/**
 * Previews links to this site's own dump, user and playlist pages from the
 * database, for `rich-content-service.ts`. No request goes out, so this works
 * even when the site runs on a private host that `fetchWithTimeout` refuses.
 *
 * @module
 */

import type { RichContent } from "../../../shared/dump.ts";
import type { RichContentProvider } from "./provider.ts";
import { getDump } from "../../services/dump-service.ts";
import { getUserByUsername } from "../../services/user-service.ts";
import { getPlaylistById } from "../../services/playlist-service.ts";
import { PUBLIC_URL, THEME_COLOR } from "../../config.ts";
import { isSelfUrl } from "../../lib/self-url.ts";

const DUMP_RE = /^\/dumps\/([^/]+)$/;
const USER_RE = /^\/users\/([^/]+)$/;
const PLAYLIST_RE = /^\/playlists\/([^/]+)$/;

/**
 * Gives a link to this site without a thumbnail a placeholder in the site's
 * icon and color.
 */
const SELF_BRANDING = {
  siteName: "gerbeur",
  faviconUrl: `${PUBLIC_URL}/apple-touch-icon.png`,
  accentColor: THEME_COLOR,
} as const;

/**
 * Comes before the generic provider, and claims what `isSelfUrl` accepts. Its
 * `fetch` rejects with the services' 404 `APIException` for a missing page or
 * a private dump. A private playlist is previewed all the same.
 */
export const selfProvider: RichContentProvider = {
  name: "self",

  matches(url: string): boolean {
    try {
      return isSelfUrl(new URL(url));
    } catch {
      return false;
    }
  },

  fetch(url: string): Promise<RichContent> {
    const { pathname } = new URL(url);

    const dumpMatch = pathname.match(DUMP_RE);
    if (dumpMatch) {
      const dump = getDump(dumpMatch[1]);
      let thumbnailUrl: string | undefined;
      if (dump.kind === "file" && dump.fileMime?.startsWith("image/")) {
        thumbnailUrl = `${PUBLIC_URL}/api/files/${dump.id}`;
      } else if (dump.richContent?.thumbnailUrl) {
        thumbnailUrl = dump.richContent.thumbnailUrl;
      }
      return Promise.resolve({
        type: "generic",
        url,
        ...SELF_BRANDING,
        title: dump.title,
        description: dump.comment,
        thumbnailUrl,
      });
    }

    const userMatch = pathname.match(USER_RE);
    if (userMatch) {
      const user = getUserByUsername(userMatch[1]);
      const thumbnailUrl = user.avatarMime
        ? `${PUBLIC_URL}/api/avatars/${user.id}`
        : undefined;
      return Promise.resolve({
        type: "generic",
        url,
        ...SELF_BRANDING,
        title: user.username,
        description: user.description,
        thumbnailUrl,
      });
    }

    const playlistMatch = pathname.match(PLAYLIST_RE);
    if (playlistMatch) {
      const playlist = getPlaylistById(playlistMatch[1]);
      const thumbnailUrl = playlist.imageMime
        ? `${PUBLIC_URL}/api/playlists/${playlist.id}/image`
        : undefined;
      return Promise.resolve({
        type: "generic",
        url,
        ...SELF_BRANDING,
        title: playlist.title,
        description: playlist.description,
        thumbnailUrl,
      });
    }

    // Unreachable: isSelfUrl accepts only the three paths above.
    return Promise.resolve({ type: "generic", url });
  },
};