/**
 * @packageDocumentation
 * @module Voice
 * @internalapi
 */
// @ts-nocheck

import EventTarget from './eventtarget';

const POLL_INTERVAL_MS = 500;

let nativeMediaDevices = null;

/**
 * Make a custom MediaDevices object, and proxy through existing functionality. If
 *   devicechange is present, we simply reemit the event. If not, we will do the
 *   detection ourselves and fire the event when necessary. The same logic exists
 *   for deviceinfochange for consistency, however deviceinfochange is our own event
 *   so it is unlikely that it will ever be native. The w3c spec for devicechange
 *   is unclear as to whether MediaDeviceInfo changes (such as label) will
 *   trigger the devicechange event. We have an open question on this here:
 *   https://bugs.chromium.org/p/chromium/issues/detail?id=585096
 */
class MediaDevicesShim extends EventTarget {
  constructor() {
    super();

    this._defineEventHandler('devicechange');
    this._defineEventHandler('deviceinfochange');

    const knownDevices = [];
    Object.defineProperties(this, {
      _deviceChangeIsNative: { value: reemitNativeEvent(this, 'devicechange') },
      _deviceInfoChangeIsNative: { value: reemitNativeEvent(this, 'deviceinfochange') },
      _knownDevices: { value: knownDevices },
      _pollInterval: {
        value: null,
        writable: true,
      },
    });

    if (typeof nativeMediaDevices.enumerateDevices === 'function') {
      nativeMediaDevices.enumerateDevices().then(devices => {
        devices.sort(sortDevicesById).forEach(d => knownDevices.push(d));
      });
    }

    this._eventEmitter.on('newListener', function maybeStartPolling(eventName) {
      if (eventName !== 'devicechange' && eventName !== 'deviceinfochange') {
        return;
      }

      // TODO: Remove polling in the next major release.
      this._pollInterval = this._pollInterval
        || setInterval(sampleDevices.bind(null, this), POLL_INTERVAL_MS);
    }.bind(this));

    this._eventEmitter.on('removeListener', function maybeStopPolling() {
      if (this._pollInterval && !hasChangeListeners(this)) {
        clearInterval(this._pollInterval);
        this._pollInterval = null;
      }
    }.bind(this));
  }
}

MediaDevicesShim.prototype.enumerateDevices = function enumerateDevices() {
  if (nativeMediaDevices && typeof nativeMediaDevices.enumerateDevices === 'function') {
    return nativeMediaDevices.enumerateDevices(...arguments);
  }
  return null;
};

MediaDevicesShim.prototype.getUserMedia = function getUserMedia() {
  return nativeMediaDevices.getUserMedia(...arguments);
};

function deviceInfosHaveChanged(newDevices, oldDevices) {
  newDevices = newDevices.filter(d => d.kind === 'audioinput' || d.kind === 'audiooutput');
  oldDevices = oldDevices.filter(d => d.kind === 'audioinput' || d.kind === 'audiooutput');

  // On certain browsers, we cannot use deviceId as a key for comparison.
  // It's missing along with the device label if the customer has not granted permission.
  // The following checks whether some old devices have empty labels and if they are now available.
  // This means, the user has granted permissions and the device info have changed.
  if (oldDevices.some(d => !d.deviceId) &&
    newDevices.some(d => !!d.deviceId)) {
    return true;
  }

  // Use both deviceId and "kind" to create a unique key
  // since deviceId is not unique across different kinds of devices.
  const oldLabels = oldDevices.reduce((map, device) =>
    map.set(`${device.deviceId}-${device.kind}`, device.label), new Map());

  return newDevices.some(device => {
    const oldLabel = oldLabels.get(`${device.deviceId}-${device.kind}`);
    return typeof oldLabel !== 'undefined' && oldLabel !== device.label;
  });
}

function devicesHaveChanged(newDevices, oldDevices) {
  return newDevices.length !== oldDevices.length
    || propertyHasChanged('deviceId', newDevices, oldDevices);
}

function hasChangeListeners(mediaDevices) {
  return ['devicechange', 'deviceinfochange'].reduce((count, event) => count + mediaDevices._eventEmitter.listenerCount(event), 0) > 0;
}

/**
 * Sample the current set of devices and emit devicechange event if a device has been
 *   added or removed, and deviceinfochange if a device's label has changed.
 * @param {MediaDevicesShim} mediaDevices
 * @private
 */
function sampleDevices(mediaDevices) {
  nativeMediaDevices.enumerateDevices().then(newDevices => {
    const knownDevices = mediaDevices._knownDevices;
    const oldDevices = knownDevices.slice();

    // Replace known devices in-place
    [].splice.apply(knownDevices, [0, knownDevices.length]
      .concat(newDevices.sort(sortDevicesById)));

    if (!mediaDevices._deviceChangeIsNative
      && devicesHaveChanged(knownDevices, oldDevices)) {
      mediaDevices.dispatchEvent(new Event('devicechange'));
    }

    if (!mediaDevices._deviceInfoChangeIsNative
      && deviceInfosHaveChanged(knownDevices, oldDevices)) {
      mediaDevices.dispatchEvent(new Event('deviceinfochange'));
    }
  });
}

/**
 * Accepts two sorted arrays and the name of a property to compare on objects from each.
 *   Arrays should also be of the same length.
 * @param {string} propertyName - Name of the property to compare on each object
 * @param {Array<Object>} as - The left-side array of objects to compare.
 * @param {Array<Object>} bs - The right-side array of objects to compare.
 * @private
 * @returns {boolean} True if the property of any object in array A is different than
 *   the same property of its corresponding object in array B.
 */
function propertyHasChanged(propertyName, as, bs) {
  return as.some((a, i) => a[propertyName] !== bs[i][propertyName]);
}

/**
 * Re-emit the native event, if the native mediaDevices has the corresponding property.
 * @param {MediaDevicesShim} mediaDevices
 * @param {string} eventName - Name of the event
 * @private
 * @returns {boolean} Whether the native mediaDevice had the corresponding property
 */
function reemitNativeEvent(mediaDevices, eventName) {
  const methodName = `on${eventName}`;

  function dispatchEvent(event) {
    mediaDevices.dispatchEvent(event);
  }

  if (methodName in nativeMediaDevices) {
    // Use addEventListener if it's available so we don't stomp on any other listeners
    // for this event. Currently, navigator.mediaDevices.addEventListener does not exist in Safari.
    if ('addEventListener' in nativeMediaDevices) {
      nativeMediaDevices.addEventListener(eventName, dispatchEvent);
    } else {
      nativeMediaDevices[methodName] = dispatchEvent;
    }

    return true;
  }

  return false;
}

function sortDevicesById(a, b) {
  return a.deviceId < b.deviceId;
}

const getMediaDevicesInstance = () => {
  nativeMediaDevices = typeof navigator !== 'undefined' ? navigator.mediaDevices : null;
  return nativeMediaDevices ? new MediaDevicesShim() : null;
};

export default getMediaDevicesInstance;