/**
 * Serves playlists, their dumps and their covers. `:playlistId` is a
 * playlist's id; its page reads it by its path, through
 * `GET /api/users/:key/playlists/:slug`.
 *
 * - `POST /api/playlists` — signed in. Creates a playlist.
 * - `GET /api/playlists/:playlistId` — optional sign-in. Answers a playlist
 *   with the dumps the caller may see in it. A private one 404s but for its
 *   owner.
 * - `PUT /api/playlists/:playlistId` — signed in, as its owner or with
 *   `playlist:moderate`. Updates its title, slug, description and visibility.
 *   A new slug keeps the old one as an alias, 3 times a day at most but for
 *   those with `playlist:moderate`.
 * - `DELETE /api/playlists/:playlistId` — signed in, as its owner or with
 *   `playlist:moderate`. Deletes it.
 * - `POST /api/playlists/:playlistId/dumps/:dumpId` — signed in, as its owner
 *   or with `playlist:moderate`. Adds a dump at the top.
 * - `DELETE /api/playlists/:playlistId/dumps/:dumpId` — signed in, as its owner
 *   or with `playlist:moderate`. Removes a dump.
 * - `PUT /api/playlists/:playlistId/cover` — signed in, as its owner or with
 *   `playlist:moderate`. Replaces its cover (multipart `file`, at most 5 MB).
 * - `GET /api/playlists/:playlistId/cover?token=` — public, but a private
 *   playlist's cover needs its owner's media `token`. Serves its cover, or 404s
 *   without one.
 * - `PUT /api/playlists/:playlistId/order` — signed in, as its owner or with
 *   `playlist:moderate`. Reorders the dumps the caller can see in it.
 *
 * Which of the caller's playlists hold a dump is `GET /api/me/playlists`'s.
 *
 * @module
 */

import { Router } from "@oak/oak";
import { authenticateMedia, parseOptionalAuth } from "../lib/auth.ts";
import { type APIResponse } from "../../shared/api.ts";
import { APIException } from "../lib/api-exception.ts";
import {
  isCreatePlaylistRequest,
  isReorderPlaylistRequest,
  isUpdatePlaylistRequest,
} from "../validators/playlist.ts";
import type { Playlist, PlaylistWithDumps } from "../../shared/playlist.ts";
import { authMiddleware, type AuthState } from "../middleware/auth.ts";
import { can } from "../lib/permissions.ts";
import {
  addDumpToPlaylist,
  createPlaylist,
  deletePlaylist,
  getEditablePlaylist,
  getPlaylist,
  getPlaylistImageInfo,
  removeDumpFromPlaylist,
  reorderPlaylist,
  setPlaylistImage,
  updatePlaylist,
} from "../services/playlist-service.ts";
import {
  replaceUploadedFile,
  serveUploadedFile,
  validateImageUpload,
} from "../lib/upload.ts";
import { PLAYLIST_IMAGES_DIR } from "../config.ts";

/**
 * Mounted by `api/main.ts` behind the error, Open Graph and CORS middleware.
 * An `APIException` thrown by a handler becomes the JSON error response there.
 */
const router: Router<AuthState> = new Router<AuthState>({
  prefix: "/api/playlists",
});

router.post("/", authMiddleware, async (ctx) => {
  const body: unknown = await ctx.request.body.json();
  if (!isCreatePlaylistRequest(body)) {
    throw new APIException(400, "Invalid request");
  }
  const responseBody: APIResponse<Playlist> = {
    success: true,
    data: createPlaylist(body, ctx.state.user.userId),
  };
  ctx.response.status = 201;
  ctx.response.body = responseBody;
});

router.get("/:playlistId", async (ctx) => {
  const requestingUserId = await parseOptionalAuth(ctx);
  const responseBody: APIResponse<PlaylistWithDumps> = {
    success: true,
    data: getPlaylist(ctx.params.playlistId, requestingUserId),
  };
  ctx.response.body = responseBody;
});

router.put("/:playlistId", authMiddleware, async (ctx) => {
  const body: unknown = await ctx.request.body.json();
  if (!isUpdatePlaylistRequest(body)) {
    throw new APIException(400, "Invalid request");
  }
  const playlist = updatePlaylist(
    ctx.params.playlistId,
    body,
    ctx.state.user.userId,
    can(ctx.state.user, "playlist:moderate"),
  );
  const responseBody: APIResponse<Playlist> = { success: true, data: playlist };
  ctx.response.body = responseBody;
});

router.delete("/:playlistId", authMiddleware, (ctx) => {
  deletePlaylist(
    ctx.params.playlistId,
    ctx.state.user.userId,
    can(ctx.state.user, "playlist:moderate"),
  );
  ctx.response.status = 204;
});

router.post("/:playlistId/dumps/:dumpId", authMiddleware, (ctx) => {
  addDumpToPlaylist(
    ctx.params.playlistId,
    ctx.params.dumpId,
    ctx.state.user.userId,
    can(ctx.state.user, "playlist:moderate"),
  );
  ctx.response.status = 204;
});

router.delete("/:playlistId/dumps/:dumpId", authMiddleware, (ctx) => {
  removeDumpFromPlaylist(
    ctx.params.playlistId,
    ctx.params.dumpId,
    ctx.state.user.userId,
    can(ctx.state.user, "playlist:moderate"),
  );
  ctx.response.status = 204;
});

router.put("/:playlistId/cover", authMiddleware, async (ctx) => {
  const contentType = ctx.request.headers.get("content-type") ?? "";
  if (!contentType.includes("multipart/form-data")) {
    throw new APIException(400, "Expected multipart/form-data");
  }

  const body = await ctx.request.body.formData();
  const file = body.get("file");

  if (!(file instanceof File)) {
    throw new APIException(400, "Missing file field");
  }

  const data = new Uint8Array(await file.arrayBuffer());
  const mime = validateImageUpload(data);

  // Written before setPlaylistImage announces it, or clients would fetch the
  // new `?v=` URL too early and cache the old cover under it.
  const { id } = getEditablePlaylist(
    ctx.params.playlistId,
    ctx.state.user.userId,
    can(ctx.state.user, "playlist:moderate"),
  );
  await replaceUploadedFile(`${PLAYLIST_IMAGES_DIR}/${id}`, data);
  const playlist = setPlaylistImage(
    id,
    mime,
    ctx.state.user.userId,
    can(ctx.state.user, "playlist:moderate"),
  );
  const responseBody: APIResponse<Playlist> = { success: true, data: playlist };
  ctx.response.body = responseBody;
});

router.get("/:playlistId/cover", async (ctx) => {
  // An <img> can't send an Authorization header, so a private playlist's owner
  // is known by the media token in the query string, as for dump files.
  const token = ctx.request.url.searchParams.get("token");
  const viewerId = token ? await authenticateMedia(token) : null;
  const info = getPlaylistImageInfo(ctx.params.playlistId, viewerId);
  if (!info) {
    ctx.response.status = 404;
    return;
  }
  // The URL may carry a media token, which a Referer would leak.
  ctx.response.headers.set("Referrer-Policy", "no-referrer");
  await serveUploadedFile(
    ctx,
    `${PLAYLIST_IMAGES_DIR}/${info.id}`,
    info.imageMime,
    3600,
    !info.isPublic,
  );
});

router.put("/:playlistId/order", authMiddleware, async (ctx) => {
  const body: unknown = await ctx.request.body.json();
  if (!isReorderPlaylistRequest(body)) {
    throw new APIException(400, "Invalid request");
  }
  reorderPlaylist(
    ctx.params.playlistId,
    body.dumpIds,
    ctx.state.user.userId,
    can(ctx.state.user, "playlist:moderate"),
  );
  const responseBody: APIResponse<null> = { success: true, data: null };
  ctx.response.body = responseBody;
});

export default router;