/**
 * Device picker helper exposed for customers who want to build their
 * own "choose your camera and mic" screen.
 *
 * Browsers hide device labels (returning empty strings) until the page
 * has been granted permission to at least one device of that kind.
 * This helper handles the two-step dance:
 *
 *   1. Optionally call `getUserMedia({ video, audio })` once just to
 *      unlock labels (a "probe" stream).
 *   2. Stop the probe stream immediately.
 *   3. Call `enumerateDevices()` and return the labelled list.
 *
 * Without step 1, labels are empty strings — customers building a
 * picker hit this gotcha first thing if they try `enumerateDevices()`
 * directly. We default to probing for both video and audio so the
 * returned list is fully labelled.
 *
 * Must be called inside a user-activation handler when `probe` is
 * true (because step 1 calls getUserMedia, which has activation
 * requirements). With `probe: false`, this is just a thin wrapper
 * around enumerateDevices and labels may be empty.
 */

export interface MediaDeviceInfoLite {
  deviceId: string;
  label: string;
}

export interface MediaDeviceList {
  cameras: MediaDeviceInfoLite[];
  mics: MediaDeviceInfoLite[];
  /** audiooutput devices (speakers/headphones). Note: Safari does not expose
   *  these, so the list can be empty even when a speaker is in use. */
  speakers: MediaDeviceInfoLite[];
}

export interface EnumerateOptions {
  /**
   * If true (default), probe with a one-shot getUserMedia call to
   * unlock device labels. Set false if the page already has camera
   * AND mic permissions and you just want a labelled list.
   */
  probe?: boolean;
  /** Probe for video labels. Default: true. */
  video?: boolean;
  /** Probe for audio labels. Default: true. */
  audio?: boolean;
}

export async function enumerateMediaDevices(
  options: EnumerateOptions = {},
): Promise<MediaDeviceList> {
  const opts = {
    probe: options.probe ?? true,
    video: options.video ?? true,
    audio: options.audio ?? true,
  };

  if (typeof navigator === "undefined" || !navigator.mediaDevices?.enumerateDevices) {
    return { cameras: [], mics: [], speakers: [] };
  }

  if (opts.probe && (opts.video || opts.audio)) {
    let probeStream: MediaStream | null = null;
    try {
      probeStream = await navigator.mediaDevices.getUserMedia({
        video: opts.video,
        audio: opts.audio,
      });
    } catch {
      // Probe failed (permission denied, no devices, in-use). Fall
      // through and enumerate anyway — labels may be empty but
      // deviceIds are still useful for picker UIs that show generic
      // entries like "Camera 1", "Camera 2".
    } finally {
      probeStream?.getTracks().forEach((t) => t.stop());
    }
  }

  const devices = await navigator.mediaDevices.enumerateDevices();
  const cameras: MediaDeviceInfoLite[] = [];
  const mics: MediaDeviceInfoLite[] = [];
  const speakers: MediaDeviceInfoLite[] = [];
  for (const d of devices) {
    if (d.kind === "videoinput") {
      cameras.push({ deviceId: d.deviceId, label: d.label });
    } else if (d.kind === "audioinput") {
      mics.push({ deviceId: d.deviceId, label: d.label });
    } else if (d.kind === "audiooutput") {
      speakers.push({ deviceId: d.deviceId, label: d.label });
    }
  }
  return { cameras, mics, speakers };
}