/**
 * Checks the rows `follow-service.ts` reads from `follows` to answer what a
 * user follows.
 *
 * @module
 */

import type { SQLOutputValue } from "node:sqlite";

/**
 * Read by `getFollowStatus`. Exactly one of `followed_user_id` and
 * `followed_playlist_id` is set, as the table's CHECK constraint requires.
 */
export interface FollowRow {
  id: string;
  follower_id: string;
  followed_user_id: string | null;
  followed_playlist_id: string | null;
  created_at: string;
  [key: string]: SQLOutputValue;
}

/**
 * Checks whether `obj`, a row `getFollowStatus` selected, is a
 * {@link FollowRow}.
 */
export function isFollowRow(
  obj: unknown,
): obj is FollowRow {
  return !!obj && typeof obj === "object" &&
    "id" in obj && typeof obj.id === "string" &&
    "follower_id" in obj && typeof obj.follower_id === "string" &&
    "created_at" in obj && typeof obj.created_at === "string" &&
    "followed_user_id" in obj && (obj.followed_user_id === null ||
      typeof obj.followed_user_id === "string") &&
    "followed_playlist_id" in obj && (obj.followed_playlist_id === null ||
      typeof obj.followed_playlist_id === "string");
}