ama-team / voxengine-sdk

var Slf4j = require('../logger').Slf4j

// TODO: use interfaces instead of direct cancellation token class references

/**

 * This class exists to propagate cancellation through different concurrent

 * branches.

 *

 * In many task end user will need to track several execution branches,

 * cancelling ones that did not win as soon as winner is found, e.g.

 * simultaneously waiting for callee to pick up and caller to hang up. To do

 * so, a cancellation token may be passed and activated, so parallel branch

 * may know if it's competitor has won.

 *

 * @see https://msdn.microsoft.com/en-us/library/system.threading.cancellationtoken.aspx

 *

 * @class

 *

 * @param {CancellationToken[]} [deps] Token dependencies

 * @param {string} [name] Optional token name

 */

function CancellationToken (deps, name) {

  var future = new Future()

  var flag = false

  var self = this

  var loggerName = 'ama-team.voxengine-sdk.concurrent.cancellation-token'

  var logger = Slf4j.create(loggerName)

  logger.attach('name', name)

  /**

   * @return {boolean}

   */

  this.cancel = function () {

    logger.trace('Token has been cancelled')

    future.resolve()

    flag = true

  }

  /**

   * @function CancellationToken#then

   *

   * @param {Function}

   *

   * @return {Thenable}

   */

  this.then = future.then

  /**

   * Adds new dependency

   *

   * @param {CancellationToken} token

   */

  this.addDependency = function (token) { token !== self && token.then(self.cancel) }

  deps = deps || []

  deps.forEach(this.addDependency)

}

module.exports = {

  CancellationToken: CancellationToken

}