#include "Rendering/ShadowPass.h"


ShadowPass::ShadowPass(IRenderer * renderer)
{
	m_Renderer = renderer;

	InitializeFrameBuffers();
	InitializeShaderPrograms();
}

ShadowPass::~ShadowPass()
{

}

void ShadowPass::InitializeCameras(RenderScene & scene)
{
	for (int i = 0; i < m_CurrentNrOfSplits; i++) {
		m_shadowFrusta[i].AspectRatio = scene.Camera->AspectRatio();
		m_shadowFrusta[i].FOV = scene.Camera->FOV();
	}
}

// UpdateSplitDist computes the near and far distances for every frustum slice
// in camera eye space - that is, at what distance does a slice start and end
void ShadowPass::UpdateSplitDist(std::array<Frustum, MAX_SPLITS>& frusta, float near_distance, float far_distance)
{
	float lambda = m_SplitWeight;
	float ratio = far_distance / near_distance;

	frusta[0].NearClip = near_distance;

	for (int i = 1; i < m_CurrentNrOfSplits; i++) {
		float si = i / static_cast<float>(m_CurrentNrOfSplits);

		frusta[i].NearClip = lambda * (near_distance * powf(ratio, si)) + (1 - lambda) * (near_distance + (far_distance - near_distance) * si);
		frusta[i - 1].FarClip = frusta[i].NearClip * 1.005f;
	}

	frusta[m_CurrentNrOfSplits - 1].FarClip = far_distance;
}

// Compute the 8 corner points of the current view frustum in world space
void ShadowPass::UpdateFrustumPoints(Frustum& frustum, glm::vec3 camera_position, glm::vec3 view_dir, glm::mat4 p, glm::mat4 v)
{
	glm::vec3 up = glm::vec3(0.f, 1.f, 0.f);
	glm::vec3 right = glm::normalize(glm::cross(view_dir, up));

	glm::vec3 far_center = camera_position + glm::normalize(view_dir) * frustum.FarClip;
	glm::vec3 near_center = camera_position + glm::normalize(view_dir) * frustum.NearClip;
	frustum.MiddlePoint = near_center + (far_center - near_center) * 0.5f;

 	up = glm::normalize(glm::cross(right, view_dir));

	// these heights and widths are half the heights and widths of the near and far plane rectangles.
	float near_height = tan(frustum.FOV / 2.f) * frustum.NearClip;
	float near_width = near_height * frustum.AspectRatio;
	float far_height = tan(frustum.FOV / 2.f) * frustum.FarClip;
	float far_width = far_height * frustum.AspectRatio;

	frustum.CornerPoint[0] = near_center - up * near_height - right * near_width;
	frustum.CornerPoint[1] = near_center + up * near_height - right * near_width;
	frustum.CornerPoint[2] = near_center + up * near_height + right * near_width;
	frustum.CornerPoint[3] = near_center - up * near_height + right * near_width;

	frustum.CornerPoint[4] = far_center - up * far_height - right * far_width;
	frustum.CornerPoint[5] = far_center + up * far_height - right * far_width;
	frustum.CornerPoint[6] = far_center + up * far_height + right * far_width;
	frustum.CornerPoint[7] = far_center - up * far_height + right * far_width;

	// Alternative way.
	//std::array<glm::vec4, 8> CornerPoint = { 
	//	glm::vec4(-1.f, -1.f,	-1.f,	1.f),
	//	glm::vec4(-1.f, 1.f,	-1.f,	1.f),
	//	glm::vec4(1.f,	1.f,	-1.f,	1.f),
	//	glm::vec4(1.f,	-1.f,	-1.f,	1.f),
	//	glm::vec4(-1.f,	-1.f,	1.f,	1.f),
	//	glm::vec4(-1.f,	1.f,	1.f,	1.f),
	//	glm::vec4(1.f,	1.f,	1.f,	1.f),
	//	glm::vec4(1.f,	-1.f,	1.f,	1.f) };

	//std::array<glm::vec3, 8> FinalPoints;

	//for (int i = 0; i < 8; i++) {
	//	glm::vec4 NDC = glm::inverse(p) * CornerPoint[i];
	//	NDC = NDC / NDC.w;
	//	FinalPoints[i] = glm::vec3(glm::inverse(v) * NDC);
	//}
}

float ShadowPass::FindRadius(Frustum& frustum)
{
	float radius = 0.f;

	for (int i = 0; i < 8; i++) {
		float distance = glm::distance(frustum.MiddlePoint, frustum.CornerPoint[i]);
		if (distance > radius) {
			radius = distance;
		}
	}

	frustum.Radius = radius;
	return radius;
}

void ShadowPass::InitializeFrameBuffers()
{
    // Depth texture
    glGenTextures(m_CurrentNrOfSplits, m_DepthMap.data());

	for (int i = 0; i < m_CurrentNrOfSplits; i++) {
		glBindTexture(GL_TEXTURE_2D, m_DepthMap[i]);
		glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT16, m_ResolutionSizeWidth / (1 /*+ i*/), m_ResolutionSizeHeigth + (1 /*+ i*/), 0, GL_DEPTH_COMPONENT, GL_UNSIGNED_INT, nullptr);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_BORDER);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_BORDER);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_MODE, GL_COMPARE_R_TO_TEXTURE);
		glTexParameterfv(GL_TEXTURE_2D, GL_TEXTURE_BORDER_COLOR, glm::vec4(1.f).data);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_FUNC, GL_LEQUAL);
		//glTexParameteri(GL_TEXTURE_2D, GL_DEPTH_TEXTURE_MODE, GL_INTENSITY);

		m_DepthBuffer[i].AddResource(std::shared_ptr<BufferResource>(new Texture2D(&m_DepthMap[i], GL_DEPTH_ATTACHMENT)));
		m_DepthBuffer[i].Generate();
	}

    GLERROR("depthMap failed");
}

void ShadowPass::InitializeShaderPrograms()
{
    m_ShadowProgram = ResourceManager::Load<ShaderProgram>("#ShadowProgram");
    m_ShadowProgram->AddShader(std::shared_ptr<Shader>(new VertexShader("Shaders/Shadow.vert.glsl")));
    m_ShadowProgram->AddShader(std::shared_ptr<Shader>(new FragmentShader("Shaders/Shadow.frag.glsl")));
    m_ShadowProgram->Compile();
    m_ShadowProgram->BindFragDataLocation(0, "ShadowMap");
    m_ShadowProgram->Link();
}

void ShadowPass::ClearBuffer()
{
	for (int i = 0; i < m_CurrentNrOfSplits; i++) {
		m_DepthBuffer[i].Bind();
		glClearColor(0.f, 0.f, 0.f, 0.f);
		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
		m_DepthBuffer[i].Unbind();
	}
}

void ShadowPass::PointsToLightspace(Frustum& frustum, glm::mat4 v)
{
	float left = INFINITY;
	float right = -INFINITY;
	float bottom = INFINITY;
	float top = -INFINITY;

	for (int i = 0; i < 8; i++)
	{
		glm::vec3 tempPoint = glm::vec3(v * glm::vec4(frustum.CornerPoint[i], 1.f));

		if (tempPoint.x < left) { left = tempPoint.x; }
		if (tempPoint.x > right) { right = tempPoint.x; }
		if (tempPoint.y < bottom) { bottom = tempPoint.y; }
		if (tempPoint.y > top) { top = tempPoint.y; }
	}

	frustum.LRBT = { left, right, bottom, top };
}

void ShadowPass::RadiusToLightspace(Frustum& frustum, glm::mat4 v)
{
	float left = -frustum.Radius;
	float right = frustum.Radius;
	float bottom = -frustum.Radius;
	float top =frustum.Radius;

	frustum.LRBT = { left, right, bottom, top };
}

void ShadowPass::Draw(RenderScene & scene)
{
	ImGui::DragFloat4("ShadowMapCam", m_LRBT, 1.f, -1000.f, 1000.f);
	ImGui::DragFloat2("ShadowMapNearFar", m_NearFarPlane, 1.f, -1000.f, 1000.f);
	ImGui::Checkbox("EnableShadow", &m_ShadowOn);
	ImGui::DragInt("ShadowLevel", &m_ShadowLevel, 0.05f, 0, m_CurrentNrOfSplits - 1);

	InitializeCameras(scene);
	UpdateSplitDist(m_shadowFrusta, scene.Camera->NearClip(), scene.Camera->FarClip());
	
	for (int i = 0; i < m_CurrentNrOfSplits; i++) {
		UpdateFrustumPoints(m_shadowFrusta[i], scene.Camera->Position(), scene.Camera->Forward(), scene.Camera->ProjectionMatrix(), scene.Camera->ViewMatrix());
		//float test = FindRadius(m_shadFrusta[i]);

		ShadowPassState* state = new ShadowPassState(m_DepthBuffer[i].GetHandle());

		GLuint shaderHandle = m_ShadowProgram->GetHandle();
		m_ShadowProgram->Bind();

		glViewport(0, 0, m_ResolutionSizeWidth / (1/* + i*/), m_ResolutionSizeHeigth);
		glDisable(GL_TEXTURE_2D);
		glCullFace(GL_FRONT);
		//state->Disable(GL_CULL_FACE);

		if (m_ShadowOn == true)
		{
			for (auto &job : scene.DirectionalLightJobs) {
				auto directionalLightJob = std::dynamic_pointer_cast<DirectionalLightJob>(job);

				if (directionalLightJob) {
					m_LightView[i] = glm::lookAt(glm::vec3(-directionalLightJob->Direction) + m_shadowFrusta[i].MiddlePoint, m_shadowFrusta[i].MiddlePoint, glm::vec3(0.f, 1.f, 0.f));
					
					PointsToLightspace(m_shadowFrusta[i], m_LightView[i]);
					m_LightProjection[i] = glm::ortho(m_shadowFrusta[i].LRBT[Left], m_shadowFrusta[i].LRBT[Right], m_shadowFrusta[i].LRBT[Bottom], m_shadowFrusta[i].LRBT[Top], -30.f, 30.f);

					glUniformMatrix4fv(glGetUniformLocation(shaderHandle, "P"), 1, GL_FALSE, glm::value_ptr(m_LightProjection[i]));
					glUniformMatrix4fv(glGetUniformLocation(shaderHandle, "V"), 1, GL_FALSE, glm::value_ptr(m_LightView[i]));

					GLERROR("ShadowLight ERROR");

					for (auto &objectJob : scene.OpaqueObjects) {
						auto modelJob = std::dynamic_pointer_cast<ModelJob>(objectJob);
						
						glUniformMatrix4fv(glGetUniformLocation(shaderHandle, "M"), 1, GL_FALSE, glm::value_ptr(modelJob->Matrix));

						glBindVertexArray(modelJob->Model->VAO);
						glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, modelJob->Model->ElementBuffer);
						glDrawElements(GL_TRIANGLES, modelJob->EndIndex - modelJob->StartIndex + 1, GL_UNSIGNED_INT, (void*)(modelJob->StartIndex * sizeof(unsigned int)));

						GLERROR("Shadow Draw ERROR");
					}
				}
				m_DepthBuffer[i].Unbind();

				delete state;
			}
		}

		glViewport(0, 0, m_Renderer->GetViewportSize().Width, m_Renderer->GetViewportSize().Height);
		glEnable(GL_TEXTURE_2D);
		glCullFace(GL_BACK);

		m_ShadowProgram->Unbind();

	}
}