varying vec2 v_vTexcoord;
varying vec4 v_vColour;

uniform vec2  dimension;
uniform vec2  pos1;
uniform vec2  pos2;
uniform int   usePath;
uniform int   pathResolution;
uniform vec2  pathList[1024];

uniform float radius;
uniform float radius2;
uniform float intensity;
uniform float falloff;
uniform float pushIntens;

#region /////////////// SAMPLING ///////////////

	const float PI = 3.14159265358979323846;
	uniform int  interpolation;
	uniform vec2 sampleDimension;
	
	const int RSIN_RADIUS = 1;
	
	float sinc ( float x ) { return x == 0.? 1. : sin(x * PI) / (x * PI); }
	
	vec4 texture2D_bilinear( sampler2D texture, vec2 uv ) {
		uv = uv * sampleDimension - .5;
		vec2 iuv = floor( uv );
		vec2 fuv = fract( uv );
		
		vec4 mixed = mix(
			mix(
				texture2D( texture, (iuv + vec2(0., 0.)) / sampleDimension ),
				texture2D( texture, (iuv + vec2(1., 0.)) / sampleDimension ),
				fuv.x
			), 
			mix(
				texture2D( texture, (iuv + vec2(0., 1.)) / sampleDimension ),
				texture2D( texture, (iuv + vec2(1., 1.)) / sampleDimension ),
				fuv.x
			), 
			fuv.y
		);
		
		mixed.rgb /= mixed.a;
		
		return mixed;
	}
	
	vec4 texture2D_rsin( sampler2D texture, vec2 uv ) {
	    vec2 tx = 1.0 / sampleDimension;
	    vec2 p  = uv * sampleDimension - vec2(0.5);
	    
		vec4 sum = vec4(0.0);
	    float weights = 0.;
	    
	    for (int x = -RSIN_RADIUS; x <= RSIN_RADIUS; x++)
		for (int y = -RSIN_RADIUS; y <= RSIN_RADIUS; y++) {
	        float a = length(vec2(float(x), float(y))) / float(RSIN_RADIUS);
			if(a > 1.) continue;
	        float w = sinc(a * PI * tx.x) * sinc(a * PI * tx.y);
	        vec2 offset = vec2(float(x), float(y)) * tx;
	        vec4 sample = texture2D_bilinear(texture, (p + offset + vec2(0.5)) / sampleDimension);
	        sum += w * sample;
	        weights += w;
	    }
		
	    return sum / weights;
	}
	
	vec4 texture2D_bicubic( sampler2D texture, vec2 uv ) {
		uv = uv * sampleDimension + 0.5;
		vec2 iuv = floor( uv );
		vec2 fuv = fract( uv );
		uv = iuv + fuv * fuv * (3.0 - 2.0 * fuv);
		uv = (uv - 0.5) / sampleDimension;
		return texture2D_bilinear( texture, uv );
	}
	
	vec4 texture2Dintp( sampler2D texture, vec2 uv ) {
		     if(interpolation == 1)	return texture2D_bilinear( texture, uv );
		else if(interpolation == 2)	return texture2D_bicubic(  texture, uv );
		else if(interpolation == 3)	return texture2D_rsin(     texture, uv );
		return texture2D( texture, uv );
	}

#endregion /////////////// SAMPLING ///////////////

vec2 closestPointOnLine(vec2 P, vec2 A, vec2 B, out float t) {
    vec2 AP = P - A;
    vec2 AB = B - A;
    t = dot(AP, AB) / dot(AB, AB);
    t = clamp(t, 0.0, 1.0);
    return A + t * AB;
}

void main() {
    vec2  tx  = 1. / dimension;
    vec2  pushPoint = vec2(0.); 
    vec2  pushDir   = vec2(0.);
    float pushT     = 0.;
    float inf = 0.;
    vec2  stx = v_vTexcoord;
    vec2  p1, p2;
    
    if(usePath == 0) {
        p1 = pos1 * tx;
        p2 = pos2 * tx;
        pushDir = p2 - p1;
        
        pushPoint = closestPointOnLine(v_vTexcoord, p1, p2, pushT);
        float dis = distance(v_vTexcoord * dimension, pushPoint * dimension);
        float rad = mix(radius, radius2, pushT);
        inf = 1. - smoothstep(rad - falloff, rad + falloff, dis);
        stx -= (pushPoint - stx) * inf * intensity * pushIntens;
        stx -=  pushDir * inf * intensity * pushT;
        
    } else {
        float minDist = 9999.;
        float _intRes = intensity;
        float _pshRes = pushIntens / float(pathResolution);
        vec2 cpc;
        
        for(int i = pathResolution - 2; i >= 0; i--) {
            p1  = pathList[i]     * tx;
            p2  = pathList[i + 1] * tx;
            cpc = closestPointOnLine(stx, p1, p2, pushT);
            
            pushPoint = cpc;
            pushDir   = p2 - p1;
            
            float rad = mix(radius, radius2, (float(i) + pushT) / float(pathResolution));
            float dis = distance(stx * dimension, pushPoint * dimension);
            inf = 1. - smoothstep(rad - falloff, rad + falloff, dis);
            
            stx += (pushPoint - v_vTexcoord) * inf * _intRes * _pshRes;
            stx -=  pushDir * inf * _intRes * pushT;
        }
    }
    
    gl_FragColor = texture2Dintp( gm_BaseTexture, stx );
}