text: /**
   * @author       Richard Davey <rich@photonstorm.com>
   * @copyright    2019 Photon Storm Ltd.
   * @license      {@link https://github.com/photonstorm/phaser/blob/master/license.txt|MIT License}
   */
  
  var Clamp = require('../../../math/Clamp');
  var Class = require('../../../utils/Class');
  var Events = require('../events');
  var Vector2 = require('../../../math/Vector2');
  
  /**
   * @classdesc
   * A Camera Shake effect.
   *
   * This effect will shake the camera viewport by a random amount, bounded by the specified intensity, each frame.
   *
   * Only the camera viewport is moved. None of the objects it is displaying are impacted, i.e. their positions do
   * not change.
   *
   * The effect will dispatch several events on the Camera itself and you can also specify an `onUpdate` callback,
   * which is invoked each frame for the duration of the effect if required.
   *
   * @class Shake
   * @memberof Phaser.Cameras.Scene2D.Effects
   * @constructor
   * @since 3.5.0
   *
   * @param {Phaser.Cameras.Scene2D.Camera} camera - The camera this effect is acting upon.
   */
  var Shake = new Class({
  
      initialize:
  
      function Shake (camera)
      {
          /**
           * The Camera this effect belongs to.
           *
           * @name Phaser.Cameras.Scene2D.Effects.Shake#camera
           * @type {Phaser.Cameras.Scene2D.Camera}
           * @readonly
           * @since 3.5.0
           */
          this.camera = camera;
  
          /**
           * Is this effect actively running?
           *
           * @name Phaser.Cameras.Scene2D.Effects.Shake#isRunning
           * @type {boolean}
           * @readonly
           * @default false
           * @since 3.5.0
           */
          this.isRunning = false;
  
          /**
           * The duration of the effect, in milliseconds.
           *
           * @name Phaser.Cameras.Scene2D.Effects.Shake#duration
           * @type {integer}
           * @readonly
           * @default 0
           * @since 3.5.0
           */
          this.duration = 0;
  
          /**
           * The intensity of the effect. Use small float values. The default when the effect starts is 0.05.
           * This is a Vector2 object, allowing you to control the shake intensity independently across x and y.
           * You can modify this value while the effect is active to create more varied shake effects.
           *
           * @name Phaser.Cameras.Scene2D.Effects.Shake#intensity
           * @type {Phaser.Math.Vector2}
           * @since 3.5.0
           */
          this.intensity = new Vector2();
  
          /**
           * If this effect is running this holds the current percentage of the progress, a value between 0 and 1.
           *
           * @name Phaser.Cameras.Scene2D.Effects.Shake#progress
           * @type {number}
           * @since 3.5.0
           */
          this.progress = 0;
  
          /**
           * Effect elapsed timer.
           *
           * @name Phaser.Cameras.Scene2D.Effects.Shake#_elapsed
           * @type {number}
           * @private
           * @since 3.5.0
           */
          this._elapsed = 0;
  
          /**
           * How much to offset the camera by horizontally.
           *
           * @name Phaser.Cameras.Scene2D.Effects.Shake#_offsetX
           * @type {number}
           * @private
           * @default 0
           * @since 3.0.0
           */
          this._offsetX = 0;
  
          /**
           * How much to offset the camera by vertically.
           *
           * @name Phaser.Cameras.Scene2D.Effects.Shake#_offsetY
           * @type {number}
           * @private
           * @default 0
           * @since 3.0.0
           */
          this._offsetY = 0;
  
          /**
           * @callback CameraShakeCallback
           *
           * @param {Phaser.Cameras.Scene2D.Camera} camera - The camera on which the effect is running.
           * @param {number} progress - The progress of the effect. A value between 0 and 1.
           */
  
          /**
           * This callback is invoked every frame for the duration of the effect.
           *
           * @name Phaser.Cameras.Scene2D.Effects.Shake#_onUpdate
           * @type {?CameraShakeCallback}
           * @private
           * @default null
           * @since 3.5.0
           */
          this._onUpdate;
  
          /**
           * On Complete callback scope.
           *
           * @name Phaser.Cameras.Scene2D.Effects.Shake#_onUpdateScope
           * @type {any}
           * @private
           * @since 3.5.0
           */
          this._onUpdateScope;
      },
  
      /**
       * Shakes the Camera by the given intensity over the duration specified.
       *
       * @method Phaser.Cameras.Scene2D.Effects.Shake#start
       * @fires Phaser.Cameras.Scene2D.Events#SHAKE_START
       * @fires Phaser.Cameras.Scene2D.Events#SHAKE_COMPLETE
       * @since 3.5.0
       *
       * @param {integer} [duration=100] - The duration of the effect in milliseconds.
       * @param {number} [intensity=0.05] - The intensity of the shake.
       * @param {boolean} [force=false] - Force the shake effect to start immediately, even if already running.
       * @param {CameraShakeCallback} [callback] - This callback will be invoked every frame for the duration of the effect.
       * It is sent two arguments: A reference to the camera and a progress amount between 0 and 1 indicating how complete the effect is.
       * @param {any} [context] - The context in which the callback is invoked. Defaults to the Scene to which the Camera belongs.
       *
       * @return {Phaser.Cameras.Scene2D.Camera} The Camera on which the effect was started.
       */
      start: function (duration, intensity, force, callback, context)
      {
          if (duration === undefined) { duration = 100; }
          if (intensity === undefined) { intensity = 0.05; }
          if (force === undefined) { force = false; }
          if (callback === undefined) { callback = null; }
          if (context === undefined) { context = this.camera.scene; }
  
          if (!force && this.isRunning)
          {
              return this.camera;
          }
  
          this.isRunning = true;
          this.duration = duration;
          this.progress = 0;
  
          if (typeof intensity === 'number')
          {
              this.intensity.set(intensity);
          }
          else
          {
              this.intensity.set(intensity.x, intensity.y);
          }
  
          this._elapsed = 0;
          this._offsetX = 0;
          this._offsetY = 0;
  
          this._onUpdate = callback;
          this._onUpdateScope = context;
  
          this.camera.emit(Events.SHAKE_START, this.camera, this, duration, intensity);
  
          return this.camera;
      },
  
      /**
       * The pre-render step for this effect. Called automatically by the Camera.
       *
       * @method Phaser.Cameras.Scene2D.Effects.Shake#preRender
       * @since 3.5.0
       */
      preRender: function ()
      {
          if (this.isRunning)
          {
              this.camera.matrix.translate(this._offsetX, this._offsetY);
          }
      },
  
      /**
       * The main update loop for this effect. Called automatically by the Camera.
       *
       * @method Phaser.Cameras.Scene2D.Effects.Shake#update
       * @since 3.5.0
       *
       * @param {integer} time - The current timestamp as generated by the Request Animation Frame or SetTimeout.
       * @param {number} delta - The delta time, in ms, elapsed since the last frame.
       */
      update: function (time, delta)
      {
          if (!this.isRunning)
          {
              return;
          }
  
          this._elapsed += delta;
  
          this.progress = Clamp(this._elapsed / this.duration, 0, 1);
  
          if (this._onUpdate)
          {
              this._onUpdate.call(this._onUpdateScope, this.camera, this.progress);
          }
  
          if (this._elapsed < this.duration)
          {
              var intensity = this.intensity;
              var width = this.camera._cw;
              var height = this.camera._ch;
              var zoom = this.camera.zoom;
  
              this._offsetX = (Math.random() * intensity.x * width * 2 - intensity.x * width) * zoom;
              this._offsetY = (Math.random() * intensity.y * height * 2 - intensity.y * height) * zoom;
  
              if (this.camera.roundPixels)
              {
                  this._offsetX = Math.round(this._offsetX);
                  this._offsetY = Math.round(this._offsetY);
              }
          }
          else
          {
              this.effectComplete();
          }
      },
  
      /**
       * Called internally when the effect completes.
       *
       * @method Phaser.Cameras.Scene2D.Effects.Shake#effectComplete
       * @fires Phaser.Cameras.Scene2D.Events#SHAKE_COMPLETE
       * @since 3.5.0
       */
      effectComplete: function ()
      {
          this._offsetX = 0;
          this._offsetY = 0;
  
          this._onUpdate = null;
          this._onUpdateScope = null;
  
          this.isRunning = false;
  
          this.camera.emit(Events.SHAKE_COMPLETE, this.camera, this);
      },
  
      /**
       * Resets this camera effect.
       * If it was previously running, it stops instantly without calling its onComplete callback or emitting an event.
       *
       * @method Phaser.Cameras.Scene2D.Effects.Shake#reset
       * @since 3.5.0
       */
      reset: function ()
      {
          this.isRunning = false;
  
          this._offsetX = 0;
          this._offsetY = 0;
  
          this._onUpdate = null;
          this._onUpdateScope = null;
      },
  
      /**
       * Destroys this effect, releasing it from the Camera.
       *
       * @method Phaser.Cameras.Scene2D.Effects.Shake#destroy
       * @since 3.5.0
       */
      destroy: function ()
      {
          this.reset();
  
          this.camera = null;
          this.intensity = null;
      }
  
  });
  
  module.exports = Shake;
  