger.hilt.android.AndroidEntryPoint;
@@ -46,29 +45,22 @@ import okhttp3.RequestBody;
 public class ProductDetailFragment extends Fragment {
 
     private FragmentProductDetailBinding binding;
+    private ProductDetailViewModel viewModel;
+    private ImagePickerHelper imagePickerHelper;
 
-    private long prodId = -1;
-    private boolean isEditing = false;
     private long preselectedCategoryId = -1;
     private boolean hasImage = false;
     private boolean isImageChanged = false;
     private boolean isImageRemoved = false;
-
-    private List<CategoryDTO> categoryList = new ArrayList<>();
     private Uri photoUri;
-    private ProductViewModel viewModel;
-    private ImagePickerHelper imagePickerHelper;
 
     @Inject @Named("baseUrl") String baseUrl;
     @Inject TokenManager tokenManager;
 
-    /**
-     * Initializes activity launchers and the ImagePickerHelper.
-     */
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
-        viewModel = new ViewModelProvider(this).get(ProductViewModel.class);
+        viewModel = new ViewModelProvider(this).get(ProductDetailViewModel.class);
 
         imagePickerHelper = new ImagePickerHelper(this, "product_photo.jpg", new ImagePickerHelper.ImagePickerListener() {
             @Override
@@ -95,9 +87,6 @@ public class ProductDetailFragment extends Fragment {
         });
     }
 
-    /**
-     * Inflates the layout.
-     */
     @Override
     public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container,
                              Bundle savedInstanceState) {
@@ -105,14 +94,11 @@ public class ProductDetailFragment extends Fragment {
         return binding.getRoot();
     }
 
-    /**
-     * Sets up UI components and listeners after the view is created.
-     */
     @Override
     public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
         super.onViewCreated(view, savedInstanceState);
 
-        loadCategories();
+        observeViewModel();
         handleArguments();
 
         binding.btnProductBack.setOnClickListener(v -> navigateBack());
@@ -121,34 +107,33 @@ public class ProductDetailFragment extends Fragment {
         binding.ivProductImage.setOnClickListener(v -> imagePickerHelper.showImagePickerDialog("Select Product Image", hasImage));
     }
 
+    private void observeViewModel() {
+        viewModel.getCategoryList().observe(getViewLifecycleOwner(), list -> updateCategorySpinner());
+        
+        viewModel.loadCategories().observe(getViewLifecycleOwner(), resource -> {
+            if (resource != null && resource.status == Resource.Status.SUCCESS && resource.data != null) {
+                viewModel.setCategoryList(resource.data.getContent());
+            }
+        });
+    }
+
+    private void updateCategorySpinner() {
+        SpinnerUtils.populateSpinner(requireContext(), binding.spinnerProductCategory, viewModel.getCategoryList().getValue(),
+                CategoryDTO::getCategoryName, "-- Select Category --",
+                preselectedCategoryId, CategoryDTO::getCategoryId);
+    }
+
     @Override
     public void onDestroyView() {
         super.onDestroyView();
         binding = null;
     }
 
-    /**
-     * Fetches all product categories for the selection spinner.
-     */
-    private void loadCategories() {
-        viewModel.getAllCategories(0, 100).observe(getViewLifecycleOwner(), resource -> {
-            if (resource != null && resource.status == Resource.Status.SUCCESS && resource.data != null) {
-                categoryList = resource.data.getContent();
-                SpinnerUtils.populateSpinner(requireContext(), binding.spinnerProductCategory, categoryList,
-                        CategoryDTO::getCategoryName, "-- Select Category --",
-                        preselectedCategoryId, CategoryDTO::getCategoryId);
-            }
-        });
-    }
-
-    /**
-     * Checks if the fragment was opened with existing product data for editing.
-     */
     private void handleArguments() {
         Bundle a = getArguments();
         if (a != null && a.containsKey("prodId")) {
-            isEditing = true;
+            long prodId = a.getLong("prodId");
-            prodId = a.getLong("prodId");
+            viewModel.setProdId(prodId);
             binding.tvProductMode.setText("Edit Product");
             binding.tvProductId.setText("ID: " + prodId);
             binding.tvProductId.setVisibility(View.VISIBLE);
@@ -156,6 +141,7 @@ public class ProductDetailFragment extends Fragment {
             loadProductData();
             loadProductImage();
         } else {
+            viewModel.setProdId(-1);
             binding.tvProductMode.setText("Add Product");
             binding.btnDeleteProduct.setVisibility(View.GONE);
             binding.tvProductId.setVisibility(View.GONE);
@@ -163,11 +149,8 @@ public class ProductDetailFragment extends Fragment {
         }
     }
 
-    /**
-     * Loads the product data from the backend.
-     */
     private void loadProductData() {
-        viewModel.getProductById(prodId).observe(getViewLifecycleOwner(), resource -> {
+        viewModel.loadProduct().observe(getViewLifecycleOwner(), resource -> {
             if (resource == null) return;
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 ProductDTO p = resource.data;
@@ -175,24 +158,15 @@ public class ProductDetailFragment extends Fragment {
                 binding.etProductDesc.setText(p.getProdDesc());
                 binding.etProductPrice.setText(p.getProdPrice() != null ? p.getProdPrice().toString() : "");
                 preselectedCategoryId = p.getCategoryId() != null ? p.getCategoryId() : -1;
-                
+                updateCategorySpinner();
-                // Refresh spinner selection once data is loaded
-                if (!categoryList.isEmpty()) {
-                    SpinnerUtils.populateSpinner(requireContext(), binding.spinnerProductCategory, categoryList,
-                            CategoryDTO::getCategoryName, "-- Select Category --",
-                            preselectedCategoryId, CategoryDTO::getCategoryId);
-                }
             } else if (resource.status == Resource.Status.ERROR) {
                 Toast.makeText(getContext(), "Failed to load product: " + resource.message, Toast.LENGTH_SHORT).show();
             }
         });
     }
 
-    /**
-     * Loads the product image from the backend.
-     */
     private void loadProductImage() {
-        String imageUrl = baseUrl + String.format(Locale.US, ProductApi.PRODUCT_IMAGE_PATH, prodId);
+        String imageUrl = baseUrl + String.format(Locale.US, ProductApi.PRODUCT_IMAGE_PATH, viewModel.getProdId());
         String token = tokenManager.getToken();
 
         GlideUtils.loadImageWithToken(requireContext(), binding.ivProductImage, imageUrl, token, R.drawable.placeholder2, new GlideUtils.ImageLoadListener() {
@@ -208,12 +182,9 @@ public class ProductDetailFragment extends Fragment {
         });
     }
 
-    /**
-     * Performs image related actions (upload/delete) after product details are saved.
-     */
     private void performPendingImageActions(String successMsg) {
         if (isImageRemoved) {
-            viewModel.deleteProductImage(prodId).observe(getViewLifecycleOwner(), resource -> {
+            viewModel.deleteProductImage().observe(getViewLifecycleOwner(), resource -> {
                 if (resource != null && resource.status != Resource.Status.LOADING) {
                     if (resource.status == Resource.Status.SUCCESS) {
                         Toast.makeText(getContext(), successMsg, Toast.LENGTH_SHORT).show();
@@ -231,9 +202,6 @@ public class ProductDetailFragment extends Fragment {
         }
     }
 
-    /**
-     * Uploads the selected image file to the server.
-     */
     private void uploadProductImageAndNavigate(Uri uri, String successMsg) {
         File file = FileUtils.getFileFromUri(requireContext(), uri);
         if (file == null) {
@@ -245,7 +213,7 @@ 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);
 
-        viewModel.uploadProductImage(prodId, body).observe(getViewLifecycleOwner(), resource -> {
+        viewModel.uploadProductImage(body).observe(getViewLifecycleOwner(), resource -> {
             if (resource != null && resource.status != Resource.Status.LOADING) {
                 if (resource.status == Resource.Status.SUCCESS) {
                     Toast.makeText(getContext(), successMsg, Toast.LENGTH_SHORT).show();
@@ -257,9 +225,6 @@ public class ProductDetailFragment extends Fragment {
         });
     }
 
-    /**
-     * Validates input fields and saves product information to the backend.
-     */
     private void saveProduct() {
         if (!InputValidator.isNotEmpty(binding.etProductName, "Product Name")) return;
 
@@ -276,39 +241,26 @@ public class ProductDetailFragment extends Fragment {
         String desc = binding.etProductDesc.getText().toString().trim();
         BigDecimal price = new BigDecimal(binding.etProductPrice.getText().toString().trim());
 
-        CategoryDTO category = categoryList.get(binding.spinnerProductCategory.getSelectedItemPosition() - 1);
+        CategoryDTO category = viewModel.getCategoryList().getValue().get(binding.spinnerProductCategory.getSelectedItemPosition() - 1);
         ProductDTO dto = new ProductDTO(name, category.getCategoryId(), desc, price);
 
-        if (isEditing) {
+        viewModel.saveProduct(dto).observe(getViewLifecycleOwner(), resource -> {
-            viewModel.updateProduct(prodId, dto).observe(getViewLifecycleOwner(), resource -> {
             if (resource != null && resource.status != Resource.Status.LOADING) {
                 if (resource.status == Resource.Status.SUCCESS) {
-                        performPendingImageActions("Updated");
+                    if (resource.data != null) {
+                        viewModel.setProdId(resource.data.getProdId());
+                    }
+                    performPendingImageActions(viewModel.isEditing() ? "Updated" : "Saved");
                 } else {
                     Toast.makeText(getContext(), "Error: " + resource.message, Toast.LENGTH_SHORT).show();
                 }
             }
         });
-        } else {
-            viewModel.createProduct(dto).observe(getViewLifecycleOwner(), resource -> {
-                if (resource != null && resource.status != Resource.Status.LOADING) {
-                    if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
-                        prodId = resource.data.getProdId();
-                        performPendingImageActions("Saved");
-                    } else {
-                        Toast.makeText(getContext(), "Error saving: " + resource.message, Toast.LENGTH_SHORT).show();
-                    }
-                }
-            });
-        }
     }
 
-    /**
-     * Displays a confirmation dialog before deleting the product.
-     */
     private void confirmDelete() {
         DialogUtils.showDeleteConfirmDialog(requireContext(), "Product", () -> 
-                viewModel.deleteProduct(prodId).observe(getViewLifecycleOwner(), resource -> {
+                viewModel.deleteProduct().observe(getViewLifecycleOwner(), resource -> {
                     if (resource != null && resource.status == Resource.Status.SUCCESS) {
                         navigateBack();
                     } else if (resource != null && resource.status == Resource.Status.ERROR) {
@@ -317,9 +269,6 @@ public class ProductDetailFragment extends Fragment {
                 }));
     }
 
-    /**
-     * Navigates back to the previous fragment.
-     */
     private void navigateBack() {
         NavHostFragment.findNavController(this).popBackStack();
     }

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

@@ -15,9 +15,7 @@ import com.example.petstoremobile.utils.DialogUtils;
 import com.example.petstoremobile.utils.InputValidator;
 import com.example.petstoremobile.utils.Resource;
 import com.example.petstoremobile.utils.SpinnerUtils;
-import com.example.petstoremobile.viewmodels.ProductSupplierViewModel;
+import com.example.petstoremobile.viewmodels.ProductSupplierDetailViewModel;
-import com.example.petstoremobile.viewmodels.ProductViewModel;
-import com.example.petstoremobile.viewmodels.SupplierViewModel;
 
 import java.math.BigDecimal;
 import java.util.*;
@@ -31,26 +29,15 @@ import dagger.hilt.android.AndroidEntryPoint;
 public class ProductSupplierDetailFragment extends Fragment {
 
     private FragmentProductSupplierDetailBinding binding;
+    private ProductSupplierDetailViewModel viewModel;
 
-    private boolean isEditing = false;
-    private long editProductId = -1;
-    private long editSupplierId = -1;
     private long preselectedProductId = -1;
     private long preselectedSupplierId = -1;
 
-    private List<ProductDTO> productList = new ArrayList<>();
-    private List<SupplierDTO> supplierList = new ArrayList<>();
-
-    private ProductSupplierViewModel psViewModel;
-    private ProductViewModel productViewModel;
-    private SupplierViewModel supplierViewModel;
-
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
-        psViewModel = new ViewModelProvider(this).get(ProductSupplierViewModel.class);
+        viewModel = new ViewModelProvider(this).get(ProductSupplierDetailViewModel.class);
-        productViewModel = new ViewModelProvider(this).get(ProductViewModel.class);
-        supplierViewModel = new ViewModelProvider(this).get(SupplierViewModel.class);
     }
 
     @Override
@@ -63,6 +50,7 @@ public class ProductSupplierDetailFragment extends Fragment {
     @Override
     public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
         super.onViewCreated(view, savedInstanceState);
+        observeViewModel();
         loadSpinnersData();
         handleArguments();
 
@@ -71,81 +59,59 @@ public class ProductSupplierDetailFragment extends Fragment {
         binding.btnDeletePS.setOnClickListener(v -> confirmDelete());
     }
 
+    private void observeViewModel() {
+        viewModel.getProductList().observe(getViewLifecycleOwner(), list -> refreshProductSpinner());
+        viewModel.getSupplierList().observe(getViewLifecycleOwner(), list -> refreshSupplierSpinner());
+    }
+
     @Override
     public void onDestroyView() {
         super.onDestroyView();
         binding = null;
     }
 
-    /**
-     * Fetches products and suppliers to populate the spinners.
-     */
     private void loadSpinnersData() {
-        loadProducts();
+        viewModel.loadProducts().observe(getViewLifecycleOwner(), resource -> {
-        loadSuppliers();
-    }
-
-    /**
-     * Loads the list of products from the API.
-     */
-    private void loadProducts() {
-        productViewModel.getAllProducts(null, null, 0, 200, "prodName").observe(getViewLifecycleOwner(), resource -> {
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
-                productList = resource.data.getContent();
+                viewModel.setProductList(resource.data.getContent());
-                refreshProductSpinner();
+            }
+        });
+        viewModel.loadSuppliers().observe(getViewLifecycleOwner(), resource -> {
+            if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
+                viewModel.setSupplierList(resource.data.getContent());
             }
         });
     }
 
     private void refreshProductSpinner() {
-        SpinnerUtils.populateSpinner(requireContext(), binding.spinnerPSProduct, productList,
+        SpinnerUtils.populateSpinner(requireContext(), binding.spinnerPSProduct, viewModel.getProductList().getValue(),
                 ProductDTO::getProdName, "-- Select Product --",
                 preselectedProductId, ProductDTO::getProdId);
     }
 
-    /**
-     * Loads the list of suppliers from the API.
-     */
-    private void loadSuppliers() {
-        supplierViewModel.getAllSuppliers(0, 200, null, "supCompany").observe(getViewLifecycleOwner(), resource -> {
-            if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
-                supplierList = resource.data.getContent();
-                refreshSupplierSpinner();
-            }
-        });
-    }
-
     private void refreshSupplierSpinner() {
-        SpinnerUtils.populateSpinner(requireContext(), binding.spinnerPSSupplier, supplierList,
+        SpinnerUtils.populateSpinner(requireContext(), binding.spinnerPSSupplier, viewModel.getSupplierList().getValue(),
                 SupplierDTO::getSupCompany, "-- Select Supplier --",
                 preselectedSupplierId, SupplierDTO::getSupId);
     }
 
-    /**
-     * Handles arguments to determine if the fragment is in edit or add mode.
-     */
     private void handleArguments() {
         Bundle a = getArguments();
         if (a != null && a.containsKey("productId") && a.containsKey("supplierId")) {
-            isEditing = true;
+            long productId = a.getLong("productId");
-            editProductId = a.getLong("productId");
+            long supplierId = a.getLong("supplierId");
-            editSupplierId = a.getLong("supplierId");
+            viewModel.setEditMode(productId, supplierId);
-            preselectedProductId = editProductId;
+            preselectedProductId = productId;
-            preselectedSupplierId = editSupplierId;
+            preselectedSupplierId = supplierId;
             
             binding.tvPSMode.setText("Edit Product Supplier");
             binding.btnDeletePS.setVisibility(View.VISIBLE);
-
         } else {
             binding.tvPSMode.setText("Add Product Supplier");
             binding.btnDeletePS.setVisibility(View.GONE);
         }
     }
 
-
-    /**
-     * Validates input and saves the product-supplier to the backend.
-     */
     private void save() {
         if (binding.spinnerPSProduct.getSelectedItemPosition() == 0) {
             Toast.makeText(getContext(), "Select a product", Toast.LENGTH_SHORT).show(); return;
@@ -159,40 +125,25 @@ public class ProductSupplierDetailFragment extends Fragment {
             return;
         }
 
-        ProductDTO product   = productList.get(binding.spinnerPSProduct.getSelectedItemPosition() - 1);
+        ProductDTO product   = viewModel.getProductList().getValue().get(binding.spinnerPSProduct.getSelectedItemPosition() - 1);
-        SupplierDTO supplier = supplierList.get(binding.spinnerPSSupplier.getSelectedItemPosition() - 1);
+        SupplierDTO supplier = viewModel.getSupplierList().getValue().get(binding.spinnerPSSupplier.getSelectedItemPosition() - 1);
         BigDecimal cost = new BigDecimal(binding.etPSCost.getText().toString().trim());
 
-        ProductSupplierDTO dto = new ProductSupplierDTO(
+        ProductSupplierDTO dto = new ProductSupplierDTO(product.getProdId(), supplier.getSupId(), cost);
-                product.getProdId(), supplier.getSupId(), cost);
 
-        if (isEditing) {
+        viewModel.saveProductSupplier(dto).observe(getViewLifecycleOwner(), resource -> {
-            psViewModel.updateProductSupplier(editProductId, editSupplierId, dto).observe(getViewLifecycleOwner(), resource -> {
             if (resource.status == Resource.Status.SUCCESS) {
-                    Toast.makeText(getContext(), "Updated", Toast.LENGTH_SHORT).show();
+                Toast.makeText(getContext(), viewModel.isEditing() ? "Updated" : "Saved", Toast.LENGTH_SHORT).show();
-                    navigateBack();
-                } else if (resource.status == Resource.Status.ERROR) {
-                    Toast.makeText(getContext(), "Error: " + resource.message, Toast.LENGTH_SHORT).show();
-                }
-            });
-        } else {
-            psViewModel.createProductSupplier(dto).observe(getViewLifecycleOwner(), resource -> {
-                if (resource.status == Resource.Status.SUCCESS) {
-                    Toast.makeText(getContext(), "Saved", Toast.LENGTH_SHORT).show();
                 navigateBack();
             } else if (resource.status == Resource.Status.ERROR) {
                 Toast.makeText(getContext(), "Error: " + resource.message, Toast.LENGTH_SHORT).show();
             }
         });
     }
-    }
 
-    /**
-     * Shows a confirmation dialog before deleting a product-supplier relationship.
-     */
     private void confirmDelete() {
         DialogUtils.showDeleteConfirmDialog(requireContext(), "Product Supplier", () ->
-                psViewModel.deleteProductSupplier(editProductId, editSupplierId).observe(getViewLifecycleOwner(), resource -> {
+                viewModel.deleteProductSupplier().observe(getViewLifecycleOwner(), resource -> {
                     if (resource.status == Resource.Status.SUCCESS) {
                         Toast.makeText(getContext(), "Deleted", Toast.LENGTH_SHORT).show();
                         navigateBack();
@@ -202,9 +153,6 @@ public class ProductSupplierDetailFragment extends Fragment {
                 }));
     }
 
-    /**
-     * Navigates back to the previous screen.
-     */
     private void navigateBack() {
         NavHostFragment.findNavController(this).popBackStack();
     }

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

@@ -14,7 +14,7 @@ import androidx.navigation.fragment.NavHostFragment;
 import com.example.petstoremobile.databinding.FragmentPurchaseOrderDetailBinding;
 import com.example.petstoremobile.dtos.PurchaseOrderDTO;
 import com.example.petstoremobile.utils.Resource;
-import com.example.petstoremobile.viewmodels.PurchaseOrderViewModel;
+import com.example.petstoremobile.viewmodels.PurchaseOrderDetailViewModel;
 
 import dagger.hilt.android.AndroidEntryPoint;
 
@@ -25,13 +25,13 @@ import dagger.hilt.android.AndroidEntryPoint;
 public class PurchaseOrderDetailFragment extends Fragment {
 
     private FragmentPurchaseOrderDetailBinding binding;
-    private PurchaseOrderViewModel viewModel;
+    private PurchaseOrderDetailViewModel viewModel;
     private long purchaseOrderId;
 
     @Override
     public void onCreate(@Nullable Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
-        viewModel = new ViewModelProvider(this).get(PurchaseOrderViewModel.class);
+        viewModel = new ViewModelProvider(this).get(PurchaseOrderDetailViewModel.class);
     }
 
     /**
@@ -67,7 +67,7 @@ public class PurchaseOrderDetailFragment extends Fragment {
     }
 
     private void loadPurchaseOrderData() {
-        viewModel.getPurchaseOrderById(purchaseOrderId).observe(getViewLifecycleOwner(), resource -> {
+        viewModel.loadPurchaseOrder(purchaseOrderId).observe(getViewLifecycleOwner(), resource -> {
             if (resource == null) return;
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 PurchaseOrderDTO po = resource.data;

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

@@ -12,7 +12,8 @@ import androidx.navigation.fragment.NavHostFragment;
 import com.example.petstoremobile.R;
 import com.example.petstoremobile.databinding.FragmentRefundBinding;
 import com.example.petstoremobile.dtos.SaleDTO;
-import com.example.petstoremobile.viewmodels.SaleViewModel;
+import com.example.petstoremobile.viewmodels.RefundViewModel;
+import com.example.petstoremobile.utils.Resource;
 import dagger.hilt.android.AndroidEntryPoint;
 import java.math.BigDecimal;
 import java.math.RoundingMode;
@@ -22,53 +23,23 @@ import java.util.*;
 public class RefundFragment extends Fragment {
 
     private FragmentRefundBinding binding;
-    private SaleViewModel saleViewModel;
+    private RefundViewModel viewModel;
-    private SaleDTO currentSale;
-    private List<SaleDTO> allSales = new ArrayList<>();
-
-    // Items available to refund (after accounting for previous refunds)
-    private List<RefundItem> availableItems = new ArrayList<>();
-    // Items user has added to refund cart
-    private List<RefundItem> refundCart = new ArrayList<>();
 
     private final String[] PAYMENT_METHODS = {"Cash", "Card"};
 
-    // Inner class to track refund items
-    static class RefundItem {
-        long prodId;
-        String productName;
-        int quantity;
-        BigDecimal unitPrice;
-
-        RefundItem(long prodId, String productName, int quantity, BigDecimal unitPrice) {
-            this.prodId = prodId;
-            this.productName = productName;
-            this.quantity = quantity;
-            this.unitPrice = unitPrice;
-        }
-
-        BigDecimal getTotal() {
-            return unitPrice != null
-                    ? unitPrice.multiply(BigDecimal.valueOf(quantity))
-                    : BigDecimal.ZERO;
-        }
-    }
-
     @Override
     public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container,
                              Bundle savedInstanceState) {
         binding = FragmentRefundBinding.inflate(inflater, container, false);
-        saleViewModel = new ViewModelProvider(this).get(SaleViewModel.class);
+        viewModel = new ViewModelProvider(this).get(RefundViewModel.class);
         
         setupSpinner();
+        observeViewModel();
         loadAllSales();
 
-        // Pre-fill sale ID if passed from SaleFragment
         Bundle args = getArguments();
         if (args != null && args.containsKey("saleId")) {
-            long saleId = args.getLong("saleId");
+            binding.etRefundSaleId.setText(String.valueOf(args.getLong("saleId")));
-            binding.etRefundSaleId.setText(String.valueOf(saleId));
-            // Auto-load after sales are fetched
         }
 
         binding.btnLoadSale.setOnClickListener(v -> loadSale());
@@ -83,26 +54,24 @@ public class RefundFragment extends Fragment {
                 android.R.layout.simple_spinner_item, PAYMENT_METHODS));
     }
 
+    private void observeViewModel() {
+        viewModel.getAvailableItems().observe(getViewLifecycleOwner(), items -> renderOriginalItems());
+        viewModel.getRefundCart().observe(getViewLifecycleOwner(), cart -> {
+            renderRefundCart();
+            updateRefundTotal();
+            renderOriginalItems(); // Re-render to reflect quantities in cart
+        });
+    }
+
     private void loadAllSales() {
-        saleViewModel.getAllSales(0, 1000, null, null, null, "saleDate,desc")
+        viewModel.loadAllSales().observe(getViewLifecycleOwner(), resource -> {
-                .observe(getViewLifecycleOwner(), resource -> {
+            if (resource != null && resource.status == Resource.Status.SUCCESS && resource.data != null) {
-                    if (resource != null) {
+                viewModel.setAllSales(resource.data.getContent());
-                        switch (resource.status) {
-                            case SUCCESS:
-                                if (resource.data != null) {
-                                    allSales = resource.data.getContent();
-                                    // Auto-load if saleId was pre-filled
                 Bundle args = getArguments();
                 if (args != null && args.containsKey("saleId")) {
                     loadSale();
                 }
             }
-                                break;
-                            case ERROR:
-                                Log.e("Refund", "Failed to load sales: " + resource.message);
-                                break;
-                        }
-                    }
         });
     }
 
@@ -120,13 +89,14 @@ public class RefundFragment extends Fragment {
             return;
         }
 
-        // Find sale in loaded list
         SaleDTO found = null;
-        for (SaleDTO s : allSales) {
+        if (viewModel.getAllSalesList() != null) {
+            for (SaleDTO s : viewModel.getAllSalesList()) {
                 if (s.getSaleId() != null && s.getSaleId() == saleId) {
                     found = s; break;
                 }
             }
+        }
 
         if (found == null) {
             Toast.makeText(getContext(), "Sale #" + saleId + " not found", Toast.LENGTH_SHORT).show();
@@ -139,9 +109,9 @@ public class RefundFragment extends Fragment {
             return;
         }
 
-        currentSale = found;
+        viewModel.setCurrentSale(found);
+        SaleDTO currentSale = viewModel.getCurrentSale();
 
-        // Show sale info
         binding.tvSaleInfo.setVisibility(View.VISIBLE);
         binding.tvSaleInfo.setText("Sale #" + currentSale.getSaleId()
                 + " | " + (currentSale.getSaleDate() != null
@@ -151,7 +121,6 @@ public class RefundFragment extends Fragment {
                 + " | Total: $" + currentSale.getTotalAmount()
                 + " | Payment: " + currentSale.getPaymentMethod());
 
-        // Pre-select payment method
         if (currentSale.getPaymentMethod() != null) {
             for (int i = 0; i < PAYMENT_METHODS.length; i++) {
                 if (PAYMENT_METHODS[i].equalsIgnoreCase(currentSale.getPaymentMethod())) {
@@ -160,85 +129,40 @@ public class RefundFragment extends Fragment {
             }
         }
 
-        // Build refundable items accounting for previous refunds
+        if (viewModel.getAvailableItems().getValue() == null || viewModel.getAvailableItems().getValue().isEmpty()) {
-        buildRefundableItems();
+            Toast.makeText(getContext(), "This sale has no remaining refundable items", Toast.LENGTH_LONG).show();
-
-        if (availableItems.isEmpty()) {
-            Toast.makeText(getContext(),
-                    "This sale has no remaining refundable items", Toast.LENGTH_LONG).show();
             return;
         }
 
-        // Reset refund cart
-        refundCart.clear();
-
-        // Show cards
         binding.cardOriginalItems.setVisibility(View.VISIBLE);
         binding.cardRefundItems.setVisibility(View.VISIBLE);
         binding.cardPayment.setVisibility(View.VISIBLE);
         binding.btnProcessRefund.setVisibility(View.VISIBLE);
-
-        renderOriginalItems();
-        renderRefundCart();
-        updateRefundTotal();
-    }
-
-    private void buildRefundableItems() {
-        availableItems.clear();
-        if (currentSale.getItems() == null) return;
-
-        // Find all previous refunds for this sale
-        Map<Long, Integer> alreadyRefunded = new HashMap<>();
-        for (SaleDTO s : allSales) {
-            if (Boolean.TRUE.equals(s.getIsRefund())
-                    && currentSale.getSaleId().equals(s.getOriginalSaleId())
-                    && s.getItems() != null) {
-                for (SaleDTO.SaleItemDTO item : s.getItems()) {
-                    if (item.getProdId() != null && item.getQuantity() != null) {
-                        alreadyRefunded.merge(item.getProdId(),
-                                Math.abs(item.getQuantity()), Integer::sum);
-                    }
-                }
-            }
-        }
-
-        // Build available items
-        for (SaleDTO.SaleItemDTO item : currentSale.getItems()) {
-            if (item.getProdId() == null || item.getQuantity() == null) continue;
-            int refunded = alreadyRefunded.getOrDefault(item.getProdId(), 0);
-            int remaining = item.getQuantity() - refunded;
-            if (remaining > 0) {
-                availableItems.add(new RefundItem(
-                        item.getProdId(),
-                        item.getProductName() != null ? item.getProductName() : "Unknown",
-                        remaining,
-                        item.getUnitPrice()
-                ));
-            }
-        }
     }
 
     private void renderOriginalItems() {
         binding.llOriginalItems.removeAllViews();
+        List<RefundViewModel.RefundItem> available = viewModel.getAvailableItems().getValue();
+        if (available == null) return;
 
-        // Header
         addTableHeader(binding.llOriginalItems);
 
-        for (RefundItem item : availableItems) {
+        for (RefundViewModel.RefundItem item : available) {
-            // Calculate pending in cart
+            int inCart = 0;
-            int pendingQty = 0;
+            if (viewModel.getRefundCart().getValue() != null) {
-            for (RefundItem r : refundCart) {
+                for (RefundViewModel.RefundItem r : viewModel.getRefundCart().getValue()) {
-                if (r.prodId == item.prodId) { pendingQty = r.quantity; break; }
+                    if (r.prodId == item.prodId) { inCart = r.quantity; break; }
                 }
-            int displayQty = item.quantity - pendingQty;
+            }
+            int displayQty = item.quantity - inCart;
             if (displayQty <= 0) continue;
 
             LinearLayout row = buildItemRow(
                     item.productName,
                     displayQty,
                     item.unitPrice,
-                    true, // show add button
+                    true,
-                    () -> showQuantityDialog(item)
+                    () -> showQuantityDialog(item, displayQty)
             );
             binding.llOriginalItems.addView(row);
         }
@@ -246,8 +170,9 @@ public class RefundFragment extends Fragment {
 
     private void renderRefundCart() {
         binding.llRefundItems.removeAllViews();
+        List<RefundViewModel.RefundItem> cart = viewModel.getRefundCart().getValue();
 
-        if (refundCart.isEmpty()) {
+        if (cart == null || cart.isEmpty()) {
             TextView empty = new TextView(getContext());
             empty.setText("No items added to refund yet");
             empty.setTextColor(0xFF888780);
@@ -258,18 +183,13 @@ public class RefundFragment extends Fragment {
 
         addTableHeader(binding.llRefundItems);
 
-        for (RefundItem item : refundCart) {
+        for (RefundViewModel.RefundItem item : cart) {
             LinearLayout row = buildItemRow(
                     item.productName,
                     item.quantity,
                     item.unitPrice,
-                    false, // show remove button
+                    false,
-                    () -> {
+                    () -> viewModel.removeFromCart(item)
-                        refundCart.remove(item);
-                        renderOriginalItems();
-                        renderRefundCart();
-                        updateRefundTotal();
-                    }
             );
             binding.llRefundItems.addView(row);
         }
@@ -342,24 +262,10 @@ public class RefundFragment extends Fragment {
         return row;
     }
 
-    private void showQuantityDialog(RefundItem item) {
+    private void showQuantityDialog(RefundViewModel.RefundItem item, int available) {
-        // Calculate how many are already in cart
-        int inCart = 0;
-        for (RefundItem r : refundCart) {
-            if (r.prodId == item.prodId) { inCart = r.quantity; break; }
-        }
-        int available = item.quantity - inCart;
-        if (available <= 0) {
-            Toast.makeText(getContext(), "All units already added to refund",
-                    Toast.LENGTH_SHORT).show();
-            return;
-        }
-
-        // Build dialog
         AlertDialog.Builder builder = new AlertDialog.Builder(requireContext());
         builder.setTitle("Refund Quantity");
-        builder.setMessage("Product: " + item.productName
+        builder.setMessage("Product: " + item.productName + "\nAvailable: " + available);
-                + "\nAvailable: " + available);
 
         EditText input = new EditText(getContext());
         input.setInputType(android.text.InputType.TYPE_CLASS_NUMBER);
@@ -377,36 +283,15 @@ public class RefundFragment extends Fragment {
                 return;
             }
             if (qty <= 0) {
-                Toast.makeText(getContext(), "Quantity must be at least 1",
+                Toast.makeText(getContext(), "Quantity must be at least 1", Toast.LENGTH_SHORT).show();
-                        Toast.LENGTH_SHORT).show();
                 return;
             }
             if (qty > available) {
-                Toast.makeText(getContext(), "Cannot exceed " + available,
+                Toast.makeText(getContext(), "Cannot exceed " + available, Toast.LENGTH_SHORT).show();
-                        Toast.LENGTH_SHORT).show();
                 return;
             }
 
-            // Add or merge into cart
+            viewModel.addToCart(item, qty);
-            boolean merged = false;
-            for (int i = 0; i < refundCart.size(); i++) {
-                if (refundCart.get(i).prodId == item.prodId) {
-                    RefundItem existing = refundCart.get(i);
-                    refundCart.set(i, new RefundItem(existing.prodId,
-                            existing.productName,
-                            existing.quantity + qty,
-                            existing.unitPrice));
-                    merged = true; break;
-                }
-            }
-            if (!merged) {
-                refundCart.add(new RefundItem(item.prodId, item.productName,
-                        qty, item.unitPrice));
-            }
-
-            renderOriginalItems();
-            renderRefundCart();
-            updateRefundTotal();
         });
 
         builder.setNegativeButton("Cancel", null);
@@ -415,31 +300,31 @@ public class RefundFragment extends Fragment {
 
     private void updateRefundTotal() {
         BigDecimal total = BigDecimal.ZERO;
-        for (RefundItem item : refundCart) total = total.add(item.getTotal());
+        List<RefundViewModel.RefundItem> cart = viewModel.getRefundCart().getValue();
+        if (cart != null) {
+            for (RefundViewModel.RefundItem item : cart) total = total.add(item.getTotal());
+        }
         binding.tvRefundTotal.setText("Refund Total: $" + total.setScale(2, RoundingMode.HALF_UP));
     }
 
     private void processRefund() {
-        if (currentSale == null) {
+        if (viewModel.getCurrentSale() == null) {
             Toast.makeText(getContext(), "Load a sale first", Toast.LENGTH_SHORT).show();
             return;
         }
-        if (refundCart.isEmpty()) {
+        if (viewModel.getRefundCart().getValue() == null || viewModel.getRefundCart().getValue().isEmpty()) {
-            Toast.makeText(getContext(), "Add at least one item to refund",
+            Toast.makeText(getContext(), "Add at least one item to refund", Toast.LENGTH_SHORT).show();
-                    Toast.LENGTH_SHORT).show();
             return;
         }
 
         String payment = PAYMENT_METHODS[binding.spinnerRefundPayment.getSelectedItemPosition()];
-
-        // Confirm dialog
         BigDecimal total = BigDecimal.ZERO;
-        for (RefundItem item : refundCart) total = total.add(item.getTotal());
+        for (RefundViewModel.RefundItem item : viewModel.getRefundCart().getValue()) total = total.add(item.getTotal());
         final BigDecimal finalTotal = total;
 
         new AlertDialog.Builder(requireContext())
                 .setTitle("Confirm Refund")
-                .setMessage("Process refund for Sale #" + currentSale.getSaleId()
+                .setMessage("Process refund for Sale #" + viewModel.getCurrentSale().getSaleId()
                         + "?\nRefund amount: $" + finalTotal.setScale(2, RoundingMode.HALF_UP))
                 .setPositiveButton("Yes", (d, w) -> submitRefund(payment))
                 .setNegativeButton("No", null)
@@ -447,41 +332,13 @@ public class RefundFragment extends Fragment {
     }
 
     private void submitRefund(String payment) {
-        // Build sale items list
+        viewModel.submitRefund(payment).observe(getViewLifecycleOwner(), resource -> {
-        List<SaleDTO.SaleItemDTO> items = new ArrayList<>();
-        for (RefundItem item : refundCart) {
-            // Backend expects negative quantity for refunds
-            items.add(new SaleDTO.SaleItemDTO(item.prodId, -item.quantity));
-        }
-
-        SaleDTO dto = new SaleDTO(
-                currentSale.getStoreId(),
-                payment,
-                items,
-                true,                        // isRefund = true
-                currentSale.getSaleId(),     // originalSaleId
-                null                         // no customer needed
-        );
-
-        Log.d("REFUND", "Submitting refund for saleId=" + currentSale.getSaleId()
-                + " items=" + items.size());
-
-        saleViewModel.createSale(dto).observe(getViewLifecycleOwner(), resource -> {
             if (resource != null) {
-                switch (resource.status) {
+                if (resource.status == Resource.Status.SUCCESS) {
-                    case SUCCESS:
+                    Toast.makeText(getContext(), "Refund processed successfully!", Toast.LENGTH_LONG).show();
-                        if (resource.data != null) {
-                            Toast.makeText(getContext(),
-                                    "Refund #" + resource.data.getSaleId() + " processed successfully!",
-                                    Toast.LENGTH_LONG).show();
                     navigateBack();
-                        }
+                } else if (resource.status == Resource.Status.ERROR) {
-                        break;
+                    Toast.makeText(getContext(), "Error: " + resource.message, Toast.LENGTH_LONG).show();
-                    case ERROR:
-                        Log.e("REFUND", "Error: " + resource.message);
-                        Toast.makeText(getContext(), "Error: " + resource.message,
-                                Toast.LENGTH_LONG).show();
-                        break;
                 }
             }
         });

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

@@ -11,7 +11,7 @@ import androidx.navigation.fragment.NavHostFragment;
 import com.example.petstoremobile.R;
 import com.example.petstoremobile.databinding.FragmentSaleDetailBinding;
 import com.example.petstoremobile.dtos.*;
-import com.example.petstoremobile.viewmodels.*;
+import com.example.petstoremobile.viewmodels.SaleDetailViewModel;
 import com.example.petstoremobile.utils.SpinnerUtils;
 import com.example.petstoremobile.utils.DialogUtils;
 import com.example.petstoremobile.utils.Resource;
@@ -24,18 +24,7 @@ import java.util.*;
 public class SaleDetailFragment extends Fragment {
 
     private FragmentSaleDetailBinding binding;
-    private SaleViewModel saleViewModel;
+    private SaleDetailViewModel viewModel;
-    private StoreViewModel storeViewModel;
-    private CustomerViewModel customerViewModel;
-    private ProductViewModel productViewModel;
-
-    private boolean viewOnly = false;
-    private long saleId = -1;
-
-    private List<DropdownDTO> storeList = new ArrayList<>();
-    private List<DropdownDTO> customerList = new ArrayList<>();
-    private List<ProductDTO> productList = new ArrayList<>();
-    private List<SaleDTO.SaleItemDTO> cartItems = new ArrayList<>();
 
     private final String[] PAYMENT_METHODS = { "Cash", "Card"};
 
@@ -43,17 +32,14 @@ public class SaleDetailFragment extends Fragment {
     public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container,
                              Bundle savedInstanceState) {
         binding = FragmentSaleDetailBinding.inflate(inflater, container, false);
-        
+        viewModel = new ViewModelProvider(this).get(SaleDetailViewModel.class);
-        saleViewModel = new ViewModelProvider(this).get(SaleViewModel.class);
-        storeViewModel = new ViewModelProvider(this).get(StoreViewModel.class);
-        customerViewModel = new ViewModelProvider(this).get(CustomerViewModel.class);
-        productViewModel = new ViewModelProvider(this).get(ProductViewModel.class);
 
         SpinnerUtils.setupStringSpinner(requireContext(), binding.spinnerPaymentMethod, PAYMENT_METHODS);
 
+        observeViewModel();
         handleArguments();
 
-        if (!viewOnly) {
+        if (!viewModel.isViewOnly()) {
             loadData();
             setupAddItem();
         }
@@ -65,20 +51,42 @@ public class SaleDetailFragment extends Fragment {
         return binding.getRoot();
     }
 
+    private void observeViewModel() {
+        viewModel.getStoreList().observe(getViewLifecycleOwner(), list -> {
+            SpinnerUtils.populateSpinner(requireContext(), binding.spinnerSaleStore, list,
+                    DropdownDTO::getLabel, "-- Select Store --", -1L, DropdownDTO::getId);
+        });
+
+        viewModel.getCustomerList().observe(getViewLifecycleOwner(), list -> {
+            SpinnerUtils.populateSpinner(requireContext(), binding.spinnerSaleCustomer, list,
+                    DropdownDTO::getLabel, "-- No Customer --", -1L, DropdownDTO::getId);
+        });
+
+        viewModel.getProductList().observe(getViewLifecycleOwner(), list -> {
+            SpinnerUtils.populateSpinner(requireContext(), binding.spinnerSaleProduct, list,
+                    ProductDTO::getProdName, "Select Product", -1L, ProductDTO::getProdId);
+        });
+
+        viewModel.getCartItems().observe(getViewLifecycleOwner(), items -> {
+            renderCartItems();
+            updateTotal();
+        });
+    }
+
     private void handleArguments() {
         Bundle a = getArguments();
         if (a != null && a.containsKey("saleId")) {
-            saleId = a.getLong("saleId");
+            long saleId = a.getLong("saleId");
-            viewOnly = a.getBoolean("viewOnly", false);
+            boolean viewOnly = a.getBoolean("viewOnly", false);
+            viewModel.setSaleId(saleId, viewOnly);
+            
             binding.tvSaleMode.setText("Sale #" + saleId);
             binding.tvSaleDetailId.setText("ID: " + saleId);
 
-            // Show refund button for existing non-refund sales
             if (!a.getBoolean("isRefund", false)) {
                 binding.btnRefundSale.setVisibility(View.VISIBLE);
             }
 
-            // Hide save and input controls for view only
             if (viewOnly) {
                 binding.btnSaveSale.setVisibility(View.GONE);
                 UIUtils.setViewsEnabled(false, 
@@ -89,9 +97,9 @@ public class SaleDetailFragment extends Fragment {
                 binding.llExtraInfo.setVisibility(View.VISIBLE);
             }
 
-            // Load sale details
             loadSaleDetails();
         } else {
+            viewModel.setSaleId(-1, false);
             binding.tvSaleMode.setText("New Sale");
             binding.tvSaleDetailId.setVisibility(View.GONE);
             binding.btnRefundSale.setVisibility(View.GONE);
@@ -100,52 +108,21 @@ public class SaleDetailFragment extends Fragment {
     }
 
     private void loadData() {
-        loadStores();
+        viewModel.loadStores().observe(getViewLifecycleOwner(), resource -> {
-        loadCustomers();
+            if (resource.status == Resource.Status.SUCCESS && resource.data != null) viewModel.setStoreList(resource.data);
-        loadProducts();
-    }
-
-    private void loadStores() {
-        storeViewModel.getStoreDropdowns().observe(getViewLifecycleOwner(), resource -> {
-            if (resource != null && resource.status == Resource.Status.SUCCESS && resource.data != null) {
-                storeList = resource.data;
-                if (binding != null) {
-                    SpinnerUtils.populateSpinner(requireContext(), binding.spinnerSaleStore, storeList,
-                            DropdownDTO::getLabel, "-- Select Store --", -1L, DropdownDTO::getId);
-                }
-            }
         });
-    }
+        viewModel.loadCustomers().observe(getViewLifecycleOwner(), resource -> {
-
+            if (resource.status == Resource.Status.SUCCESS && resource.data != null) viewModel.setCustomerList(resource.data);
-    private void loadCustomers() {
-        customerViewModel.getCustomerDropdowns().observe(getViewLifecycleOwner(), resource -> {
-            if (resource != null && resource.status == Resource.Status.SUCCESS && resource.data != null) {
-                customerList = resource.data;
-                if (binding != null) {
-                    SpinnerUtils.populateSpinner(requireContext(), binding.spinnerSaleCustomer, customerList,
-                            DropdownDTO::getLabel, "-- No Customer --", -1L, DropdownDTO::getId);
-                }
-            }
         });
-    }
+        viewModel.loadProducts().observe(getViewLifecycleOwner(), resource -> {
-
+            if (resource.status == Resource.Status.SUCCESS && resource.data != null) viewModel.setProductList(resource.data.getContent());
-    private void loadProducts() {
-        productViewModel.getAllProducts(null, null, 0, 200, null).observe(getViewLifecycleOwner(), resource -> {
-            if (resource != null && resource.status == Resource.Status.SUCCESS && resource.data != null) {
-                productList = resource.data.getContent();
-                if (binding != null) {
-                    SpinnerUtils.populateSpinner(requireContext(), binding.spinnerSaleProduct, productList,
-                            ProductDTO::getProdName, "Select Product", -1L, ProductDTO::getProdId);
-                }
-            }
         });
     }
 
     private void loadSaleDetails() {
-        saleViewModel.getSaleById(saleId).observe(getViewLifecycleOwner(), resource -> {
+        viewModel.loadSaleDetails().observe(getViewLifecycleOwner(), resource -> {
             if (resource != null && resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 SaleDTO sale = resource.data;
-                if (binding != null) {
                 binding.tvSaleDetailTotal.setText("Total: $" + sale.getTotalAmount());
                 binding.tvSaleSubtotal.setText("$" + (sale.getSubtotalAmount() != null ? sale.getSubtotalAmount() : sale.getTotalAmount()));
                 
@@ -168,14 +145,10 @@ public class SaleDetailFragment extends Fragment {
 
                 SpinnerUtils.setSelectionByValue(binding.spinnerPaymentMethod, sale.getPaymentMethod());
 
-                    // Display items
                 if (sale.getItems() != null) {
                     binding.llSaleItems.removeAllViews();
                     for (SaleDTO.SaleItemDTO item : sale.getItems()) {
-                            addItemRow(item.getProductName(),
+                        addItemRow(item.getProductName(), Math.abs(item.getQuantity()), item.getUnitPrice());
-                                    Math.abs(item.getQuantity()),
-                                    item.getUnitPrice());
-                        }
                     }
                 }
             }
@@ -194,31 +167,46 @@ public class SaleDetailFragment extends Fragment {
                 return;
             }
             int qty;
-            try {
+            try { qty = Integer.parseInt(qtyStr); }
-                qty = Integer.parseInt(qtyStr);
+            catch (Exception e) {
-            } catch (Exception e) {
                 binding.etSaleQuantity.setError("Invalid quantity");
                 return;
             }
 
-            ProductDTO product = productList.get(binding.spinnerSaleProduct.getSelectedItemPosition() - 1);
+            ProductDTO product = viewModel.getProductList().getValue().get(binding.spinnerSaleProduct.getSelectedItemPosition() - 1);
 
-            // Check if product already in cart
+            for (SaleDTO.SaleItemDTO existing : viewModel.getCartItems().getValue()) {
-            for (SaleDTO.SaleItemDTO existing : cartItems) {
                 if (existing.getProdId().equals(product.getProdId())) {
                     Toast.makeText(getContext(), "Product already added", Toast.LENGTH_SHORT).show();
                     return;
                 }
             }
 
-            SaleDTO.SaleItemDTO item = new SaleDTO.SaleItemDTO(product.getProdId(), qty);
+            viewModel.addToCart(new SaleDTO.SaleItemDTO(product.getProdId(), qty));
-            cartItems.add(item);
-            addItemRow(product.getProdName(), qty, product.getProdPrice());
-            updateTotal();
             binding.etSaleQuantity.setText("");
         });
     }
 
+    private void renderCartItems() {
+        binding.llSaleItems.removeAllViews();
+        List<SaleDTO.SaleItemDTO> items = viewModel.getCartItems().getValue();
+        List<ProductDTO> products = viewModel.getProductList().getValue();
+        if (items == null || products == null) return;
+
+        for (SaleDTO.SaleItemDTO item : items) {
+            String name = "Unknown";
+            BigDecimal price = BigDecimal.ZERO;
+            for (ProductDTO p : products) {
+                if (p.getProdId().equals(item.getProdId())) {
+                    name = p.getProdName();
+                    price = p.getProdPrice();
+                    break;
+                }
+            }
+            addItemRow(name, item.getQuantity(), price);
+        }
+    }
+
     private void addItemRow(String name, int qty, BigDecimal price) {
         if (getContext() == null) return;
         LinearLayout row = new LinearLayout(getContext());
@@ -226,18 +214,15 @@ public class SaleDetailFragment extends Fragment {
         row.setPadding(0, 8, 0, 8);
 
         TextView tvName = new TextView(getContext());
-        tvName.setLayoutParams(new LinearLayout.LayoutParams(
+        tvName.setLayoutParams(new LinearLayout.LayoutParams(0, LinearLayout.LayoutParams.WRAP_CONTENT, 2f));
-                0, LinearLayout.LayoutParams.WRAP_CONTENT, 2f));
         tvName.setText(name);
 
         TextView tvQty = new TextView(getContext());
-        tvQty.setLayoutParams(new LinearLayout.LayoutParams(
+        tvQty.setLayoutParams(new LinearLayout.LayoutParams(0, LinearLayout.LayoutParams.WRAP_CONTENT, 1f));
-                0, LinearLayout.LayoutParams.WRAP_CONTENT, 1f));
         tvQty.setText("x" + qty);
 
         TextView tvPrice = new TextView(getContext());
-        tvPrice.setLayoutParams(new LinearLayout.LayoutParams(
+        tvPrice.setLayoutParams(new LinearLayout.LayoutParams(0, LinearLayout.LayoutParams.WRAP_CONTENT, 1f));
-                0, LinearLayout.LayoutParams.WRAP_CONTENT, 1f));
         tvPrice.setText(price != null ? "$" + price : "");
 
         row.addView(tvName);
@@ -247,16 +232,7 @@ public class SaleDetailFragment extends Fragment {
     }
 
     private void updateTotal() {
-        BigDecimal total = BigDecimal.ZERO;
+        BigDecimal total = viewModel.calculateSubtotal();
-        for (SaleDTO.SaleItemDTO item : cartItems) {
-            for (ProductDTO p : productList) {
-                if (p.getProdId().equals(item.getProdId()) && p.getProdPrice() != null) {
-                    total = total.add(p.getProdPrice()
-                            .multiply(BigDecimal.valueOf(item.getQuantity())));
-                    break;
-                }
-            }
-        }
         binding.tvSaleSubtotal.setText("$" + total);
         binding.tvSaleDetailTotal.setText("Total: $" + total);
     }
@@ -266,40 +242,28 @@ public class SaleDetailFragment extends Fragment {
             Toast.makeText(getContext(), "Select a store", Toast.LENGTH_SHORT).show();
             return;
         }
-        if (cartItems.isEmpty()) {
+        if (viewModel.getCartItems().getValue() == null || viewModel.getCartItems().getValue().isEmpty()) {
             Toast.makeText(getContext(), "Add at least one item", Toast.LENGTH_SHORT).show();
             return;
         }
 
-        DropdownDTO store = storeList.get(binding.spinnerSaleStore.getSelectedItemPosition() - 1);
+        DropdownDTO store = viewModel.getStoreList().getValue().get(binding.spinnerSaleStore.getSelectedItemPosition() - 1);
         String payment = PAYMENT_METHODS[binding.spinnerPaymentMethod.getSelectedItemPosition()];
 
-        // Optional customer
         Long customerId = null;
         if (binding.spinnerSaleCustomer.getSelectedItemPosition() > 0) {
-            customerId = customerList.get(binding.spinnerSaleCustomer.getSelectedItemPosition() - 1)
+            customerId = viewModel.getCustomerList().getValue().get(binding.spinnerSaleCustomer.getSelectedItemPosition() - 1).getId();
-                    .getId();
         }
 
-        SaleDTO dto = new SaleDTO(
+        SaleDTO dto = new SaleDTO(store.getId(), payment, viewModel.getCartItems().getValue(), false, null, customerId);
-                store.getId(),
-                payment,
-                cartItems,
-                false,
-                null,
-                customerId);
 
-        saleViewModel.createSale(dto).observe(getViewLifecycleOwner(), resource -> {
+        viewModel.createSale(dto).observe(getViewLifecycleOwner(), resource -> {
             if (resource != null) {
-                switch (resource.status) {
+                if (resource.status == Resource.Status.SUCCESS) {
-                    case SUCCESS:
                     Toast.makeText(getContext(), "Sale saved!", Toast.LENGTH_SHORT).show();
                     navigateBack();
-                        break;
+                } else if (resource.status == Resource.Status.ERROR) {
-                    case ERROR:
-                        Log.e("SALE_SAVE", "Error: " + resource.message);
                     DialogUtils.showInfoDialog(requireContext(), "Save Error", resource.message);
-                        break;
                 }
             }
         });
@@ -309,7 +273,7 @@ public class SaleDetailFragment extends Fragment {
         DialogUtils.showConfirmDialog(requireContext(), "Process Refund", 
             "Are you sure you want to process a refund for this sale?", () -> {
             Bundle args = new Bundle();
-            args.putLong("saleId", saleId);
+            args.putLong("saleId", viewModel.getSaleId());
             NavHostFragment.findNavController(this).navigate(R.id.nav_refund, args);
         });
     }

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

@@ -20,7 +20,7 @@ import com.example.petstoremobile.utils.ActivityLogger;
 import com.example.petstoremobile.utils.DialogUtils;
 import com.example.petstoremobile.utils.InputValidator;
 import com.example.petstoremobile.utils.Resource;
-import com.example.petstoremobile.viewmodels.ServiceViewModel;
+import com.example.petstoremobile.viewmodels.ServiceDetailViewModel;
 
 import dagger.hilt.android.AndroidEntryPoint;
 
@@ -31,15 +31,12 @@ import dagger.hilt.android.AndroidEntryPoint;
 public class ServiceDetailFragment extends Fragment {
 
     private FragmentServiceDetailBinding binding;
-    private long serviceId;
+    private ServiceDetailViewModel viewModel;
-    private boolean isEditing = false;
-
-    private ServiceViewModel viewModel;
 
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
-        viewModel = new ViewModelProvider(this).get(ServiceViewModel.class);
+        viewModel = new ViewModelProvider(this).get(ServiceDetailViewModel.class);
     }
 
     @Override
@@ -53,10 +50,8 @@ public class ServiceDetailFragment extends Fragment {
     public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
         super.onViewCreated(view, savedInstanceState);
 
-        //get controls from layout and display the view depending on the mode
         handleArguments();
 
-        //set button click listeners
         binding.btnBack.setOnClickListener(v -> navigateBack());
         binding.btnSaveService.setOnClickListener(v -> saveService());
         binding.btnDeleteService.setOnClickListener(v -> deleteService());
@@ -68,63 +63,44 @@ public class ServiceDetailFragment extends Fragment {
         binding = null;
     }
 
-    /**
-     * Handles the saving of service data (adding or updating).
-     */
     private void saveService() {
-        // Validates all fields using InputValidator
         if (!InputValidator.isNotEmpty(binding.etServiceName, "Service Name")) return;
         if (!InputValidator.isNotEmpty(binding.etServiceDesc, "Description")) return;
         if (!InputValidator.isPositiveInteger(binding.etServiceDuration, "Duration")) return;
         if (!InputValidator.isPositiveDecimal(binding.etServicePrice, "Price")) return;
 
-        //get all the values from the fields
         String name = binding.etServiceName.getText().toString().trim();
         String desc = binding.etServiceDesc.getText().toString().trim();
         int duration = Integer.parseInt(binding.etServiceDuration.getText().toString().trim());
         double price = Double.parseDouble(binding.etServicePrice.getText().toString().trim());
 
-        //create a service object to send to the API
         ServiceDTO serviceDTO = new ServiceDTO();
         serviceDTO.setServiceName(name);
         serviceDTO.setServiceDesc(desc);
         serviceDTO.setServiceDuration(duration);
         serviceDTO.setServicePrice(price);
 
-        //check if the service is being edited or added
+        viewModel.saveService(serviceDTO).observe(getViewLifecycleOwner(), resource -> {
-        if (isEditing) {
-            // Update existing service
-            serviceDTO.setServiceId(serviceId);
-            viewModel.updateService(serviceId, serviceDTO).observe(getViewLifecycleOwner(), resource -> {
             if (resource.status == Resource.Status.SUCCESS) {
-                    ActivityLogger.logChange(requireContext(), "Service", "UPDATED", (int) serviceId);
+                if (viewModel.isEditing()) {
+                    ActivityLogger.logChange(requireContext(), "Service", "UPDATED", (int) viewModel.getServiceId());
                     Toast.makeText(getContext(), "Service updated successfully!", Toast.LENGTH_SHORT).show();
-                    navigateBack();
-                } else if (resource.status == Resource.Status.ERROR) {
-                    Toast.makeText(getContext(), "Error: " + resource.message, Toast.LENGTH_SHORT).show();
-                }
-            });
                 } else {
-            viewModel.createService(serviceDTO).observe(getViewLifecycleOwner(), resource -> {
-                if (resource.status == Resource.Status.SUCCESS) {
                     ActivityLogger.log(requireContext(), "Added new Service: " + name);
                     Toast.makeText(getContext(), "Service added successfully!", Toast.LENGTH_SHORT).show();
+                }
                 navigateBack();
             } else if (resource.status == Resource.Status.ERROR) {
                 Toast.makeText(getContext(), "Error: " + resource.message, Toast.LENGTH_SHORT).show();
             }
         });
     }
-    }
 
-    /**
-     * Displays a confirmation dialog and handles the deletion of a service.
-     */
     private void deleteService() {
         DialogUtils.showDeleteConfirmDialog(requireContext(), "Service", () -> 
-                viewModel.deleteService(serviceId).observe(getViewLifecycleOwner(), resource -> {
+                viewModel.deleteService().observe(getViewLifecycleOwner(), resource -> {
                     if (resource.status == Resource.Status.SUCCESS) {
-                        ActivityLogger.logChange(requireContext(), "Service", "DELETED", (int) serviceId);
+                        ActivityLogger.logChange(requireContext(), "Service", "DELETED", (int) viewModel.getServiceId());
                         Toast.makeText(getContext(), "Service deleted successfully!", Toast.LENGTH_SHORT).show();
                         navigateBack();
                     } else if (resource.status == Resource.Status.ERROR) {
@@ -133,30 +109,20 @@ public class ServiceDetailFragment extends Fragment {
                 }));
     }
 
-    /**
-     * Navigates back to the previous screen.
-     */
     private void navigateBack() {
         NavHostFragment.findNavController(this).popBackStack();
     }
 
-    /**
-     * Handles arguments passed to the fragment to determine if it's in edit or add mode.
-     */
     private void handleArguments() {
-        // Service is being edited if the bundle contains a serviceId
         if (getArguments() != null && getArguments().containsKey("serviceId")) {
-            // Get service data from arguments and populate fields
+            long serviceId = getArguments().getLong("serviceId");
-            isEditing = true;
+            viewModel.setServiceId(serviceId);
-            serviceId = getArguments().getLong("serviceId");
             binding.tvMode.setText("Edit Service");
             binding.tvServiceId.setText("ID: " + serviceId);
             binding.btnDeleteService.setVisibility(View.VISIBLE);
             loadServiceData();
         } else {
-            // Service is being added
+            viewModel.setServiceId(-1);
-            // Set default values for add a new service
-            isEditing = false;
             binding.tvMode.setText("Add Service");
             binding.tvServiceId.setVisibility(View.GONE);
             binding.btnDeleteService.setVisibility(View.GONE);
@@ -164,11 +130,8 @@ public class ServiceDetailFragment extends Fragment {
         }
     }
 
-    /**
-     * Fetches specific service details from the backend using the ID.
-     */
     private void loadServiceData() {
-        viewModel.getServiceById(serviceId).observe(getViewLifecycleOwner(), resource -> {
+        viewModel.loadService().observe(getViewLifecycleOwner(), resource -> {
             if (resource == null) return;
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 ServiceDTO s = resource.data;

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

@@ -1,7 +1,6 @@
 package com.example.petstoremobile.fragments.listfragments.detailfragments;
 
 import android.os.Bundle;
-import android.util.Log;
 import android.view.*;
 import android.widget.*;
 import androidx.annotation.NonNull;
@@ -12,16 +11,15 @@ import androidx.navigation.fragment.NavHostFragment;
 import com.example.petstoremobile.R;
 import com.example.petstoremobile.databinding.FragmentStaffDetailBinding;
 import com.example.petstoremobile.dtos.EmployeeDTO;
-import com.example.petstoremobile.viewmodels.EmployeeViewModel;
+import com.example.petstoremobile.viewmodels.StaffDetailViewModel;
+import com.example.petstoremobile.utils.Resource;
 import dagger.hilt.android.AndroidEntryPoint;
 
 @AndroidEntryPoint
 public class StaffDetailFragment extends Fragment {
 
     private FragmentStaffDetailBinding binding;
-    private EmployeeViewModel employeeViewModel;
+    private StaffDetailViewModel viewModel;
-    private long employeeId = -1;
-    private boolean isEditing = false;
 
     private final String[] ROLES = {"STAFF", "ADMIN"};
     private final String[] STATUSES = {"Active", "Inactive"};
@@ -30,7 +28,7 @@ public class StaffDetailFragment extends Fragment {
     public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container,
                              Bundle savedInstanceState) {
         binding = FragmentStaffDetailBinding.inflate(inflater, container, false);
-        employeeViewModel = new ViewModelProvider(this).get(EmployeeViewModel.class);
+        viewModel = new ViewModelProvider(this).get(StaffDetailViewModel.class);
         
         setupSpinners();
         handleArguments();
@@ -51,8 +49,8 @@ public class StaffDetailFragment extends Fragment {
     private void handleArguments() {
         Bundle a = getArguments();
         if (a != null && a.getBoolean("isEditing", false)) {
-            isEditing = true;
+            long employeeId = a.getLong("employeeId", -1);
-            employeeId = a.getLong("employeeId", -1);
+            viewModel.setEmployeeId(employeeId, true);
 
             binding.tvStaffMode.setText("Edit Staff Account");
             binding.tvStaffId.setText("ID: " + employeeId);
@@ -64,7 +62,6 @@ public class StaffDetailFragment extends Fragment {
             binding.etStaffPhone.setText(a.getString("phone", ""));
             binding.btnDeleteStaff.setVisibility(View.VISIBLE);
 
-            // Pre-fill role
             String role = a.getString("role", "STAFF");
             for (int i = 0; i < ROLES.length; i++) {
                 if (ROLES[i].equals(role)) {
@@ -73,13 +70,11 @@ public class StaffDetailFragment extends Fragment {
                 }
             }
 
-            // Pre-fill status
             boolean active = a.getBoolean("active", true);
             binding.spinnerStaffStatus.setSelection(active ? 0 : 1);
 
         } else {
-            isEditing = false;
+            viewModel.setEmployeeId(-1, false);
-            employeeId = -1;
             binding.tvStaffMode.setText("Add Staff Account");
             binding.btnDeleteStaff.setVisibility(View.GONE);
             binding.tvStaffId.setVisibility(View.GONE);
@@ -97,12 +92,11 @@ public class StaffDetailFragment extends Fragment {
         String role      = ROLES[binding.spinnerStaffRole.getSelectedItemPosition()];
         boolean active   = binding.spinnerStaffStatus.getSelectedItemPosition() == 0;
 
-        // Validation
         if (username.isEmpty()) { binding.etStaffUsername.setError("Required"); return; }
-        if (!isEditing && password.isEmpty()) {
+        if (!viewModel.isEditing() && password.isEmpty()) {
             binding.etStaffPassword.setError("Required for new account"); return;
         }
-        if (!isEditing && password.length() < 6) {
+        if (!viewModel.isEditing() && password.length() < 6) {
             binding.etStaffPassword.setError("At least 6 characters"); return;
         }
         if (firstName.isEmpty()) { binding.etStaffFirstName.setError("Required"); return; }
@@ -121,35 +115,16 @@ public class StaffDetailFragment extends Fragment {
                 active
         );
 
-        if (isEditing && employeeId > 0) {
+        viewModel.saveEmployee(dto).observe(getViewLifecycleOwner(), resource -> {
-            employeeViewModel.updateEmployee(employeeId, dto).observe(getViewLifecycleOwner(), resource -> {
             if (resource != null) {
-                    switch (resource.status) {
+                if (resource.status == Resource.Status.SUCCESS) {
-                        case SUCCESS:
+                    Toast.makeText(getContext(), viewModel.isEditing() ? "Updated successfully" : "Staff account created", Toast.LENGTH_SHORT).show();
-                            Toast.makeText(getContext(), "Updated successfully", Toast.LENGTH_SHORT).show();
                     navigateBack();
-                            break;
+                } else if (resource.status == Resource.Status.ERROR) {
-                        case ERROR:
                     Toast.makeText(getContext(), "Error: " + resource.message, Toast.LENGTH_LONG).show();
-                            break;
                 }
             }
         });
-        } else {
-            employeeViewModel.createEmployee(dto).observe(getViewLifecycleOwner(), resource -> {
-                if (resource != null) {
-                    switch (resource.status) {
-                        case SUCCESS:
-                            Toast.makeText(getContext(), "Staff account created", Toast.LENGTH_SHORT).show();
-                            navigateBack();
-                            break;
-                        case ERROR:
-                            Toast.makeText(getContext(), "Error: " + resource.message, Toast.LENGTH_LONG).show();
-                            break;
-                    }
-                }
-            });
-        }
     }
 
     private void confirmDelete() {
@@ -157,16 +132,13 @@ public class StaffDetailFragment extends Fragment {
                 .setTitle("Delete Staff Account?")
                 .setMessage("This will permanently delete this staff account.")
                 .setPositiveButton("Yes", (d, w) ->
-                        employeeViewModel.deleteEmployee(employeeId).observe(getViewLifecycleOwner(), resource -> {
+                        viewModel.deleteEmployee().observe(getViewLifecycleOwner(), resource -> {
                             if (resource != null) {
-                                switch (resource.status) {
+                                if (resource.status == Resource.Status.SUCCESS) {
-                                    case SUCCESS:
                                     navigateBack();
-                                        break;
+                                } else if (resource.status == Resource.Status.ERROR) {
-                                    case ERROR:
                                     Toast.makeText(getContext(), "Delete failed: " + resource.message,
                                             Toast.LENGTH_SHORT).show();
-                                        break;
                                 }
                             }
                         }))

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

@@ -20,7 +20,7 @@ import com.example.petstoremobile.utils.DialogUtils;
 import com.example.petstoremobile.utils.InputValidator;
 import com.example.petstoremobile.utils.Resource;
 import com.example.petstoremobile.utils.UIUtils;
-import com.example.petstoremobile.viewmodels.SupplierViewModel;
+import com.example.petstoremobile.viewmodels.SupplierDetailViewModel;
 
 import dagger.hilt.android.AndroidEntryPoint;
 
@@ -31,15 +31,12 @@ import dagger.hilt.android.AndroidEntryPoint;
 public class SupplierDetailFragment extends Fragment {
 
     private FragmentSupplierDetailBinding binding;
-    private long supId;
+    private SupplierDetailViewModel viewModel;
-    private boolean isEditing = false;
-
-    private SupplierViewModel viewModel;
 
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
-        viewModel = new ViewModelProvider(this).get(SupplierViewModel.class);
+        viewModel = new ViewModelProvider(this).get(SupplierDetailViewModel.class);
     }
 
     @Override
@@ -53,12 +50,9 @@ public class SupplierDetailFragment extends Fragment {
     public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
         super.onViewCreated(view, savedInstanceState);
 
-        // Add phone number formatting (CA) and limit length to 14 characters
         UIUtils.formatPhoneInput(binding.etSupPhone);
-
         handleArguments();
 
-        //set button click listeners
         binding.btnBack.setOnClickListener(v -> navigateBack());
         binding.btnSaveSupplier.setOnClickListener(v -> saveSupplier());
         binding.btnDeleteSupplier.setOnClickListener(v -> deleteSupplier());
@@ -70,25 +64,19 @@ public class SupplierDetailFragment extends Fragment {
         binding = null;
     }
 
-    /**
-     * Handles the saving of supplier data (adding or updating).
-     */
     private void saveSupplier() {
-        // Validates all fields using InputValidator
         if (!InputValidator.isNotEmpty(binding.etSupCompany, "Company Name")) return;
         if (!InputValidator.isNotEmpty(binding.etSupContactFirstName, "First Name")) return;
         if (!InputValidator.isNotEmpty(binding.etSupContactLastName, "Last Name")) return;
         if (!InputValidator.isValidEmail(binding.etSupEmail)) return;
         if (!InputValidator.isValidPhone(binding.etSupPhone)) return;
 
-        //get all the values from the fields
         String company = binding.etSupCompany.getText().toString().trim();
         String firstName = binding.etSupContactFirstName.getText().toString().trim();
         String lastName = binding.etSupContactLastName.getText().toString().trim();
         String email = binding.etSupEmail.getText().toString().trim();
         String phone = binding.etSupPhone.getText().toString().trim();
 
-        //create a supplier object to send to the API
         SupplierDTO supplierDTO = new SupplierDTO();
         supplierDTO.setSupCompany(company);
         supplierDTO.setSupContactFirstName(firstName);
@@ -96,41 +84,27 @@ public class SupplierDetailFragment extends Fragment {
         supplierDTO.setSupEmail(email);
         supplierDTO.setSupPhone(phone);
 
-        //check if the supplier is being edited or added
+        viewModel.saveSupplier(supplierDTO).observe(getViewLifecycleOwner(), resource -> {
-        if (isEditing) {
-            // Update existing supplier
-            supplierDTO.setSupId(supId);
-            viewModel.updateSupplier(supId, supplierDTO).observe(getViewLifecycleOwner(), resource -> {
             if (resource.status == Resource.Status.SUCCESS) {
-                    ActivityLogger.logChange(requireContext(), "Supplier", "UPDATED", (int) supId);
+                if (viewModel.isEditing()) {
+                    ActivityLogger.logChange(requireContext(), "Supplier", "UPDATED", (int) viewModel.getSupId());
                     Toast.makeText(getContext(), "Supplier updated successfully!", Toast.LENGTH_SHORT).show();
-                    navigateBack();
-                } else if (resource.status == Resource.Status.ERROR) {
-                    Toast.makeText(getContext(), "Error: " + resource.message, Toast.LENGTH_SHORT).show();
-                }
-            });
                 } else {
-            // Add new supplier
-            viewModel.createSupplier(supplierDTO).observe(getViewLifecycleOwner(), resource -> {
-                if (resource.status == Resource.Status.SUCCESS) {
                     ActivityLogger.log(requireContext(), "Added new Supplier: " + company);
                     Toast.makeText(getContext(), "Supplier added successfully!", Toast.LENGTH_SHORT).show();
+                }
                 navigateBack();
             } else if (resource.status == Resource.Status.ERROR) {
                 Toast.makeText(getContext(), "Error: " + resource.message, Toast.LENGTH_SHORT).show();
             }
         });
     }
-    }
 
-    /**
-     * Displays a confirmation dialog and handles the deletion of a supplier.
-     */
     private void deleteSupplier() {
         DialogUtils.showDeleteConfirmDialog(requireContext(), "Supplier", () ->
-                viewModel.deleteSupplier(supId).observe(getViewLifecycleOwner(), resource -> {
+                viewModel.deleteSupplier().observe(getViewLifecycleOwner(), resource -> {
                     if (resource.status == Resource.Status.SUCCESS) {
-                        ActivityLogger.logChange(requireContext(), "Supplier", "DELETED", (int) supId);
+                        ActivityLogger.logChange(requireContext(), "Supplier", "DELETED", (int) viewModel.getSupId());
                         Toast.makeText(getContext(), "Supplier deleted successfully!", Toast.LENGTH_SHORT).show();
                         navigateBack();
                     } else if (resource.status == Resource.Status.ERROR) {
@@ -139,31 +113,21 @@ public class SupplierDetailFragment extends Fragment {
                 }));
     }
 
-    /**
-     * Navigates back to the previous screen.
-     */
     private void navigateBack() {
         NavHostFragment.findNavController(this).popBackStack();
     }
 
-    /**
-     * Handles arguments passed to the fragment to determine if it's in edit or add mode.
-     */
     private void handleArguments() {
-        // Supplier is being edited if the bundle contains a supId
         if (getArguments() != null && getArguments().containsKey("supId")) {
-            // Get supplier data from arguments and populate fields
+            long supId = getArguments().getLong("supId");
-            isEditing = true;
+            viewModel.setSupId(supId);
-            supId = getArguments().getLong("supId");
             binding.tvMode.setText("Edit Supplier");
             binding.tvSupId.setText("ID: " + supId);
             binding.tvSupId.setVisibility(View.VISIBLE);
             binding.btnDeleteSupplier.setVisibility(View.VISIBLE);
             loadSupplierData();
         } else {
-            // Supplier is being added
+            viewModel.setSupId(-1);
-            // Set default values for add a new supplier
-            isEditing = false;
             binding.tvMode.setText("Add Supplier");
             binding.tvSupId.setVisibility(View.GONE);
             binding.btnDeleteSupplier.setVisibility(View.GONE);
@@ -171,11 +135,8 @@ public class SupplierDetailFragment extends Fragment {
         }
     }
 
-    /**
-     * Fetches specific supplier details from the backend using the ID.
-     */
     private void loadSupplierData() {
-        viewModel.getSupplierById(supId).observe(getViewLifecycleOwner(), resource -> {
+        viewModel.loadSupplier().observe(getViewLifecycleOwner(), resource -> {
             if (resource == null) return;
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 SupplierDTO s = resource.data;

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

@@ -0,0 +1,102 @@
+package com.example.petstoremobile.viewmodels;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+import androidx.lifecycle.ViewModel;
+
+import com.example.petstoremobile.dtos.AdoptionDTO;
+import com.example.petstoremobile.dtos.DropdownDTO;
+import com.example.petstoremobile.repositories.AdoptionRepository;
+import com.example.petstoremobile.repositories.CustomerRepository;
+import com.example.petstoremobile.repositories.PetRepository;
+import com.example.petstoremobile.repositories.StoreRepository;
+import com.example.petstoremobile.utils.Resource;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import javax.inject.Inject;
+
+import dagger.hilt.android.lifecycle.HiltViewModel;
+
+@HiltViewModel
+public class AdoptionDetailViewModel extends ViewModel {
+    private final AdoptionRepository adoptionRepository;
+    private final PetRepository petRepository;
+    private final CustomerRepository customerRepository;
+    private final StoreRepository storeRepository;
+
+    private long adoptionId = -1;
+    private boolean isEditing = false;
+
+    private final MutableLiveData<List<DropdownDTO>> petList = new MutableLiveData<>(new ArrayList<>());
+    private final MutableLiveData<List<DropdownDTO>> customerList = new MutableLiveData<>(new ArrayList<>());
+    private final MutableLiveData<List<DropdownDTO>> storeList = new MutableLiveData<>(new ArrayList<>());
+    private final MutableLiveData<List<DropdownDTO>> employeeList = new MutableLiveData<>(new ArrayList<>());
+
+    @Inject
+    public AdoptionDetailViewModel(AdoptionRepository adoptionRepository, PetRepository petRepository,
+                                   CustomerRepository customerRepository, StoreRepository storeRepository) {
+        this.adoptionRepository = adoptionRepository;
+        this.petRepository = petRepository;
+        this.customerRepository = customerRepository;
+        this.storeRepository = storeRepository;
+    }
+
+    public void setAdoptionId(long id) {
+        this.adoptionId = id;
+        this.isEditing = id != -1;
+    }
+
+    public long getAdoptionId() {
+        return adoptionId;
+    }
+
+    public boolean isEditing() {
+        return isEditing;
+    }
+
+    public LiveData<Resource<AdoptionDTO>> loadAdoption() {
+        return adoptionRepository.getAdoptionById(adoptionId);
+    }
+
+    public LiveData<Resource<List<DropdownDTO>>> loadPets() {
+        return petRepository.getAdoptionPets();
+    }
+
+    public LiveData<Resource<List<DropdownDTO>>> loadCustomers() {
+        return customerRepository.getCustomerDropdowns();
+    }
+
+    public LiveData<Resource<List<DropdownDTO>>> loadStores() {
+        return storeRepository.getStoreDropdowns();
+    }
+
+    public LiveData<Resource<List<DropdownDTO>>> loadEmployees(Long storeId) {
+        return storeRepository.getStoreEmployees(storeId);
+    }
+
+    public LiveData<Resource<AdoptionDTO>> saveAdoption(AdoptionDTO dto) {
+        if (isEditing) {
+            return adoptionRepository.updateAdoption(adoptionId, dto);
+        } else {
+            return adoptionRepository.createAdoption(dto);
+        }
+    }
+
+    public LiveData<Resource<Void>> deleteAdoption() {
+        return adoptionRepository.deleteAdoption(adoptionId);
+    }
+
+    public void setPetList(List<DropdownDTO> list) { petList.setValue(list); }
+    public LiveData<List<DropdownDTO>> getPetList() { return petList; }
+
+    public void setCustomerList(List<DropdownDTO> list) { customerList.setValue(list); }
+    public LiveData<List<DropdownDTO>> getCustomerList() { return customerList; }
+
+    public void setStoreList(List<DropdownDTO> list) { storeList.setValue(list); }
+    public LiveData<List<DropdownDTO>> getStoreList() { return storeList; }
+
+    public void setEmployeeList(List<DropdownDTO> list) { employeeList.setValue(list); }
+    public LiveData<List<DropdownDTO>> getEmployeeList() { return employeeList; }
+}

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

@@ -0,0 +1,79 @@
+package com.example.petstoremobile.viewmodels;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+import androidx.lifecycle.ViewModel;
+
+import com.example.petstoremobile.dtos.DropdownDTO;
+import com.example.petstoremobile.dtos.InventoryDTO;
+import com.example.petstoremobile.dtos.PageResponse;
+import com.example.petstoremobile.dtos.ProductDTO;
+import com.example.petstoremobile.repositories.InventoryRepository;
+import com.example.petstoremobile.repositories.ProductRepository;
+import com.example.petstoremobile.repositories.StoreRepository;
+import com.example.petstoremobile.utils.Resource;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import javax.inject.Inject;
+
+import dagger.hilt.android.lifecycle.HiltViewModel;
+
+@HiltViewModel
+public class InventoryDetailViewModel extends ViewModel {
+    private final InventoryRepository inventoryRepository;
+    private final StoreRepository storeRepository;
+    private final ProductRepository productRepository;
+
+    private long inventoryId = -1;
+    private boolean isEditing = false;
+
+    private final MutableLiveData<List<DropdownDTO>> storeList = new MutableLiveData<>(new ArrayList<>());
+    private final MutableLiveData<List<ProductDTO>> productList = new MutableLiveData<>(new ArrayList<>());
+
+    @Inject
+    public InventoryDetailViewModel(InventoryRepository inventoryRepository, StoreRepository storeRepository, ProductRepository productRepository) {
+        this.inventoryRepository = inventoryRepository;
+        this.storeRepository = storeRepository;
+        this.productRepository = productRepository;
+    }
+
+    public void setInventoryId(long id) {
+        this.inventoryId = id;
+        this.isEditing = id != -1;
+    }
+
+    public long getInventoryId() { return inventoryId; }
+    public boolean isEditing() { return isEditing; }
+
+    public LiveData<Resource<InventoryDTO>> loadInventory() {
+        return inventoryRepository.getInventoryById(inventoryId);
+    }
+
+    public LiveData<Resource<List<DropdownDTO>>> loadStores() {
+        return storeRepository.getStoreDropdowns();
+    }
+
+    public LiveData<Resource<PageResponse<ProductDTO>>> loadProducts() {
+        return productRepository.getAllProducts(null, null, 0, 500, "prodName");
+    }
+
+    public LiveData<Resource<InventoryDTO>> saveInventory(InventoryDTO dto) {
+        if (isEditing) {
+            return inventoryRepository.updateInventory(inventoryId, dto);
+        } else {
+            return inventoryRepository.createInventory(dto);
+        }
+    }
+
+    public LiveData<Resource<Void>> deleteInventory() {
+        return inventoryRepository.deleteInventory(inventoryId);
+    }
+
+    public void setStoreList(List<DropdownDTO> list) { storeList.setValue(list); }
+    public LiveData<List<DropdownDTO>> getStoreList() { return storeList; }
+
+    public void setProductList(List<ProductDTO> list) { productList.setValue(list); }
+    public LiveData<List<ProductDTO>> getProductList() { return productList; }
+}

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

@@ -0,0 +1,94 @@
+package com.example.petstoremobile.viewmodels;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+import androidx.lifecycle.ViewModel;
+
+import com.example.petstoremobile.dtos.DropdownDTO;
+import com.example.petstoremobile.dtos.PetDTO;
+import com.example.petstoremobile.repositories.CustomerRepository;
+import com.example.petstoremobile.repositories.PetRepository;
+import com.example.petstoremobile.repositories.StoreRepository;
+import com.example.petstoremobile.utils.Resource;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import javax.inject.Inject;
+
+import dagger.hilt.android.lifecycle.HiltViewModel;
+
+@HiltViewModel
+public class PetDetailViewModel extends ViewModel {
+    private final PetRepository petRepository;
+    private final CustomerRepository customerRepository;
+    private final StoreRepository storeRepository;
+
+    private final MutableLiveData<PetDTO> petState = new MutableLiveData<>();
+    private final MutableLiveData<List<DropdownDTO>> customerList = new MutableLiveData<>(new ArrayList<>());
+    private final MutableLiveData<List<DropdownDTO>> storeList = new MutableLiveData<>(new ArrayList<>());
+    
+    private long petId = -1;
+    private boolean isEditing = false;
+
+    @Inject
+    public PetDetailViewModel(PetRepository petRepository, CustomerRepository customerRepository, StoreRepository storeRepository) {
+        this.petRepository = petRepository;
+        this.customerRepository = customerRepository;
+        this.storeRepository = storeRepository;
+    }
+
+    public void setPetId(long id) {
+        this.petId = id;
+        this.isEditing = id != -1;
+    }
+
+    public long getPetId() {
+        return petId;
+    }
+
+    public boolean isEditing() {
+        return isEditing;
+    }
+
+    public LiveData<Resource<PetDTO>> loadPet() {
+        return petRepository.getPetById(petId);
+    }
+
+    public LiveData<Resource<List<DropdownDTO>>> loadCustomers() {
+        return customerRepository.getCustomerDropdowns();
+    }
+
+    public LiveData<Resource<List<DropdownDTO>>> loadStores() {
+        return storeRepository.getStoreDropdowns();
+    }
+
+    public LiveData<Resource<PetDTO>> savePet(PetDTO petDTO) {
+        if (isEditing) {
+            petDTO.setPetId(petId);
+            return petRepository.updatePet(petId, petDTO);
+        } else {
+            return petRepository.createPet(petDTO);
+        }
+    }
+
+    public LiveData<Resource<Void>> deletePet() {
+        return petRepository.deletePet(petId);
+    }
+
+    public void setCustomerList(List<DropdownDTO> list) {
+        customerList.setValue(list);
+    }
+
+    public LiveData<List<DropdownDTO>> getCustomerList() {
+        return customerList;
+    }
+
+    public void setStoreList(List<DropdownDTO> list) {
+        storeList.setValue(list);
+    }
+
+    public LiveData<List<DropdownDTO>> getStoreList() {
+        return storeList;
+    }
+}

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

@@ -0,0 +1,85 @@
+package com.example.petstoremobile.viewmodels;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+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 java.util.ArrayList;
+import java.util.List;
+
+import javax.inject.Inject;
+
+import dagger.hilt.android.lifecycle.HiltViewModel;
+import okhttp3.MultipartBody;
+
+@HiltViewModel
+public class ProductDetailViewModel extends ViewModel {
+    private final ProductRepository productRepository;
+    private final CategoryRepository categoryRepository;
+
+    private final MutableLiveData<List<CategoryDTO>> categoryList = new MutableLiveData<>(new ArrayList<>());
+    private long prodId = -1;
+    private boolean isEditing = false;
+
+    @Inject
+    public ProductDetailViewModel(ProductRepository productRepository, CategoryRepository categoryRepository) {
+        this.productRepository = productRepository;
+        this.categoryRepository = categoryRepository;
+    }
+
+    public void setProdId(long id) {
+        this.prodId = id;
+        this.isEditing = id != -1;
+    }
+
+    public long getProdId() {
+        return prodId;
+    }
+
+    public boolean isEditing() {
+        return isEditing;
+    }
+
+    public LiveData<Resource<PageResponse<CategoryDTO>>> loadCategories() {
+        return categoryRepository.getAllCategories(0, 100);
+    }
+
+    public LiveData<Resource<ProductDTO>> loadProduct() {
+        return productRepository.getProductById(prodId);
+    }
+
+    public LiveData<Resource<ProductDTO>> saveProduct(ProductDTO dto) {
+        if (isEditing) {
+            return productRepository.updateProduct(prodId, dto);
+        } else {
+            return productRepository.createProduct(dto);
+        }
+    }
+
+    public LiveData<Resource<Void>> deleteProduct() {
+        return productRepository.deleteProduct(prodId);
+    }
+
+    public LiveData<Resource<Void>> uploadProductImage(MultipartBody.Part image) {
+        return productRepository.uploadProductImage(prodId, image);
+    }
+
+    public LiveData<Resource<Void>> deleteProductImage() {
+        return productRepository.deleteProductImage(prodId);
+    }
+
+    public void setCategoryList(List<CategoryDTO> list) {
+        categoryList.setValue(list);
+    }
+
+    public LiveData<List<CategoryDTO>> getCategoryList() {
+        return categoryList;
+    }
+}

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

@@ -0,0 +1,78 @@
+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.ProductDTO;
+import com.example.petstoremobile.dtos.ProductSupplierDTO;
+import com.example.petstoremobile.dtos.SupplierDTO;
+import com.example.petstoremobile.repositories.ProductRepository;
+import com.example.petstoremobile.repositories.ProductSupplierRepository;
+import com.example.petstoremobile.repositories.SupplierRepository;
+import com.example.petstoremobile.utils.Resource;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import javax.inject.Inject;
+
+import dagger.hilt.android.lifecycle.HiltViewModel;
+
+@HiltViewModel
+public class ProductSupplierDetailViewModel extends ViewModel {
+    private final ProductSupplierRepository psRepository;
+    private final ProductRepository productRepository;
+    private final SupplierRepository supplierRepository;
+
+    private boolean isEditing = false;
+    private long editProductId = -1;
+    private long editSupplierId = -1;
+
+    private final MutableLiveData<List<ProductDTO>> productList = new MutableLiveData<>(new ArrayList<>());
+    private final MutableLiveData<List<SupplierDTO>> supplierList = new MutableLiveData<>(new ArrayList<>());
+
+    @Inject
+    public ProductSupplierDetailViewModel(ProductSupplierRepository psRepository, ProductRepository productRepository, SupplierRepository supplierRepository) {
+        this.psRepository = psRepository;
+        this.productRepository = productRepository;
+        this.supplierRepository = supplierRepository;
+    }
+
+    public void setEditMode(long productId, long supplierId) {
+        this.isEditing = true;
+        this.editProductId = productId;
+        this.editSupplierId = supplierId;
+    }
+
+    public boolean isEditing() { return isEditing; }
+    public long getEditProductId() { return editProductId; }
+    public long getEditSupplierId() { return editSupplierId; }
+
+    public LiveData<Resource<PageResponse<ProductDTO>>> loadProducts() {
+        return productRepository.getAllProducts(null, null, 0, 200, "prodName");
+    }
+
+    public LiveData<Resource<PageResponse<SupplierDTO>>> loadSuppliers() {
+        return supplierRepository.getAllSuppliers(0, 200, null, "supCompany");
+    }
+
+    public LiveData<Resource<ProductSupplierDTO>> saveProductSupplier(ProductSupplierDTO dto) {
+        if (isEditing) {
+            return psRepository.updateProductSupplier(editProductId, editSupplierId, dto);
+        } else {
+            return psRepository.createProductSupplier(dto);
+        }
+    }
+
+    public LiveData<Resource<Void>> deleteProductSupplier() {
+        return psRepository.deleteProductSupplier(editProductId, editSupplierId);
+    }
+
+    public void setProductList(List<ProductDTO> list) { productList.setValue(list); }
+    public LiveData<List<ProductDTO>> getProductList() { return productList; }
+
+    public void setSupplierList(List<SupplierDTO> list) { supplierList.setValue(list); }
+    public LiveData<List<SupplierDTO>> getSupplierList() { return supplierList; }
+}

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

@@ -0,0 +1,26 @@
+package com.example.petstoremobile.viewmodels;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.ViewModel;
+
+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 PurchaseOrderDetailViewModel extends ViewModel {
+    private final PurchaseOrderRepository repository;
+
+    @Inject
+    public PurchaseOrderDetailViewModel(PurchaseOrderRepository repository) {
+        this.repository = repository;
+    }
+
+    public LiveData<Resource<PurchaseOrderDTO>> loadPurchaseOrder(long id) {
+        return repository.getPurchaseOrderById(id);
+    }
+}

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

@@ -0,0 +1,167 @@
+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.SaleDTO;
+import com.example.petstoremobile.repositories.SaleRepository;
+import com.example.petstoremobile.utils.Resource;
+
+import java.math.BigDecimal;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import javax.inject.Inject;
+
+import dagger.hilt.android.lifecycle.HiltViewModel;
+
+@HiltViewModel
+public class RefundViewModel extends ViewModel {
+    private final SaleRepository saleRepository;
+
+    private final MutableLiveData<List<SaleDTO>> allSales = new MutableLiveData<>(new ArrayList<>());
+    private final MutableLiveData<SaleDTO> currentSale = new MutableLiveData<>();
+    private final MutableLiveData<List<RefundItem>> availableItems = new MutableLiveData<>(new ArrayList<>());
+    private final MutableLiveData<List<RefundItem>> refundCart = new MutableLiveData<>(new ArrayList<>());
+
+    @Inject
+    public RefundViewModel(SaleRepository saleRepository) {
+        this.saleRepository = saleRepository;
+    }
+
+    public LiveData<Resource<PageResponse<SaleDTO>>> loadAllSales() {
+        return saleRepository.getAllSales(0, 1000, null, null, null, "saleDate,desc");
+    }
+
+    public void setAllSales(List<SaleDTO> sales) {
+        allSales.setValue(sales);
+    }
+
+    public List<SaleDTO> getAllSalesList() {
+        return allSales.getValue();
+    }
+
+    public void setCurrentSale(SaleDTO sale) {
+        currentSale.setValue(sale);
+        buildRefundableItems();
+    }
+
+    public SaleDTO getCurrentSale() {
+        return currentSale.getValue();
+    }
+
+    public LiveData<List<RefundItem>> getAvailableItems() {
+        return availableItems;
+    }
+
+    public LiveData<List<RefundItem>> getRefundCart() {
+        return refundCart;
+    }
+
+    private void buildRefundableItems() {
+        SaleDTO sale = currentSale.getValue();
+        List<SaleDTO> sales = allSales.getValue();
+        if (sale == null || sales == null || sale.getItems() == null) {
+            availableItems.setValue(new ArrayList<>());
+            return;
+        }
+
+        Map<Long, Integer> alreadyRefunded = new HashMap<>();
+        for (SaleDTO s : sales) {
+            if (Boolean.TRUE.equals(s.getIsRefund())
+                    && sale.getSaleId().equals(s.getOriginalSaleId())
+                    && s.getItems() != null) {
+                for (SaleDTO.SaleItemDTO item : s.getItems()) {
+                    if (item.getProdId() != null && item.getQuantity() != null) {
+                        alreadyRefunded.merge(item.getProdId(),
+                                Math.abs(item.getQuantity()), Integer::sum);
+                    }
+                }
+            }
+        }
+
+        List<RefundItem> items = new ArrayList<>();
+        for (SaleDTO.SaleItemDTO item : sale.getItems()) {
+            if (item.getProdId() == null || item.getQuantity() == null) continue;
+            int refunded = alreadyRefunded.getOrDefault(item.getProdId(), 0);
+            int remaining = item.getQuantity() - refunded;
+            if (remaining > 0) {
+                items.add(new RefundItem(
+                        item.getProdId(),
+                        item.getProductName() != null ? item.getProductName() : "Unknown",
+                        remaining,
+                        item.getUnitPrice()
+                ));
+            }
+        }
+        availableItems.setValue(items);
+        refundCart.setValue(new ArrayList<>());
+    }
+
+    public void addToCart(RefundItem item, int qty) {
+        List<RefundItem> cart = new ArrayList<>(refundCart.getValue());
+        boolean merged = false;
+        for (int i = 0; i < cart.size(); i++) {
+            if (cart.get(i).prodId == item.prodId) {
+                RefundItem existing = cart.get(i);
+                cart.set(i, new RefundItem(existing.prodId, existing.productName, existing.quantity + qty, existing.unitPrice));
+                merged = true;
+                break;
+            }
+        }
+        if (!merged) {
+            cart.add(new RefundItem(item.prodId, item.productName, qty, item.unitPrice));
+        }
+        refundCart.setValue(cart);
+    }
+
+    public void removeFromCart(RefundItem item) {
+        List<RefundItem> cart = new ArrayList<>(refundCart.getValue());
+        cart.remove(item);
+        refundCart.setValue(cart);
+    }
+
+    public LiveData<Resource<SaleDTO>> submitRefund(String paymentMethod) {
+        SaleDTO sale = currentSale.getValue();
+        List<RefundItem> cart = refundCart.getValue();
+        if (sale == null || cart == null || cart.isEmpty()) return null;
+
+        List<SaleDTO.SaleItemDTO> items = new ArrayList<>();
+        for (RefundItem item : cart) {
+            items.add(new SaleDTO.SaleItemDTO(item.prodId, -item.quantity));
+        }
+
+        SaleDTO dto = new SaleDTO(
+                sale.getStoreId(),
+                paymentMethod,
+                items,
+                true,
+                sale.getSaleId(),
+                null
+        );
+
+        return saleRepository.createSale(dto);
+    }
+
+    public static class RefundItem {
+        public long prodId;
+        public String productName;
+        public int quantity;
+        public BigDecimal unitPrice;
+
+        public RefundItem(long prodId, String productName, int quantity, BigDecimal unitPrice) {
+            this.prodId = prodId;
+            this.productName = productName;
+            this.quantity = quantity;
+            this.unitPrice = unitPrice;
+        }
+
+        public BigDecimal getTotal() {
+            return unitPrice != null ? unitPrice.multiply(BigDecimal.valueOf(quantity)) : BigDecimal.ZERO;
+        }
+    }
+}

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

@@ -0,0 +1,109 @@
+package com.example.petstoremobile.viewmodels;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+import androidx.lifecycle.ViewModel;
+
+import com.example.petstoremobile.dtos.DropdownDTO;
+import com.example.petstoremobile.dtos.ProductDTO;
+import com.example.petstoremobile.dtos.SaleDTO;
+import com.example.petstoremobile.repositories.CustomerRepository;
+import com.example.petstoremobile.repositories.ProductRepository;
+import com.example.petstoremobile.repositories.SaleRepository;
+import com.example.petstoremobile.repositories.StoreRepository;
+import com.example.petstoremobile.utils.Resource;
+
+import java.math.BigDecimal;
+import java.util.ArrayList;
+import java.util.List;
+
+import javax.inject.Inject;
+
+import dagger.hilt.android.lifecycle.HiltViewModel;
+
+@HiltViewModel
+public class SaleDetailViewModel extends ViewModel {
+    private final SaleRepository saleRepository;
+    private final StoreRepository storeRepository;
+    private final CustomerRepository customerRepository;
+    private final ProductRepository productRepository;
+
+    private long saleId = -1;
+    private boolean viewOnly = false;
+
+    private final MutableLiveData<List<DropdownDTO>> storeList = new MutableLiveData<>(new ArrayList<>());
+    private final MutableLiveData<List<DropdownDTO>> customerList = new MutableLiveData<>(new ArrayList<>());
+    private final MutableLiveData<List<ProductDTO>> productList = new MutableLiveData<>(new ArrayList<>());
+    private final MutableLiveData<List<SaleDTO.SaleItemDTO>> cartItems = new MutableLiveData<>(new ArrayList<>());
+
+    @Inject
+    public SaleDetailViewModel(SaleRepository saleRepository, StoreRepository storeRepository,
+                               CustomerRepository customerRepository, ProductRepository productRepository) {
+        this.saleRepository = saleRepository;
+        this.storeRepository = storeRepository;
+        this.customerRepository = customerRepository;
+        this.productRepository = productRepository;
+    }
+
+    public void setSaleId(long id, boolean viewOnly) {
+        this.saleId = id;
+        this.viewOnly = viewOnly;
+    }
+
+    public long getSaleId() { return saleId; }
+    public boolean isViewOnly() { return viewOnly; }
+
+    public LiveData<Resource<SaleDTO>> loadSaleDetails() {
+        return saleRepository.getSaleById(saleId);
+    }
+
+    public LiveData<Resource<List<DropdownDTO>>> loadStores() {
+        return storeRepository.getStoreDropdowns();
+    }
+
+    public LiveData<Resource<List<DropdownDTO>>> loadCustomers() {
+        return customerRepository.getCustomerDropdowns();
+    }
+
+    public LiveData<Resource<com.example.petstoremobile.dtos.PageResponse<ProductDTO>>> loadProducts() {
+        return productRepository.getAllProducts(null, null, 0, 200, null);
+    }
+
+    public LiveData<Resource<SaleDTO>> createSale(SaleDTO sale) {
+        return saleRepository.createSale(sale);
+    }
+
+    public void setStoreList(List<DropdownDTO> list) { storeList.setValue(list); }
+    public LiveData<List<DropdownDTO>> getStoreList() { return storeList; }
+
+    public void setCustomerList(List<DropdownDTO> list) { customerList.setValue(list); }
+    public LiveData<List<DropdownDTO>> getCustomerList() { return customerList; }
+
+    public void setProductList(List<ProductDTO> list) { productList.setValue(list); }
+    public LiveData<List<ProductDTO>> getProductList() { return productList; }
+
+    public void addToCart(SaleDTO.SaleItemDTO item) {
+        List<SaleDTO.SaleItemDTO> currentCart = new ArrayList<>(cartItems.getValue());
+        currentCart.add(item);
+        cartItems.setValue(currentCart);
+    }
+
+    public LiveData<List<SaleDTO.SaleItemDTO>> getCartItems() { return cartItems; }
+
+    public BigDecimal calculateSubtotal() {
+        BigDecimal total = BigDecimal.ZERO;
+        List<SaleDTO.SaleItemDTO> items = cartItems.getValue();
+        List<ProductDTO> products = productList.getValue();
+        if (items != null && products != null) {
+            for (SaleDTO.SaleItemDTO item : items) {
+                for (ProductDTO p : products) {
+                    if (p.getProdId().equals(item.getProdId()) && p.getProdPrice() != null) {
+                        total = total.add(p.getProdPrice().multiply(BigDecimal.valueOf(item.getQuantity())));
+                        break;
+                    }
+                }
+            }
+        }
+        return total;
+    }
+}

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

@@ -0,0 +1,54 @@
+package com.example.petstoremobile.viewmodels;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.ViewModel;
+
+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 ServiceDetailViewModel extends ViewModel {
+    private final ServiceRepository repository;
+    private long serviceId = -1;
+    private boolean isEditing = false;
+
+    @Inject
+    public ServiceDetailViewModel(ServiceRepository repository) {
+        this.repository = repository;
+    }
+
+    public void setServiceId(long id) {
+        this.serviceId = id;
+        this.isEditing = id != -1;
+    }
+
+    public long getServiceId() {
+        return serviceId;
+    }
+
+    public boolean isEditing() {
+        return isEditing;
+    }
+
+    public LiveData<Resource<ServiceDTO>> loadService() {
+        return repository.getServiceById(serviceId);
+    }
+
+    public LiveData<Resource<ServiceDTO>> saveService(ServiceDTO dto) {
+        if (isEditing) {
+            dto.setServiceId(serviceId);
+            return repository.updateService(serviceId, dto);
+        } else {
+            return repository.createService(dto);
+        }
+    }
+
+    public LiveData<Resource<Void>> deleteService() {
+        return repository.deleteService(serviceId);
+    }
+}

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

@@ -0,0 +1,49 @@
+package com.example.petstoremobile.viewmodels;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.ViewModel;
+
+import com.example.petstoremobile.dtos.EmployeeDTO;
+import com.example.petstoremobile.repositories.EmployeeRepository;
+import com.example.petstoremobile.utils.Resource;
+
+import javax.inject.Inject;
+
+import dagger.hilt.android.lifecycle.HiltViewModel;
+
+@HiltViewModel
+public class StaffDetailViewModel extends ViewModel {
+    private final EmployeeRepository repository;
+    private long employeeId = -1;
+    private boolean isEditing = false;
+
+    @Inject
+    public StaffDetailViewModel(EmployeeRepository repository) {
+        this.repository = repository;
+    }
+
+    public void setEmployeeId(long id, boolean isEditing) {
+        this.employeeId = id;
+        this.isEditing = isEditing;
+    }
+
+    public long getEmployeeId() {
+        return employeeId;
+    }
+
+    public boolean isEditing() {
+        return isEditing;
+    }
+
+    public LiveData<Resource<EmployeeDTO>> saveEmployee(EmployeeDTO dto) {
+        if (isEditing && employeeId > 0) {
+            return repository.updateEmployee(employeeId, dto);
+        } else {
+            return repository.createEmployee(dto);
+        }
+    }
+
+    public LiveData<Resource<Void>> deleteEmployee() {
+        return repository.deleteEmployee(employeeId);
+    }
+}

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

@@ -0,0 +1,54 @@
+package com.example.petstoremobile.viewmodels;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.ViewModel;
+
+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 SupplierDetailViewModel extends ViewModel {
+    private final SupplierRepository repository;
+    private long supId = -1;
+    private boolean isEditing = false;
+
+    @Inject
+    public SupplierDetailViewModel(SupplierRepository repository) {
+        this.repository = repository;
+    }
+
+    public void setSupId(long id) {
+        this.supId = id;
+        this.isEditing = id != -1;
+    }
+
+    public long getSupId() {
+        return supId;
+    }
+
+    public boolean isEditing() {
+        return isEditing;
+    }
+
+    public LiveData<Resource<SupplierDTO>> loadSupplier() {
+        return repository.getSupplierById(supId);
+    }
+
+    public LiveData<Resource<SupplierDTO>> saveSupplier(SupplierDTO dto) {
+        if (isEditing) {
+            dto.setSupId(supId);
+            return repository.updateSupplier(supId, dto);
+        } else {
+            return repository.createSupplier(dto);
+        }
+    }
+
+    public LiveData<Resource<Void>> deleteSupplier() {
+        return repository.deleteSupplier(supId);
+    }
+}