/**
 * The follow routes, all for what the caller follows.
 *
 * - `GET /api/follows/status` — signed in. Answers the ids of the users and
 *   playlists they follow.
 * - `GET /api/follows/feed/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/follows/feed/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.
 * - `POST /api/follows/users/:userId` — signed in. Follows a user.
 * - `DELETE /api/follows/users/:userId` — signed in. Stops following a user.
 * - `POST /api/follows/playlists/:playlistId` — signed in. Follows a public
 *   playlist.
 * - `DELETE /api/follows/playlists/:playlistId` — signed in. Stops following a
 *   playlist.
 *
 * @module
 */

import { Router } from "@oak/oak";
import { authMiddleware } from "../middleware/auth.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 { getCategoryIdBySlug } from "../services/category-service.ts";

/**
 * Resolves the optional ?category=<slug> filter. Returns the matching category
 * id, or "missing" when a slug was given but matches nothing (so the feed comes
 * back empty rather than unfiltered), or undefined when no filter was
 * requested.
 */
function resolveCategoryFilter(
  params: URLSearchParams,
): string | "missing" | undefined {
  const slug = params.get("category");
  if (!slug) return undefined;
  return getCategoryIdBySlug(slug) ?? "missing";
}

/** The feed a filter naming no category yields. */
const EMPTY_FEED: Page<Dump> = { items: [], hasMore: false };

/** The router serving the endpoints the module doc lists. */
const router: Router = new Router({ prefix: "/api/follows" });

// Static routes first to prevent Oak matching "status"/"feed" as a :param

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

router.get("/feed/users", authMiddleware, (ctx) => {
  const { page, limit } = parsePagination(ctx.request.url.searchParams);
  const categoryId = resolveCategoryFilter(ctx.request.url.searchParams);
  const { items, hasMore } = categoryId === "missing"
    ? EMPTY_FEED
    : getFollowedUsersDumpFeed(ctx.state.user.userId, page, limit, categoryId);
  const data: PaginatedData<Dump> = {
    items,
    hasMore,
  };
  const body: APIResponse<PaginatedData<Dump>> = { success: true, data };
  ctx.response.body = body;
});

router.get("/feed/playlists", authMiddleware, (ctx) => {
  const { page, limit } = parsePagination(ctx.request.url.searchParams);
  const categoryId = resolveCategoryFilter(ctx.request.url.searchParams);
  const { items, hasMore } = categoryId === "missing"
    ? EMPTY_FEED
    : getFollowedPlaylistsDumpFeed(
      ctx.state.user.userId,
      page,
      limit,
      categoryId,
    );
  const data: PaginatedData<Dump> = {
    items,
    hasMore,
  };
  const body: APIResponse<PaginatedData<Dump>> = { success: true, data };
  ctx.response.body = body;
});

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

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

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

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

export default router;