// An adapter of stream audit (wai/extensions/stream-audit.md §13) for a web player whose
// configuration takes a loader class: it wraps the player's default loader, so that every
// playlist and fragment the player loads reaches the session (./audit.js) as it reaches the
// player, and key loads never do (§4.1). The player's own interface is named here, and only
// here, because the adapter has to call it. // allow-name: the open-source web player whose loader interface this adapter wraps
//
//   const audit = loaderAudit(Hls, session);                // allow-name: the player's constructor
//   const player = new Hls({ loader: audit.Loader });       // allow-name: the player's constructor
//   attach(video, session, { programMs: () => audit.programMs(player) });

const enc = new TextEncoder();

/**
 * The loader class to configure, and the program time of the position (the player's
 * `playingDate`, from `EXT-X-PROGRAM-DATE-TIME`), for `session`.
 */
export function loaderAudit(Player, session) {
  const Base = Player.DefaultConfig.loader;
  class Loader extends Base {
    load(context, config, callbacks) {
      if (context.type === "key" || context.keyInfo) return super.load(context, config, callbacks);
      const onSuccess = callbacks.onSuccess;
      const wrapped = {
        ...callbacks,
        onSuccess: (response, stats, ctx, details) => {
          try {
            record(response, ctx, details);
          } catch {
            // The audit never stands in the player's way.
          }
          onSuccess(response, stats, ctx, details);
        },
      };
      return super.load(context, config, wrapped);
    }
  }
  const header = (details, h) => details?.getResponseHeader?.(h) ?? details?.headers?.get?.(h) ?? null;
  function record(response, ctx, details) {
    const url = response.url || ctx.url;
    const text = typeof response.data === "string" ? response.data : null;
    const bytes = text !== null ? enc.encode(text) : new Uint8Array(response.data);
    const media = ctx.type === "media-fragment" || !!ctx.frag;
    if (text !== null && text.includes("#EXTINF")) session.playlist(text, url);
    session.object({ url, bytes, media, status: response.code ?? 200, cmsdStatic: header(details, "cmsd-static"), cmsdDynamic: header(details, "cmsd-dynamic") });
  }
  return { Loader, programMs: (player) => player.playingDate?.getTime() ?? null };
}