// 
//---------------------------------------------------------------------------
// 1D dynamic shadow maps
// Copyright(C) 2017 Magnus Norddahl
// All rights reserved.
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with this program.  If not, see http://www.gnu.org/licenses/
//
//--------------------------------------------------------------------------
//

#include "gl/system/gl_system.h"
#include "gl/shaders/gl_shader.h"
#include "gl/dynlights/gl_shadowmap.h"
#include "gl/dynlights/gl_dynlight.h"
#include "gl/system/gl_interface.h"
#include "gl/system/gl_debug.h"
#include "gl/renderer/gl_renderer.h"
#include "gl/renderer/gl_postprocessstate.h"
#include "gl/renderer/gl_renderbuffers.h"
#include "gl/shaders/gl_shadowmapshader.h"
#include "r_state.h"

void FShadowMap::Update()
{
	UploadAABBTree();
	UploadLights();

	FGLDebug::PushGroup("ShadowMap");
	FGLPostProcessState savedState;

	GLRenderer->mBuffers->BindShadowMapFB();

	GLRenderer->mShadowMapShader->Bind();
	glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 4, mLightList);
	glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 2, mNodesBuffer);
	glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 3, mLinesBuffer);

	glViewport(0, 0, 1024, 1024);
	GLRenderer->RenderScreenQuad();

	const auto &viewport = GLRenderer->mScreenViewport;
	glViewport(viewport.left, viewport.top, viewport.width, viewport.height);

	glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 4, 0);
	glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 2, 0);
	glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 3, 0);

	GLRenderer->mBuffers->BindShadowMapTexture(16);

	FGLDebug::PopGroup();
}

bool FShadowMap::ShadowTest(ADynamicLight *light, const DVector3 &pos)
{
	if (mAABBTree)
		return mAABBTree->RayTest(light->Pos(), pos) >= 1.0f;
	else
		return true;
}

void FShadowMap::UploadLights()
{
	mLights.Clear();
	mLightToShadowmap.Clear(mLightToShadowmap.CountUsed() * 2); // To do: allow clearing a TMap while building up a reserve

	TThinkerIterator<ADynamicLight> it(STAT_DLIGHT);
	while (true)
	{
		ADynamicLight *light = it.Next();
		if (!light) break;

		mLightToShadowmap[light] = mLights.Size() / 4;

		mLights.Push(light->X());
		mLights.Push(light->Y());
		mLights.Push(light->Z());
		mLights.Push(light->GetRadius());

		if (mLights.Size() == 1024) // Only 1024 lights for now
			break;
	}

	while (mLights.Size() < 1024 * 4)
		mLights.Push(0.0f);

	if (mLightList == 0)
		glGenBuffers(1, (GLuint*)&mLightList);

	int oldBinding = 0;
	glGetIntegerv(GL_SHADER_STORAGE_BUFFER_BINDING, &oldBinding);
	glBindBuffer(GL_SHADER_STORAGE_BUFFER, mLightList);
	glBufferData(GL_SHADER_STORAGE_BUFFER, sizeof(float) * mLights.Size(), &mLights[0], GL_STATIC_DRAW);
	glBindBuffer(GL_SHADER_STORAGE_BUFFER, oldBinding);
}

void FShadowMap::UploadAABBTree()
{
	if (numnodes != mLastNumNodes || numsegs != mLastNumSegs) // To do: there is probably a better way to detect a map change than this..
		Clear();

	if (mAABBTree)
		return;

	mAABBTree.reset(new LevelAABBTree());

	int oldBinding = 0;
	glGetIntegerv(GL_SHADER_STORAGE_BUFFER_BINDING, &oldBinding);

	glGenBuffers(1, (GLuint*)&mNodesBuffer);
	glBindBuffer(GL_SHADER_STORAGE_BUFFER, mNodesBuffer);
	glBufferData(GL_SHADER_STORAGE_BUFFER, sizeof(AABBTreeNode) * mAABBTree->nodes.Size(), &mAABBTree->nodes[0], GL_STATIC_DRAW);

	glGenBuffers(1, (GLuint*)&mLinesBuffer);
	glBindBuffer(GL_SHADER_STORAGE_BUFFER, mLinesBuffer);
	glBufferData(GL_SHADER_STORAGE_BUFFER, sizeof(AABBTreeLine) * mAABBTree->lines.Size(), &mAABBTree->lines[0], GL_STATIC_DRAW);

	glBindBuffer(GL_SHADER_STORAGE_BUFFER, oldBinding);
}

void FShadowMap::Clear()
{
	if (mLightList != 0)
	{
		glDeleteBuffers(1, (GLuint*)&mLightList);
		mLightList = 0;
	}

	if (mNodesBuffer != 0)
	{
		glDeleteBuffers(1, (GLuint*)&mNodesBuffer);
		mNodesBuffer = 0;
	}

	if (mLinesBuffer != 0)
	{
		glDeleteBuffers(1, (GLuint*)&mLinesBuffer);
		mLinesBuffer = 0;
	}

	mAABBTree.reset();

	mLastNumNodes = numnodes;
	mLastNumSegs = numsegs;
}