var core = require('../../core')

var GAUSSIAN_VALUES = {
	5:[0.153388, 0.221461, 0.250301],
	7:[0.071303, 0.131514, 0.189879, 0.214607],
	9:[0.028532, 0.067234, 0.124009, 0.179044, 0.20236],
	11:[0.0093, 0.028002, 0.065984, 0.121703, 0.175713, 0.198596],
	13:[0.002406, 0.009255, 0.027867, 0.065666, 0.121117, 0.174868, 0.197641],
    15:[0.000489, 0.002403, 0.009246, 0.02784, 0.065602, 0.120999, 0.174697, 0.197448]
}


var generateFragBlurSource = function(kernelSize)
{
    var kernel = GAUSSIAN_VALUES[kernelSize];
    var halfLength = kernel.length;

    var fragSource = fragTemplate;

    var blurLoop = '';
    var template = 'gl_FragColor += texture2D(uSampler, vBlurTexCoords[%index%]) * %value%;' 

    for (var i = 0; i < kernelSize; i++) 
    {
    	var blur = template.replace('%index%', i);

    	value = i;
    	
    	if(i >= halfLength)
    	{
    		value = kernelSize - i - 1; 
    	}


    	blur = blur.replace('%value%', kernel[value]);
    	
    	blurLoop += blur;
    	blurLoop += '\n';
    };

    fragSource = fragSource.replace('%blur%', blurLoop)
    fragSource = fragSource.replace('%size%', kernelSize)


    return fragSource;
}

var fragTemplate = [
		
	'precision mediump float;',

	'varying vec2 vBlurTexCoords[%size%];',
	'uniform sampler2D uSampler;',

	'void main(void)',
	'{',
	'	gl_FragColor = vec4(0.0);',
	'	%blur%',
	'}'

].join('\n');

module.exports = generateFragBlurSource;