(function(){

  var getPointer = fabric.util.getPointer,
      degreesToRadians = fabric.util.degreesToRadians;

  fabric.util.object.extend(fabric.Object.prototype, /** @scope fabric.Object.prototype */ {

    /**
     * Determines which one of the four corners has been clicked
     * @method _findTargetCorner
     * @private
     * @param e {Event} event object
     * @param offset {Object} canvas offset
     * @return {String|Boolean} corner code (tl, tr, bl, br, etc.), or false if nothing is found
     */
    _findTargetCorner: function(e, offset) {
      if (!this.hasControls || !this.active) return false;

      var pointer = getPointer(e, this.canvas.upperCanvasEl),
          ex = pointer.x - offset.left,
          ey = pointer.y - offset.top,
          xpoints,
          lines;

      for (var i in this.oCoords) {

        if (i === 'mtr' && !this.hasRotatingPoint) {
          continue;
        }

        if (this.get('lockUniScaling') && (i === 'mt' || i === 'mr' || i === 'mb' || i === 'ml')) {
          continue;
        }

        lines = this._getImageLines(this.oCoords[i].corner, i);

        // debugging

        // canvas.contextTop.fillRect(lines.bottomline.d.x, lines.bottomline.d.y, 2, 2);
        // canvas.contextTop.fillRect(lines.bottomline.o.x, lines.bottomline.o.y, 2, 2);

        // canvas.contextTop.fillRect(lines.leftline.d.x, lines.leftline.d.y, 2, 2);
        // canvas.contextTop.fillRect(lines.leftline.o.x, lines.leftline.o.y, 2, 2);

        // canvas.contextTop.fillRect(lines.topline.d.x, lines.topline.d.y, 2, 2);
        // canvas.contextTop.fillRect(lines.topline.o.x, lines.topline.o.y, 2, 2);

        // canvas.contextTop.fillRect(lines.rightline.d.x, lines.rightline.d.y, 2, 2);
        // canvas.contextTop.fillRect(lines.rightline.o.x, lines.rightline.o.y, 2, 2);

        xpoints = this._findCrossPoints(ex, ey, lines);
        if (xpoints % 2 === 1 && xpoints !== 0) {
          this.__corner = i;
          return i;
        }
      }
      return false;
    },

    /**
     * Helper method to determine how many cross points are between the 4 image edges
     * and the horizontal line determined by the position of our mouse when clicked on canvas
     * @method _findCrossPoints
     * @private
     * @param ex {Number} x coordinate of the mouse
     * @param ey {Number} y coordinate of the mouse
     * @param oCoords {Object} Coordinates of the image being evaluated
     */
    _findCrossPoints: function(ex, ey, oCoords) {
      var b1, b2, a1, a2, xi, yi,
          xcount = 0,
          iLine;

      for (var lineKey in oCoords) {
        iLine = oCoords[lineKey];
        // optimisation 1: line below dot. no cross
        if ((iLine.o.y < ey) && (iLine.d.y < ey)) {
          continue;
        }
        // optimisation 2: line above dot. no cross
        if ((iLine.o.y >= ey) && (iLine.d.y >= ey)) {
          continue;
        }
        // optimisation 3: vertical line case
        if ((iLine.o.x === iLine.d.x) && (iLine.o.x >= ex)) {
          xi = iLine.o.x;
          yi = ey;
        }
        // calculate the intersection point
        else {
          b1 = 0;
          b2 = (iLine.d.y-iLine.o.y)/(iLine.d.x-iLine.o.x);
          a1 = ey-b1*ex;
          a2 = iLine.o.y-b2*iLine.o.x;

          xi = - (a1-a2)/(b1-b2);
          yi = a1+b1*xi;
        }
        // dont count xi < ex cases
        if (xi >= ex) {
          xcount += 1;
        }
        // optimisation 4: specific for square images
        if (xcount === 2) {
          break;
        }
      }
      return xcount;
    },

    /**
     * Method that returns an object with the image lines in it given the coordinates of the corners
     * @method _getImageLines
     * @private
     * @param oCoords {Object} coordinates of the image corners
     */
    _getImageLines: function(oCoords) {
      return {
        topline: {
          o: oCoords.tl,
          d: oCoords.tr
        },
        rightline: {
          o: oCoords.tr,
          d: oCoords.br
        },
        bottomline: {
          o: oCoords.br,
          d: oCoords.bl
        },
        leftline: {
          o: oCoords.bl,
          d: oCoords.tl
        }
      };
    },

    /**
     * Sets the coordinates of the draggable boxes in the corners of
     * the image used to scale/rotate it.
     * @method _setCornerCoords
     * @private
     */
    _setCornerCoords: function() {
      var coords = this.oCoords,
          theta = degreesToRadians(this.angle),
          newTheta = degreesToRadians(45 - this.angle),
          cornerHypotenuse = Math.sqrt(2 * Math.pow(this.cornerSize, 2)) / 2,
          cosHalfOffset = cornerHypotenuse * Math.cos(newTheta),
          sinHalfOffset = cornerHypotenuse * Math.sin(newTheta),
          sinTh = Math.sin(theta),
          cosTh = Math.cos(theta);

      coords.tl.corner = {
        tl: {
          x: coords.tl.x - sinHalfOffset,
          y: coords.tl.y - cosHalfOffset
        },
        tr: {
          x: coords.tl.x + cosHalfOffset,
          y: coords.tl.y - sinHalfOffset
        },
        bl: {
          x: coords.tl.x - cosHalfOffset,
          y: coords.tl.y + sinHalfOffset
        },
        br: {
          x: coords.tl.x + sinHalfOffset,
          y: coords.tl.y + cosHalfOffset
        }
      };

      coords.tr.corner = {
        tl: {
          x: coords.tr.x - sinHalfOffset,
          y: coords.tr.y - cosHalfOffset
        },
        tr: {
          x: coords.tr.x + cosHalfOffset,
          y: coords.tr.y - sinHalfOffset
        },
        br: {
          x: coords.tr.x + sinHalfOffset,
          y: coords.tr.y + cosHalfOffset
        },
        bl: {
          x: coords.tr.x - cosHalfOffset,
          y: coords.tr.y + sinHalfOffset
        }
      };

      coords.bl.corner = {
        tl: {
          x: coords.bl.x - sinHalfOffset,
          y: coords.bl.y - cosHalfOffset
        },
        bl: {
          x: coords.bl.x - cosHalfOffset,
          y: coords.bl.y + sinHalfOffset
        },
        br: {
          x: coords.bl.x + sinHalfOffset,
          y: coords.bl.y + cosHalfOffset
        },
        tr: {
          x: coords.bl.x + cosHalfOffset,
          y: coords.bl.y - sinHalfOffset
        }
      };

      coords.br.corner = {
        tr: {
          x: coords.br.x + cosHalfOffset,
          y: coords.br.y - sinHalfOffset
        },
        bl: {
          x: coords.br.x - cosHalfOffset,
          y: coords.br.y + sinHalfOffset
        },
        br: {
          x: coords.br.x + sinHalfOffset,
          y: coords.br.y + cosHalfOffset
        },
        tl: {
          x: coords.br.x - sinHalfOffset,
          y: coords.br.y - cosHalfOffset
        }
      };

      coords.ml.corner = {
        tl: {
          x: coords.ml.x - sinHalfOffset,
          y: coords.ml.y - cosHalfOffset
        },
        tr: {
          x: coords.ml.x + cosHalfOffset,
          y: coords.ml.y - sinHalfOffset
        },
        bl: {
          x: coords.ml.x - cosHalfOffset,
          y: coords.ml.y + sinHalfOffset
        },
        br: {
          x: coords.ml.x + sinHalfOffset,
          y: coords.ml.y + cosHalfOffset
        }
      };

      coords.mt.corner = {
        tl: {
          x: coords.mt.x - sinHalfOffset,
          y: coords.mt.y - cosHalfOffset
        },
        tr: {
          x: coords.mt.x + cosHalfOffset,
          y: coords.mt.y - sinHalfOffset
        },
        bl: {
          x: coords.mt.x - cosHalfOffset,
          y: coords.mt.y + sinHalfOffset
        },
        br: {
          x: coords.mt.x + sinHalfOffset,
          y: coords.mt.y + cosHalfOffset
        }
      };

      coords.mr.corner = {
        tl: {
          x: coords.mr.x - sinHalfOffset,
          y: coords.mr.y - cosHalfOffset
        },
        tr: {
          x: coords.mr.x + cosHalfOffset,
          y: coords.mr.y - sinHalfOffset
        },
        bl: {
          x: coords.mr.x - cosHalfOffset,
          y: coords.mr.y + sinHalfOffset
        },
        br: {
          x: coords.mr.x + sinHalfOffset,
          y: coords.mr.y + cosHalfOffset
        }
      };

      coords.mb.corner = {
        tl: {
          x: coords.mb.x - sinHalfOffset,
          y: coords.mb.y - cosHalfOffset
        },
        tr: {
          x: coords.mb.x + cosHalfOffset,
          y: coords.mb.y - sinHalfOffset
        },
        bl: {
          x: coords.mb.x - cosHalfOffset,
          y: coords.mb.y + sinHalfOffset
        },
        br: {
          x: coords.mb.x + sinHalfOffset,
          y: coords.mb.y + cosHalfOffset
        }
      };

      coords.mtr.corner = {
        tl: {
          x: coords.mtr.x - sinHalfOffset + (sinTh * this.rotatingPointOffset),
          y: coords.mtr.y - cosHalfOffset - (cosTh * this.rotatingPointOffset)
        },
        tr: {
          x: coords.mtr.x + cosHalfOffset + (sinTh * this.rotatingPointOffset),
          y: coords.mtr.y - sinHalfOffset - (cosTh * this.rotatingPointOffset)
        },
        bl: {
          x: coords.mtr.x - cosHalfOffset + (sinTh * this.rotatingPointOffset),
          y: coords.mtr.y + sinHalfOffset - (cosTh * this.rotatingPointOffset)
        },
        br: {
          x: coords.mtr.x + sinHalfOffset + (sinTh * this.rotatingPointOffset),
          y: coords.mtr.y + cosHalfOffset - (cosTh * this.rotatingPointOffset)
        }
      };
    },
    /**
     * Draws borders of an object's bounding box.
     * Requires public properties: width, height
     * Requires public options: padding, borderColor
     * @method drawBorders
     * @param {CanvasRenderingContext2D} ctx Context to draw on
     * @return {fabric.Object} thisArg
     * @chainable
     */
    drawBorders: function(ctx) {
      if (!this.hasBorders) return this;

      var padding = this.padding,
          padding2 = padding * 2,
          strokeWidth = this.strokeWidth > 1 ? this.strokeWidth : 0;

      ctx.save();

      ctx.globalAlpha = this.isMoving ? this.borderOpacityWhenMoving : 1;
      ctx.strokeStyle = this.borderColor;

      var scaleX = 1 / this._constrainScale(this.scaleX),
          scaleY = 1 / this._constrainScale(this.scaleY);

      ctx.lineWidth = 1 / this.borderScaleFactor;

      ctx.scale(scaleX, scaleY);

      var w = this.getWidth(),
          h = this.getHeight();

      ctx.strokeRect(
        ~~(-(w / 2) - padding - strokeWidth / 2 * this.scaleX) + 0.5, // offset needed to make lines look sharper
        ~~(-(h / 2) - padding - strokeWidth / 2 * this.scaleY) + 0.5,
        ~~(w + padding2 + strokeWidth * this.scaleX),
        ~~(h + padding2 + strokeWidth * this.scaleY)
      );

      if (this.hasRotatingPoint && !this.get('lockRotation') && this.hasControls) {

        var rotateHeight = (
          this.flipY
            ? h + (strokeWidth * this.scaleY) + (padding * 2)
            : -h - (strokeWidth * this.scaleY) - (padding * 2)
        ) / 2;

        ctx.beginPath();
        ctx.moveTo(0, rotateHeight);
        ctx.lineTo(0, rotateHeight + (this.flipY ? this.rotatingPointOffset : -this.rotatingPointOffset));
        ctx.closePath();
        ctx.stroke();
      }

      ctx.restore();
      return this;
    },

    /**
     * Draws corners of an object's bounding box.
     * Requires public properties: width, height, scaleX, scaleY
     * Requires public options: cornerSize, padding
     * @method drawControls
     * @param {CanvasRenderingContext2D} ctx Context to draw on
     * @return {fabric.Object} thisArg
     * @chainable
     */
    drawControls: function(ctx) {
      if (!this.hasControls) return this;

      var size = this.cornerSize,
          size2 = size / 2,
          strokeWidth2 = this.strokeWidth / 2,
          left = -(this.width / 2),
          top = -(this.height / 2),
          _left,
          _top,
          sizeX = size / this.scaleX,
          sizeY = size / this.scaleY,
          paddingX = this.padding / this.scaleX,
          paddingY = this.padding / this.scaleY,
          scaleOffsetY = size2 / this.scaleY,
          scaleOffsetX = size2 / this.scaleX,
          scaleOffsetSizeX = (size2 - size) / this.scaleX,
          scaleOffsetSizeY = (size2 - size) / this.scaleY,
          height = this.height,
          width = this.width,
          methodName = this.transparentCorners ? 'strokeRect' : 'fillRect',
          isVML = typeof G_vmlCanvasManager !== 'undefined';

      ctx.save();

      ctx.lineWidth = 1 / Math.max(this.scaleX, this.scaleY);

      ctx.globalAlpha = this.isMoving ? this.borderOpacityWhenMoving : 1;
      ctx.strokeStyle = ctx.fillStyle = this.cornerColor;

      // top-left
      _left = left - scaleOffsetX - strokeWidth2 - paddingX;
      _top = top - scaleOffsetY - strokeWidth2 - paddingY;

      isVML || ctx.clearRect(_left, _top, sizeX, sizeY);
      ctx[methodName](_left, _top, sizeX, sizeY);

      // top-right
      _left = left + width - scaleOffsetX + strokeWidth2 + paddingX;
      _top = top - scaleOffsetY - strokeWidth2 - paddingY;

      isVML || ctx.clearRect(_left, _top, sizeX, sizeY);
      ctx[methodName](_left, _top, sizeX, sizeY);

      // bottom-left
      _left = left - scaleOffsetX - strokeWidth2 - paddingX;
      _top = top + height + scaleOffsetSizeY + strokeWidth2 + paddingY;

      isVML || ctx.clearRect(_left, _top, sizeX, sizeY);
      ctx[methodName](_left, _top, sizeX, sizeY);

      // bottom-right
      _left = left + width + scaleOffsetSizeX + strokeWidth2 + paddingX;
      _top = top + height + scaleOffsetSizeY + strokeWidth2 + paddingY;

      isVML || ctx.clearRect(_left, _top, sizeX, sizeY);
      ctx[methodName](_left, _top, sizeX, sizeY);

      if (!this.get('lockUniScaling')) {
        // middle-top
        _left = left + width/2 - scaleOffsetX;
        _top = top - scaleOffsetY - strokeWidth2 - paddingY;

        isVML || ctx.clearRect(_left, _top, sizeX, sizeY);
        ctx[methodName](_left, _top, sizeX, sizeY);

        // middle-bottom
        _left = left + width/2 - scaleOffsetX;
        _top = top + height + scaleOffsetSizeY + strokeWidth2 + paddingY;

        isVML || ctx.clearRect(_left, _top, sizeX, sizeY);
        ctx[methodName](_left, _top, sizeX, sizeY);

        // middle-right
        _left = left + width + scaleOffsetSizeX + strokeWidth2 + paddingX;
        _top = top + height/2 - scaleOffsetY;

        isVML || ctx.clearRect(_left, _top, sizeX, sizeY);
        ctx[methodName](_left, _top, sizeX, sizeY);

        // middle-left
        _left = left - scaleOffsetX - strokeWidth2 - paddingX;
        _top = top + height/2 - scaleOffsetY;

        isVML || ctx.clearRect(_left, _top, sizeX, sizeY);
        ctx[methodName](_left, _top, sizeX, sizeY);
      }

      // middle-top-rotate
      if (this.hasRotatingPoint) {

        _left = left + width/2 - scaleOffsetX;
        _top = this.flipY ?
          (top + height + (this.rotatingPointOffset / this.scaleY) - sizeY/2 + strokeWidth2 + paddingY)
          : (top - (this.rotatingPointOffset / this.scaleY) - sizeY/2 - strokeWidth2 - paddingY);

        isVML || ctx.clearRect(_left, _top, sizeX, sizeY);
        ctx[methodName](_left, _top, sizeX, sizeY);
      }

      ctx.restore();

      return this;
    }
  });
})();