backend/src/main/java/com/petshop/backend/controller/ChatController.java

@@ -7,6 +7,7 @@ import com.petshop.backend.dto.chat.MessageResponse;
 import com.petshop.backend.dto.chat.UpdateConversationRequest;
 import com.petshop.backend.entity.Message;
 import com.petshop.backend.entity.User;
+import com.petshop.backend.exception.ResourceNotFoundException;
 import com.petshop.backend.repository.MessageRepository;
 import com.petshop.backend.repository.UserRepository;
 import com.petshop.backend.service.ChatAttachmentStorageService;
@@ -115,7 +116,7 @@ public class ChatController {
     public ResponseEntity<Resource> getMessageAttachment(@PathVariable Long messageId) {
         User user = getCurrentUser();
         Message message = messageRepository.findById(messageId)
-                .orElseThrow(() -> new RuntimeException("Message not found"));
+                .orElseThrow(() -> new ResourceNotFoundException("Message not found with id: " + messageId));
 
         if (!chatService.hasConversationAccess(message.getConversationId(), user.getId(), user.getRole())) {
             throw new AccessDeniedException("Access denied to this message attachment");

backend/src/main/java/com/petshop/backend/controller/ContactController.java

@@ -1,6 +1,7 @@
 package com.petshop.backend.controller;
 
 import com.petshop.backend.entity.User;
+import com.petshop.backend.exception.ResourceNotFoundException;
 import com.petshop.backend.repository.UserRepository;
 import com.petshop.backend.service.EmailService;
 import com.petshop.backend.util.AuthenticationHelper;
@@ -33,7 +34,7 @@ public class ContactController {
     @PostMapping
     public ResponseEntity<Void> sendContactEmail(@Valid @RequestBody ContactRequest req) {
         Long userId = AuthenticationHelper.getAuthenticatedUserId();
-        User user = userRepository.findById(userId).orElseThrow();
+        User user = userRepository.findById(userId).orElseThrow(() -> new ResourceNotFoundException("User not found with id: " + userId));
         emailService.sendContactMessage(user, req.subject(), req.body());
         return ResponseEntity.ok().build();
     }

backend/src/main/java/com/petshop/backend/controller/SaleController.java

@@ -40,7 +40,7 @@ public class SaleController {
     }
 
     @PostMapping
-    @PreAuthorize("hasRole('STAFF')")
+    @PreAuthorize("hasAnyRole('STAFF', 'ADMIN')")
     public ResponseEntity<SaleResponse> createSale(@Valid @RequestBody SaleRequest request) {
         return ResponseEntity.status(HttpStatus.CREATED).body(saleService.createSale(request));
     }

backend/src/main/java/com/petshop/backend/controller/StoreController.java

@@ -35,11 +35,13 @@ public class StoreController {
     }
 
     @PostMapping
+    @PreAuthorize("hasRole('ADMIN')")
     public ResponseEntity<StoreResponse> createStore(@Valid @RequestBody StoreRequest request) {
         return ResponseEntity.status(HttpStatus.CREATED).body(storeService.createStore(request));
     }
 
     @PutMapping("/{id}")
+    @PreAuthorize("hasRole('ADMIN')")
     public ResponseEntity<StoreResponse> updateStore(
             @PathVariable Long id,
             @Valid @RequestBody StoreRequest request) {
@@ -47,12 +49,14 @@ public class StoreController {
     }
 
     @DeleteMapping("/{id}")
+    @PreAuthorize("hasRole('ADMIN')")
     public ResponseEntity<Void> deleteStore(@PathVariable Long id) {
         storeService.deleteStore(id);
         return ResponseEntity.noContent().build();
     }
 
     @DeleteMapping
+    @PreAuthorize("hasRole('ADMIN')")
     public ResponseEntity<Void> bulkDeleteStores(@Valid @RequestBody BulkDeleteRequest request) {
         storeService.bulkDeleteStores(request);
         return ResponseEntity.noContent().build();

backend/src/main/java/com/petshop/backend/dto/adoption/AdoptionRequest.java

@@ -20,6 +20,7 @@ public class AdoptionRequest {
 
     private Long employeeId;
 
+    @NotNull(message = "Source store ID is required")
     private Long sourceStoreId;
 
     private String paymentMethod;

backend/src/main/java/com/petshop/backend/dto/appointment/AppointmentRequest.java

@@ -1,5 +1,6 @@
 package com.petshop.backend.dto.appointment;
 
+import jakarta.validation.constraints.NotBlank;
 import jakarta.validation.constraints.NotNull;
 import java.time.LocalDate;
 import java.time.LocalTime;
@@ -21,7 +22,7 @@ public class AppointmentRequest {
     @NotNull(message = "Appointment time is required")
     private LocalTime appointmentTime;
 
-    @NotNull(message = "Appointment status is required")
+    @NotBlank(message = "Appointment status is required")
     private String appointmentStatus;
 
     private Long petId;

backend/src/main/java/com/petshop/backend/dto/pet/PetRequest.java

@@ -100,7 +100,7 @@ public class PetRequest {
                 Objects.equals(petSpecies, that.petSpecies) &&
                 Objects.equals(petBreed, that.petBreed) &&
                 Objects.equals(petAge, that.petAge) &&
-                petStatus == that.petStatus &&
+                Objects.equals(petStatus, that.petStatus) &&
                 Objects.equals(petPrice, that.petPrice);
     }
 

backend/src/main/java/com/petshop/backend/dto/sale/SaleItemRequest.java

@@ -9,6 +9,7 @@ public class SaleItemRequest {
     private Long prodId;
 
     @NotNull(message = "Quantity is required")
+    @Positive(message = "Quantity must be positive")
     private Integer quantity;
 
     public Long getProdId() {

backend/src/main/java/com/petshop/backend/dto/service/ServiceRequest.java

@@ -18,6 +18,7 @@ public class ServiceRequest {
     @Positive(message = "Price must be positive")
     private BigDecimal servicePrice;
 
+    @NotNull(message = "Service duration is required")
     @Positive(message = "Duration must be positive")
     private Integer serviceDuration;
 

backend/src/main/java/com/petshop/backend/event/AdoptionConfirmedEvent.java

@@ -0,0 +1,3 @@
+package com.petshop.backend.event;
+
+public record AdoptionConfirmedEvent(Long adoptionId) {}

backend/src/main/java/com/petshop/backend/event/AdoptionReminderEvent.java

@@ -0,0 +1,3 @@
+package com.petshop.backend.event;
+
+public record AdoptionReminderEvent(Long adoptionId) {}

backend/src/main/java/com/petshop/backend/event/AppointmentConfirmedEvent.java

@@ -0,0 +1,3 @@
+package com.petshop.backend.event;
+
+public record AppointmentConfirmedEvent(Long appointmentId) {}

backend/src/main/java/com/petshop/backend/event/AppointmentReminderEvent.java

@@ -0,0 +1,3 @@
+package com.petshop.backend.event;
+
+public record AppointmentReminderEvent(Long appointmentId) {}

backend/src/main/java/com/petshop/backend/event/EmailEventListener.java

@@ -0,0 +1,62 @@
+package com.petshop.backend.event;
+
+import com.petshop.backend.repository.AdoptionRepository;
+import com.petshop.backend.repository.AppointmentRepository;
+import com.petshop.backend.repository.SaleRepository;
+import com.petshop.backend.service.EmailService;
+import org.springframework.stereotype.Component;
+import org.springframework.transaction.annotation.Propagation;
+import org.springframework.transaction.annotation.Transactional;
+import org.springframework.transaction.event.TransactionPhase;
+import org.springframework.transaction.event.TransactionalEventListener;
+
+@Component
+public class EmailEventListener {
+
+    private final AdoptionRepository adoptionRepository;
+    private final AppointmentRepository appointmentRepository;
+    private final SaleRepository saleRepository;
+    private final EmailService emailService;
+
+    public EmailEventListener(AdoptionRepository adoptionRepository, AppointmentRepository appointmentRepository, SaleRepository saleRepository, EmailService emailService) {
+        this.adoptionRepository = adoptionRepository;
+        this.appointmentRepository = appointmentRepository;
+        this.saleRepository = saleRepository;
+        this.emailService = emailService;
+    }
+
+    @TransactionalEventListener(phase = TransactionPhase.AFTER_COMMIT)
+    @Transactional(propagation = Propagation.REQUIRES_NEW)
+    public void onAdoptionConfirmed(AdoptionConfirmedEvent event) {
+        adoptionRepository.findById(event.adoptionId())
+                .ifPresent(emailService::sendAdoptionConfirmation);
+    }
+
+    @TransactionalEventListener(phase = TransactionPhase.AFTER_COMMIT)
+    @Transactional(propagation = Propagation.REQUIRES_NEW)
+    public void onAdoptionReminder(AdoptionReminderEvent event) {
+        adoptionRepository.findById(event.adoptionId())
+                .ifPresent(emailService::sendAdoptionReminder);
+    }
+
+    @TransactionalEventListener(phase = TransactionPhase.AFTER_COMMIT)
+    @Transactional(propagation = Propagation.REQUIRES_NEW)
+    public void onAppointmentConfirmed(AppointmentConfirmedEvent event) {
+        appointmentRepository.findById(event.appointmentId())
+                .ifPresent(emailService::sendAppointmentConfirmation);
+    }
+
+    @TransactionalEventListener(phase = TransactionPhase.AFTER_COMMIT)
+    @Transactional(propagation = Propagation.REQUIRES_NEW)
+    public void onAppointmentReminder(AppointmentReminderEvent event) {
+        appointmentRepository.findById(event.appointmentId())
+                .ifPresent(emailService::sendAppointmentReminder);
+    }
+
+    @TransactionalEventListener(phase = TransactionPhase.AFTER_COMMIT)
+    @Transactional(propagation = Propagation.REQUIRES_NEW)
+    public void onSaleReceipt(SaleReceiptEvent event) {
+        saleRepository.findById(event.saleId())
+                .ifPresent(emailService::sendPurchaseReceipt);
+    }
+}

backend/src/main/java/com/petshop/backend/event/SaleReceiptEvent.java

@@ -0,0 +1,3 @@
+package com.petshop.backend.event;
+
+public record SaleReceiptEvent(Long saleId) {}

backend/src/main/java/com/petshop/backend/service/AdoptionService.java

@@ -9,11 +9,14 @@ import com.petshop.backend.entity.Sale;
 import com.petshop.backend.entity.StoreLocation;
 import com.petshop.backend.entity.User;
 import com.petshop.backend.exception.ResourceNotFoundException;
+import com.petshop.backend.event.AdoptionConfirmedEvent;
+import com.petshop.backend.event.SaleReceiptEvent;
 import com.petshop.backend.repository.AdoptionRepository;
 import com.petshop.backend.repository.PetRepository;
 import com.petshop.backend.repository.SaleRepository;
 import com.petshop.backend.repository.StoreRepository;
 import com.petshop.backend.repository.UserRepository;
+import org.springframework.context.ApplicationEventPublisher;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
 import org.springframework.stereotype.Service;
@@ -40,15 +43,15 @@ public class AdoptionService {
     private final UserRepository userRepository;
     private final StoreRepository storeRepository;
     private final SaleRepository saleRepository;
-    private final EmailService emailService;
+    private final ApplicationEventPublisher eventPublisher;
 
-    public AdoptionService(AdoptionRepository adoptionRepository, PetRepository petRepository, UserRepository userRepository, StoreRepository storeRepository, SaleRepository saleRepository, EmailService emailService) {
+    public AdoptionService(AdoptionRepository adoptionRepository, PetRepository petRepository, UserRepository userRepository, StoreRepository storeRepository, SaleRepository saleRepository, ApplicationEventPublisher eventPublisher) {
         this.adoptionRepository = adoptionRepository;
         this.petRepository = petRepository;
         this.userRepository = userRepository;
         this.storeRepository = storeRepository;
         this.saleRepository = saleRepository;
-        this.emailService = emailService;
+        this.eventPublisher = eventPublisher;
     }
 
     public Page<AdoptionResponse> getAllAdoptions(String query, Long customerId, String status, Long storeId, LocalDate date, Pageable pageable) {
@@ -110,7 +113,7 @@ public class AdoptionService {
             createSaleForAdoption(adoption, request.getPaymentMethod());
         }
         if (ADOPTION_STATUS_PENDING.equalsIgnoreCase(adoptionStatus) || ADOPTION_STATUS_COMPLETED.equalsIgnoreCase(adoptionStatus)) {
-            emailService.sendAdoptionConfirmation(adoption);
+            eventPublisher.publishEvent(new AdoptionConfirmedEvent(adoption.getAdoptionId()));
         }
         return mapToResponse(adoption);
     }
@@ -153,7 +156,7 @@ public class AdoptionService {
         }
         boolean statusChanged = !adoptionStatus.equalsIgnoreCase(previousStatus);
         if (statusChanged && (ADOPTION_STATUS_PENDING.equalsIgnoreCase(adoptionStatus) || ADOPTION_STATUS_COMPLETED.equalsIgnoreCase(adoptionStatus))) {
-            emailService.sendAdoptionConfirmation(adoption);
+            eventPublisher.publishEvent(new AdoptionConfirmedEvent(adoption.getAdoptionId()));
         }
         return mapToResponse(adoption);
     }
@@ -343,7 +346,7 @@ public class AdoptionService {
         sale.setIsRefund(false);
         sale.setChannel("ADOPTION");
         Sale savedSale = saleRepository.save(sale);
-        emailService.sendPurchaseReceipt(savedSale);
+        eventPublisher.publishEvent(new SaleReceiptEvent(savedSale.getSaleId()));
     }
 
     private void syncPetStatus(Pet pet, String adoptionStatus, Long adoptionId, User customer) {

backend/src/main/java/com/petshop/backend/service/AppointmentService.java

@@ -10,6 +10,9 @@ import com.petshop.backend.entity.StoreLocation;
 import com.petshop.backend.entity.User;
 import com.petshop.backend.exception.BusinessException;
 import com.petshop.backend.exception.ResourceNotFoundException;
+import com.petshop.backend.event.AdoptionReminderEvent;
+import com.petshop.backend.event.AppointmentConfirmedEvent;
+import com.petshop.backend.event.AppointmentReminderEvent;
 import com.petshop.backend.repository.AdoptionRepository;
 import com.petshop.backend.repository.AppointmentRepository;
 import com.petshop.backend.repository.PetRepository;
@@ -17,6 +20,7 @@ import com.petshop.backend.repository.ServiceRepository;
 import com.petshop.backend.repository.StoreRepository;
 import com.petshop.backend.repository.UserRepository;
 import com.petshop.backend.util.AuthenticationHelper;
+import org.springframework.context.ApplicationEventPublisher;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
 import org.springframework.scheduling.annotation.Scheduled;
@@ -41,16 +45,16 @@ public class AppointmentService {
     private final StoreRepository storeRepository;
     private final UserRepository userRepository;
     private final AdoptionRepository adoptionRepository;
-    private final EmailService emailService;
+    private final ApplicationEventPublisher eventPublisher;
 
-    public AppointmentService(AppointmentRepository appointmentRepository, ServiceRepository serviceRepository, PetRepository petRepository, StoreRepository storeRepository, UserRepository userRepository, AdoptionRepository adoptionRepository, EmailService emailService) {
+    public AppointmentService(AppointmentRepository appointmentRepository, ServiceRepository serviceRepository, PetRepository petRepository, StoreRepository storeRepository, UserRepository userRepository, AdoptionRepository adoptionRepository, ApplicationEventPublisher eventPublisher) {
         this.appointmentRepository = appointmentRepository;
         this.serviceRepository = serviceRepository;
         this.petRepository = petRepository;
         this.storeRepository = storeRepository;
         this.userRepository = userRepository;
         this.adoptionRepository = adoptionRepository;
-        this.emailService = emailService;
+        this.eventPublisher = eventPublisher;
     }
 
     @Transactional(readOnly = true)
@@ -140,7 +144,7 @@ public class AppointmentService {
         appointment.setPet(pet);
 
         appointment = appointmentRepository.save(appointment);
-        emailService.sendAppointmentConfirmation(appointment);
+        eventPublisher.publishEvent(new AppointmentConfirmedEvent(appointment.getAppointmentId()));
         return mapToResponse(appointment);
     }
 
@@ -179,7 +183,7 @@ public class AppointmentService {
         appointment.setEmployee(employee);
 
         appointment = appointmentRepository.save(appointment);
-        emailService.sendAppointmentConfirmation(appointment);
+        eventPublisher.publishEvent(new AppointmentConfirmedEvent(appointment.getAppointmentId()));
         return mapToResponse(appointment);
     }
 
@@ -264,7 +268,7 @@ public class AppointmentService {
         List<Appointment> pastBookedAppointments = appointmentRepository.findPastBookedAppointments(currentDate, currentTime);
 
         for (Appointment appointment : pastBookedAppointments) {
-            appointment.setAppointmentStatus("COMPLETED");
+            appointment.setAppointmentStatus("Completed");
             appointmentRepository.save(appointment);
         }
 
@@ -273,13 +277,13 @@ public class AppointmentService {
         List<Appointment> tomorrowAppointments = appointmentRepository
                 .findByAppointmentDateAndAppointmentStatusIgnoreCase(tomorrow, "Booked");
         for (Appointment appointment : tomorrowAppointments) {
-            emailService.sendAppointmentReminder(appointment);
+            eventPublisher.publishEvent(new AppointmentReminderEvent(appointment.getAppointmentId()));
         }
 
         List<Adoption> tomorrowAdoptions = adoptionRepository
                 .findByAdoptionDateAndAdoptionStatusIgnoreCase(tomorrow, "Pending");
         for (Adoption adoption : tomorrowAdoptions) {
-            emailService.sendAdoptionReminder(adoption);
+            eventPublisher.publishEvent(new AdoptionReminderEvent(adoption.getAdoptionId()));
         }
     }
 

backend/src/main/java/com/petshop/backend/service/SaleService.java

@@ -5,8 +5,10 @@ import com.petshop.backend.dto.sale.SaleResponse;
 import com.petshop.backend.entity.*;
 import com.petshop.backend.exception.BusinessException;
 import com.petshop.backend.exception.ResourceNotFoundException;
+import com.petshop.backend.event.SaleReceiptEvent;
 import com.petshop.backend.repository.*;
 import com.petshop.backend.util.AuthenticationHelper;
+import org.springframework.context.ApplicationEventPublisher;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
 import org.springframework.stereotype.Service;
@@ -31,9 +33,9 @@ public class SaleService {
     private final UserRepository userRepository;
     private final CouponRepository couponRepository;
     private final CartRepository cartRepository;
-    private final EmailService emailService;
+    private final ApplicationEventPublisher eventPublisher;
 
-    public SaleService(SaleRepository saleRepository, ProductRepository productRepository, StoreRepository storeRepository, InventoryRepository inventoryRepository, UserRepository userRepository, CouponRepository couponRepository, CartRepository cartRepository, EmailService emailService) {
+    public SaleService(SaleRepository saleRepository, ProductRepository productRepository, StoreRepository storeRepository, InventoryRepository inventoryRepository, UserRepository userRepository, CouponRepository couponRepository, CartRepository cartRepository, ApplicationEventPublisher eventPublisher) {
         this.saleRepository = saleRepository;
         this.productRepository = productRepository;
         this.storeRepository = storeRepository;
@@ -41,7 +43,7 @@ public class SaleService {
         this.userRepository = userRepository;
         this.couponRepository = couponRepository;
         this.cartRepository = cartRepository;
-        this.emailService = emailService;
+        this.eventPublisher = eventPublisher;
     }
 
     @Transactional(readOnly = true)
@@ -172,7 +174,7 @@ public class SaleService {
             BigDecimal refundTotal;
 
             if (originalSubtotal != null && originalSubtotal.compareTo(BigDecimal.ZERO) > 0) {
-                BigDecimal ratio = subtotalAmount.divide(originalSubtotal, 10, RoundingMode.HALF_UP);
+                BigDecimal ratio = subtotalAmount.abs().divide(originalSubtotal, 10, RoundingMode.HALF_UP);
                 refundTotal = originalSale.getTotalAmount().abs().multiply(ratio).negate().setScale(2, RoundingMode.HALF_UP);
                 if (originalSale.getLoyaltyDiscountAmount() != null) {
                     loyaltyDiscountRefunded = originalSale.getLoyaltyDiscountAmount().multiply(ratio).setScale(2, RoundingMode.HALF_UP);
@@ -272,7 +274,7 @@ public class SaleService {
         Sale savedSale = saleRepository.save(sale);
 
         if (!Boolean.TRUE.equals(savedSale.getIsRefund()) && savedSale.getCustomer() != null) {
-            emailService.sendPurchaseReceipt(savedSale);
+            eventPublisher.publishEvent(new SaleReceiptEvent(savedSale.getSaleId()));
         }
 
         return mapToResponse(savedSale);