/**
 * Checks the playlist request bodies, for the playlist routes to answer a 400.
 *
 * @module
 */

import type {
  CreatePlaylistRequest,
  ReorderPlaylistRequest,
  UpdatePlaylistRequest,
} from "../../shared/playlist.ts";
import { VALIDATION } from "../../shared/validation.ts";

/** Checks that `categoryIds`, when `o` has it, is a list of strings. */
function hasValidCategoryIds(o: Record<string, unknown>): boolean {
  return !("categoryIds" in o) ||
    (Array.isArray(o.categoryIds) &&
      o.categoryIds.every((id) => typeof id === "string"));
}

/** Checks that `title` isn't blank and, trimmed, fits the limit. */
function isValidTitle(title: string): boolean {
  const trimmed = title.trim();
  return trimmed.length > 0 && trimmed.length <= VALIDATION.PLAYLIST_TITLE_MAX;
}

/**
 * Checks whether `obj` is a {@link CreatePlaylistRequest} with a title that
 * isn't blank, and a title and description within the `VALIDATION` limits. A
 * null description passes. Whether its category ids name playlist categories
 * is the playlist service's to check.
 */
export function isCreatePlaylistRequest(
  obj: unknown,
): obj is CreatePlaylistRequest {
  if (
    !obj || typeof obj !== "object" ||
    !("title" in obj) || typeof obj.title !== "string" ||
    !("isPublic" in obj) || typeof obj.isPublic !== "boolean"
  ) return false;
  const o = obj as Record<string, unknown>;
  if (!isValidTitle(o.title as string)) return false;
  if (
    "description" in o && typeof o.description !== "string" &&
    o.description !== null
  ) return false;
  if (
    typeof o.description === "string" &&
    (o.description as string).length > VALIDATION.PLAYLIST_DESCRIPTION_MAX
  ) return false;
  return hasValidCategoryIds(o);
}

/**
 * Checks whether `obj` is an {@link UpdatePlaylistRequest} whose title, if
 * given, isn't blank, with a title and description within the `VALIDATION`
 * limits.
 */
export function isUpdatePlaylistRequest(
  obj: unknown,
): obj is UpdatePlaylistRequest {
  if (!obj || typeof obj !== "object") return false;
  const o = obj as Record<string, unknown>;
  // Its format is changeSlug's check, which says what is wrong.
  if ("slug" in o && typeof o.slug !== "string") return false;
  if ("title" in o) {
    if (typeof o.title !== "string") return false;
    if (!isValidTitle(o.title as string)) return false;
  }
  if (
    "description" in o && typeof o.description !== "string" &&
    o.description !== null
  ) return false;
  if (
    typeof o.description === "string" &&
    (o.description as string).length > VALIDATION.PLAYLIST_DESCRIPTION_MAX
  ) return false;
  if ("isPublic" in o && typeof o.isPublic !== "boolean") return false;
  return hasValidCategoryIds(o);
}

/**
 * Checks whether `obj` is a {@link ReorderPlaylistRequest}. Whether its ids
 * match the playlist is `reorderPlaylist`'s to check.
 */
export function isReorderPlaylistRequest(
  obj: unknown,
): obj is ReorderPlaylistRequest {
  return !!obj && typeof obj === "object" &&
    "dumpIds" in obj && Array.isArray(obj.dumpIds) &&
    (obj.dumpIds as unknown[]).every((id) => typeof id === "string");
}