#version 330

in vec4 diffuseColor;
in vec3 vertexNormal;
in vec3 cameraSpacePosition;

out vec4 outputColor;

uniform vec3 modelSpaceLightPos;

uniform vec4 lightIntensity;
uniform vec4 ambientIntensity;

uniform vec3 cameraSpaceLightPos;

uniform float lightAttenuation;

const vec4 specularColor = vec4(0.25, 0.25, 0.25, 1.0);
uniform float shininessFactor;


float CalcAttenuation(in vec3 cameraSpacePosition, out vec3 lightDirection)
{
	vec3 lightDifference =  cameraSpaceLightPos - cameraSpacePosition;
	float lightDistanceSqr = dot(lightDifference, lightDifference);
	lightDirection = lightDifference * inversesqrt(lightDistanceSqr);
	
	return (1 / ( 1.0 + lightAttenuation * sqrt(lightDistanceSqr)));
}

void main()
{
	vec3 lightDir = vec3(0.0);
	float atten = CalcAttenuation(cameraSpacePosition, lightDir);
	vec4 attenIntensity = atten * lightIntensity;
	
	vec3 surfaceNormal = normalize(vertexNormal);
	
	vec3 viewDirection = normalize(-cameraSpacePosition);
	
	vec3 halfAngle = normalize(lightDir + viewDirection);
	float blinnTerm = dot(surfaceNormal, halfAngle);
	blinnTerm = clamp(blinnTerm, 0, 1);
	blinnTerm = dot(surfaceNormal, lightDir) >= 0.0 ? blinnTerm : 0.0;
	blinnTerm = pow(blinnTerm, shininessFactor);

	outputColor = (specularColor * attenIntensity * blinnTerm) +
		(diffuseColor * ambientIntensity);
}
