(function(global) {

  var sqrt = Math.sqrt,
      atan2 = Math.atan2,
      pow = Math.pow,
      abs = Math.abs,
      PiBy180 = Math.PI / 180,
      PiBy2 = Math.PI / 2;

  /**
   * @namespace fabric.util
   */
  fabric.util = {

    /**
     * Calculate the cos of an angle, avoiding returning floats for known results
     * @static
     * @memberOf fabric.util
     * @param {Number} angle the angle in radians or in degree
     * @return {Number}
     */
    cos: function(angle) {
      if (angle === 0) { return 1; }
      if (angle < 0) {
        // cos(a) = cos(-a)
        angle = -angle;
      }
      var angleSlice = angle / PiBy2;
      switch (angleSlice) {
        case 1: case 3: return 0;
        case 2: return -1;
      }
      return Math.cos(angle);
    },

    /**
     * Calculate the sin of an angle, avoiding returning floats for known results
     * @static
     * @memberOf fabric.util
     * @param {Number} angle the angle in radians or in degree
     * @return {Number}
     */
    sin: function(angle) {
      if (angle === 0) { return 0; }
      var angleSlice = angle / PiBy2, sign = 1;
      if (angle < 0) {
        // sin(-a) = -sin(a)
        sign = -1;
      }
      switch (angleSlice) {
        case 1: return sign;
        case 2: return 0;
        case 3: return -sign;
      }
      return Math.sin(angle);
    },

    /**
     * Removes value from an array.
     * Presence of value (and its position in an array) is determined via `Array.prototype.indexOf`
     * @static
     * @memberOf fabric.util
     * @param {Array} array
     * @param {*} value
     * @return {Array} original array
     */
    removeFromArray: function(array, value) {
      var idx = array.indexOf(value);
      if (idx !== -1) {
        array.splice(idx, 1);
      }
      return array;
    },

    /**
     * Returns random number between 2 specified ones.
     * @static
     * @memberOf fabric.util
     * @param {Number} min lower limit
     * @param {Number} max upper limit
     * @return {Number} random value (between min and max)
     */
    getRandomInt: function(min, max) {
      return Math.floor(Math.random() * (max - min + 1)) + min;
    },

    /**
     * Transforms degrees to radians.
     * @static
     * @memberOf fabric.util
     * @param {Number} degrees value in degrees
     * @return {Number} value in radians
     */
    degreesToRadians: function(degrees) {
      return degrees * PiBy180;
    },

    /**
     * Transforms radians to degrees.
     * @static
     * @memberOf fabric.util
     * @param {Number} radians value in radians
     * @return {Number} value in degrees
     */
    radiansToDegrees: function(radians) {
      return radians / PiBy180;
    },

    /**
     * Rotates `point` around `origin` with `radians`
     * @static
     * @memberOf fabric.util
     * @param {fabric.Point} point The point to rotate
     * @param {fabric.Point} origin The origin of the rotation
     * @param {Number} radians The radians of the angle for the rotation
     * @return {fabric.Point} The new rotated point
     */
    rotatePoint: function(point, origin, radians) {
      point.subtractEquals(origin);
      var v = fabric.util.rotateVector(point, radians);
      return new fabric.Point(v.x, v.y).addEquals(origin);
    },

    /**
     * Rotates `vector` with `radians`
     * @static
     * @memberOf fabric.util
     * @param {Object} vector The vector to rotate (x and y)
     * @param {Number} radians The radians of the angle for the rotation
     * @return {Object} The new rotated point
     */
    rotateVector: function(vector, radians) {
      var sin = fabric.util.sin(radians),
          cos = fabric.util.cos(radians),
          rx = vector.x * cos - vector.y * sin,
          ry = vector.x * sin + vector.y * cos;
      return {
        x: rx,
        y: ry
      };
    },

    /**
     * Apply transform t to point p
     * @static
     * @memberOf fabric.util
     * @param  {fabric.Point} p The point to transform
     * @param  {Array} t The transform
     * @param  {Boolean} [ignoreOffset] Indicates that the offset should not be applied
     * @return {fabric.Point} The transformed point
     */
    transformPoint: function(p, t, ignoreOffset) {
      if (ignoreOffset) {
        return new fabric.Point(
          t[0] * p.x + t[2] * p.y,
          t[1] * p.x + t[3] * p.y
        );
      }
      return new fabric.Point(
        t[0] * p.x + t[2] * p.y + t[4],
        t[1] * p.x + t[3] * p.y + t[5]
      );
    },

    /**
     * Returns coordinates of points's bounding rectangle (left, top, width, height)
     * @param {Array} points 4 points array
     * @return {Object} Object with left, top, width, height properties
     */
    makeBoundingBoxFromPoints: function(points) {
      var xPoints = [points[0].x, points[1].x, points[2].x, points[3].x],
          minX = fabric.util.array.min(xPoints),
          maxX = fabric.util.array.max(xPoints),
          width = maxX - minX,
          yPoints = [points[0].y, points[1].y, points[2].y, points[3].y],
          minY = fabric.util.array.min(yPoints),
          maxY = fabric.util.array.max(yPoints),
          height = maxY - minY;

      return {
        left: minX,
        top: minY,
        width: width,
        height: height
      };
    },

    /**
     * Invert transformation t
     * @static
     * @memberOf fabric.util
     * @param {Array} t The transform
     * @return {Array} The inverted transform
     */
    invertTransform: function(t) {
      var a = 1 / (t[0] * t[3] - t[1] * t[2]),
          r = [a * t[3], -a * t[1], -a * t[2], a * t[0]],
          o = fabric.util.transformPoint({ x: t[4], y: t[5] }, r, true);
      r[4] = -o.x;
      r[5] = -o.y;
      return r;
    },

    /**
     * A wrapper around Number#toFixed, which contrary to native method returns number, not string.
     * @static
     * @memberOf fabric.util
     * @param {Number|String} number number to operate on
     * @param {Number} fractionDigits number of fraction digits to "leave"
     * @return {Number}
     */
    toFixed: function(number, fractionDigits) {
      return parseFloat(Number(number).toFixed(fractionDigits));
    },

    /**
     * Converts from attribute value to pixel value if applicable.
     * Returns converted pixels or original value not converted.
     * @param {Number|String} value number to operate on
     * @param {Number} fontSize
     * @return {Number|String}
     */
    parseUnit: function(value, fontSize) {
      var unit = /\D{0,2}$/.exec(value),
          number = parseFloat(value);
      if (!fontSize) {
        fontSize = fabric.Text.DEFAULT_SVG_FONT_SIZE;
      }
      switch (unit[0]) {
        case 'mm':
          return number * fabric.DPI / 25.4;

        case 'cm':
          return number * fabric.DPI / 2.54;

        case 'in':
          return number * fabric.DPI;

        case 'pt':
          return number * fabric.DPI / 72; // or * 4 / 3

        case 'pc':
          return number * fabric.DPI / 72 * 12; // or * 16

        case 'em':
          return number * fontSize;

        default:
          return number;
      }
    },

    /**
     * Function which always returns `false`.
     * @static
     * @memberOf fabric.util
     * @return {Boolean}
     */
    falseFunction: function() {
      return false;
    },

    /**
     * Returns klass "Class" object of given namespace
     * @memberOf fabric.util
     * @param {String} type Type of object (eg. 'circle')
     * @param {String} namespace Namespace to get klass "Class" object from
     * @return {Object} klass "Class"
     */
    getKlass: function(type, namespace) {
      // capitalize first letter only
      type = fabric.util.string.camelize(type.charAt(0).toUpperCase() + type.slice(1));
      return fabric.util.resolveNamespace(namespace)[type];
    },

    /**
     * Returns array of attributes for given svg that fabric parses
     * @memberOf fabric.util
     * @param {String} type Type of svg element (eg. 'circle')
     * @return {Array} string names of supported attributes
     */
    getSvgAttributes: function(type) {
      var attributes = [
        'instantiated_by_use',
        'style',
        'id',
        'class'
      ];
      switch (type) {
        case 'linearGradient':
          attributes = attributes.concat(['x1', 'y1', 'x2', 'y2', 'gradientUnits', 'gradientTransform']);
          break;
        case 'radialGradient':
          attributes = attributes.concat(['gradientUnits', 'gradientTransform', 'cx', 'cy', 'r', 'fx', 'fy', 'fr']);
          break;
        case 'stop':
          attributes = attributes.concat(['offset', 'stop-color', 'stop-opacity']);
          break;
      }
      return attributes;
    },

    /**
     * Returns object of given namespace
     * @memberOf fabric.util
     * @param {String} namespace Namespace string e.g. 'fabric.Image.filter' or 'fabric'
     * @return {Object} Object for given namespace (default fabric)
     */
    resolveNamespace: function(namespace) {
      if (!namespace) {
        return fabric;
      }

      var parts = namespace.split('.'),
          len = parts.length, i,
          obj = global || fabric.window;

      for (i = 0; i < len; ++i) {
        obj = obj[parts[i]];
      }

      return obj;
    },

    /**
     * Loads image element from given url and passes it to a callback
     * @memberOf fabric.util
     * @param {String} url URL representing an image
     * @param {Function} callback Callback; invoked with loaded image
     * @param {*} [context] Context to invoke callback in
     * @param {Object} [crossOrigin] crossOrigin value to set image element to
     */
    loadImage: function(url, callback, context, crossOrigin) {
      if (!url) {
        callback && callback.call(context, url);
        return;
      }

      var img = fabric.util.createImage();

      /** @ignore */
      var onLoadCallback = function () {
        callback && callback.call(context, img);
        img = img.onload = img.onerror = null;
      };

      img.onload = onLoadCallback;
      /** @ignore */
      img.onerror = function() {
        fabric.log('Error loading ' + img.src);
        callback && callback.call(context, null, true);
        img = img.onload = img.onerror = null;
      };

      // data-urls appear to be buggy with crossOrigin
      // https://github.com/kangax/fabric.js/commit/d0abb90f1cd5c5ef9d2a94d3fb21a22330da3e0a#commitcomment-4513767
      // see https://code.google.com/p/chromium/issues/detail?id=315152
      //     https://bugzilla.mozilla.org/show_bug.cgi?id=935069
      if (url.indexOf('data') !== 0 && crossOrigin) {
        img.crossOrigin = crossOrigin;
      }

      // IE10 / IE11-Fix: SVG contents from data: URI
      // will only be available if the IMG is present
      // in the DOM (and visible)
      if (url.substring(0,14) === 'data:image/svg') {
        img.onload = null;
        fabric.util.loadImageInDom(img, onLoadCallback);
      }

      img.src = url;
    },

    /**
     * Attaches SVG image with data: URL to the dom
     * @memberOf fabric.util
     * @param {Object} img Image object with data:image/svg src
     * @param {Function} callback Callback; invoked with loaded image
     * @return {Object} DOM element (div containing the SVG image)
     */
    loadImageInDom: function(img, onLoadCallback) {
      var div = fabric.document.createElement('div');
      div.style.width = div.style.height = '1px';
      div.style.left = div.style.top = '-100%';
      div.style.position = 'absolute';
      div.appendChild(img);
      fabric.document.querySelector('body').appendChild(div);
      /**
       * Wrap in function to:
       *   1. Call existing callback
       *   2. Cleanup DOM
       */
      img.onload = function () {
        onLoadCallback();
        div.parentNode.removeChild(div);
        div = null;
      };
    },

    /**
     * Creates corresponding fabric instances from their object representations
     * @static
     * @memberOf fabric.util
     * @param {Array} objects Objects to enliven
     * @param {Function} callback Callback to invoke when all objects are created
     * @param {String} namespace Namespace to get klass "Class" object from
     * @param {Function} reviver Method for further parsing of object elements,
     * called after each fabric object created.
     */
    enlivenObjects: function(objects, callback, namespace, reviver) {
      objects = objects || [];

      function onLoaded() {
        if (++numLoadedObjects === numTotalObjects) {
          callback && callback(enlivenedObjects);
        }
      }

      var enlivenedObjects = [],
          numLoadedObjects = 0,
          numTotalObjects = objects.length;

      if (!numTotalObjects) {
        callback && callback(enlivenedObjects);
        return;
      }

      objects.forEach(function (o, index) {
        // if sparse array
        if (!o || !o.type) {
          onLoaded();
          return;
        }
        var klass = fabric.util.getKlass(o.type, namespace);
        klass.fromObject(o, function (obj, error) {
          error || (enlivenedObjects[index] = obj);
          reviver && reviver(o, obj, error);
          onLoaded();
        });
      });
    },

    /**
     * Create and wait for loading of patterns
     * @static
     * @memberOf fabric.util
     * @param {Array} patterns Objects to enliven
     * @param {Function} callback Callback to invoke when all objects are created
     * called after each fabric object created.
     */
    enlivenPatterns: function(patterns, callback) {
      patterns = patterns || [];

      function onLoaded() {
        if (++numLoadedPatterns === numPatterns) {
          callback && callback(enlivenedPatterns);
        }
      }

      var enlivenedPatterns = [],
          numLoadedPatterns = 0,
          numPatterns = patterns.length;

      if (!numPatterns) {
        callback && callback(enlivenedPatterns);
        return;
      }

      patterns.forEach(function (p, index) {
        if (p && p.source) {
          new fabric.Pattern(p, function(pattern) {
            enlivenedPatterns[index] = pattern;
            onLoaded();
          });
        }
        else {
          enlivenedPatterns[index] = p;
          onLoaded();
        }
      });
    },

    /**
     * Groups SVG elements (usually those retrieved from SVG document)
     * @static
     * @memberOf fabric.util
     * @param {Array} elements SVG elements to group
     * @param {Object} [options] Options object
     * @param {String} path Value to set sourcePath to
     * @return {fabric.Object|fabric.Group}
     */
    groupSVGElements: function(elements, options, path) {
      var object;
      if (elements && elements.length === 1) {
        return elements[0];
      }
      if (options) {
        if (options.width && options.height) {
          options.centerPoint = {
            x: options.width / 2,
            y: options.height / 2
          };
        }
        else {
          delete options.width;
          delete options.height;
        }
      }
      object = new fabric.Group(elements, options);
      if (typeof path !== 'undefined') {
        object.sourcePath = path;
      }
      return object;
    },

    /**
     * Populates an object with properties of another object
     * @static
     * @memberOf fabric.util
     * @param {Object} source Source object
     * @param {Object} destination Destination object
     * @return {Array} properties Properties names to include
     */
    populateWithProperties: function(source, destination, properties) {
      if (properties && Object.prototype.toString.call(properties) === '[object Array]') {
        for (var i = 0, len = properties.length; i < len; i++) {
          if (properties[i] in source) {
            destination[properties[i]] = source[properties[i]];
          }
        }
      }
    },

    /**
     * Draws a dashed line between two points
     *
     * This method is used to draw dashed line around selection area.
     * See <a href="http://stackoverflow.com/questions/4576724/dotted-stroke-in-canvas">dotted stroke in canvas</a>
     *
     * @param {CanvasRenderingContext2D} ctx context
     * @param {Number} x  start x coordinate
     * @param {Number} y start y coordinate
     * @param {Number} x2 end x coordinate
     * @param {Number} y2 end y coordinate
     * @param {Array} da dash array pattern
     */
    drawDashedLine: function(ctx, x, y, x2, y2, da) {
      var dx = x2 - x,
          dy = y2 - y,
          len = sqrt(dx * dx + dy * dy),
          rot = atan2(dy, dx),
          dc = da.length,
          di = 0,
          draw = true;

      ctx.save();
      ctx.translate(x, y);
      ctx.moveTo(0, 0);
      ctx.rotate(rot);

      x = 0;
      while (len > x) {
        x += da[di++ % dc];
        if (x > len) {
          x = len;
        }
        ctx[draw ? 'lineTo' : 'moveTo'](x, 0);
        draw = !draw;
      }

      ctx.restore();
    },

    /**
     * Creates canvas element
     * @static
     * @memberOf fabric.util
     * @return {CanvasElement} initialized canvas element
     */
    createCanvasElement: function() {
      return fabric.document.createElement('canvas');
    },

    /**
     * Creates a canvas element that is a copy of another and is also painted
     * @static
     * @memberOf fabric.util
     * @return {CanvasElement} initialized canvas element
     */
    copyCanvasElement: function(canvas) {
      var newCanvas = fabric.document.createElement('canvas');
      newCanvas.width = canvas.width;
      newCanvas.height = canvas.height;
      newCanvas.getContext('2d').drawImage(canvas, 0, 0);
      return newCanvas;
    },

    /**
     * Creates image element (works on client and node)
     * @static
     * @memberOf fabric.util
     * @return {HTMLImageElement} HTML image element
     */
    createImage: function() {
      return fabric.document.createElement('img');
    },

    /**
     * @static
     * @memberOf fabric.util
     * @deprecated since 2.0.0
     * @param {fabric.Object} receiver Object implementing `clipTo` method
     * @param {CanvasRenderingContext2D} ctx Context to clip
     */
    clipContext: function(receiver, ctx) {
      ctx.save();
      ctx.beginPath();
      receiver.clipTo(ctx);
      ctx.clip();
    },

    /**
     * Multiply matrix A by matrix B to nest transformations
     * @static
     * @memberOf fabric.util
     * @param  {Array} a First transformMatrix
     * @param  {Array} b Second transformMatrix
     * @param  {Boolean} is2x2 flag to multiply matrices as 2x2 matrices
     * @return {Array} The product of the two transform matrices
     */
    multiplyTransformMatrices: function(a, b, is2x2) {
      // Matrix multiply a * b
      return [
        a[0] * b[0] + a[2] * b[1],
        a[1] * b[0] + a[3] * b[1],
        a[0] * b[2] + a[2] * b[3],
        a[1] * b[2] + a[3] * b[3],
        is2x2 ? 0 : a[0] * b[4] + a[2] * b[5] + a[4],
        is2x2 ? 0 : a[1] * b[4] + a[3] * b[5] + a[5]
      ];
    },

    /**
     * Decomposes standard 2x2 matrix into transform componentes
     * @static
     * @memberOf fabric.util
     * @param  {Array} a transformMatrix
     * @return {Object} Components of transform
     */
    qrDecompose: function(a) {
      var angle = atan2(a[1], a[0]),
          denom = pow(a[0], 2) + pow(a[1], 2),
          scaleX = sqrt(denom),
          scaleY = (a[0] * a[3] - a[2] * a [1]) / scaleX,
          skewX = atan2(a[0] * a[2] + a[1] * a [3], denom);
      return {
        angle: angle  / PiBy180,
        scaleX: scaleX,
        scaleY: scaleY,
        skewX: skewX / PiBy180,
        skewY: 0,
        translateX: a[4],
        translateY: a[5]
      };
    },

    customTransformMatrix: function(scaleX, scaleY, skewX) {
      var skewMatrixX = [1, 0, abs(Math.tan(skewX * PiBy180)), 1],
          scaleMatrix = [abs(scaleX), 0, 0, abs(scaleY)];
      return fabric.util.multiplyTransformMatrices(scaleMatrix, skewMatrixX, true);
    },

    /**
     * reset an object transform state to neutral. Top and left are not accounted for
     * @static
     * @memberOf fabric.util
     * @param  {fabric.Object} target object to transform
     */
    resetObjectTransform: function (target) {
      target.scaleX = 1;
      target.scaleY = 1;
      target.skewX = 0;
      target.skewY = 0;
      target.flipX = false;
      target.flipY = false;
      target.rotate(0);
    },

    /**
     * Extract Object transform values
     * @static
     * @memberOf fabric.util
     * @param  {fabric.Object} target object to read from
     * @return {Object} Components of transform
     */
    saveObjectTransform: function (target) {
      return {
        scaleX: target.scaleX,
        scaleY: target.scaleY,
        skewX: target.skewX,
        skewY: target.skewY,
        angle: target.angle,
        left: target.left,
        flipX: target.flipX,
        flipY: target.flipY,
        top: target.top
      };
    },

    /**
     * Returns string representation of function body
     * @param {Function} fn Function to get body of
     * @return {String} Function body
     */
    getFunctionBody: function(fn) {
      return (String(fn).match(/function[^{]*\{([\s\S]*)\}/) || {})[1];
    },

    /**
     * Returns true if context has transparent pixel
     * at specified location (taking tolerance into account)
     * @param {CanvasRenderingContext2D} ctx context
     * @param {Number} x x coordinate
     * @param {Number} y y coordinate
     * @param {Number} tolerance Tolerance
     */
    isTransparent: function(ctx, x, y, tolerance) {

      // If tolerance is > 0 adjust start coords to take into account.
      // If moves off Canvas fix to 0
      if (tolerance > 0) {
        if (x > tolerance) {
          x -= tolerance;
        }
        else {
          x = 0;
        }
        if (y > tolerance) {
          y -= tolerance;
        }
        else {
          y = 0;
        }
      }

      var _isTransparent = true, i, temp,
          imageData = ctx.getImageData(x, y, (tolerance * 2) || 1, (tolerance * 2) || 1),
          l = imageData.data.length;

      // Split image data - for tolerance > 1, pixelDataSize = 4;
      for (i = 3; i < l; i += 4) {
        temp = imageData.data[i];
        _isTransparent = temp <= 0;
        if (_isTransparent === false) {
          break; // Stop if colour found
        }
      }

      imageData = null;

      return _isTransparent;
    },

    /**
     * Parse preserveAspectRatio attribute from element
     * @param {string} attribute to be parsed
     * @return {Object} an object containing align and meetOrSlice attribute
     */
    parsePreserveAspectRatioAttribute: function(attribute) {
      var meetOrSlice = 'meet', alignX = 'Mid', alignY = 'Mid',
          aspectRatioAttrs = attribute.split(' '), align;

      if (aspectRatioAttrs && aspectRatioAttrs.length) {
        meetOrSlice = aspectRatioAttrs.pop();
        if (meetOrSlice !== 'meet' && meetOrSlice !== 'slice') {
          align = meetOrSlice;
          meetOrSlice = 'meet';
        }
        else if (aspectRatioAttrs.length) {
          align = aspectRatioAttrs.pop();
        }
      }
      //divide align in alignX and alignY
      alignX = align !== 'none' ? align.slice(1, 4) : 'none';
      alignY = align !== 'none' ? align.slice(5, 8) : 'none';
      return {
        meetOrSlice: meetOrSlice,
        alignX: alignX,
        alignY: alignY
      };
    },

    /**
     * Clear char widths cache for the given font family or all the cache if no
     * fontFamily is specified.
     * Use it if you know you are loading fonts in a lazy way and you are not waiting
     * for custom fonts to load properly when adding text objects to the canvas.
     * If a text object is added when its own font is not loaded yet, you will get wrong
     * measurement and so wrong bounding boxes.
     * After the font cache is cleared, either change the textObject text content or call
     * initDimensions() to trigger a recalculation
     * @memberOf fabric.util
     * @param {String} [fontFamily] font family to clear
     */
    clearFabricFontCache: function(fontFamily) {
      fontFamily = (fontFamily || '').toLowerCase();
      if (!fontFamily) {
        fabric.charWidthsCache = { };
      }
      else if (fabric.charWidthsCache[fontFamily]) {
        delete fabric.charWidthsCache[fontFamily];
      }
    },

    /**
     * Given current aspect ratio, determines the max width and height that can
     * respect the total allowed area for the cache.
     * @memberOf fabric.util
     * @param {Number} ar aspect ratio
     * @param {Number} maximumArea Maximum area you want to achieve
     * @return {Object.x} Limited dimensions by X
     * @return {Object.y} Limited dimensions by Y
     */
    limitDimsByArea: function(ar, maximumArea) {
      var roughWidth = Math.sqrt(maximumArea * ar),
          perfLimitSizeY = Math.floor(maximumArea / roughWidth);
      return { x: Math.floor(roughWidth), y: perfLimitSizeY };
    },

    capValue: function(min, value, max) {
      return Math.max(min, Math.min(value, max));
    },

    findScaleToFit: function(source, destination) {
      return Math.min(destination.width / source.width, destination.height / source.height);
    },

    findScaleToCover: function(source, destination) {
      return Math.max(destination.width / source.width, destination.height / source.height);
    }
  };
})(typeof exports !== 'undefined' ? exports : this);
