(function() {
  /**
   * ObjectTracker utility.
   * @constructor
   * @param {string|Array.<string|Array.<number>>} opt_classifiers Optional
   *     object classifiers to track.
   * @extends {tracking.Tracker}
   */
  tracking.ObjectTracker = function(opt_classifiers) {
    tracking.ObjectTracker.base(this, 'constructor');

    if (opt_classifiers) {
      if (!Array.isArray(opt_classifiers)) {
        opt_classifiers = [opt_classifiers];
      }

      if (Array.isArray(opt_classifiers)) {
        opt_classifiers.forEach(function(classifier, i) {
          if (typeof classifier === 'string') {
            opt_classifiers[i] = tracking.ViolaJones.classifiers[classifier];
          }
          if (!opt_classifiers[i]) {
            throw new Error('Object classifier not valid, try `new tracking.ObjectTracker("face")`.');
          }
        });
      }
    }

    this.setClassifiers(opt_classifiers);
  };

  tracking.inherits(tracking.ObjectTracker, tracking.Tracker);

  /**
   * Specifies the edges density of a block in order to decide whether to skip
   * it or not.
   * @default 0.2
   * @type {number}
   */
  tracking.ObjectTracker.prototype.edgesDensity = 0.2;

  /**
   * Specifies the initial scale to start the feature block scaling.
   * @default 1.0
   * @type {number}
   */
  tracking.ObjectTracker.prototype.initialScale = 1.0;

  /**
   * Specifies the scale factor to scale the feature block.
   * @default 1.25
   * @type {number}
   */
  tracking.ObjectTracker.prototype.scaleFactor = 1.25;

  /**
   * Specifies the block step size.
   * @default 1.5
   * @type {number}
   */
  tracking.ObjectTracker.prototype.stepSize = 1.5;

  /**
   * Gets the tracker HAAR classifiers.
   * @return {TypedArray.<number>}
   */
  tracking.ObjectTracker.prototype.getClassifiers = function() {
    return this.classifiers;
  };

  /**
   * Gets the edges density value.
   * @return {number}
   */
  tracking.ObjectTracker.prototype.getEdgesDensity = function() {
    return this.edgesDensity;
  };

  /**
   * Gets the initial scale to start the feature block scaling.
   * @return {number}
   */
  tracking.ObjectTracker.prototype.getInitialScale = function() {
    return this.initialScale;
  };

  /**
   * Gets the scale factor to scale the feature block.
   * @return {number}
   */
  tracking.ObjectTracker.prototype.getScaleFactor = function() {
    return this.scaleFactor;
  };

  /**
   * Gets the block step size.
   * @return {number}
   */
  tracking.ObjectTracker.prototype.getStepSize = function() {
    return this.stepSize;
  };

  /**
   * Tracks the `Video` frames. This method is called for each video frame in
   * order to emit `track` event.
   * @param {Uint8ClampedArray} pixels The pixels data to track.
   * @param {number} width The pixels canvas width.
   * @param {number} height The pixels canvas height.
   */
  tracking.ObjectTracker.prototype.track = function(pixels, width, height) {
    var self = this;
    var classifiers = this.getClassifiers();

    if (!classifiers) {
      throw new Error('Object classifier not specified, try `new tracking.ObjectTracker("face")`.');
    }

    var results = [];

    classifiers.forEach(function(classifier) {
      results = results.concat(tracking.ViolaJones.detect(pixels, width, height, self.getInitialScale(), self.getScaleFactor(), self.getStepSize(), self.getEdgesDensity(), classifier));
    });

    this.emit('track', {
      data: results
    });
  };

  /**
   * Sets the tracker HAAR classifiers.
   * @param {TypedArray.<number>} classifiers
   */
  tracking.ObjectTracker.prototype.setClassifiers = function(classifiers) {
    this.classifiers = classifiers;
  };

  /**
   * Sets the edges density.
   * @param {number} edgesDensity
   */
  tracking.ObjectTracker.prototype.setEdgesDensity = function(edgesDensity) {
    this.edgesDensity = edgesDensity;
  };

  /**
   * Sets the initial scale to start the block scaling.
   * @param {number} initialScale
   */
  tracking.ObjectTracker.prototype.setInitialScale = function(initialScale) {
    this.initialScale = initialScale;
  };

  /**
   * Sets the scale factor to scale the feature block.
   * @param {number} scaleFactor
   */
  tracking.ObjectTracker.prototype.setScaleFactor = function(scaleFactor) {
    this.scaleFactor = scaleFactor;
  };

  /**
   * Sets the block step size.
   * @param {number} stepSize
   */
  tracking.ObjectTracker.prototype.setStepSize = function(stepSize) {
    this.stepSize = stepSize;
  };

}());