feat: add post mention

internal/repository/mention_repo.go

@@ -0,0 +1,165 @@
+package repository
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/prabhupadasays/spsays-bff/internal/model"
+)
+
+// maxMentionsPerPost caps how many users a post can tag.
+const maxMentionsPerPost = 30
+
+// MentionRepo handles post_mentions membership + mention suggestions.
+type MentionRepo struct{ pg *Postgres }
+
+func NewMentionRepo(pg *Postgres) *MentionRepo { return &MentionRepo{pg: pg} }
+
+// Suggest returns up to `limit` users to mention, prioritised: people the
+// viewer follows (rank 0), then people who follow the viewer (rank 1), then
+// everyone else (rank 2). Excludes the viewer. Optional name/handle search.
+// Offset paginates for the infinite-scroll popover.
+func (r *MentionRepo) Suggest(ctx context.Context, viewerID, q string, limit, offset int) ([]model.UserSummary, error) {
+	like := "%" + q + "%"
+	rows, err := r.pg.Pool.Query(ctx, `
+		SELECT u.id, u.handle, u.name, u.avatar_url,
+		       CASE
+		         WHEN EXISTS (SELECT 1 FROM follows f
+		                      WHERE f.follower_id = $1 AND f.following_id = u.id
+		                        AND f.status = 'accepted') THEN 0
+		         WHEN EXISTS (SELECT 1 FROM follows f
+		                      WHERE f.follower_id = u.id AND f.following_id = $1
+		                        AND f.status = 'accepted') THEN 1
+		         ELSE 2
+		       END AS rank
+		FROM users u
+		WHERE u.id <> $1
+		  AND ($2 = '' OR u.name ILIKE $3 OR u.handle ILIKE $3)
+		ORDER BY rank, u.name, u.id
+		LIMIT $4 OFFSET $5`,
+		viewerID, q, like, limit, offset,
+	)
+	if err != nil {
+		return nil, fmt.Errorf("suggest mentions: %w", err)
+	}
+	defer rows.Close()
+	out := make([]model.UserSummary, 0, limit)
+	for rows.Next() {
+		var s model.UserSummary
+		var rank int
+		if err := rows.Scan(&s.ID, &s.Handle, &s.Name, &s.AvatarURL, &rank); err != nil {
+			return nil, fmt.Errorf("scan suggestion: %w", err)
+		}
+		out = append(out, s)
+	}
+	return out, rows.Err()
+}
+
+// AddMany tags the given users on a post (idempotent, capped). Used on create.
+func (r *MentionRepo) AddMany(ctx context.Context, postID string, userIDs []string) error {
+	if len(userIDs) > maxMentionsPerPost {
+		userIDs = userIDs[:maxMentionsPerPost]
+	}
+	for _, uid := range userIDs {
+		if _, err := r.pg.Pool.Exec(ctx,
+			`INSERT INTO post_mentions (post_id, user_id) VALUES ($1, $2)
+			 ON CONFLICT (post_id, user_id) DO NOTHING`,
+			postID, uid,
+		); err != nil {
+			return fmt.Errorf("add mention: %w", err)
+		}
+	}
+	return nil
+}
+
+// Add tags a single user (idempotent), enforcing the per-post cap.
+func (r *MentionRepo) Add(ctx context.Context, postID, userID string) error {
+	var n int
+	if err := r.pg.Pool.QueryRow(ctx,
+		`SELECT count(*) FROM post_mentions WHERE post_id = $1`, postID,
+	).Scan(&n); err != nil {
+		return fmt.Errorf("count mentions: %w", err)
+	}
+	if n >= maxMentionsPerPost {
+		return fmt.Errorf("a post can mention at most %d people", maxMentionsPerPost)
+	}
+	if _, err := r.pg.Pool.Exec(ctx,
+		`INSERT INTO post_mentions (post_id, user_id) VALUES ($1, $2)
+		 ON CONFLICT (post_id, user_id) DO NOTHING`,
+		postID, userID,
+	); err != nil {
+		return fmt.Errorf("add mention: %w", err)
+	}
+	return nil
+}
+
+// Remove untags a user from a post.
+func (r *MentionRepo) Remove(ctx context.Context, postID, userID string) error {
+	if _, err := r.pg.Pool.Exec(ctx,
+		`DELETE FROM post_mentions WHERE post_id = $1 AND user_id = $2`,
+		postID, userID,
+	); err != nil {
+		return fmt.Errorf("remove mention: %w", err)
+	}
+	return nil
+}
+
+// ListForPost returns the users tagged on a post (insertion order).
+func (r *MentionRepo) ListForPost(ctx context.Context, postID string) ([]model.UserSummary, error) {
+	rows, err := r.pg.Pool.Query(ctx, `
+		SELECT u.id, u.handle, u.name, u.avatar_url
+		FROM post_mentions m JOIN users u ON u.id = m.user_id
+		WHERE m.post_id = $1
+		ORDER BY m.created_at ASC`, postID)
+	if err != nil {
+		return nil, fmt.Errorf("list mentions: %w", err)
+	}
+	defer rows.Close()
+	out := []model.UserSummary{}
+	for rows.Next() {
+		var s model.UserSummary
+		if err := rows.Scan(&s.ID, &s.Handle, &s.Name, &s.AvatarURL); err != nil {
+			return nil, fmt.Errorf("scan mention: %w", err)
+		}
+		out = append(out, s)
+	}
+	return out, rows.Err()
+}
+
+// HydrateCounts fills MentionsCount on the given posts (one grouped query).
+func (r *MentionRepo) HydrateCounts(ctx context.Context, posts []*model.Post) error {
+	ids := make([]string, 0, len(posts))
+	for _, p := range posts {
+		if p != nil {
+			ids = append(ids, p.ID)
+		}
+	}
+	if len(ids) == 0 {
+		return nil
+	}
+	rows, err := r.pg.Pool.Query(ctx,
+		`SELECT post_id, count(*) FROM post_mentions WHERE post_id = ANY($1) GROUP BY post_id`, ids)
+	if err != nil {
+		return fmt.Errorf("hydrate mention counts: %w", err)
+	}
+	counts := make(map[string]int, len(ids))
+	for rows.Next() {
+		var id string
+		var c int
+		if err := rows.Scan(&id, &c); err != nil {
+			rows.Close()
+			return fmt.Errorf("scan mention count: %w", err)
+		}
+		counts[id] = c
+	}
+	rows.Close()
+	if err := rows.Err(); err != nil {
+		return err
+	}
+	for _, p := range posts {
+		if p != nil {
+			p.MentionsCount = counts[p.ID]
+		}
+	}
+	return nil
+}

internal/repository/post_repo.go

@@ -171,6 +171,32 @@ func (r *PostRepo) ListByHandle(ctx context.Context, handle string, limit, offse
 	return r.ListByUser(ctx, userID, limit, offset)
 }
 
+// ListMentioningByHandle returns posts that tag the given user (handle),
+// newest first — the "Mentions" profile tab. Same shape as the profile feed.
+func (r *PostRepo) ListMentioningByHandle(ctx context.Context, handle string, limit, offset int) ([]model.Post, int, error) {
+	var userID string
+	if err := r.pg.Pool.QueryRow(ctx, `SELECT id FROM users WHERE handle = $1`, handle).Scan(&userID); err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return []model.Post{}, 0, nil
+		}
+		return nil, 0, fmt.Errorf("lookup user by handle: %w", err)
+	}
+
+	var total int
+	if err := r.pg.Pool.QueryRow(ctx,
+		`SELECT count(*) FROM posts p JOIN post_mentions pm ON pm.post_id = p.id WHERE pm.user_id = $1`,
+		userID,
+	).Scan(&total); err != nil {
+		return nil, 0, fmt.Errorf("count mentioning posts: %w", err)
+	}
+	q := `SELECT ` + postSelectColumns + postSelectFrom + `
+		JOIN post_mentions pm ON pm.post_id = p.id
+		WHERE pm.user_id = $1
+		ORDER BY p.created_at DESC, p.id
+		LIMIT $2 OFFSET $3`
+	return r.collectPosts(ctx, total, q, userID, limit, offset)
+}
+
 // ListByUser returns the user's profile feed — every post they own,
 // authored or reshared. Reshares are interleaved naturally because
 // they're stored as real rows; sort by created_at gets the right order

internal/repository/social_graph_repo.go

@@ -380,6 +380,20 @@ func (r *NotificationRepo) UpsertLike(ctx context.Context, userID, actorID, post
 	return count, emailDue, nil
 }
 
+// CreateMention persists a "you were mentioned" notification linked to the
+// post. Unlike likes there's no aggregation — a mention is a deliberate,
+// low-volume event.
+func (r *NotificationRepo) CreateMention(ctx context.Context, userID, actorID, postID string) error {
+	if _, err := r.pg.Pool.Exec(ctx,
+		`INSERT INTO notifications (user_id, actor_id, kind, post_id)
+		 VALUES ($1, $2, 'post_mention', $3)`,
+		userID, actorID, postID,
+	); err != nil {
+		return fmt.Errorf("create mention notification: %w", err)
+	}
+	return nil
+}
+
 // LikeEmailsEnabled reports whether the user wants aggregated like emails.
 func (r *NotificationRepo) LikeEmailsEnabled(ctx context.Context, userID string) (bool, error) {
 	var enabled bool