#version 330

uniform mat4 P;   //projection matrix
uniform mat4 C;   //camera matrix
uniform mat4 M;   //modelview matrix: M = C * mR * mT
uniform mat3 N;   //inverse transpose of upperleft 3x3 of M
uniform mat4 Lr;  //light rotation matrix
uniform vec4 lightPos;    //light position
uniform vec4 camPos;      //camera position

uniform sampler2D texId;
//uniform sampler2DRect texId;

in vec4 smoothColor;
in vec3 smoothPos;
in vec3 smoothNorm;
in vec4 visiblePos;

layout(location = 0) out vec4 fragColor;

vec4 reflectance(in vec3 pos, in vec3 norm, in vec3 colorIn, in float visibilityFactor)
{
	return vec4(0.3)*smoothColor*vec4(1)+//ambient
	smoothColor*clamp(dot(normalize(C*Lr*lightPos - M*vec4(pos, 1)),vec4(N*normalize(norm), 0)), 0, 1) * visibilityFactor*vec4(1)+//diffuse
	pow(clamp(dot(normalize(vec4(0)-M*vec4(pos, 1)),normalize(reflect(-normalize(C*Lr*lightPos - M*vec4(pos, 1)),vec4(N*normalize(norm), 0)))), 0, 1), 10) * visibilityFactor*vec4(1);//specular
}

float getBias()
{
	//could do more complex stuff related to normals
	return 0.004;
}

vec4 getVisiblePoint()
{
	vec4 shp = visiblePos;
	
	//TODO5: homogenize to fix the perspective divide
	
	return shp / shp.w;
}

float getVisibility()
{
	//float visibilityFactor = 1.0;
	vec4 shadowPoint = getVisiblePoint();
	
	float visibleDistance = 1.0;
	float occlusionDistance = 1.0;
	
	//TODO6: set the visible distance based on the visible point's z value
	visibleDistance = shadowPoint.z;

	//TODO6: set the occlusion distance based on the shadow map value
	// The u,v lookup values should be the same as the visible point's x,y values
	occlusionDistance = texture(texId, shadowPoint.xy).z;
	
	//TODO7: adjust the difference by the bias amount
	float diff = occlusionDistance - visibleDistance + getBias();
	return diff;
}

void main()
{
	float depthDiff = getVisibility();
	
	float visibility = 1.0;
	if(depthDiff < 0)
		visibility = 0.0;
	
	fragColor = reflectance(smoothPos, smoothNorm, smoothColor.xyz, visibility);
	//if (depthDiff < 0) fragColor *= 0;
	
	//TODO6: comment this line to show the reflectance colors
	//fragColor = getVisiblePoint();
	//fragColor = texture(texId, getVisiblePoint().xy).zzzz - getVisiblePoint().zzzz + 0.5;
	//fragColor = getVisiblePoint().zzzz;
}