#version 450 core

//#define USE_RANDOM

layout( location = 0 ) uniform sampler2D u_Input;
layout( location = 1 ) uniform sampler2D u_Depth;
layout( location = 2 ) uniform vec4 u_Parameters;
layout( location = 3 ) uniform float u_Samples;
layout( location = 4 ) uniform vec3 u_ResolutionTime;

#define uSharpDist (u_Parameters.x)
#define uSharpRange (u_Parameters.y)
#define uBlurFalloff (u_Parameters.z)
#define uMaxBlur (u_Parameters.w)

#define uResolution (u_ResolutionTime.xy)
#define uTime (u_ResolutionTime.z)

float CoC( float z )
{
	return uMaxBlur * min( 1 ,
		max( 0 , abs( z - uSharpDist ) - uSharpRange ) / uBlurFalloff );
}

layout( location = 0 ) out vec3 o_Color;

float hash1( vec2 p )
{
	p = fract(p * vec2(5.3987, 5.4421));
	p += dot(p.yx, p.xy + vec2(21.5351, 14.3137));
	return fract(p.x * p.y * 95.4307);
}

// z: z at UV
// coc: blur radius at UV
// uv: initial coordinate
// blurvec: smudge direction
vec3 depthDirectionalBlur( float z , float coc , vec2 uv , vec2 blurvec )
{
	vec3 sumcol = vec3( 0. );
	for ( int i = 0 ; i < u_Samples ; i++ ) {
		float r = i;
#ifdef USE_RANDOM
		r += hash1( uv + float( i + uTime ) ) - .5;
#endif
		r = r / float( u_Samples - 1 ) - .5;
		vec2 p = uv + r * coc * blurvec;
		vec3 smpl = texture( u_Input , p ).xyz;
		float sz = texture( u_Depth , p ).x;
		if ( sz < z ) {
			// if sample is closer consider it's CoC
			p = uv + r * min( coc , CoC( sz ) ) * blurvec;
			p = uv + r * CoC( sz ) * blurvec;
			smpl = texture( u_Input , p ).xyz;
		}
		sumcol += smpl;
	}
	sumcol /= float( u_Samples );
	sumcol = max( sumcol , 0. );
	return sumcol;
}