const 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]
};

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

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

].join('\n');

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

    let fragSource = fragTemplate;

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

    for (let i = 0; i < kernelSize; i++)
    {
    	let 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;
};

export default generateFragBlurSource;