/**
 * RGB Halftone shader for three.js.
 *	NOTE:
 * 		Shape (1 = Dot, 2 = Ellipse, 3 = Line, 4 = Square)
 *		Blending Mode (1 = Linear, 2 = Multiply, 3 = Add, 4 = Lighter, 5 = Darker)
 */

THREE.HalftoneShader = {

	uniforms: {
		'tDiffuse': { value: null },
		'shape': { value: 1 },
		'radius': { value: 4 },
		'rotateR': { value: Math.PI / 12 * 1 },
		'rotateG': { value: Math.PI / 12 * 2 },
		'rotateB': { value: Math.PI / 12 * 3 },
		'scatter': { value: 0 },
		'width': { value: 1 },
		'height': { value: 1 },
		'blending': { value: 1 },
		'blendingMode': { value: 1 },
		'greyscale': { value: false },
		'disable': { value: false }
	},

	vertexShader: [

		'varying vec2 vUV;',

		'void main() {',

		'	vUV = uv;',
		'	gl_Position = projectionMatrix * modelViewMatrix * vec4(position, 1.0);',

		'}'

	].join( '\n' ),

	fragmentShader: [

		'#define SQRT2_MINUS_ONE 0.41421356',
		'#define SQRT2_HALF_MINUS_ONE 0.20710678',
		'#define PI2 6.28318531',
		'#define SHAPE_DOT 1',
		'#define SHAPE_ELLIPSE 2',
		'#define SHAPE_LINE 3',
		'#define SHAPE_SQUARE 4',
		'#define BLENDING_LINEAR 1',
		'#define BLENDING_MULTIPLY 2',
		'#define BLENDING_ADD 3',
		'#define BLENDING_LIGHTER 4',
		'#define BLENDING_DARKER 5',
		'uniform sampler2D tDiffuse;',
		'uniform float radius;',
		'uniform float rotateR;',
		'uniform float rotateG;',
		'uniform float rotateB;',
		'uniform float scatter;',
		'uniform float width;',
		'uniform float height;',
		'uniform int shape;',
		'uniform bool disable;',
		'uniform float blending;',
		'uniform int blendingMode;',
		'varying vec2 vUV;',
		'uniform bool greyscale;',
		'const int samples = 8;',

		'float blend( float a, float b, float t ) {',

		// linear blend
		'	return a * ( 1.0 - t ) + b * t;',

		'}',

		'float hypot( float x, float y ) {',

		// vector magnitude
		'	return sqrt( x * x + y * y );',

		'}',

		'float rand( vec2 seed ){',

		// get pseudo-random number
	    'return fract( sin( dot( seed.xy, vec2( 12.9898, 78.233 ) ) ) * 43758.5453 );',

		'}',

		'float distanceToDotRadius( float channel, vec2 coord, vec2 normal, vec2 p, float angle, float rad_max ) {',

		// apply shape-specific transforms
		'	float dist = hypot( coord.x - p.x, coord.y - p.y );',
		'	float rad = channel;',

		'	if ( shape == SHAPE_DOT ) {',

		'		rad = pow( abs( rad ), 1.125 ) * rad_max;',

		'	} else if ( shape == SHAPE_ELLIPSE ) {',

		'		rad = pow( abs( rad ), 1.125 ) * rad_max;',

		'		if ( dist != 0.0 ) {',
		'			float dot_p = abs( ( p.x - coord.x ) / dist * normal.x + ( p.y - coord.y ) / dist * normal.y );',
		'			dist = ( dist * ( 1.0 - SQRT2_HALF_MINUS_ONE ) ) + dot_p * dist * SQRT2_MINUS_ONE;',
		'		}',

		'	} else if ( shape == SHAPE_LINE ) {',

		'		rad = pow( abs( rad ), 1.5) * rad_max;',
		'		float dot_p = ( p.x - coord.x ) * normal.x + ( p.y - coord.y ) * normal.y;',
		'		dist = hypot( normal.x * dot_p, normal.y * dot_p );',

		'	} else if ( shape == SHAPE_SQUARE ) {',

		'		float theta = atan( p.y - coord.y, p.x - coord.x ) - angle;',
		'		float sin_t = abs( sin( theta ) );',
		'		float cos_t = abs( cos( theta ) );',
		'		rad = pow( abs( rad ), 1.4 );',
		'		rad = rad_max * ( rad + ( ( sin_t > cos_t ) ? rad - sin_t * rad : rad - cos_t * rad ) );',

		'	}',

		'	return rad - dist;',

		'}',

		'struct Cell {',

		// grid sample positions
		'	vec2 normal;',
		'	vec2 p1;',
		'	vec2 p2;',
		'	vec2 p3;',
		'	vec2 p4;',
		'	float samp2;',
		'	float samp1;',
		'	float samp3;',
		'	float samp4;',

		'};',

		'vec4 getSample( vec2 point ) {',

		// multi-sampled point
		'	vec4 tex = texture2D( tDiffuse, vec2( point.x / width, point.y / height ) );',
		'	float base = rand( vec2( floor( point.x ), floor( point.y ) ) ) * PI2;',
		'	float step = PI2 / float( samples );',
		'	float dist = radius * 0.66;',

		'	for ( int i = 0; i < samples; ++i ) {',

		'		float r = base + step * float( i );',
		'		vec2 coord = point + vec2( cos( r ) * dist, sin( r ) * dist );',
		'		tex += texture2D( tDiffuse, vec2( coord.x / width, coord.y / height ) );',

		'	}',

		'	tex /= float( samples ) + 1.0;',
		'	return tex;',

		'}',

		'float getDotColour( Cell c, vec2 p, int channel, float angle, float aa ) {',

		// get colour for given point
		'	float dist_c_1, dist_c_2, dist_c_3, dist_c_4, res;',

		'	if ( channel == 0 ) {',

		'		c.samp1 = getSample( c.p1 ).r;',
		'		c.samp2 = getSample( c.p2 ).r;',
		'		c.samp3 = getSample( c.p3 ).r;',
		'		c.samp4 = getSample( c.p4 ).r;',

		'	} else if (channel == 1) {',

		'		c.samp1 = getSample( c.p1 ).g;',
		'		c.samp2 = getSample( c.p2 ).g;',
		'		c.samp3 = getSample( c.p3 ).g;',
		'		c.samp4 = getSample( c.p4 ).g;',

		'	} else {',

		'		c.samp1 = getSample( c.p1 ).b;',
		'		c.samp3 = getSample( c.p3 ).b;',
		'		c.samp2 = getSample( c.p2 ).b;',
		'		c.samp4 = getSample( c.p4 ).b;',

		'	}',

		'	dist_c_1 = distanceToDotRadius( c.samp1, c.p1, c.normal, p, angle, radius );',
		'	dist_c_2 = distanceToDotRadius( c.samp2, c.p2, c.normal, p, angle, radius );',
		'	dist_c_3 = distanceToDotRadius( c.samp3, c.p3, c.normal, p, angle, radius );',
		'	dist_c_4 = distanceToDotRadius( c.samp4, c.p4, c.normal, p, angle, radius );',
		'	res = ( dist_c_1 > 0.0 ) ? clamp( dist_c_1 / aa, 0.0, 1.0 ) : 0.0;',
		'	res += ( dist_c_2 > 0.0 ) ? clamp( dist_c_2 / aa, 0.0, 1.0 ) : 0.0;',
		'	res += ( dist_c_3 > 0.0 ) ? clamp( dist_c_3 / aa, 0.0, 1.0 ) : 0.0;',
		'	res += ( dist_c_4 > 0.0 ) ? clamp( dist_c_4 / aa, 0.0, 1.0 ) : 0.0;',
		'	res = clamp( res, 0.0, 1.0 );',

		'	return res;',

		'}',

		'Cell getReferenceCell( vec2 p, vec2 origin, float grid_angle, float step ) {',

		// get containing cell
		'	Cell c;',

		// calc grid
		'	vec2 n = vec2( cos( grid_angle ), sin( grid_angle ) );',
		'	float threshold = step * 0.5;',
		'	float dot_normal = n.x * ( p.x - origin.x ) + n.y * ( p.y - origin.y );',
		'	float dot_line = -n.y * ( p.x - origin.x ) + n.x * ( p.y - origin.y );',
		'	vec2 offset = vec2( n.x * dot_normal, n.y * dot_normal );',
		'	float offset_normal = mod( hypot( offset.x, offset.y ), step );',
		'	float normal_dir = ( dot_normal < 0.0 ) ? 1.0 : -1.0;',
		'	float normal_scale = ( ( offset_normal < threshold ) ? -offset_normal : step - offset_normal ) * normal_dir;',
		'	float offset_line = mod( hypot( ( p.x - offset.x ) - origin.x, ( p.y - offset.y ) - origin.y ), step );',
		'	float line_dir = ( dot_line < 0.0 ) ? 1.0 : -1.0;',
		'	float line_scale = ( ( offset_line < threshold ) ? -offset_line : step - offset_line ) * line_dir;',

		// get closest corner
		'	c.normal = n;',
		'	c.p1.x = p.x - n.x * normal_scale + n.y * line_scale;',
		'	c.p1.y = p.y - n.y * normal_scale - n.x * line_scale;',

		// scatter
		'	if ( scatter != 0.0 ) {',

		'		float off_mag = scatter * threshold * 0.5;',
		'		float off_angle = rand( vec2( floor( c.p1.x ), floor( c.p1.y ) ) ) * PI2;',
		'		c.p1.x += cos( off_angle ) * off_mag;',
		'		c.p1.y += sin( off_angle ) * off_mag;',

		'	}',

		// find corners
		'	float normal_step = normal_dir * ( ( offset_normal < threshold ) ? step : -step );',
		'	float line_step = line_dir * ( ( offset_line < threshold ) ? step : -step );',
		'	c.p2.x = c.p1.x - n.x * normal_step;',
		'	c.p2.y = c.p1.y - n.y * normal_step;',
		'	c.p3.x = c.p1.x + n.y * line_step;',
		'	c.p3.y = c.p1.y - n.x * line_step;',
		'	c.p4.x = c.p1.x - n.x * normal_step + n.y * line_step;',
		'	c.p4.y = c.p1.y - n.y * normal_step - n.x * line_step;',

		'	return c;',

		'}',

		'float blendColour( float a, float b, float t ) {',

		// blend colours
		'	if ( blendingMode == BLENDING_LINEAR ) {',
		'		return blend( a, b, 1.0 - t );',
		'	} else if ( blendingMode == BLENDING_ADD ) {',
		'		return blend( a, min( 1.0, a + b ), t );',
		'	} else if ( blendingMode == BLENDING_MULTIPLY ) {',
		'		return blend( a, max( 0.0, a * b ), t );',
		'	} else if ( blendingMode == BLENDING_LIGHTER ) {',
		'		return blend( a, max( a, b ), t );',
		'	} else if ( blendingMode == BLENDING_DARKER ) {',
		'		return blend( a, min( a, b ), t );',
		'	} else {',
		'		return blend( a, b, 1.0 - t );',
		'	}',

		'}',

		'void main() {',

		'	if ( ! disable ) {',

		// setup
		'		vec2 p = vec2( vUV.x * width, vUV.y * height );',
		'		vec2 origin = vec2( 0, 0 );',
		'		float aa = ( radius < 2.5 ) ? radius * 0.5 : 1.25;',

		// get channel samples
		'		Cell cell_r = getReferenceCell( p, origin, rotateR, radius );',
		'		Cell cell_g = getReferenceCell( p, origin, rotateG, radius );',
		'		Cell cell_b = getReferenceCell( p, origin, rotateB, radius );',
		'		float r = getDotColour( cell_r, p, 0, rotateR, aa );',
		'		float g = getDotColour( cell_g, p, 1, rotateG, aa );',
		'		float b = getDotColour( cell_b, p, 2, rotateB, aa );',

		// blend with original
		'		vec4 colour = texture2D( tDiffuse, vUV );',
		'		r = blendColour( r, colour.r, blending );',
		'		g = blendColour( g, colour.g, blending );',
		'		b = blendColour( b, colour.b, blending );',

		'		if ( greyscale ) {',
		'			r = g = b = (r + b + g) / 3.0;',
		'		}',

		'		gl_FragColor = vec4( r, g, b, 1.0 );',

		'	} else {',

		'		gl_FragColor = texture2D( tDiffuse, vUV );',

		'	}',

		'}'

	].join( '\n' )

};
