#version 310 es
precision highp float;
precision highp int;

//uniform float     iChannelTime[4];       // channel playback time (in seconds)
//uniform vec3      iChannelResolution[4]; // channel resolution (in pixels)
//vec4      iMouse = vec4(0,0,0,0);                // mouse pixel coords. xy: current (if MLB down), zw: click
//layout(binding = 0) uniform sampler2D iChannel0;          // input channel. XX = 2D/Cube

/*by musk License Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
 
 Trying to get some interesting looking lens flares.
 
 13/08/13:
 published
 
 muuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuusk!*/


layout(std140, binding = 0) uniform fs_ub {
    vec2 center;
    vec2 resolution;
    vec2 u_screenSize;
    vec4 u_Time;
};

float noise(float t)
{
	return 0.;
}
float noise(vec2 t)
{
	return 0.;
}

vec3 lensflare(vec2 uv,vec2 pos)
{
	vec2 main = uv-pos;
	vec2 uvd = uv*(length(uv));
	
	float ang = atan(main.x,main.y);
	float dist=length(main); dist = pow(dist,.1);
	float n = noise(vec2(ang*16.0,dist*32.0));
	
	float f0 = 1.0/(length(uv-pos)*16.0+1.0);
	
	f0 = f0+f0*(sin(noise((pos.x+pos.y)*2.2+ang*4.0+5.954)*16.0)*.1+dist*.1+.8);
	
	float f1 = max(0.01-pow(length(uv+1.2*pos),1.9),.0)*7.0;
    
	float f2 = max(1.0/(1.0+32.0*pow(length(uvd+0.8*pos),2.0)),.0)*00.25;
	float f22 = max(1.0/(1.0+32.0*pow(length(uvd+0.85*pos),2.0)),.0)*00.23;
	float f23 = max(1.0/(1.0+32.0*pow(length(uvd+0.9*pos),2.0)),.0)*00.21;
	
	vec2 uvx = mix(uv,uvd,-0.5);
	
	float f4 = max(0.01-pow(length(uvx+0.4*pos),2.4),.0)*6.0;
	float f42 = max(0.01-pow(length(uvx+0.45*pos),2.4),.0)*5.0;
	float f43 = max(0.01-pow(length(uvx+0.5*pos),2.4),.0)*3.0;
	
	uvx = mix(uv,uvd,-.4);
	
	float f5 = max(0.01-pow(length(uvx+0.2*pos),5.5),.0)*2.0;
	float f52 = max(0.01-pow(length(uvx+0.4*pos),5.5),.0)*2.0;
	float f53 = max(0.01-pow(length(uvx+0.6*pos),5.5),.0)*2.0;
	
	uvx = mix(uv,uvd,-0.5);
	
	float f6 = max(0.01-pow(length(uvx-0.3*pos),1.6),.0)*6.0;
	float f62 = max(0.01-pow(length(uvx-0.325*pos),1.6),.0)*3.0;
	float f63 = max(0.01-pow(length(uvx-0.35*pos),1.6),.0)*5.0;
	
	vec3 c = vec3(.0);
	
	c.r+=f2+f4+f5+f6; c.g+=f22+f42+f52+f62; c.b+=f23+f43+f53+f63;
	c = c*1.3 - vec3(length(uvd)*.05);
	c+=vec3(f0);
	
	return c;
}

vec3 cc(vec3 color, float factor,float factor2) // color modifier
{
	float w = color.x+color.y+color.z;
	return mix(color,vec3(w)*factor,w*factor2);
}

layout(location = SV_Target0) out vec4 FragColor;

void main(void)
{
#ifdef METAL
	vec2 fragCoord = vec2(gl_FragCoord.x, u_screenSize.y - gl_FragCoord.y);
#else
	vec2 fragCoord = gl_FragCoord.xy;
#endif
    vec2   iResolution = resolution;           // viewport resolution (in pixels)
    float  iGlobalTime = u_Time[1];           // shader playback time (in seconds)

	//vec2 uv = gl_FragCoord.xy / iResolution.xy - 0.5;
    vec2 uv = (fragCoord.xy - center.xy) / iResolution.xy;
	uv.x *= iResolution.x/iResolution.y; //fix aspect ratio
	// vec3 hover = vec3(iMouse.xy/iResolution.xy - 0.5,iMouse.z-.5);
    vec3 hover = vec3(-0.5, -0.5, -0.5);
	hover.x *= iResolution.x/iResolution.y; //fix aspect ratio
	// if (hover.z<.5)
	//{
		hover.x=sin(iGlobalTime)*.5;
		hover.y=sin(iGlobalTime*.913)*.5;
	//}
	
	vec3 color = vec3(1.4,1.2,1.0)*lensflare(uv,hover.xy);
	color -= noise(fragCoord.xy)*.015;
	color = cc(color,.5,.1);
	FragColor = vec4(color,1.0);
}