(function(global) {

  "use strict";

  var fabric  = global.fabric || (global.fabric = { }),
      piBy2   = Math.PI * 2,
      extend = fabric.util.object.extend;

  if (fabric.Circle) {
    fabric.warn('fabric.Circle is already defined.');
    return;
  }

  /**
   * Circle class
   * @class Circle
   * @extends fabric.Object
   */
  fabric.Circle = fabric.util.createClass(fabric.Object, /** @scope fabric.Circle.prototype */ {

    /**
     * Type of an object
     * @property
     * @type String
     */
    type: 'circle',

    /**
     * Constructor
     * @method initialize
     * @param {Object} [options] Options object
     * @return {fabric.Circle} thisArg
     */
    initialize: function(options) {
      options = options || { };

      this.set('radius', options.radius || 0);
      this.callSuper('initialize', options);

      var diameter = this.get('radius') * 2;
      this.set('width', diameter).set('height', diameter);
    },

    /**
     * Returns object representation of an instance
     * @method toObject
     * @param {Array} propertiesToInclude
     * @return {Object} object representation of an instance
     */
    toObject: function(propertiesToInclude) {
      return extend(this.callSuper('toObject', propertiesToInclude), {
        radius: this.get('radius')
      });
    },

    /**
     * Returns svg representation of an instance
     * @method toSVG
     * @return {String} svg representation of an instance
     */
    toSVG: function() {
      return ('<circle ' +
        'cx="0" cy="0" ' +
        'r="' + this.radius + '" ' +
        'style="' + this.getSvgStyles() + '" ' +
        'transform="' + this.getSvgTransform() + '" ' +
        '/>');
    },

    /**
     * @private
     * @method _render
     * @param ctx {CanvasRenderingContext2D} context to render on
     */
    _render: function(ctx, noTransform) {
      ctx.beginPath();
      // multiply by currently set alpha (the one that was set by path group where this object is contained, for example)
      ctx.globalAlpha = this.group ? (ctx.globalAlpha * this.opacity) : this.opacity;
      ctx.arc(noTransform ? this.left : 0, noTransform ? this.top : 0, this.radius, 0, piBy2, false);
      ctx.closePath();
      if (this.fill) {
        ctx.fill();
      }
      if (this.stroke) {
        ctx.stroke();
      }
    },

    /**
     * Returns horizontal radius of an object (according to how an object is scaled)
     * @method getRadiusX
     * @return {Number}
     */
    getRadiusX: function() {
      return this.get('radius') * this.get('scaleX');
    },

    /**
     * Returns vertical radius of an object (according to how an object is scaled)
     * @method getRadiusY
     * @return {Number}
     */
    getRadiusY: function() {
      return this.get('radius') * this.get('scaleY');
    },

    /**
     * Sets radius of an object (and updates width accordingly)
     * @method setRadius
     * @return {Number}
     */
    setRadius: function(value) {
      this.radius = value;
      this.set('width', value * 2).set('height', value * 2);
    },

    /**
     * Returns complexity of an instance
     * @method complexity
     * @return {Number} complexity of this instance
     */
    complexity: function() {
      return 1;
    }
  });

  /**
   * List of attribute names to account for when parsing SVG element (used by {@link fabric.Circle.fromElement})
   * @static
   * @see: http://www.w3.org/TR/SVG/shapes.html#CircleElement
   */
  fabric.Circle.ATTRIBUTE_NAMES = 'cx cy r fill fill-opacity opacity stroke stroke-width transform'.split(' ');

  /**
   * Returns {@link fabric.Circle} instance from an SVG element
   * @static
   * @method fabric.Circle.fromElement
   * @param {SVGElement} element Element to parse
   * @param {Object} [options] Options object
   * @throws {Error} If value of `r` attribute is missing or invalid
   * @return {Object} Instance of fabric.Circle
   */
  fabric.Circle.fromElement = function(element, options) {
    options || (options = { });
    var parsedAttributes = fabric.parseAttributes(element, fabric.Circle.ATTRIBUTE_NAMES);
    if (!isValidRadius(parsedAttributes)) {
      throw new Error('value of `r` attribute is required and can not be negative');
    }
    if ('left' in parsedAttributes) {
      parsedAttributes.left -= (options.width / 2) || 0;
    }
    if ('top' in parsedAttributes) {
      parsedAttributes.top -= (options.height / 2) || 0;
    }
    var obj = new fabric.Circle(extend(parsedAttributes, options));

    obj.cx = parseFloat(element.getAttribute('cx')) || 0;
    obj.cy = parseFloat(element.getAttribute('cy')) || 0;

    return obj;
  };

  /**
   * @private
   */
  function isValidRadius(attributes) {
    return (('radius' in attributes) && (attributes.radius > 0));
  }

  /**
   * Returns {@link fabric.Circle} instance from an object representation
   * @static
   * @method fabric.Circle.fromObject
   * @param {Object} object Object to create an instance from
   * @return {Object} Instance of fabric.Circle
   */
  fabric.Circle.fromObject = function(object) {
    return new fabric.Circle(object);
  };

})(typeof exports !== 'undefined' ? exports : this);