// Phong fragment shader phong-tex.frag matched with phong-tex.vert
#version 330

// Some drivers require the following
precision highp float;

struct lightStruct
{
	vec4 ambient;
	vec4 diffuse;
	vec4 specular;
};

struct materialStruct
{
	vec4 ambient;
	vec4 diffuse;
	vec4 specular;
	float shininess;
};

uniform float attConst;
uniform float attLinear;
uniform float attQuadratic;
in float ex_D;

uniform lightStruct light;
uniform materialStruct material;
uniform sampler2D textureUnit0;

in vec3 ex_N;
in vec3 ex_V;
in vec3 ex_L;
in vec2 ex_TexCoord;
layout(location = 0) out vec4 out_Color;

void main(void) {

	// Ambient intensity
	vec4 ambientI = light.ambient * material.ambient;

	// Diffuse intensity
	vec4 diffuseI = light.diffuse * material.diffuse;
	diffuseI = diffuseI * max(dot(normalize(ex_N),normalize(ex_L)),0);

	// Specular intensity
	// Calculate R - reflection of light
	vec3 R = normalize(reflect(normalize(-ex_L),normalize(ex_N)));

	vec4 specularI = light.specular * material.specular;
	specularI = specularI * pow(max(dot(R,ex_V),0), material.shininess);

	float attenuation = attConst + attLinear * ex_D + attQuadratic * ex_D*ex_D;
	attenuation = 1/attenuation;
	vec4 tmp_Color = (diffuseI + specularI);//attenuation does not
	//affect ambient light
	vec4 litColour = ambientI+vec4(tmp_Color.rgb / attenuation, 1.0);

	// Fragment colour
	out_Color = litColour * texture(textureUnit0, ex_TexCoord);
}