feat: add unread message count API

- Added `GET /messages/unread-count` endpoint to retrieve the count of unread messages for a user.
- Implemented `getUnreadCount` method in `MessagesService` and `MessagesRepository`.
- Updated frontend service to support fetching unread message count via API.

backend/src/messages/messages.controller.ts

@@ -22,6 +22,11 @@ export class MessagesController {
 		return this.messagesService.getConversations(req.user.sub);
 	}
 
+	@Get("unread-count")
+	getUnreadCount(@Req() req: AuthenticatedRequest) {
+		return this.messagesService.getUnreadCount(req.user.sub);
+	}
+
 	@Get("conversations/with/:userId")
 	getConversationWithUser(
 		@Req() req: AuthenticatedRequest,

backend/src/messages/messages.service.ts

@@ -42,6 +42,10 @@ export class MessagesService {
 		return this.messagesRepository.findAllConversations(userId);
 	}
 
+	async getUnreadCount(userId: string) {
+		return this.messagesRepository.countUnreadMessages(userId);
+	}
+
 	async getConversationWithUser(userId: string, targetUserId: string) {
 		return this.messagesRepository.findConversationBetweenUsers(
 			userId,

backend/src/messages/repositories/messages.repository.ts

@@ -133,4 +133,35 @@ export class MessagesRepository {
 			.from(conversationParticipants)
 			.where(eq(conversationParticipants.conversationId, conversationId));
 	}
+
+	async markAsRead(conversationId: string, userId: string) {
+		await this.databaseService.db
+			.update(messages)
+			.set({ readAt: new Date() })
+			.where(
+				and(
+					eq(messages.conversationId, conversationId),
+					sql`${messages.senderId} != ${userId}`,
+					sql`${messages.readAt} IS NULL`,
+				),
+			);
+	}
+
+	async countUnreadMessages(userId: string) {
+		const result = await this.databaseService.db
+			.select({ count: sql<number>`count(*)` })
+			.from(messages)
+			.innerJoin(
+				conversationParticipants,
+				eq(messages.conversationId, conversationParticipants.conversationId),
+			)
+			.where(
+				and(
+					eq(conversationParticipants.userId, userId),
+					sql`${messages.senderId} != ${userId}`,
+					sql`${messages.readAt} IS NULL`,
+				),
+			);
+		return Number(result[0]?.count || 0);
+	}
 }