Texture2D MainTexture;
SamplerState MainSampler;

cbuffer LightBuffer // has to be always 16 byte aligned
{
    float3 LightVector;
    float LightIntensity;
    float4 DiffuseColor;
    float4 SpecularColor;
    float3 CameraPosition;
    float Phong;
};

struct PixelInput
{
    float4 position : SV_POSITION;
    float3 positionWorld : POSITION1;
    float3 normal : NORMAL;
    float2 uv : TEXCOORD;
};

float4 main(PixelInput INPUT) : SV_TARGET
{
    float4 texColor = MainTexture.Sample(MainSampler, INPUT.uv);
    float4 ambientColor = float4(0.2f, 0.2f, 0.2f, 1.0f);
    float4 diffuseColor = DiffuseColor;
    float4 specularColor = SpecularColor;
    float4 emissionColor = float4(0.0f, 0.0f, 0.0f, 1.0f);
    
    float3 lightVector = normalize(-LightVector);
    float3 normalVector = normalize(INPUT.normal);
    
    // diffuse color
    float diffuse = dot(lightVector, normalVector); // diffuse intensity
    diffuseColor *= diffuse * LightIntensity;
    
    // specular color
    float3 reflectVector = normalize(reflect(-lightVector, normalVector));
    //float3 reflectVector = 2 * normalVector * diffuse - lightVector;
    float3 viewVector = normalize(CameraPosition - INPUT.positionWorld);
    float specular = pow(max(dot(reflectVector, viewVector), 0), Phong);
    specularColor *= specular * LightIntensity;
    
    return saturate(saturate(texColor * saturate(ambientColor + diffuseColor) + specularColor) + emissionColor);
}