/*
 * Copyright (C) 2022 Riyyi
 *
 * SPDX-License-Identifier: MIT
 */

#include <algorithm> // std::min
#include <utility>   // std::move

#include "glad/glad.h"
#include "ruc/format/log.h"

#include "inferno/render/buffer.h"
#include "inferno/render/renderer.h"
#include "inferno/render/shader.h"
#include "inferno/render/texture.h"

namespace Inferno {

void RenderCommand::initialize()
{
	setDepthTest(true);

	// Enable transparency
	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
	glEnable(GL_BLEND);

	ruc::info("RenderCommand initialized");
}

void RenderCommand::destroy()
{
}

void RenderCommand::clear()
{
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
}

void RenderCommand::clearColor(const glm::vec4& color)
{
	glClearColor(color.r, color.g, color.b, color.a);
}

void RenderCommand::drawIndexed(const VertexArray& vertexArray, uint32_t indexCount)
{
	uint32_t count = indexCount ? indexCount : vertexArray.getIndexBuffer()->getCount();
	glDrawElements(GL_TRIANGLES, count, GL_UNSIGNED_INT, nullptr);
}

void RenderCommand::setViewport(int32_t x, int32_t y, uint32_t width, uint32_t height)
{
	glViewport(x, y, width, height);
}

void RenderCommand::setDepthTest(bool enabled)
{
	// Set z-buffer / depth buffer
	enabled ? glEnable(GL_DEPTH_TEST) : glDisable(GL_DEPTH_TEST);
}

bool RenderCommand::depthTest()
{
	unsigned char depthTest = GL_FALSE;
	glGetBooleanv(GL_DEPTH_TEST, &depthTest);
	return depthTest == GL_TRUE;
}

int32_t RenderCommand::textureUnitAmount()
{
	int32_t amount = 0;
	glGetIntegerv(GL_MAX_TEXTURE_IMAGE_UNITS, &amount);
	return amount;
}

// -----------------------------------------

uint32_t Renderer::m_supportedTextureUnitPerBatch = 0;

void Renderer::initialize()
{
	// Get amount of texture units supported by the GPU
	uint32_t constTextureUnitCount = textureUnitPerBatch;
	uint32_t gpuTextureUnitCount = RenderCommand::textureUnitAmount();
	m_supportedTextureUnitPerBatch = std::min(constTextureUnitCount, gpuTextureUnitCount);

	// Texture unit 0 is reserved for no texture
	m_textureUnits[0] = nullptr;

	// Create texture unit samplers
	int32_t samplers[textureUnitPerBatch];
	for (uint32_t i = 0; i < textureUnitPerBatch; i++) {
		samplers[i] = i;
	}

	// Create shader
	loadShader();
	m_shader->bind();
	m_shader->setInt("u_textures", samplers, textureUnitPerBatch);
	m_shader->unbind();

	// Create vertex array
	m_vertexArray = std::make_shared<VertexArray>();
}

void Renderer::destroy()
{
}

uint32_t Renderer::addTextureUnit(std::shared_ptr<Texture> texture)
{
	if (texture == nullptr) {
		return 0;
	}

	// Create a new batch if the texture unit limit has been reached
	if (m_textureUnitIndex >= m_supportedTextureUnitPerBatch) {
		nextBatch();
	}

	// If texure was already added
	for (uint32_t i = 1; i < m_textureUnitIndex; i++) {
		if (m_textureUnits[i] == texture) {
			return i;
		}
	}

	// Add texture
	uint32_t textureUnitIndex = m_textureUnitIndex;
	m_textureUnits[textureUnitIndex] = texture;
	m_textureUnitIndex++;

	return textureUnitIndex;
}

void Renderer::bind()
{
	m_shader->bind();

	for (uint32_t i = 1; i < m_textureUnitIndex; i++) {
		m_textureUnits[i]->bind(i);
	}

	m_vertexArray->bind();
}

void Renderer::unbind()
{
	m_vertexArray->unbind();

	for (uint32_t i = 1; i < m_textureUnitIndex; i++) {
		m_textureUnits[i]->unbind();
	}

	m_shader->unbind();
}

// -----------------------------------------

Renderer2D::Renderer2D(s)
{
	Renderer::initialize();

	// CPU
	// ---------------------------------

	// Create array for storing quads vertices
	m_vertexBufferBase = std::make_unique<QuadVertex[]>(vertexCount);
	m_vertexBufferPtr = m_vertexBufferBase.get();

	// Set default quad vertex positions
	m_vertexPositions[0] = { -0.5f, -0.5f, 0.0f, 1.0f };
	m_vertexPositions[1] = { 0.5f, -0.5f, 0.0f, 1.0f };
	m_vertexPositions[2] = { 0.5f, 0.5f, 0.0f, 1.0f };
	m_vertexPositions[3] = { -0.5f, 0.5f, 0.0f, 1.0f };

	// Generate indices

	uint32_t* indices = new uint32_t[indexCount];

	uint32_t offset = 0;
	for (uint32_t i = 0; i < indexCount; i += indexPerQuad) {
		indices[i + 0] = offset + 0;
		indices[i + 1] = offset + 1;
		indices[i + 2] = offset + 2;
		indices[i + 3] = offset + 2;
		indices[i + 4] = offset + 3;
		indices[i + 5] = offset + 0;

		offset += vertexPerQuad;
	}

	// GPU
	// ---------------------------------

	// Create vertex buffer
	auto vertexBuffer = std::make_shared<VertexBuffer>(sizeof(QuadVertex) * vertexCount);
	vertexBuffer->setLayout({
		{ BufferElementType::Vec3, "a_position" },
		{ BufferElementType::Vec4, "a_color" },
		{ BufferElementType::Vec2, "a_textureCoordinates" },
		{ BufferElementType::Float, "a_textureIndex" },
	});
	m_vertexArray->addVertexBuffer(vertexBuffer);

	// Create index buffer
	auto indexBuffer = std::make_shared<IndexBuffer>(indices, sizeof(uint32_t) * indexCount);
	m_vertexArray->setIndexBuffer(indexBuffer);
	delete[] indices;

	ruc::info("Renderer2D initialized");
}

Renderer2D::~Renderer2D()
{
	Renderer::destroy();
}

void Renderer2D::beginScene(glm::mat4 cameraProjectionView)
{
	m_shader->bind();
	m_shader->setFloat("u_projectionView", cameraProjectionView);
	m_shader->unbind();
}

void Renderer2D::endScene()
{
	nextBatch();
}

void Renderer2D::drawQuad(const TransformComponent& transform, glm::vec4 color)
{
	drawQuad(transform, color, nullptr);
}

void Renderer2D::drawQuad(const TransformComponent& transform, glm::mat4 color)
{
	drawQuad(transform, color, nullptr);
}

void Renderer2D::drawQuad(const TransformComponent& transform, glm::vec4 color, std::shared_ptr<Texture> texture)
{
	drawQuad(transform, glm::mat4(color, color, color, color), texture);
}

void Renderer2D::drawQuad(const TransformComponent& transform, glm::mat4 color, std::shared_ptr<Texture> texture)
{
	// Create a new batch if the quad limit has been reached
	if (m_quadIndex >= quadCount) {
		nextBatch();
	}

	constexpr glm::vec2 textureCoordinates[] = {
		{ 0.0f, 0.0f },
		{ 1.0f, 0.0f },
		{ 1.0f, 1.0f },
		{ 0.0f, 1.0f }
	};

	uint32_t textureUnitIndex = addTextureUnit(texture);

	// Add the quads 4 vertices
	for (uint32_t i = 0; i < vertexPerQuad; i++) {
		m_vertexBufferPtr->position = transform.transform * m_vertexPositions[i];
		m_vertexBufferPtr->color = color[i];
		m_vertexBufferPtr->textureCoordinates = textureCoordinates[i];
		m_vertexBufferPtr->textureIndex = (float)textureUnitIndex;
		m_vertexBufferPtr++;
	}

	m_quadIndex++;
}

void Renderer2D::loadShader()
{
	m_shader = ShaderManager::the().load("assets/glsl/batch-quad");
}

void Renderer2D::flush()
{
	if (m_quadIndex == 0) {
		return;
	}

	// Upload vertex data to GPU
	m_vertexArray->getVertexBuffers().at(0)->uploadData(
		m_vertexBufferBase.get(),
		m_quadIndex * vertexPerQuad * sizeof(QuadVertex));

	bind();

	// Render
	RenderCommand::drawIndexed(*m_vertexArray, m_quadIndex * indexPerQuad);

	unbind();
}

void Renderer2D::startBatch()
{
	m_quadIndex = 0;
	m_vertexBufferPtr = m_vertexBufferBase.get();

	m_textureUnitIndex = 1;
}

void Renderer2D::nextBatch()
{
	flush();
	startBatch();
}

// -----------------------------------------

RendererCharacter::RendererCharacter(s)
{
	Renderer::initialize();

	// CPU
	// ---------------------------------

	// Create array for storing quads vertices
	m_vertexBufferBase = std::make_unique<CharacterVertex[]>(vertexCount);
	m_vertexBufferPtr = m_vertexBufferBase.get();

	// Generate indices

	uint32_t* indices = new uint32_t[indexCount];

	uint32_t offset = 0;
	for (uint32_t i = 0; i < indexCount; i += indexPerQuad) {
		indices[i + 0] = offset + 0;
		indices[i + 1] = offset + 1;
		indices[i + 2] = offset + 2;
		indices[i + 3] = offset + 2;
		indices[i + 4] = offset + 3;
		indices[i + 5] = offset + 0;

		offset += vertexPerQuad;
	}

	// GPU
	// ---------------------------------

	// Create vertex buffer
	auto vertexBuffer = std::make_shared<VertexBuffer>(sizeof(CharacterVertex) * vertexCount);
	vertexBuffer->setLayout({
		{ BufferElementType::Vec3, "a_position" },
		{ BufferElementType::Vec4, "a_color" },
		{ BufferElementType::Vec2, "a_textureCoordinates" },
		{ BufferElementType::Float, "a_textureIndex" },
		{ BufferElementType::Float, "a_width" },
		{ BufferElementType::Float, "a_edge" },
		{ BufferElementType::Float, "a_borderWidth" },
		{ BufferElementType::Float, "a_borderEdge" },
		{ BufferElementType::Vec4, "a_borderColor" },
		{ BufferElementType::Float, "a_offset" },
	});
	m_vertexArray->addVertexBuffer(vertexBuffer);

	// Create index buffer
	auto indexBuffer = std::make_shared<IndexBuffer>(indices, sizeof(uint32_t) * indexCount);
	m_vertexArray->setIndexBuffer(indexBuffer);
	delete[] indices;

	ruc::info("RendererCharacter initialized");
}

RendererCharacter::~RendererCharacter()
{
	Renderer::destroy();
}

void RendererCharacter::beginScene()
{
}

void RendererCharacter::endScene()
{
	nextBatch();
}

void RendererCharacter::drawCharacter(std::array<CharacterVertex, vertexPerQuad>& characterQuad, std::shared_ptr<Texture> texture)
{
	// Create a new batch if the quad limit has been reached
	if (m_quadIndex >= quadCount) {
		nextBatch();
	}

	uint32_t textureUnitIndex = addTextureUnit(texture);

	// Add the quads 4 vertices
	for (uint32_t i = 0; i < vertexPerQuad; i++) {
		m_vertexBufferPtr->quad.position = characterQuad[i].quad.position;
		m_vertexBufferPtr->quad.color = characterQuad[i].quad.color;
		m_vertexBufferPtr->quad.textureCoordinates = characterQuad[i].quad.textureCoordinates;
		m_vertexBufferPtr->quad.textureIndex = (float)textureUnitIndex;

		m_vertexBufferPtr->width = characterQuad[i].width;
		m_vertexBufferPtr->edge = characterQuad[i].edge;
		m_vertexBufferPtr->borderWidth = characterQuad[i].borderWidth;
		m_vertexBufferPtr->borderEdge = characterQuad[i].borderEdge;
		m_vertexBufferPtr->borderColor = characterQuad[i].borderColor;
		m_vertexBufferPtr->offset = characterQuad[i].offset;

		m_vertexBufferPtr++;
	}

	m_quadIndex++;
}

void RendererCharacter::loadShader()
{
	m_shader = ShaderManager::the().load("assets/glsl/batch-font");
}

void RendererCharacter::flush()
{
	if (m_quadIndex == 0) {
		return;
	}

	// Upload vertex data to GPU
	m_vertexArray->getVertexBuffers().at(0)->uploadData(
		m_vertexBufferBase.get(),
		m_quadIndex * vertexPerQuad * sizeof(CharacterVertex));

	bind();

	// Render
	bool depthTest = RenderCommand::depthTest();
	RenderCommand::setDepthTest(false);
	RenderCommand::drawIndexed(*m_vertexArray, m_quadIndex * indexPerQuad);
	RenderCommand::setDepthTest(depthTest);

	unbind();
}

void RendererCharacter::startBatch()
{
	m_quadIndex = 0;
	m_vertexBufferPtr = m_vertexBufferBase.get();

	m_textureUnitIndex = 1;
}

void RendererCharacter::nextBatch()
{
	flush();
	startBatch();
}

} // namespace Inferno