feat: add stickers

internal/repository/chat_repo.go

@@ -23,6 +23,9 @@ var (
 	ErrAttachmentGone     = errors.New("attachment not found")
 	ErrMessageNotHere     = errors.New("message is not in this conversation")
 	ErrUserGone           = errors.New("user not found")
+	// ErrStickerNotOwned covers both "no such sticker" and "not yours" on
+	// purpose: the catalog shouldn't be enumerable by probing keys.
+	ErrStickerNotOwned = errors.New("sticker not available")
 )
 
 type ChatRepo struct{ pg *Postgres }
@@ -1227,6 +1230,101 @@ func (r *ChatRepo) ClearReaction(ctx context.Context, messageID, userID string)
 	return conversationID, nil
 }
 
+// Stickers lists everything a user may send: rewards they earned through
+// sādhana, plus stickers they saved from a chat.
+//
+// One UNION rather than two calls and a merge in Go — "may I send this?" and
+// "what can I send?" then have exactly one answer, and it stays correct if a
+// user both earns and is sent the same sticker.
+func (r *ChatRepo) Stickers(ctx context.Context, userID string) ([]model.Sticker, error) {
+	rows, err := r.pg.Pool.Query(ctx, `
+		SELECT sr.key, sr.name, sr.image_url, bool_and(src.saved) AS saved
+		FROM (
+		    SELECT reward_id, FALSE AS saved FROM sadhna_reward_grants WHERE user_id = $1
+		    UNION ALL
+		    SELECT reward_id, TRUE  AS saved FROM saved_stickers      WHERE user_id = $1
+		) src
+		JOIN sadhna_rewards sr ON sr.id = src.reward_id
+		WHERE sr.active
+		GROUP BY sr.key, sr.name, sr.image_url, sr.sort
+		ORDER BY sr.sort, sr.name`, userID)
+	if err != nil {
+		return nil, fmt.Errorf("stickers: %w", err)
+	}
+	defer rows.Close()
+
+	out := []model.Sticker{}
+	for rows.Next() {
+		var s model.Sticker
+		if err := rows.Scan(&s.Key, &s.Name, &s.ImageURL, &s.Saved); err != nil {
+			return nil, fmt.Errorf("scan sticker: %w", err)
+		}
+		out = append(out, s)
+	}
+	return out, rows.Err()
+}
+
+// Sticker looks up one piece of artwork a user is entitled to send.
+// ErrStickerNotOwned when they have neither earned nor saved it.
+func (r *ChatRepo) Sticker(ctx context.Context, userID, key string) (*model.Sticker, error) {
+	var s model.Sticker
+	err := r.pg.Pool.QueryRow(ctx, `
+		SELECT sr.key, sr.name, sr.image_url
+		FROM sadhna_rewards sr
+		WHERE sr.key = $2 AND sr.active
+		  AND (EXISTS (SELECT 1 FROM sadhna_reward_grants g
+		               WHERE g.user_id = $1 AND g.reward_id = sr.id)
+		    OR EXISTS (SELECT 1 FROM saved_stickers ss
+		               WHERE ss.user_id = $1 AND ss.reward_id = sr.id))`,
+		userID, key).Scan(&s.Key, &s.Name, &s.ImageURL)
+	if errors.Is(err, pgx.ErrNoRows) {
+		return nil, ErrStickerNotOwned
+	}
+	if err != nil {
+		return nil, fmt.Errorf("sticker: %w", err)
+	}
+	return &s, nil
+}
+
+// SaveSticker keeps a sticker someone sent. Idempotent.
+//
+// Only stickers that actually appear on a message in a thread the caller is
+// in can be saved — otherwise knowing a key would be enough to collect the
+// whole catalog without earning any of it.
+func (r *ChatRepo) SaveSticker(ctx context.Context, userID, key, fromMessageID string) error {
+	tag, err := r.pg.Pool.Exec(ctx, `
+		INSERT INTO saved_stickers (user_id, reward_id, saved_from)
+		SELECT $1, sr.id, m.sender_id
+		FROM message_attachments a
+		JOIN messages m ON m.id = a.message_id
+		JOIN conversation_participants p
+		  ON p.conversation_id = m.conversation_id AND p.user_id = $1 AND p.left_at IS NULL
+		JOIN sadhna_rewards sr ON sr.key = a.entity_id AND sr.active
+		WHERE a.message_id = $3 AND a.kind = 'sticker' AND a.entity_id = $2
+		ON CONFLICT (user_id, reward_id) DO NOTHING`,
+		userID, key, fromMessageID)
+	if err != nil {
+		return fmt.Errorf("save sticker: %w", err)
+	}
+	// Zero rows means the sticker isn't on that message, or the caller isn't
+	// in the thread. Both are "you can't have this", not "already saved" —
+	// a repeat save conflicts instead, which also reports zero.
+	if tag.RowsAffected() == 0 {
+		var exists bool
+		if err := r.pg.Pool.QueryRow(ctx, `
+			SELECT EXISTS (SELECT 1 FROM saved_stickers ss
+			               JOIN sadhna_rewards sr ON sr.id = ss.reward_id
+			               WHERE ss.user_id = $1 AND sr.key = $2)`,
+			userID, key).Scan(&exists); err != nil {
+			return fmt.Errorf("save sticker check: %w", err)
+		}
+		if !exists {
+			return ErrStickerNotOwned
+		}
+	}
+	return nil
+}
+
 // ReactionDetails lists everyone who reacted to one message, newest first.
 //
 // Separate from ReactionsFor: the grouped counts are what a thread renders,