feat: add notification system for comments and likes

- Notify post authors when their content receives a new comment.
- Notify parent comment authors when their comment receives a reply.
- Send notifications to comment authors when their comments are liked.
- Handle notification errors gracefully with error

backend/src/comments/comments.service.ts

@@ -1,8 +1,11 @@
 import {
 	ForbiddenException,
+	Inject,
 	Injectable,
 	NotFoundException,
+	forwardRef,
 } from "@nestjs/common";
+import { ContentsRepository } from "../contents/repositories/contents.repository";
 import { EventsGateway } from "../realtime/events.gateway";
 import { S3Service } from "../s3/s3.service";
 import type { CreateCommentDto } from "./dto/create-comment.dto";
@@ -14,6 +17,8 @@ export class CommentsService {
 	constructor(
 		private readonly commentsRepository: CommentsRepository,
 		private readonly commentLikesRepository: CommentLikesRepository,
+		@Inject(forwardRef(() => ContentsRepository))
+		private readonly contentsRepository: ContentsRepository,
 		private readonly s3Service: S3Service,
 		private readonly eventsGateway: EventsGateway,
 	) {}
@@ -29,9 +34,48 @@ export class CommentsService {
 		// Récupérer le commentaire avec les infos utilisateur pour le WebSocket
 		const enrichedComment = await this.findOneEnriched(comment.id, userId);
 
-		// Notifier les autres utilisateurs sur ce contenu
+		// Notifier les autres utilisateurs sur ce contenu (room de contenu)
 		this.eventsGateway.sendToContent(contentId, "new_comment", enrichedComment);
 
+		// Notifications ciblées
+		try {
+			// 1. Notifier l'auteur du post
+			const content = await this.contentsRepository.findOne(contentId);
+			if (content && content.userId !== userId) {
+				this.eventsGateway.sendToUser(content.userId, "notification", {
+					type: "comment",
+					userId: userId,
+					username: enrichedComment.user.username,
+					contentId: contentId,
+					commentId: comment.id,
+					text: `a commenté votre post : "${dto.text.substring(0, 30)}${dto.text.length > 30 ? "..." : ""}"`,
+				});
+			}
+
+			// 2. Si c'est une réponse, notifier l'auteur du commentaire parent
+			if (dto.parentId) {
+				const parentComment = await this.commentsRepository.findOne(
+					dto.parentId,
+				);
+				if (
+					parentComment &&
+					parentComment.userId !== userId &&
+					(!content || parentComment.userId !== content.userId)
+				) {
+					this.eventsGateway.sendToUser(parentComment.userId, "notification", {
+						type: "reply",
+						userId: userId,
+						username: enrichedComment.user.username,
+						contentId: contentId,
+						commentId: comment.id,
+						text: `a répondu à votre commentaire : "${dto.text.substring(0, 30)}${dto.text.length > 30 ? "..." : ""}"`,
+					});
+				}
+			}
+		} catch (error) {
+			console.error("Failed to send notification:", error);
+		}
+
 		return enrichedComment;
 	}
 
@@ -105,6 +149,23 @@ export class CommentsService {
 			throw new NotFoundException("Comment not found");
 		}
 		await this.commentLikesRepository.addLike(commentId, userId);
+
+		// Notifier l'auteur du commentaire
+		if (comment.userId !== userId) {
+			try {
+				const liker = await this.findOneEnriched(commentId, userId);
+				this.eventsGateway.sendToUser(comment.userId, "notification", {
+					type: "like_comment",
+					userId: userId,
+					username: liker?.user.username,
+					contentId: comment.contentId,
+					commentId: commentId,
+					text: "a aimé votre commentaire",
+				});
+			} catch (error) {
+				console.error("Failed to send like notification:", error);
+			}
+		}
 	}
 
 	async unlike(userId: string, commentId: string) {