/*
* jQuery.eraser v0.4.2
* makes any image or canvas erasable by the user, using touch or mouse input
* https://github.com/boblemarin/jQuery.eraser
*
* Usage:
*
* $('#myImage').eraser(); // simple way
*
* $(#canvas').eraser( {
*   size: 20, // define brush size (default value is 40)
*   completeRatio: .65, // allows to call function when a erased ratio is reached (between 0 and 1, default is .7 )
*   completeFunction: myFunction // callback function when complete ratio is reached
* } );
*
* $('#image').eraser( 'clear' ); // erases all canvas content
*
* $('#image').eraser( 'reset' ); // revert back to original content
*
* $('#image').eraser( 'size', 80 ); // change the eraser size
*
*
* https://github.com/boblemarin/jQuery.eraser
* http://minimal.be/lab/jQuery.eraser/
*
* Copyright (c) 2010 boblemarin emeric@minimal.be http://www.minimal.be
*
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation
* files (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use,
* copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following
* conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
* ËزļÒÔ° - www.sucaijiayuan.com
*/

(function( $ ){
	var methods = {
		init : function( options ) {
			return this.each(function(){
				var $this = $(this),
					data = $this.data('eraser');

				if ( !data ) {
					var width = $this.width(),
						height = $this.height(),
						pos = $this.offset(),
						$canvas = $("<canvas/>"),
						canvas = $canvas.get(0),
						size = ( options && options.size )?options.size:40,
						completeRatio = ( options && options.completeRatio )?options.completeRatio:.7,
						completeFunction = ( options && options.completeFunction )?options.completeFunction:null,
						parts = [],
						colParts = Math.floor( width / size ),
						numParts = colParts * Math.floor( height / size ),
						n = numParts,
						ctx = canvas.getContext("2d");

					// replace target with canvas
					$this.after( $canvas );
					canvas.id = this.id;
					canvas.className = this.className;
					canvas.width = width;
					canvas.height = height;
					ctx.drawImage( this, 0, 0 );
					$this.remove();

					// prepare context for drawing operations
					ctx.globalCompositeOperation = "destination-out";
					ctx.strokeStyle = 'rgba(255,0,0,255)';
					ctx.lineWidth = size;

					ctx.lineCap = "round";
					// bind events
					$canvas.bind('mousedown.eraser', methods.mouseDown);
					$canvas.bind('touchstart.eraser', methods.touchStart);
					$canvas.bind('touchmove.eraser', methods.touchMove);
					$canvas.bind('touchend.eraser', methods.touchEnd);

					// reset parts
					while( n-- ) parts.push(1);

					// store values
					data = {
						posX:pos.left,
						posY:pos.top,
						touchDown: false,
						touchID:-999,
						touchX: 0,
						touchY: 0,
						ptouchX: 0,
						ptouchY: 0,
						canvas: $canvas,
						ctx: ctx,
						w:width,
						h:height,
						source: this,
						size: size,
						parts: parts,
						colParts: colParts,
						numParts: numParts,
						ratio: 0,
						complete: false,
						completeRatio: completeRatio,
						completeFunction: completeFunction
					};
					$canvas.data('eraser', data);

					// listen for resize event to update offset values
					$(window).resize( function() {
						var pos = $canvas.offset();
						data.posX = pos.left;
						data.posY = pos.top;
					});
				}
			});
		},
		touchStart: function( event ) {
			var $this = $(this),
				data = $this.data('eraser');

			if ( !data.touchDown ) {
				var t = event.originalEvent.changedTouches[0],
					tx = t.pageX - data.posX,
					ty = t.pageY - data.posY;
				methods.evaluatePoint( data, tx, ty );
				data.touchDown = true;
				data.touchID = t.identifier;
				data.touchX = tx;
				data.touchY = ty;
				event.preventDefault();
			}
		},
		touchMove: function( event ) {
			var $this = $(this),
				data = $this.data('eraser');

			if ( data.touchDown ) {
				var ta = event.originalEvent.changedTouches,
					n = ta.length;
				while( n-- )
					if ( ta[n].identifier == data.touchID ) {
						var tx = ta[n].pageX - data.posX,
							ty = ta[n].pageY - data.posY;
						methods.evaluatePoint( data, tx, ty );
						data.ctx.beginPath();
						data.ctx.moveTo( data.touchX, data.touchY );
						data.touchX = tx;
						data.touchY = ty;
						data.ctx.lineTo( data.touchX, data.touchY );
						data.ctx.stroke();
						event.preventDefault();
						break;
					}
			}
		},
		touchEnd: function( event ) {
			var $this = $(this),
				data = $this.data('eraser');

			if ( data.touchDown ) {
				var ta = event.originalEvent.changedTouches,
					n = ta.length;
				while( n-- )
					if ( ta[n].identifier == data.touchID ) {
						data.touchDown = false;
						event.preventDefault();
						break;
					}
			}
		},

		evaluatePoint: function( data, tx, ty ) {
			var p = Math.floor(tx/data.size) + Math.floor( ty / data.size ) * data.colParts;
			if ( p >= 0 && p < data.numParts ) {
				data.ratio += data.parts[p];
				data.parts[p] = 0;
				if ( !data.complete) {
					if ( data.ratio/data.numParts >= data.completeRatio ) {
						data.complete = true;
						if ( data.completeFunction != null ) data.completeFunction();
					}
				}
			}

		},

		mouseDown: function( event ) {
			var $this = $(this),
				data = $this.data('eraser'),
				tx = event.pageX - data.posX,
				ty = event.pageY - data.posY;
			methods.evaluatePoint( data, tx, ty );
			data.touchDown = true;
			data.touchX = tx;
			data.touchY = ty;
			data.ctx.beginPath();
			data.ctx.moveTo( data.touchX-1, data.touchY );
			data.ctx.lineTo( data.touchX, data.touchY );
			data.ctx.stroke();
			$this.bind('mousemove.eraser', methods.mouseMove);
			$(document).bind('mouseup.eraser', data, methods.mouseUp);
			event.preventDefault();
		},

		mouseMove: function( event ) {
			var $this = $(this),
				data = $this.data('eraser'),
				tx = event.pageX - data.posX,
				ty = event.pageY - data.posY;
			methods.evaluatePoint( data, tx, ty );
			data.ctx.beginPath();
			data.ctx.moveTo( data.touchX, data.touchY );
			data.touchX = tx;
			data.touchY = ty;
			data.ctx.lineTo( data.touchX, data.touchY );
			data.ctx.stroke();
			event.preventDefault();
		},

		mouseUp: function( event ) {
			var data = event.data,
				$this = data.canvas;
			data.touchDown = false;
			$this.unbind('mousemove.eraser');
			$(document).unbind('mouseup.eraser');
			event.preventDefault();
		},

		clear: function() {
			var $this = $(this),
				data = $this.data('eraser');
			if ( data )
			{
				data.ctx.clearRect( 0, 0, data.w, data.h );
				var n = data.numParts;
				while( n-- ) data.parts[n] = 0;
				data.ratio = data.numParts;
				data.complete = true;
				if ( data.completeFunction != null ) data.completeFunction();
			}
		},

		size: function(value) {
			var $this = $(this),
				data = $this.data('eraser');
			if ( data && value )
			{
				data.size = value;
				data.ctx.lineWidth = value;
			}
		},

		reset: function() {
			var $this = $(this),
				data = $this.data('eraser');
			if ( data )
			{
				data.ctx.globalCompositeOperation = "source-over";
				data.ctx.drawImage( data.source, 0, 0 );
				data.ctx.globalCompositeOperation = "destination-out";
				var n = data.numParts;
				while( n-- ) data.parts[n] = 1;
				data.ratio = 0;
				data.complete = false;
			}
		}

	};

	$.fn.eraser = function( method ) {
		if ( methods[method] ) {
			return methods[method].apply( this, Array.prototype.slice.call( arguments, 1 ));
		} else if ( typeof method === 'object' || ! method ) {
			return methods.init.apply( this, arguments );
		} else {
			$.error( 'Method ' +  method + ' does not yet exist on jQuery.eraser' );
		}
	};
})( jQuery );