twilio-video/lib/signaling/v2/icebox.js

Twilio Video JavaScript Library

'use strict';

const Filter = require('../../util/filter');

/**
 * An {@link IceBox} stores trickled ICE candidates. Candidates added to the
 * {@link IceBox} via {@link IceBox#update} are compared against previously
 * trickled candidates and only new candidates will be returned (assuming they
 * match the current ICE username fragment set by {@link IceBox#setUfrag}).
 * @property {?string} ufrag
 */
class IceBox {
  /**
   * Construct an {@link IceBox}.
   */
  constructor() {
    Object.defineProperties(this, {
      _filter: {
        value: new Filter({
          getKey: function getKey(iceState) {
            return iceState.ufrag;
          },
          isLessThanOrEqualTo: function isLessThanOrEqualTo(a, b) {
            return a.revision <= b.revision;
          }
        })
      },
      _ufrag: {
        writable: true,
        value: null
      },
      ufrag: {
        enumerable: true,
        get() {
          return this._ufrag;
        }
      }
    });
  }

  /**
   * Set the ICE username fragment on the {@link IceBox}. This method returns any
   * ICE candidates associated with the username fragment.
   * @param {string} ufrag
   * @returns {Array<RTCIceCandidateInit>}
   */
  setUfrag(ufrag) {
    this._ufrag = ufrag;
    const ice = this._filter.toMap().get(ufrag);
    return ice ? ice.candidates : [];
  }

  /**
   * Update the {@link IceBox}. This method returns any new ICE candidates
   * associated with the current username fragment.
   * @param {object} iceState
   * @returns {Array<RTCIceCandidateInit>}
   */
  update(iceState) {
    // NOTE(mroberts): The Server sometimes does not set the candidates property.
    iceState.candidates = iceState.candidates || [];
    const oldIceState = this._filter.toMap().get(iceState.ufrag);
    const oldCandidates = oldIceState ? oldIceState.candidates : [];
    return this._filter.update(iceState) && this._ufrag === iceState.ufrag
      ? iceState.candidates.slice(oldCandidates.length)
      : [];
  }
}

module.exports = IceBox;