feat: add post mention

internal/service/social_service.go

@@ -31,14 +31,15 @@ var (
 // ---------------------------------------------------------------------------
 
 type PostService struct {
-	posts *repository.PostRepo
-	r2    *repository.R2
-	likes *repository.LikeRepo
-	notif *NotificationService // optional; set via SetNotifier
+	posts    *repository.PostRepo
+	r2       *repository.R2
+	likes    *repository.LikeRepo
+	mentions *repository.MentionRepo
+	notif    *NotificationService // optional; set via SetNotifier
 }
 
-func NewPostService(posts *repository.PostRepo, r2 *repository.R2, likes *repository.LikeRepo) *PostService {
-	return &PostService{posts: posts, r2: r2, likes: likes}
+func NewPostService(posts *repository.PostRepo, r2 *repository.R2, likes *repository.LikeRepo, mentions *repository.MentionRepo) *PostService {
+	return &PostService{posts: posts, r2: r2, likes: likes, mentions: mentions}
 }
 
 // SetNotifier wires the notification seam after construction (the
@@ -49,7 +50,7 @@ func (s *PostService) SetNotifier(n *NotificationService) { s.notif = n }
 // the frontend to send the exact text the user selected. Source URL must be
 // a same-origin path (e.g. /books/bg/1/1?hl=…) — we strip the host if one
 // was provided so links can't be hijacked.
-func (s *PostService) Create(ctx context.Context, userID, caption, sourceURL, sourceTitle string, imageURLs []string) (*model.Post, error) {
+func (s *PostService) Create(ctx context.Context, userID, caption, sourceURL, sourceTitle string, imageURLs, mentionUserIDs []string) (*model.Post, error) {
 	caption = strings.TrimSpace(caption)
 	if caption == "" {
 		return nil, errors.New("caption is required")
@@ -64,7 +65,19 @@ func (s *PostService) Create(ctx context.Context, userID, caption, sourceURL, so
 	if len(imageURLs) > 5 {
 		return nil, errors.New("a post can hold up to 5 images")
 	}
-	return s.posts.Create(ctx, userID, caption, sourceURL, sourceTitle, imageURLs)
+	p, err := s.posts.Create(ctx, userID, caption, sourceURL, sourceTitle, imageURLs)
+	if err != nil {
+		return nil, err
+	}
+	// Tag mentioned users (best-effort, additive — a bad id never fails the
+	// post itself). Reflect the count on the returned post, then notify the
+	// tagged people (fire-and-forget on a detached context).
+	if len(mentionUserIDs) > 0 {
+		_ = s.mentions.AddMany(ctx, p.ID, mentionUserIDs)
+		_ = s.mentions.HydrateCounts(ctx, []*model.Post{p})
+		go s.notifyMentions(context.Background(), p.ID, userID, mentionUserIDs)
+	}
+	return p, nil
 }
 
 // Get returns one post (public). `viewerID` is "" for anonymous callers;
@@ -81,6 +94,9 @@ func (s *PostService) Get(ctx context.Context, id, viewerID string) (*model.Post
 	if err := s.likes.Hydrate(ctx, viewerID, []*model.Post{p}); err != nil {
 		return nil, err
 	}
+	if err := s.mentions.HydrateCounts(ctx, []*model.Post{p}); err != nil {
+		return nil, err
+	}
 	return p, nil
 }
 
@@ -183,6 +199,9 @@ func (s *PostService) ListByHandle(ctx context.Context, handle, viewerID string,
 	if err := s.hydrateLikesSlice(ctx, viewerID, posts); err != nil {
 		return nil, 0, err
 	}
+	if err := s.hydrateMentionsSlice(ctx, posts); err != nil {
+		return nil, 0, err
+	}
 	return posts, total, nil
 }
 
@@ -198,6 +217,75 @@ func (s *PostService) hydrateLikesSlice(ctx context.Context, viewerID string, po
 	return s.likes.Hydrate(ctx, viewerID, ptrs)
 }
 
+// hydrateMentionsSlice fills MentionsCount on a value slice.
+func (s *PostService) hydrateMentionsSlice(ctx context.Context, posts []model.Post) error {
+	if len(posts) == 0 {
+		return nil
+	}
+	ptrs := make([]*model.Post, len(posts))
+	for i := range posts {
+		ptrs[i] = &posts[i]
+	}
+	return s.mentions.HydrateCounts(ctx, ptrs)
+}
+
+// SuggestMentions returns prioritised mention suggestions for the composer.
+func (s *PostService) SuggestMentions(ctx context.Context, viewerID, q string, limit, offset int) ([]model.UserSummary, error) {
+	return s.mentions.Suggest(ctx, viewerID, q, limit, offset)
+}
+
+// Mentions lists the users tagged on a post.
+func (s *PostService) Mentions(ctx context.Context, postID string) ([]model.UserSummary, error) {
+	return s.mentions.ListForPost(ctx, postID)
+}
+
+// AddMention / RemoveMention edit a post's tags — author only.
+func (s *PostService) AddMention(ctx context.Context, viewerID, postID, targetUserID string) error {
+	if err := s.requireAuthor(ctx, viewerID, postID); err != nil {
+		return err
+	}
+	if err := s.mentions.Add(ctx, postID, targetUserID); err != nil {
+		return err
+	}
+	if s.notif != nil {
+		go s.notif.NotifyPostMention(context.Background(), targetUserID, viewerID, postID)
+	}
+	return nil
+}
+
+// notifyMentions notifies each freshly-tagged user (deduped, never the author).
+func (s *PostService) notifyMentions(ctx context.Context, postID, authorID string, userIDs []string) {
+	if s.notif == nil {
+		return
+	}
+	seen := make(map[string]bool, len(userIDs))
+	for _, uid := range userIDs {
+		if uid == "" || uid == authorID || seen[uid] {
+			continue
+		}
+		seen[uid] = true
+		s.notif.NotifyPostMention(ctx, uid, authorID, postID)
+	}
+}
+
+func (s *PostService) RemoveMention(ctx context.Context, viewerID, postID, targetUserID string) error {
+	if err := s.requireAuthor(ctx, viewerID, postID); err != nil {
+		return err
+	}
+	return s.mentions.Remove(ctx, postID, targetUserID)
+}
+
+func (s *PostService) requireAuthor(ctx context.Context, viewerID, postID string) error {
+	p, err := s.posts.FindByID(ctx, postID)
+	if err != nil {
+		return err
+	}
+	if p.UserID != viewerID {
+		return ErrForbidden
+	}
+	return nil
+}
+
 // Like / Unlike toggle the caller's like on a post and return the effective
 // total (likes_count + pending Redis delta).
 func (s *PostService) Like(ctx context.Context, userID, postID string) (int, error) {
@@ -256,6 +344,9 @@ func (s *PostService) ListMine(ctx context.Context, userID string, limit, offset
 	if err := s.hydrateLikesSlice(ctx, userID, posts); err != nil {
 		return nil, 0, err
 	}
+	if err := s.hydrateMentionsSlice(ctx, posts); err != nil {
+		return nil, 0, err
+	}
 	return posts, total, nil
 }