feat: add post like

internal/service/social_service.go

@@ -33,12 +33,18 @@ var (
 type PostService struct {
 	posts *repository.PostRepo
 	r2    *repository.R2
+	likes *repository.LikeRepo
+	notif *NotificationService // optional; set via SetNotifier
 }
 
-func NewPostService(posts *repository.PostRepo, r2 *repository.R2) *PostService {
-	return &PostService{posts: posts, r2: r2}
+func NewPostService(posts *repository.PostRepo, r2 *repository.R2, likes *repository.LikeRepo) *PostService {
+	return &PostService{posts: posts, r2: r2, likes: likes}
 }
 
+// SetNotifier wires the notification seam after construction (the
+// NotificationService is built later in server wiring than PostService).
+func (s *PostService) SetNotifier(n *NotificationService) { s.notif = n }
+
 // Create persists a new post. The caption is treated as opaque — we trust
 // 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
@@ -72,6 +78,9 @@ func (s *PostService) Get(ctx context.Context, id, viewerID string) (*model.Post
 	if err := s.hydrateReshareStates(ctx, viewerID, []*model.Post{p}); err != nil {
 		return nil, err
 	}
+	if err := s.likes.Hydrate(ctx, viewerID, []*model.Post{p}); err != nil {
+		return nil, err
+	}
 	return p, nil
 }
 
@@ -171,9 +180,58 @@ func (s *PostService) ListByHandle(ctx context.Context, handle, viewerID string,
 	if err := s.hydrateReshareStatesSlice(ctx, viewerID, posts); err != nil {
 		return nil, 0, err
 	}
+	if err := s.hydrateLikesSlice(ctx, viewerID, posts); err != nil {
+		return nil, 0, err
+	}
 	return posts, total, nil
 }
 
+// hydrateLikesSlice fills LikesCount + ViewerHasLiked on a value slice.
+func (s *PostService) hydrateLikesSlice(ctx context.Context, viewerID string, 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.likes.Hydrate(ctx, viewerID, ptrs)
+}
+
+// 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) {
+	changed, err := s.likes.Like(ctx, postID, userID)
+	if err != nil {
+		return 0, err
+	}
+	count, err := s.likes.EffectiveCount(ctx, postID)
+	if err != nil {
+		return 0, err
+	}
+	// Notify the author on a genuinely new like by someone else. Fire-and-
+	// forget on a detached context so it isn't cancelled when the request
+	// returns; NotifyPostLike re-checks self-like internally too.
+	if changed && s.notif != nil {
+		if authorID, aerr := s.likes.PostAuthor(ctx, postID); aerr == nil && authorID != userID {
+			go s.notif.NotifyPostLike(context.Background(), postID, authorID, userID)
+		}
+	}
+	return count, nil
+}
+
+func (s *PostService) Unlike(ctx context.Context, userID, postID string) (int, error) {
+	if _, err := s.likes.Unlike(ctx, postID, userID); err != nil {
+		return 0, err
+	}
+	return s.likes.EffectiveCount(ctx, postID)
+}
+
+// Likers returns one page of users who liked the post + the total count.
+func (s *PostService) Likers(ctx context.Context, postID, q string, limit, offset int) ([]model.UserSummary, int, error) {
+	return s.likes.ListLikers(ctx, postID, q, limit, offset)
+}
+
 // ListMine is the owner's view of their own profile feed. Every post
 // they own — authored or reshared — comes from posts.user_id, so the
 // viewer is by construction the owner. ViewerHasReshared is true for
@@ -195,6 +253,9 @@ func (s *PostService) ListMine(ctx context.Context, userID string, limit, offset
 			posts[i].ViewerHasReshared = true
 		}
 	}
+	if err := s.hydrateLikesSlice(ctx, userID, posts); err != nil {
+		return nil, 0, err
+	}
 	return posts, total, nil
 }