(function(global) {

  'use strict';

  /**
   * @name fabric
   * @namespace
   */

  var fabric = global.fabric || (global.fabric = { }),
      extend = fabric.util.object.extend,
      capitalize = fabric.util.string.capitalize,
      clone = fabric.util.object.clone,
      toFixed = fabric.util.toFixed,
      parseUnit = fabric.util.parseUnit,
      multiplyTransformMatrices = fabric.util.multiplyTransformMatrices,

      reAllowedSVGTagNames = /^(path|circle|polygon|polyline|ellipse|rect|line|image|text)$/i,
      reViewBoxTagNames = /^(symbol|image|marker|pattern|view|svg)$/i,
      reNotAllowedAncestors = /^(?:pattern|defs|symbol|metadata)$/i,
      reAllowedParents = /^(symbol|g|a|svg)$/i,

      attributesMap = {
        cx:                   'left',
        x:                    'left',
        r:                    'radius',
        cy:                   'top',
        y:                    'top',
        display:              'visible',
        visibility:           'visible',
        transform:            'transformMatrix',
        'fill-opacity':       'fillOpacity',
        'fill-rule':          'fillRule',
        'font-family':        'fontFamily',
        'font-size':          'fontSize',
        'font-style':         'fontStyle',
        'font-weight':        'fontWeight',
        'stroke-dasharray':   'strokeDashArray',
        'stroke-linecap':     'strokeLineCap',
        'stroke-linejoin':    'strokeLineJoin',
        'stroke-miterlimit':  'strokeMiterLimit',
        'stroke-opacity':     'strokeOpacity',
        'stroke-width':       'strokeWidth',
        'text-decoration':    'textDecoration',
        'text-anchor':        'originX'
      },

      colorAttributes = {
        stroke: 'strokeOpacity',
        fill:   'fillOpacity'
      };

  fabric.cssRules = { };
  fabric.gradientDefs = { };

  function normalizeAttr(attr) {
    // transform attribute names
    if (attr in attributesMap) {
      return attributesMap[attr];
    }
    return attr;
  }

  function normalizeValue(attr, value, parentAttributes, fontSize) {
    var isArray = Object.prototype.toString.call(value) === '[object Array]',
        parsed;

    if ((attr === 'fill' || attr === 'stroke') && value === 'none') {
      value = '';
    }
    else if (attr === 'strokeDashArray') {
      value = value.replace(/,/g, ' ').split(/\s+/).map(function(n) {
        return parseFloat(n);
      });
    }
    else if (attr === 'transformMatrix') {
      if (parentAttributes && parentAttributes.transformMatrix) {
        value = multiplyTransformMatrices(
          parentAttributes.transformMatrix, fabric.parseTransformAttribute(value));
      }
      else {
        value = fabric.parseTransformAttribute(value);
      }
    }
    else if (attr === 'visible') {
      value = (value === 'none' || value === 'hidden') ? false : true;
      // display=none on parent element always takes precedence over child element
      if (parentAttributes && parentAttributes.visible === false) {
        value = false;
      }
    }
    else if (attr === 'originX' /* text-anchor */) {
      value = value === 'start' ? 'left' : value === 'end' ? 'right' : 'center';
    }
    else {
      parsed = isArray ? value.map(parseUnit) : parseUnit(value, fontSize);
    }

    return (!isArray && isNaN(parsed) ? value : parsed);
  }

  /**
   * @private
   * @param {Object} attributes Array of attributes to parse
   */
  function _setStrokeFillOpacity(attributes) {
    for (var attr in colorAttributes) {

      if (!attributes[attr] || typeof attributes[colorAttributes[attr]] === 'undefined') {
        continue;
      }

      if (attributes[attr].indexOf('url(') === 0) {
        continue;
      }

      var color = new fabric.Color(attributes[attr]);
      attributes[attr] = color.setAlpha(toFixed(color.getAlpha() * attributes[colorAttributes[attr]], 2)).toRgba();
    }
    return attributes;
  }

  /**
   * Parses "transform" attribute, returning an array of values
   * @static
   * @function
   * @memberOf fabric
   * @param {String} attributeValue String containing attribute value
   * @return {Array} Array of 6 elements representing transformation matrix
   */
  fabric.parseTransformAttribute = (function() {
    function rotateMatrix(matrix, args) {
      var angle = args[0];

      matrix[0] = Math.cos(angle);
      matrix[1] = Math.sin(angle);
      matrix[2] = -Math.sin(angle);
      matrix[3] = Math.cos(angle);
    }

    function scaleMatrix(matrix, args) {
      var multiplierX = args[0],
          multiplierY = (args.length === 2) ? args[1] : args[0];

      matrix[0] = multiplierX;
      matrix[3] = multiplierY;
    }

    function skewXMatrix(matrix, args) {
      matrix[2] = Math.tan(fabric.util.degreesToRadians(args[0]));
    }

    function skewYMatrix(matrix, args) {
      matrix[1] = Math.tan(fabric.util.degreesToRadians(args[0]));
    }

    function translateMatrix(matrix, args) {
      matrix[4] = args[0];
      if (args.length === 2) {
        matrix[5] = args[1];
      }
    }

    // identity matrix
    var iMatrix = [
          1, // a
          0, // b
          0, // c
          1, // d
          0, // e
          0  // f
        ],

        // == begin transform regexp
        number = fabric.reNum,

        commaWsp = '(?:\\s+,?\\s*|,\\s*)',

        skewX = '(?:(skewX)\\s*\\(\\s*(' + number + ')\\s*\\))',

        skewY = '(?:(skewY)\\s*\\(\\s*(' + number + ')\\s*\\))',

        rotate = '(?:(rotate)\\s*\\(\\s*(' + number + ')(?:' +
                    commaWsp + '(' + number + ')' +
                    commaWsp + '(' + number + '))?\\s*\\))',

        scale = '(?:(scale)\\s*\\(\\s*(' + number + ')(?:' +
                    commaWsp + '(' + number + '))?\\s*\\))',

        translate = '(?:(translate)\\s*\\(\\s*(' + number + ')(?:' +
                    commaWsp + '(' + number + '))?\\s*\\))',

        matrix = '(?:(matrix)\\s*\\(\\s*' +
                  '(' + number + ')' + commaWsp +
                  '(' + number + ')' + commaWsp +
                  '(' + number + ')' + commaWsp +
                  '(' + number + ')' + commaWsp +
                  '(' + number + ')' + commaWsp +
                  '(' + number + ')' +
                  '\\s*\\))',

        transform = '(?:' +
                    matrix + '|' +
                    translate + '|' +
                    scale + '|' +
                    rotate + '|' +
                    skewX + '|' +
                    skewY +
                    ')',

        transforms = '(?:' + transform + '(?:' + commaWsp + transform + ')*' + ')',

        transformList = '^\\s*(?:' + transforms + '?)\\s*$',

        // http://www.w3.org/TR/SVG/coords.html#TransformAttribute
        reTransformList = new RegExp(transformList),
        // == end transform regexp

        reTransform = new RegExp(transform, 'g');

    return function(attributeValue) {

      // start with identity matrix
      var matrix = iMatrix.concat(),
          matrices = [ ];

      // return if no argument was given or
      // an argument does not match transform attribute regexp
      if (!attributeValue || (attributeValue && !reTransformList.test(attributeValue))) {
        return matrix;
      }

      attributeValue.replace(reTransform, function(match) {

        var m = new RegExp(transform).exec(match).filter(function (match) {
              return (match !== '' && match != null);
            }),
            operation = m[1],
            args = m.slice(2).map(parseFloat);

        switch (operation) {
          case 'translate':
            translateMatrix(matrix, args);
            break;
          case 'rotate':
            args[0] = fabric.util.degreesToRadians(args[0]);
            rotateMatrix(matrix, args);
            break;
          case 'scale':
            scaleMatrix(matrix, args);
            break;
          case 'skewX':
            skewXMatrix(matrix, args);
            break;
          case 'skewY':
            skewYMatrix(matrix, args);
            break;
          case 'matrix':
            matrix = args;
            break;
        }

        // snapshot current matrix into matrices array
        matrices.push(matrix.concat());
        // reset
        matrix = iMatrix.concat();
      });

      var combinedMatrix = matrices[0];
      while (matrices.length > 1) {
        matrices.shift();
        combinedMatrix = fabric.util.multiplyTransformMatrices(combinedMatrix, matrices[0]);
      }
      return combinedMatrix;
    };
  })();

  /**
   * @private
   */
  function parseStyleString(style, oStyle) {
    var attr, value;
    style.replace(/;\s*$/, '').split(';').forEach(function (chunk) {
      var pair = chunk.split(':');

      attr = normalizeAttr(pair[0].trim().toLowerCase());
      value = normalizeValue(attr, pair[1].trim());

      oStyle[attr] = value;
    });
  }

  /**
   * @private
   */
  function parseStyleObject(style, oStyle) {
    var attr, value;
    for (var prop in style) {
      if (typeof style[prop] === 'undefined') {
        continue;
      }

      attr = normalizeAttr(prop.toLowerCase());
      value = normalizeValue(attr, style[prop]);

      oStyle[attr] = value;
    }
  }

  /**
   * @private
   */
  function getGlobalStylesForElement(element, svgUid) {
    var styles = { };
    for (var rule in fabric.cssRules[svgUid]) {
      if (elementMatchesRule(element, rule.split(' '))) {
        for (var property in fabric.cssRules[svgUid][rule]) {
          styles[property] = fabric.cssRules[svgUid][rule][property];
        }
      }
    }
    return styles;
  }

  /**
   * @private
   */
  function elementMatchesRule(element, selectors) {
    var firstMatching, parentMatching = true;
    //start from rightmost selector.
    firstMatching = selectorMatches(element, selectors.pop());
    if (firstMatching && selectors.length) {
      parentMatching = doesSomeParentMatch(element, selectors);
    }
    return firstMatching && parentMatching && (selectors.length === 0);
  }

  function doesSomeParentMatch(element, selectors) {
    var selector, parentMatching = true;
    while (element.parentNode && element.parentNode.nodeType === 1 && selectors.length) {
      if (parentMatching) {
        selector = selectors.pop();
      }
      element = element.parentNode;
      parentMatching = selectorMatches(element, selector);
    }
    return selectors.length === 0;
  }

  /**
   * @private
   */
  function selectorMatches(element, selector) {
    var nodeName = element.nodeName,
        classNames = element.getAttribute('class'),
        id = element.getAttribute('id'), matcher;
    // i check if a selector matches slicing away part from it.
    // if i get empty string i should match
    matcher = new RegExp('^' + nodeName, 'i');
    selector = selector.replace(matcher, '');
    if (id && selector.length) {
      matcher = new RegExp('#' + id + '(?![a-zA-Z\\-]+)', 'i');
      selector = selector.replace(matcher, '');
    }
    if (classNames && selector.length) {
      classNames = classNames.split(' ');
      for (var i = classNames.length; i--;) {
        matcher = new RegExp('\\.' + classNames[i] + '(?![a-zA-Z\\-]+)', 'i');
        selector = selector.replace(matcher, '');
      }
    }
    return selector.length === 0;
  }

  /**
   * @private
   * to support IE8 missing getElementById on SVGdocument
   */
  function elementById(doc, id) {
    var el;
    doc.getElementById && (el = doc.getElementById(id));
    if (el) {
      return el;
    }
    var node, i, idAttr, nodelist = doc.getElementsByTagName('*');
    for (i = 0; i < nodelist.length; i++) {
      node = nodelist[i];
      if (idAttr === node.getAttribute('id')) {
        return node;
      }
    }
  }

  /**
   * @private
   */
  function parseUseDirectives(doc) {
    var nodelist = doc.getElementsByTagName('use'), i = 0;
    while (nodelist.length && i < nodelist.length) {
      var el = nodelist[i],
          xlink = el.getAttribute('xlink:href').substr(1),
          x = el.getAttribute('x') || 0,
          y = el.getAttribute('y') || 0,
          el2 = elementById(doc, xlink).cloneNode(true),
          currentTrans = (el2.getAttribute('transform') || '') + ' translate(' + x + ', ' + y + ')',
          parentNode, oldLength = nodelist.length, attr, j, attrs, l;

      applyViewboxTransform(el2);
      if (/^svg$/i.test(el2.nodeName)) {
        var el3 = el2.ownerDocument.createElement('g');
        for (j = 0, attrs = el2.attributes, l = attrs.length; j < l; j++) {
          attr = attrs.item(j);
          el3.setAttribute(attr.nodeName, attr.nodeValue);
        }
        while (el2.firstChild != null) {
          el3.appendChild(el2.firstChild);
        }
        el2 = el3;
      }

      for (j = 0, attrs = el.attributes, l = attrs.length; j < l; j++) {
        attr = attrs.item(j);
        if (attr.nodeName === 'x' || attr.nodeName === 'y' || attr.nodeName === 'xlink:href') {
          continue;
        }

        if (attr.nodeName === 'transform') {
          currentTrans = attr.nodeValue + ' ' + currentTrans;
        }
        else {
          el2.setAttribute(attr.nodeName, attr.nodeValue);
        }
      }

      el2.setAttribute('transform', currentTrans);
      el2.setAttribute('instantiated_by_use', '1');
      el2.removeAttribute('id');
      parentNode = el.parentNode;
      parentNode.replaceChild(el2, el);
      // some browsers do not shorten nodelist after replaceChild (IE8)
      if (nodelist.length === oldLength) {
        i++;
      }
    }
  }

  // http://www.w3.org/TR/SVG/coords.html#ViewBoxAttribute
  // matches, e.g.: +14.56e-12, etc.
  var reViewBoxAttrValue = new RegExp(
    '^' +
    '\\s*(' + fabric.reNum + '+)\\s*,?' +
    '\\s*(' + fabric.reNum + '+)\\s*,?' +
    '\\s*(' + fabric.reNum + '+)\\s*,?' +
    '\\s*(' + fabric.reNum + '+)\\s*' +
    '$'
  );

  /**
   * Add a <g> element that envelop all child elements and makes the viewbox transformMatrix descend on all elements
   */
  function applyViewboxTransform(element) {

    var viewBoxAttr = element.getAttribute('viewBox'),
        scaleX = 1,
        scaleY = 1,
        minX = 0,
        minY = 0,
        viewBoxWidth, viewBoxHeight, matrix, el,
        widthAttr = element.getAttribute('width'),
        heightAttr = element.getAttribute('height'),
        missingViewBox = (!viewBoxAttr || !reViewBoxTagNames.test(element.tagName)
                           || !(viewBoxAttr = viewBoxAttr.match(reViewBoxAttrValue))),
        missingDimAttr = (!widthAttr || !heightAttr || widthAttr === '100%' || heightAttr === '100%'),
        toBeParsed = missingViewBox && missingDimAttr,
        parsedDim = { };

    parsedDim.width = 0;
    parsedDim.height = 0;
    parsedDim.toBeParsed = toBeParsed;

    if (toBeParsed) {
      return parsedDim;
    }

    if (missingViewBox) {
      parsedDim.width = parseUnit(widthAttr);
      parsedDim.height = parseUnit(heightAttr);
      return parsedDim;
    }

    minX = -parseFloat(viewBoxAttr[1]),
    minY = -parseFloat(viewBoxAttr[2]),
    viewBoxWidth = parseFloat(viewBoxAttr[3]),
    viewBoxHeight = parseFloat(viewBoxAttr[4]);

    if (!missingDimAttr) {
      parsedDim.width = parseUnit(widthAttr);
      parsedDim.height = parseUnit(heightAttr);
      scaleX = parsedDim.width / viewBoxWidth;
      scaleY = parsedDim.height / viewBoxHeight;
    }
    else {
      parsedDim.width = viewBoxWidth;
      parsedDim.height = viewBoxHeight;
    }

    // default is to preserve aspect ratio
    // preserveAspectRatio attribute to be implemented
    scaleY = scaleX = (scaleX > scaleY ? scaleY : scaleX);

    if (scaleX === 1 && scaleY === 1 && minX === 0 && minY === 0) {
      return parsedDim;
    }

    matrix = ' matrix(' + scaleX +
                  ' 0' +
                  ' 0 ' +
                  scaleY + ' ' +
                  (minX * scaleX) + ' ' +
                  (minY * scaleY) + ') ';

    if (element.tagName === 'svg') {
      el = element.ownerDocument.createElement('g');
      while (element.firstChild != null) {
        el.appendChild(element.firstChild);
      }
      element.appendChild(el);
    }
    else {
      el = element;
      matrix = el.getAttribute('transform') + matrix;
    }

    el.setAttribute('transform', matrix);
    return parsedDim;
  }

  /**
   * Parses an SVG document, converts it to an array of corresponding fabric.* instances and passes them to a callback
   * @static
   * @function
   * @memberOf fabric
   * @param {SVGDocument} doc SVG document to parse
   * @param {Function} callback Callback to call when parsing is finished; It's being passed an array of elements (parsed from a document).
   * @param {Function} [reviver] Method for further parsing of SVG elements, called after each fabric object created.
   */
  fabric.parseSVGDocument = (function() {

    function hasAncestorWithNodeName(element, nodeName) {
      while (element && (element = element.parentNode)) {
        if (nodeName.test(element.nodeName) && !element.getAttribute('instantiated_by_use')) {
          return true;
        }
      }
      return false;
    }

    return function(doc, callback, reviver) {
      if (!doc) {
        return;
      }

      parseUseDirectives(doc);

      var startTime = new Date(),
          svgUid =  fabric.Object.__uid++,
          options = applyViewboxTransform(doc),
          descendants = fabric.util.toArray(doc.getElementsByTagName('*'));

      options.svgUid = svgUid;

      if (descendants.length === 0 && fabric.isLikelyNode) {
        // we're likely in node, where "o3-xml" library fails to gEBTN("*")
        // https://github.com/ajaxorg/node-o3-xml/issues/21
        descendants = doc.selectNodes('//*[name(.)!="svg"]');
        var arr = [ ];
        for (var i = 0, len = descendants.length; i < len; i++) {
          arr[i] = descendants[i];
        }
        descendants = arr;
      }

      var elements = descendants.filter(function(el) {
        applyViewboxTransform(el);
        return reAllowedSVGTagNames.test(el.tagName) &&
              !hasAncestorWithNodeName(el, reNotAllowedAncestors); // http://www.w3.org/TR/SVG/struct.html#DefsElement
      });

      if (!elements || (elements && !elements.length)) {
        callback && callback([], {});
        return;
      }

      fabric.gradientDefs[svgUid] = fabric.getGradientDefs(doc);
      fabric.cssRules[svgUid] = fabric.getCSSRules(doc);
      // Precedence of rules:   style > class > attribute
      fabric.parseElements(elements, function(instances) {
        fabric.documentParsingTime = new Date() - startTime;
        if (callback) {
          callback(instances, options);
        }
      }, clone(options), reviver);
    };
  })();

  /**
   * Used for caching SVG documents (loaded via `fabric.Canvas#loadSVGFromURL`)
   * @namespace
   */
  var svgCache = {

    /**
     * @param {String} name
     * @param {Function} callback
     */
    has: function (name, callback) {
      callback(false);
    },

    get: function () {
      /* NOOP */
    },

    set: function () {
      /* NOOP */
    }
  };

  /**
   * @private
   */
  function _enlivenCachedObject(cachedObject) {

    var objects = cachedObject.objects,
        options = cachedObject.options;

    objects = objects.map(function (o) {
      return fabric[capitalize(o.type)].fromObject(o);
    });

    return ({ objects: objects, options: options });
  }

  /**
   * @private
   */
  function _createSVGPattern(markup, canvas, property) {
    if (canvas[property] && canvas[property].toSVG) {
      markup.push(
        '\t<pattern x="0" y="0" id="', property, 'Pattern" ',
          'width="', canvas[property].source.width,
          '" height="', canvas[property].source.height,
          '" patternUnits="userSpaceOnUse">\n',
        '\t\t<image x="0" y="0" ',
        'width="', canvas[property].source.width,
        '" height="', canvas[property].source.height,
        '" xlink:href="', canvas[property].source.src,
        '"></image>\n\t</pattern>\n'
      );
    }
  }

  var reFontDeclaration = new RegExp(
    '(normal|italic)?\\s*(normal|small-caps)?\\s*' +
    '(normal|bold|bolder|lighter|100|200|300|400|500|600|700|800|900)?\\s*(' +
      fabric.reNum +
    '(?:px|cm|mm|em|pt|pc|in)*)(?:\\/(normal|' + fabric.reNum + '))?\\s+(.*)');

  extend(fabric, {
    /**
     * Parses a short font declaration, building adding its properties to a style object
     * @static
     * @function
     * @memberOf fabric
     * @param {String} value font declaration
     * @param {Object} oStyle definition
     */
    parseFontDeclaration: function(value, oStyle) {
      var match = value.match(reFontDeclaration);

      if (!match) {
        return;
      }
      var fontStyle = match[1],
          // font variant is not used
          // fontVariant = match[2],
          fontWeight = match[3],
          fontSize = match[4],
          lineHeight = match[5],
          fontFamily = match[6];

      if (fontStyle) {
        oStyle.fontStyle = fontStyle;
      }
      if (fontWeight) {
        oStyle.fontWeight = isNaN(parseFloat(fontWeight)) ? fontWeight : parseFloat(fontWeight);
      }
      if (fontSize) {
        oStyle.fontSize = parseUnit(fontSize);
      }
      if (fontFamily) {
        oStyle.fontFamily = fontFamily;
      }
      if (lineHeight) {
        oStyle.lineHeight = lineHeight === 'normal' ? 1 : lineHeight;
      }
    },

    /**
     * Parses an SVG document, returning all of the gradient declarations found in it
     * @static
     * @function
     * @memberOf fabric
     * @param {SVGDocument} doc SVG document to parse
     * @return {Object} Gradient definitions; key corresponds to element id, value -- to gradient definition element
     */
    getGradientDefs: function(doc) {
      var linearGradientEls = doc.getElementsByTagName('linearGradient'),
          radialGradientEls = doc.getElementsByTagName('radialGradient'),
          el, i, j = 0, id, xlink, elList = [ ],
          gradientDefs = { }, idsToXlinkMap = { };

      elList.length = linearGradientEls.length + radialGradientEls.length;
      i = linearGradientEls.length;
      while (i--) {
        elList[j++] = linearGradientEls[i];
      }
      i = radialGradientEls.length;
      while (i--) {
        elList[j++] = radialGradientEls[i];
      }

      while (j--) {
        el = elList[j];
        xlink = el.getAttribute('xlink:href');
        id = el.getAttribute('id');
        if (xlink) {
          idsToXlinkMap[id] = xlink.substr(1);
        }
        gradientDefs[id] = el;
      }

      for (id in idsToXlinkMap) {
        var el2 = gradientDefs[idsToXlinkMap[id]].cloneNode(true);
        el = gradientDefs[id];
        while (el2.firstChild) {
          el.appendChild(el2.firstChild);
        }
      }
      return gradientDefs;
    },

    /**
     * Returns an object of attributes' name/value, given element and an array of attribute names;
     * Parses parent "g" nodes recursively upwards.
     * @static
     * @memberOf fabric
     * @param {DOMElement} element Element to parse
     * @param {Array} attributes Array of attributes to parse
     * @return {Object} object containing parsed attributes' names/values
     */
    parseAttributes: function(element, attributes, svgUid) {

      if (!element) {
        return;
      }

      var value,
          parentAttributes = { },
          fontSize;

      if (typeof svgUid === 'undefined') {
        svgUid = element.getAttribute('svgUid');
      }
      // if there's a parent container (`g` or `a` or `symbol` node), parse its attributes recursively upwards
      if (element.parentNode && reAllowedParents.test(element.parentNode.nodeName)) {
        parentAttributes = fabric.parseAttributes(element.parentNode, attributes, svgUid);
      }
      fontSize = (parentAttributes && parentAttributes.fontSize ) ||
                 element.getAttribute('font-size') || fabric.Text.DEFAULT_SVG_FONT_SIZE;

      var ownAttributes = attributes.reduce(function(memo, attr) {
        value = element.getAttribute(attr);
        if (value) {
          attr = normalizeAttr(attr);
          value = normalizeValue(attr, value, parentAttributes, fontSize);

          memo[attr] = value;
        }
        return memo;
      }, { });

      // add values parsed from style, which take precedence over attributes
      // (see: http://www.w3.org/TR/SVG/styling.html#UsingPresentationAttributes)
      ownAttributes = extend(ownAttributes,
        extend(getGlobalStylesForElement(element, svgUid), fabric.parseStyleAttribute(element)));
      if (ownAttributes.font) {
        fabric.parseFontDeclaration(ownAttributes.font, ownAttributes);
      }
      return _setStrokeFillOpacity(extend(parentAttributes, ownAttributes));
    },

    /**
     * Transforms an array of svg elements to corresponding fabric.* instances
     * @static
     * @memberOf fabric
     * @param {Array} elements Array of elements to parse
     * @param {Function} callback Being passed an array of fabric instances (transformed from SVG elements)
     * @param {Object} [options] Options object
     * @param {Function} [reviver] Method for further parsing of SVG elements, called after each fabric object created.
     */
    parseElements: function(elements, callback, options, reviver) {
      new fabric.ElementsParser(elements, callback, options, reviver).parse();
    },

    /**
     * Parses "style" attribute, retuning an object with values
     * @static
     * @memberOf fabric
     * @param {SVGElement} element Element to parse
     * @return {Object} Objects with values parsed from style attribute of an element
     */
    parseStyleAttribute: function(element) {
      var oStyle = { },
          style = element.getAttribute('style');

      if (!style) {
        return oStyle;
      }

      if (typeof style === 'string') {
        parseStyleString(style, oStyle);
      }
      else {
        parseStyleObject(style, oStyle);
      }

      return oStyle;
    },

    /**
     * Parses "points" attribute, returning an array of values
     * @static
     * @memberOf fabric
     * @param {String} points points attribute string
     * @return {Array} array of points
     */
    parsePointsAttribute: function(points) {

      // points attribute is required and must not be empty
      if (!points) {
        return null;
      }

      // replace commas with whitespace and remove bookending whitespace
      points = points.replace(/,/g, ' ').trim();

      points = points.split(/\s+/);
      var parsedPoints = [ ], i, len;

      i = 0;
      len = points.length;
      for (; i < len; i+=2) {
        parsedPoints.push({
          x: parseFloat(points[i]),
          y: parseFloat(points[i + 1])
        });
      }

      // odd number of points is an error
      // if (parsedPoints.length % 2 !== 0) {
      //   return null;
      // }

      return parsedPoints;
    },

    /**
     * Returns CSS rules for a given SVG document
     * @static
     * @function
     * @memberOf fabric
     * @param {SVGDocument} doc SVG document to parse
     * @return {Object} CSS rules of this document
     */
    getCSSRules: function(doc) {
      var styles = doc.getElementsByTagName('style'),
          allRules = { }, rules;

      // very crude parsing of style contents
      for (var i = 0, len = styles.length; i < len; i++) {
        var styleContents = styles[i].textContent;

        // remove comments
        styleContents = styleContents.replace(/\/\*[\s\S]*?\*\//g, '');
        if (styleContents.trim() === '') {
          continue;
        }
        rules = styleContents.match(/[^{]*\{[\s\S]*?\}/g);
        rules = rules.map(function(rule) { return rule.trim(); });

        rules.forEach(function(rule) {

          var match = rule.match(/([\s\S]*?)\s*\{([^}]*)\}/),
          ruleObj = { }, declaration = match[2].trim(),
          propertyValuePairs = declaration.replace(/;$/, '').split(/\s*;\s*/);

          for (var i = 0, len = propertyValuePairs.length; i < len; i++) {
            var pair = propertyValuePairs[i].split(/\s*:\s*/),
                property = normalizeAttr(pair[0]),
                value = normalizeValue(property, pair[1], pair[0]);
            ruleObj[property] = value;
          }
          rule = match[1];
          rule.split(',').forEach(function(_rule) {
            _rule = _rule.replace(/^svg/i, '').trim();
            if (_rule === '') {
              return;
            }
            allRules[_rule] = fabric.util.object.clone(ruleObj);
          });
        });
      }
      return allRules;
    },

    /**
     * Takes url corresponding to an SVG document, and parses it into a set of fabric objects. Note that SVG is fetched via XMLHttpRequest, so it needs to conform to SOP (Same Origin Policy)
     * @memberOf fabric
     * @param {String} url
     * @param {Function} callback
     * @param {Function} [reviver] Method for further parsing of SVG elements, called after each fabric object created.
     */
    loadSVGFromURL: function(url, callback, reviver) {

      url = url.replace(/^\n\s*/, '').trim();
      svgCache.has(url, function (hasUrl) {
        if (hasUrl) {
          svgCache.get(url, function (value) {
            var enlivedRecord = _enlivenCachedObject(value);
            callback(enlivedRecord.objects, enlivedRecord.options);
          });
        }
        else {
          new fabric.util.request(url, {
            method: 'get',
            onComplete: onComplete
          });
        }
      });

      function onComplete(r) {

        var xml = r.responseXML;
        if (xml && !xml.documentElement && fabric.window.ActiveXObject && r.responseText) {
          xml = new ActiveXObject('Microsoft.XMLDOM');
          xml.async = 'false';
          //IE chokes on DOCTYPE
          xml.loadXML(r.responseText.replace(/<!DOCTYPE[\s\S]*?(\[[\s\S]*\])*?>/i, ''));
        }
        if (!xml || !xml.documentElement) {
          return;
        }

        fabric.parseSVGDocument(xml.documentElement, function (results, options) {
          svgCache.set(url, {
            objects: fabric.util.array.invoke(results, 'toObject'),
            options: options
          });
          callback(results, options);
        }, reviver);
      }
    },

    /**
     * Takes string corresponding to an SVG document, and parses it into a set of fabric objects
     * @memberOf fabric
     * @param {String} string
     * @param {Function} callback
     * @param {Function} [reviver] Method for further parsing of SVG elements, called after each fabric object created.
     */
    loadSVGFromString: function(string, callback, reviver) {
      string = string.trim();
      var doc;
      if (typeof DOMParser !== 'undefined') {
        var parser = new DOMParser();
        if (parser && parser.parseFromString) {
          doc = parser.parseFromString(string, 'text/xml');
        }
      }
      else if (fabric.window.ActiveXObject) {
        doc = new ActiveXObject('Microsoft.XMLDOM');
        doc.async = 'false';
        // IE chokes on DOCTYPE
        doc.loadXML(string.replace(/<!DOCTYPE[\s\S]*?(\[[\s\S]*\])*?>/i, ''));
      }

      fabric.parseSVGDocument(doc.documentElement, function (results, options) {
        callback(results, options);
      }, reviver);
    },

    /**
     * Creates markup containing SVG font faces
     * @param {Array} objects Array of fabric objects
     * @return {String}
     */
    createSVGFontFacesMarkup: function(objects) {
      var markup = '';

      for (var i = 0, len = objects.length; i < len; i++) {
        if (objects[i].type !== 'text' || !objects[i].path) {
          continue;
        }

        markup += [
          //jscs:disable validateIndentation
          '@font-face {',
            'font-family: ', objects[i].fontFamily, '; ',
            'src: url(\'', objects[i].path, '\')',
          '}\n'
          //jscs:enable validateIndentation
        ].join('');
      }

      if (markup) {
        markup = [
          //jscs:disable validateIndentation
          '\t<style type="text/css">',
            '<![CDATA[',
              markup,
            ']]>',
          '</style>\n'
          //jscs:enable validateIndentation
        ].join('');
      }

      return markup;
    },

    /**
     * Creates markup containing SVG referenced elements like patterns, gradients etc.
     * @param {fabric.Canvas} canvas instance of fabric.Canvas
     * @return {String}
     */
    createSVGRefElementsMarkup: function(canvas) {
      var markup = [ ];

      _createSVGPattern(markup, canvas, 'backgroundColor');
      _createSVGPattern(markup, canvas, 'overlayColor');

      return markup.join('');
    }
  });

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