#include "RuntimeRenderScene.h"

#include "../../platform/HiddenGlWindow.h"

#include <algorithm>
#include <functional>
#include <utility>

#ifndef GL_FRAMEBUFFER_BINDING
#define GL_FRAMEBUFFER_BINDING 0x8CA6
#endif

RuntimeRenderScene::~RuntimeRenderScene()
{
	ShutdownGl();
}

bool RuntimeRenderScene::StartPrepareWorker(std::unique_ptr<HiddenGlWindow> sharedWindow, std::string& error)
{
	return mPrepareWorker.Start(std::move(sharedWindow), error);
}

bool RuntimeRenderScene::CommitRenderLayers(const std::vector<RenderCadenceCompositor::RuntimeRenderLayerModel>& layers, std::string& error)
{
	ConsumePreparedPrograms();

	std::vector<std::string> nextOrder;
	std::vector<RenderCadenceCompositor::RuntimeRenderLayerModel> layersToPrepare;
	nextOrder.reserve(layers.size());
	for (const RenderCadenceCompositor::RuntimeRenderLayerModel& layer : layers)
		nextOrder.push_back(layer.id);

	for (auto layerIt = mLayers.begin(); layerIt != mLayers.end();)
	{
		const bool stillPresent = std::find(nextOrder.begin(), nextOrder.end(), layerIt->layerId) != nextOrder.end();
		if (stillPresent)
		{
			++layerIt;
			continue;
		}

		if (layerIt->renderer)
			layerIt->renderer->ShutdownGl();
		layerIt = mLayers.erase(layerIt);
	}

	for (const RenderCadenceCompositor::RuntimeRenderLayerModel& layer : layers)
	{
		if (layer.artifact.fragmentShaderSource.empty())
			continue;

		const std::string fingerprint = Fingerprint(layer.artifact);
		LayerProgram* program = FindLayer(layer.id);
		if (!program)
		{
			LayerProgram next;
			next.layerId = layer.id;
			next.renderer = std::make_unique<RuntimeShaderRenderer>();
			mLayers.push_back(std::move(next));
			program = &mLayers.back();
		}

		if (program->shaderId == layer.shaderId && program->sourceFingerprint == fingerprint && program->renderer && program->renderer->HasProgram())
			continue;
		if (program->pendingFingerprint == fingerprint)
			continue;

		program->shaderId = layer.shaderId;
		program->pendingFingerprint = fingerprint;
		layersToPrepare.push_back(layer);
	}

	mLayerOrder = std::move(nextOrder);
	if (!layersToPrepare.empty())
		mPrepareWorker.Submit(layersToPrepare);
	error.clear();
	return true;
}

bool RuntimeRenderScene::HasLayers()
{
	ConsumePreparedPrograms();

	for (const std::string& layerId : mLayerOrder)
	{
		const LayerProgram* layer = FindLayer(layerId);
		if (layer && layer->renderer && layer->renderer->HasProgram())
			return true;
	}
	return false;
}

void RuntimeRenderScene::RenderFrame(uint64_t frameIndex, unsigned width, unsigned height)
{
	ConsumePreparedPrograms();

	std::vector<LayerProgram*> readyLayers;
	for (const std::string& layerId : mLayerOrder)
	{
		LayerProgram* layer = FindLayer(layerId);
		if (!layer || !layer->renderer || !layer->renderer->HasProgram())
			continue;
		readyLayers.push_back(layer);
	}

	if (readyLayers.empty())
		return;

	GLint outputFramebuffer = 0;
	glGetIntegerv(GL_FRAMEBUFFER_BINDING, &outputFramebuffer);

	if (readyLayers.size() == 1)
	{
		readyLayers.front()->renderer->RenderFrame(frameIndex, width, height);
		return;
	}

	if (!EnsureLayerTargets(width, height))
	{
		glBindFramebuffer(GL_FRAMEBUFFER, static_cast<GLuint>(outputFramebuffer));
		readyLayers.back()->renderer->RenderFrame(frameIndex, width, height);
		return;
	}

	GLuint layerInputTexture = 0;
	std::size_t nextTargetIndex = 0;
	for (std::size_t layerIndex = 0; layerIndex < readyLayers.size(); ++layerIndex)
	{
		const bool isFinalLayer = layerIndex == readyLayers.size() - 1;
		if (isFinalLayer)
		{
			glBindFramebuffer(GL_FRAMEBUFFER, static_cast<GLuint>(outputFramebuffer));
			readyLayers[layerIndex]->renderer->RenderFrame(frameIndex, width, height, layerInputTexture, layerInputTexture);
			continue;
		}

		glBindFramebuffer(GL_FRAMEBUFFER, mLayerFramebuffers[nextTargetIndex]);
		readyLayers[layerIndex]->renderer->RenderFrame(frameIndex, width, height, layerInputTexture, layerInputTexture);
		layerInputTexture = mLayerTextures[nextTargetIndex];
		nextTargetIndex = 1 - nextTargetIndex;
	}
}

void RuntimeRenderScene::ShutdownGl()
{
	mPrepareWorker.Stop();
	for (LayerProgram& layer : mLayers)
	{
		if (layer.renderer)
			layer.renderer->ShutdownGl();
	}
	mLayers.clear();
	mLayerOrder.clear();
	DestroyLayerTargets();
}

void RuntimeRenderScene::ConsumePreparedPrograms()
{
	RuntimePreparedShaderProgram preparedProgram;
	while (mPrepareWorker.TryConsume(preparedProgram))
	{
		if (!preparedProgram.succeeded)
		{
			preparedProgram.ReleaseGl();
			continue;
		}

		LayerProgram* layer = FindLayer(preparedProgram.layerId);
		if (!layer || layer->pendingFingerprint != preparedProgram.sourceFingerprint)
		{
			preparedProgram.ReleaseGl();
			continue;
		}

		std::unique_ptr<RuntimeShaderRenderer> nextRenderer = std::make_unique<RuntimeShaderRenderer>();
		std::string error;
		if (!nextRenderer->CommitPreparedProgram(preparedProgram, error))
		{
			preparedProgram.ReleaseGl();
			continue;
		}

		if (layer->renderer)
			layer->renderer->ShutdownGl();
		layer->renderer = std::move(nextRenderer);
		layer->shaderId = preparedProgram.shaderId;
		layer->sourceFingerprint = preparedProgram.sourceFingerprint;
		layer->pendingFingerprint.clear();
	}
}

bool RuntimeRenderScene::EnsureLayerTargets(unsigned width, unsigned height)
{
	if (width == 0 || height == 0)
		return false;
	if (mLayerFramebuffers[0] != 0 && mLayerFramebuffers[1] != 0 && mLayerTextures[0] != 0 && mLayerTextures[1] != 0
		&& mLayerTargetWidth == width && mLayerTargetHeight == height)
		return true;

	DestroyLayerTargets();
	mLayerTargetWidth = width;
	mLayerTargetHeight = height;

	glGenFramebuffers(2, mLayerFramebuffers);
	glGenTextures(2, mLayerTextures);
	for (int index = 0; index < 2; ++index)
	{
		glBindTexture(GL_TEXTURE_2D, mLayerTextures[index]);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
		glTexImage2D(
			GL_TEXTURE_2D,
			0,
			GL_RGBA8,
			static_cast<GLsizei>(width),
			static_cast<GLsizei>(height),
			0,
			GL_BGRA,
			GL_UNSIGNED_INT_8_8_8_8_REV,
			nullptr);

		glBindFramebuffer(GL_FRAMEBUFFER, mLayerFramebuffers[index]);
		glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, mLayerTextures[index], 0);
		if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
		{
			glBindFramebuffer(GL_FRAMEBUFFER, 0);
			glBindTexture(GL_TEXTURE_2D, 0);
			DestroyLayerTargets();
			return false;
		}
	}

	glBindFramebuffer(GL_FRAMEBUFFER, 0);
	glBindTexture(GL_TEXTURE_2D, 0);
	return true;
}

void RuntimeRenderScene::DestroyLayerTargets()
{
	if (mLayerFramebuffers[0] != 0 || mLayerFramebuffers[1] != 0)
		glDeleteFramebuffers(2, mLayerFramebuffers);
	if (mLayerTextures[0] != 0 || mLayerTextures[1] != 0)
		glDeleteTextures(2, mLayerTextures);
	mLayerFramebuffers[0] = 0;
	mLayerFramebuffers[1] = 0;
	mLayerTextures[0] = 0;
	mLayerTextures[1] = 0;
	mLayerTargetWidth = 0;
	mLayerTargetHeight = 0;
}

RuntimeRenderScene::LayerProgram* RuntimeRenderScene::FindLayer(const std::string& layerId)
{
	for (LayerProgram& layer : mLayers)
	{
		if (layer.layerId == layerId)
			return &layer;
	}
	return nullptr;
}

const RuntimeRenderScene::LayerProgram* RuntimeRenderScene::FindLayer(const std::string& layerId) const
{
	for (const LayerProgram& layer : mLayers)
	{
		if (layer.layerId == layerId)
			return &layer;
	}
	return nullptr;
}

std::string RuntimeRenderScene::Fingerprint(const RuntimeShaderArtifact& artifact)
{
	const std::hash<std::string> hasher;
	return artifact.shaderId + ":" + std::to_string(artifact.fragmentShaderSource.size()) + ":" + std::to_string(hasher(artifact.fragmentShaderSource));
}