/**
 * Previews links to this site's own dump, user and playlist pages, as
 * `parsePagePath` reads them, 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 { getDumpByPath } from "../../services/dump-service.ts";
import { resolveUsername } from "../../services/user-service.ts";
import { getPlaylistByPath } from "../../services/playlist-service.ts";
import { APIException } from "../../lib/api-exception.ts";
import { PUBLIC_URL, THEME_COLOR } from "../../config.ts";
import { isSelfUrl } from "../../lib/self-url.ts";
import { parsePagePath } from "../../../shared/paths.ts";

/**
 * 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. A
 * profile's tab previews as the profile. Its `fetch` rejects with a 404
 * `APIException` for a missing page, a private dump or a private playlist:
 * the preview is stored in the linking dump, which others may see.
 */
export const selfProvider: RichContentProvider = {
  name: "self",

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

  fetch(url: string): Promise<RichContent> {
    // matches() let only these paths through.
    const page = parsePagePath(new URL(url).pathname)!;
    const user = resolveUsername(page.username);

    if (page.kind === "dump") {
      const dump = getDumpByPath(user.id, page.slug);
      let thumbnailUrl: string | undefined;
      if (dump.kind === "file" && dump.fileMime?.startsWith("image/")) {
        thumbnailUrl = `${PUBLIC_URL}/api/dumps/${dump.id}/file`;
      } else if (dump.richContent?.thumbnailUrl) {
        thumbnailUrl = dump.richContent.thumbnailUrl;
      }
      return Promise.resolve({
        type: "generic",
        url,
        ...SELF_BRANDING,
        title: dump.title,
        description: dump.comment,
        thumbnailUrl,
      });
    }

    if (page.kind === "playlist") {
      const playlist = getPlaylistByPath(user.id, page.slug);
      if (!playlist.isPublic) {
        throw new APIException(404, "Playlist not found");
      }
      const thumbnailUrl = playlist.imageMime
        ? `${PUBLIC_URL}/api/playlists/${playlist.id}/cover`
        : undefined;
      return Promise.resolve({
        type: "generic",
        url,
        ...SELF_BRANDING,
        title: playlist.title,
        description: playlist.description,
        thumbnailUrl,
      });
    }

    const thumbnailUrl = user.avatarMime
      ? `${PUBLIC_URL}/api/users/${user.id}/avatar`
      : undefined;
    return Promise.resolve({
      type: "generic",
      url,
      ...SELF_BRANDING,
      title: user.username,
      description: user.description,
      thumbnailUrl,
    });
  },
};