#pragma once

#include "Camera.hpp"
#include "Color.hpp"
#include "Geometry.hpp"
#include "Point.hpp"


class Light
{
public:
	ColorF32 Compute(Point& eye, Vector& normal, Material& material, Camera& camera)
	{
		// Point light intensity is a function of the falloff factors and the distance
		Vector direction = position - eye;
		direction.Normalize();
		float distance = direction.Length();

		ColorF32 totalIntensity =
			(color * intensity)
			/ (falloffConstant + (falloffLinear * distance));


		// Diffuse Light = Kr * I * (alpha + (1 - alpha) * n.d)
		float dotNormalDirection = std::max(Vector::Dot(normal, direction), 0.0f);
		float alpha = 0.2f;

		ColorF32 diffuseLight =
			material.diffuse
			* totalIntensity
			* (alpha + (1.0f - alpha) * dotNormalDirection);


		// Specular Light = Ks * I * (r.v)^sp
		Vector view = camera.position - eye;
		view.Normalize();
		Vector reflection = (normal * 2.0f * dotNormalDirection) - direction;
		float dotReflectionView = std::max(Vector::Dot(reflection, view), 0.0f);

		ColorF32 specularLight =
			material.specular
			* totalIntensity
			* powf(dotReflectionView, material.glossiness);


		// Total light is sum of all lights
		ColorF32 result = diffuseLight + specularLight;


		return result;
	}

	Point position;
	ColorF32 color;
	float intensity;
	float falloffConstant;
	float falloffLinear;
};