/**
 * Serves what the caller follows, and the index's "follow" tab built from it.
 * What another user follows is served by `routes/users.ts`.
 *
 * - `GET /api/me/follow` — signed in. Answers the ids of the users and
 *   playlists they follow.
 * - `PUT /api/me/follow/users/:userId` — signed in. Follows a user.
 * - `DELETE /api/me/follow/users/:userId` — signed in. Stops following a user.
 * - `PUT /api/me/follow/playlists/:playlistId` — signed in. Follows a public
 *   playlist.
 * - `DELETE /api/me/follow/playlists/:playlistId` — signed in. Stops following
 *   a playlist.
 * - `GET /api/me/feed?from=users&page=&limit=&category=` — signed in. Answers
 *   a page of the public dumps of the users they follow, newest first,
 *   optionally in one category.
 * - `GET /api/me/feed?from=playlists&page=&limit=&category=` — signed in.
 *   Answers a page of the public dumps in the public playlists they follow,
 *   most recently added first, optionally in one category.
 *
 * @module
 */

import { Router } from "@oak/oak";
import { authMiddleware } from "../middleware/auth.ts";
import { APIException } from "../lib/api-exception.ts";
import type { APIResponse, PaginatedData } from "../../shared/api.ts";
import type { Dump } from "../../shared/dump.ts";
import type { FollowStatus } from "../../shared/follow.ts";
import { type Page, parsePagination } from "../lib/pagination.ts";
import {
  followPlaylist,
  followUser,
  getFollowedPlaylistsDumpFeed,
  getFollowedUsersDumpFeed,
  getFollowStatus,
  unfollowPlaylist,
  unfollowUser,
} from "../services/follow-service.ts";
import { resolveCategoryFilter } from "../services/category-service.ts";

const EMPTY_FEED: Page<Dump> = { items: [], hasMore: false };

/**
 * 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 = new Router({ prefix: "/api/me" });

router.get("/follow", authMiddleware, (ctx) => {
  const status = getFollowStatus(ctx.state.user.userId);
  const body: APIResponse<FollowStatus> = { success: true, data: status };
  ctx.response.body = body;
});

router.put("/follow/users/:userId", authMiddleware, (ctx) => {
  followUser(ctx.state.user.userId, ctx.params.userId);
  ctx.response.status = 204;
});

router.delete("/follow/users/:userId", authMiddleware, (ctx) => {
  unfollowUser(ctx.state.user.userId, ctx.params.userId);
  ctx.response.status = 204;
});

router.put("/follow/playlists/:playlistId", authMiddleware, (ctx) => {
  followPlaylist(ctx.state.user.userId, ctx.params.playlistId);
  ctx.response.status = 204;
});

router.delete("/follow/playlists/:playlistId", authMiddleware, (ctx) => {
  unfollowPlaylist(ctx.state.user.userId, ctx.params.playlistId);
  ctx.response.status = 204;
});

router.get("/feed", authMiddleware, (ctx) => {
  const params = ctx.request.url.searchParams;
  const from = params.get("from");
  if (from !== "users" && from !== "playlists") {
    throw new APIException(400, "from must be users or playlists");
  }
  const { page, limit } = parsePagination(params);
  const categoryId = resolveCategoryFilter("dump", params);
  const userId = ctx.state.user.userId;
  const { items, hasMore } = categoryId === "missing"
    ? EMPTY_FEED
    : from === "users"
    ? getFollowedUsersDumpFeed(userId, page, limit, categoryId)
    : getFollowedPlaylistsDumpFeed(userId, page, limit, categoryId);
  const body: APIResponse<PaginatedData<Dump>> = {
    success: true,
    data: { items, hasMore },
  };
  ctx.response.body = body;
});

export default router;