/**
 * Previews SoundCloud links from their page, for `rich-content-service.ts`.
 *
 * @module
 */

import type { RichContent } from "../../../shared/dump.ts";
import type { RichContentProvider } from "./provider.ts";
import { parsePage } from "../html.ts";
import { fetchPage } from "../fetch.ts";
import { genericPreview } from "./generic.ts";

/** SoundCloud's own hosts, the short links' `on.` included. */
const SOUNDCLOUD_HOSTS = new Set([
  "soundcloud.com",
  "www.soundcloud.com",
  "m.soundcloud.com",
  "on.soundcloud.com",
]);

/**
 * Returns the soundcloud.com address of the page, which the embed player
 * takes: its `og:url`, or else the URL it was served from. A short link only
 * redirects, so it is never the answer; tracking parameters are dropped.
 */
function pageAddress(ogUrl: string | undefined, finalUrl: string): string {
  for (const raw of [ogUrl, finalUrl]) {
    if (!raw) continue;
    try {
      const url = new URL(raw);
      if (
        !SOUNDCLOUD_HOSTS.has(url.hostname) ||
        url.hostname === "on.soundcloud.com"
      ) continue;
      return `https://soundcloud.com${url.pathname}`;
    } catch {
      continue;
    }
  }
  return finalUrl;
}

/**
 * Claims SoundCloud's hosts, short links included, and builds the embed
 * player's URL from the page's address.
 */
export const soundcloudProvider: RichContentProvider = {
  name: "soundcloud",

  matches(url: string): boolean {
    try {
      return SOUNDCLOUD_HOSTS.has(new URL(url).hostname);
    } catch {
      return false;
    }
  },

  async fetch(url: string): Promise<RichContent> {
    const fetched = await fetchPage(url);
    const page = fetched.html === undefined
      ? undefined
      : parsePage(fetched.html, fetched.url);
    const address = pageAddress(page?.meta("og:url"), fetched.url);
    return {
      ...(page ? genericPreview(page, url, fetched.url) : { url }),
      type: "soundcloud",
      siteName: "SoundCloud",
      embedUrl: `https://w.soundcloud.com/player/?url=${
        encodeURIComponent(address)
      }&visual=true&auto_play=false`,
    };
  },
};