feat: broadcast

internal/repository/push_repo.go

@@ -54,6 +54,30 @@ func (r *PushRepo) ListByUser(ctx context.Context, userID string) ([]model.PushS
 
 // PruneToMostRecent keeps only the `keep` most-recently-used subscriptions for
 // a user, deleting older ones — a soft per-user device cap.
+// SubscribedUserIDs lists everyone with at least one live push subscription.
+//
+// Used by broadcasts, which fan out to the whole user base: iterating users
+// and asking each for subscriptions would query for the (large) majority who
+// have never enabled push.
+func (r *PushRepo) SubscribedUserIDs(ctx context.Context) ([]string, error) {
+	rows, err := r.pg.Pool.Query(ctx,
+		`SELECT DISTINCT user_id FROM push_subscriptions`)
+	if err != nil {
+		return nil, fmt.Errorf("subscribed users: %w", err)
+	}
+	defer rows.Close()
+
+	out := []string{}
+	for rows.Next() {
+		var id string
+		if err := rows.Scan(&id); err != nil {
+			return nil, fmt.Errorf("scan subscribed user: %w", err)
+		}
+		out = append(out, id)
+	}
+	return out, rows.Err()
+}
+
 func (r *PushRepo) PruneToMostRecent(ctx context.Context, userID string, keep int) error {
 	if keep < 1 {
 		keep = 1