feat: cancel invitations for both attendees and organisers

backend/src/main/java/online/wesal/wesal/controller/InvitationController.java

@@ -5,6 +5,7 @@ import io.swagger.v3.oas.annotations.tags.Tag;
 import jakarta.validation.Valid;
 import online.wesal.wesal.dto.AcceptInvitationRequest;
 import online.wesal.wesal.dto.ApiResponse;
+import online.wesal.wesal.dto.CancelInvitationRequest;
 import online.wesal.wesal.dto.CategorizedInvitationsResponse;
 import online.wesal.wesal.dto.CreateInvitationRequest;
 import online.wesal.wesal.dto.InvitationResponse;
@@ -112,4 +113,21 @@ public class InvitationController {
             return ResponseEntity.status(500).body(ApiResponse.error("Something went wrong.. We're sorry but try again later"));
         }
     }
+    
+    @PostMapping("/cancel")
+    @Operation(summary = "Cancel invitation", description = "Cancel an invitation - attendee leaves or organizer deletes entire invitation")
+    public ResponseEntity<ApiResponse<Void>> cancelInvitation(
+            @Valid @RequestBody CancelInvitationRequest request,
+            Authentication authentication) {
+        
+        try {
+            String userEmail = authentication.getName();
+            invitationService.cancelInvitation(request.getId(), userEmail);
+            return ResponseEntity.ok(new ApiResponse<>(true));
+        } catch (RuntimeException e) {
+            return ResponseEntity.badRequest().body(ApiResponse.error(e.getMessage()));
+        } catch (Exception e) {
+            return ResponseEntity.status(500).body(ApiResponse.error("Something went wrong.. We're sorry but try again later"));
+        }
+    }
 }

backend/src/main/java/online/wesal/wesal/dto/CancelInvitationRequest.java

@@ -0,0 +1,25 @@
+package online.wesal.wesal.dto;
+
+import jakarta.validation.constraints.NotNull;
+import jakarta.validation.constraints.Positive;
+
+public class CancelInvitationRequest {
+    
+    @NotNull(message = "Invitation ID is required")
+    @Positive(message = "Invitation ID must be positive")
+    private Long id;
+    
+    public CancelInvitationRequest() {}
+    
+    public CancelInvitationRequest(Long id) {
+        this.id = id;
+    }
+    
+    public Long getId() {
+        return id;
+    }
+    
+    public void setId(Long id) {
+        this.id = id;
+    }
+}

backend/src/main/java/online/wesal/wesal/repository/AttendeeRepository.java

@@ -11,4 +11,8 @@ public interface AttendeeRepository extends JpaRepository<Attendee, Long> {
     boolean existsByInvitationIdAndUserId(Long invitationId, Long userId);
     
     List<Attendee> findByInvitationId(Long invitationId);
+    
+    void deleteByInvitationId(Long invitationId);
+    
+    void deleteByInvitationIdAndUserId(Long invitationId, Long userId);
 }

backend/src/main/java/online/wesal/wesal/service/InvitationService.java

@@ -15,6 +15,7 @@ import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
+import java.time.LocalDateTime;
 import java.util.List;
 import java.util.Optional;
 import java.util.stream.Collectors;
@@ -120,6 +121,39 @@ public class InvitationService {
         invitationRepository.save(invitation);
     }
     
+    @Transactional
+    public void cancelInvitation(Long invitationId, String userEmail) {
+        User user = userRepository.findByEmail(userEmail)
+            .orElseThrow(() -> new RuntimeException("Authentication error. Please log in again"));
+        
+        Invitation invitation = invitationRepository.findById(invitationId)
+            .orElse(null);
+        
+        if (invitation == null) {
+            throw new RuntimeException("Invitation not found or already cancelled by organizer");
+        }
+        
+        if (invitation.getDateTime() != null && invitation.getDateTime().isBefore(LocalDateTime.now())) {
+            throw new RuntimeException("Cannot cancel expired invitation");
+        }
+        
+        boolean isOrganizer = invitation.getCreator().getId().equals(user.getId());
+        boolean isAttendee = attendeeRepository.existsByInvitationIdAndUserId(invitationId, user.getId());
+        
+        if (!isOrganizer && !isAttendee) {
+            throw new RuntimeException("You are not associated with this invitation");
+        }
+        
+        if (isOrganizer) {
+            attendeeRepository.deleteByInvitationId(invitationId);
+            invitationRepository.deleteById(invitationId);
+        } else {
+            attendeeRepository.deleteByInvitationIdAndUserId(invitationId, user.getId());
+            invitation.setCurrentAttendees(invitation.getCurrentAttendees() - 1);
+            invitationRepository.save(invitation);
+        }
+    }
+    
     private InvitationResponse mapToResponse(Invitation invitation) {
         InvitationResponse response = new InvitationResponse();
         response.setId(invitation.getId());

frontend/lib/constants/api_constants.dart

@@ -9,6 +9,7 @@ class ApiConstants {
   static const String updateUserEndpoint = '/updateUser';
 
   // Invitation endpoints
+  static const String invitationsEndpoint = '/invitations';
   static const String getAllInvitationsEndpoint = '/invitations/all';
   static const String acceptInvitationEndpoint = '/invitations/accept';
   static const String createInvitationEndpoint = '/invitations/create';

frontend/lib/models/invitation_models.dart

@@ -41,6 +41,29 @@ class InvitationCreator {
   }
 }
 
+class InvitationAttendee {
+  final int id;
+  final String displayName;
+  final String? avatar;
+  final DateTime joinedAt;
+
+  InvitationAttendee({
+    required this.id,
+    required this.displayName,
+    this.avatar,
+    required this.joinedAt,
+  });
+
+  factory InvitationAttendee.fromJson(Map<String, dynamic> json) {
+    return InvitationAttendee(
+      id: json['id'],
+      displayName: json['displayName'],
+      avatar: json['avatar'],
+      joinedAt: DateTime.parse(json['joinedAt']),
+    );
+  }
+}
+
 class Invitation {
   final int id;
   final String title;
@@ -128,4 +151,57 @@ class InvitationsData {
   }
   
   bool get isEmpty => created.isEmpty && accepted.isEmpty && available.isEmpty;
+}
+
+class InvitationDetails {
+  final int id;
+  final String title;
+  final String? description;
+  final DateTime? dateTime;
+  final String? location;
+  final int maxParticipants;
+  final int currentAttendees;
+  final InvitationTag tag;
+  final InvitationCreator creator;
+  final DateTime createdAt;
+  final List<InvitationAttendee> attendees;
+
+  InvitationDetails({
+    required this.id,
+    required this.title,
+    this.description,
+    this.dateTime,
+    this.location,
+    required this.maxParticipants,
+    required this.currentAttendees,
+    required this.tag,
+    required this.creator,
+    required this.createdAt,
+    required this.attendees,
+  });
+
+  factory InvitationDetails.fromJson(Map<String, dynamic> json) {
+    return InvitationDetails(
+      id: json['id'],
+      title: json['title'],
+      description: json['description'],
+      dateTime: json['dateTime'] != null ? DateTime.parse(json['dateTime']) : null,
+      location: json['location'],
+      maxParticipants: json['maxParticipants'],
+      currentAttendees: json['currentAttendees'],
+      tag: InvitationTag.fromJson(json['tag']),
+      creator: InvitationCreator.fromJson(json['creator']),
+      createdAt: DateTime.parse(json['createdAt']),
+      attendees: (json['attendees'] as List)
+          .map((item) => InvitationAttendee.fromJson(item))
+          .toList(),
+    );
+  }
+
+  String get status {
+    if (currentAttendees >= maxParticipants) {
+      return 'Full';
+    }
+    return 'Available';
+  }
 }

frontend/lib/screens/pages/invitations_page.dart

@@ -2,6 +2,7 @@ import 'package:flutter/material.dart';
 import '../../services/invitations_service.dart';
 import '../../models/invitation_models.dart';
 import '../../utils/invitation_utils.dart';
+import 'invitation_details_page.dart';
 
 class InvitationsPage extends StatefulWidget {
   @override
@@ -143,6 +144,22 @@ class _InvitationsPageState extends State<InvitationsPage>
     }
   }
 
+  Future<void> _navigateToInvitationDetails(Invitation invitation, bool isOwner) async {
+    final result = await Navigator.push(
+      context,
+      MaterialPageRoute(
+        builder: (context) => InvitationDetailsPage(
+          invitationId: invitation.id,
+          isOwner: isOwner,
+        ),
+      ),
+    );
+    
+    if (result == true) {
+      _loadInvitations();
+    }
+  }
+
   Widget _buildInvitationCard(Invitation invitation, String section) {
     final invitationKey = invitation.id.toString();
     bool isOwned = section == 'created';
@@ -305,20 +322,24 @@ class _InvitationsPageState extends State<InvitationsPage>
             width: double.infinity,
             height: 44,
             child: ElevatedButton(
-              onPressed: isOwned || isAccepted || isAccepting || hasBeenAccepted
+              onPressed: isAccepting 
-                  ? null
+                  ? null 
-                  : () {
+                  : (isOwned || isAccepted || hasBeenAccepted) 
-                      _acceptInvitation(invitation);
+                      ? () {
-                    },
+                          _navigateToInvitationDetails(invitation, isOwned);
+                        }
+                      : () {
+                          _acceptInvitation(invitation);
+                        },
               style: ElevatedButton.styleFrom(
                 backgroundColor: (isAccepted || hasBeenAccepted)
                     ? Colors.green
-                    : (isOwned ? Colors.grey[400] : Color(0xFF6A4C93)),
+                    : (isOwned ? Color(0xFF6A4C93) : Color(0xFF6A4C93)),
                 foregroundColor: Colors.white,
                 shape: RoundedRectangleBorder(
                   borderRadius: BorderRadius.circular(8),
                 ),
-                elevation: isOwned || isAccepted || hasBeenAccepted ? 0 : 2,
+                elevation: 2,
               ),
               child: isAccepting
                   ? SizedBox(
@@ -335,21 +356,18 @@ class _InvitationsPageState extends State<InvitationsPage>
                       builder: (context, child) {
                         if (animController.value < 0.5) {
                           return Text(
-                            'Accepted ✓',
+                            'View',
                             style: TextStyle(
                               fontSize: 16,
                               fontWeight: FontWeight.w600,
                             ),
                           );
                         } else {
-                          return Opacity(
+                          return Text(
-                            opacity: 1.0 - ((animController.value - 0.5) * 2),
+                            'View',
-                            child: Text(
+                            style: TextStyle(
-                              'Accepted ✓',
+                              fontSize: 16,
-                              style: TextStyle(
+                              fontWeight: FontWeight.w600,
-                                fontSize: 16,
-                                fontWeight: FontWeight.w600,
-                              ),
                             ),
                           );
                         }
@@ -357,8 +375,8 @@ class _InvitationsPageState extends State<InvitationsPage>
                     )
                   : Text(
                       (isAccepted || hasBeenAccepted)
-                          ? 'Accepted ✓'
+                          ? 'View'
-                          : (isOwned ? 'View/Edit' : 'Accept Invite'),
+                          : (isOwned ? 'View' : 'Accept Invite'),
                       style: TextStyle(
                         fontSize: 16,
                         fontWeight: FontWeight.w600,

frontend/lib/services/invitations_service.dart

@@ -131,4 +131,87 @@ class InvitationsService {
       };
     }
   }
+
+  static Future<Map<String, dynamic>> getInvitationDetails(int invitationId) async {
+    try {
+      final response = await HttpService.get(
+        '${ApiConstants.invitationsEndpoint}/get?id=$invitationId',
+      );
+
+      if (response.statusCode == 200) {
+        final responseData = jsonDecode(response.body);
+        if (responseData['status'] == true) {
+          final invitationDetails = InvitationDetails.fromJson(responseData['data']);
+          return {
+            'success': true,
+            'data': invitationDetails,
+          };
+        } else {
+          return {
+            'success': false,
+            'message': responseData['message'] ?? 'Failed to get invitation details',
+          };
+        }
+      } else if (response.statusCode == 401) {
+        return {
+          'success': false,
+          'message': 'Session expired. Please login again.',
+        };
+      } else if (response.statusCode == 403) {
+        return {
+          'success': false,
+          'message': 'Access denied. Invalid credentials.',
+        };
+      } else {
+        return {
+          'success': false,
+          'message': 'Server error (${response.statusCode})',
+        };
+      }
+    } catch (e) {
+      print('Error getting invitation details: $e');
+      return {
+        'success': false,
+        'message': 'Network error. Please check your connection.',
+      };
+    }
+  }
+
+  static Future<Map<String, dynamic>> cancelInvitation(int invitationId) async {
+    try {
+      final response = await HttpService.post(
+        '${ApiConstants.invitationsEndpoint}/cancel',
+        {'id': invitationId},
+      );
+
+      if (response.statusCode == 200) {
+        final responseData = jsonDecode(response.body);
+        return {
+          'success': responseData['status'] ?? false,
+          'message': responseData['message'] ?? 'Request completed',
+        };
+      } else if (response.statusCode == 401) {
+        return {
+          'success': false,
+          'message': 'Session expired. Please login again.',
+        };
+      } else if (response.statusCode == 403) {
+        return {
+          'success': false,
+          'message': 'Access denied. Invalid credentials.',
+        };
+      } else {
+        return {
+          'success': false,
+          'message': 'Server error (${response.statusCode})',
+        };
+      }
+    } catch (e) {
+      print('Error canceling invitation: $e');
+      return {
+        'success': false,
+        'message': 'Network error. Please check your connection.',
+      };
+    }
+  }
 }