#include "pathtracer.h"

#include <pugixml/pugixml.hpp>
#include <core/rendering/texture_renderer.h>
#include <util/files.h>

namespace glare::raytrace
{
	Pathtracer::Pathtracer(std::shared_ptr<core::SceneNode> graph_root, RayGenType ray_generator)
		: Pathtracer(std::make_shared<SceneCollector>(graph_root), ray_generator)
	{

	}

	Pathtracer::Pathtracer(RayGenType ray_generator)
		: Pathtracer(std::shared_ptr<SceneCollector>(nullptr), ray_generator)
	{
	}

	Pathtracer::Pathtracer(std::shared_ptr<SceneCollector> collector, RayGenType ray_generator)
	{
		Log_Hint << "Pathtracing Shader will now be compiled. This might take a couple of seconds.";
		if(!m_render_shader) m_render_shader = std::make_unique<core::Program>(files::shader("/pathtracer/pathtracer.comp"));
		m_ray_generator = ray_generator;

		core::Context::current().messages()->addObserver(this, tags::scene);
		m_render_target = std::make_unique<core::Texture>(core::Texture::Target::e2D, core::Texture::StoreFormat::eRGBA32Float);
		m_color_storage = std::make_unique<core::Texture>(core::Texture::Target::e2D, core::Texture::StoreFormat::eRGBA32Float);

		if (collector)
			initialize(collector);
	}

	Pathtracer::~Pathtracer()
	{
		if (core::Context::hasCurrentContext() && !core::Context::current().window().isClosing())
			core::Context::current().messages()->removeObserver(this, tags::scene);
	}

	void Pathtracer::loadSettings(const fs::path &xml_file)
	{
		pugi::xml_document preferences_file;
		Log_Info << "Pathtracer settings file load status: " << preferences_file.load_file(xml_file.c_str()).description();

		//Pathtracer
		const auto pt_child = preferences_file.child("pathtracer");

		//bounces
		const auto bounces_child = pt_child.find_child_by_attribute("group", "name", "bounces");
		m_bounce_thresholds[Effect::eDiffusion] = static_cast<uint8_t>(bounces_child.find_child_by_attribute("item", "name", "diffusion").attribute("value").as_uint(2));
		m_bounce_thresholds[Effect::eReflection] = static_cast<uint8_t>(bounces_child.find_child_by_attribute("item", "name", "reflection").attribute("value").as_uint(4));
		m_bounce_thresholds[Effect::eTransmission] = static_cast<uint8_t>(bounces_child.find_child_by_attribute("item", "name", "transmission").attribute("value").as_uint(4));
		m_bounce_thresholds[Effect::eEmission] = static_cast<uint8_t>(bounces_child.find_child_by_attribute("item", "name", "emission").attribute("value").as_uint(8));
		
		//ls thresholds
		const auto ls_thresholds_child = pt_child.find_child_by_attribute("group", "name", "ls-thresholds");
		m_linespace_bounces[Effect::eDiffusion] = static_cast<uint8_t>(ls_thresholds_child.find_child_by_attribute("item", "name", "diffusion").attribute("value").as_uint(2));
		m_linespace_bounces[Effect::eReflection] = static_cast<uint8_t>(ls_thresholds_child.find_child_by_attribute("item", "name", "reflection").attribute("value").as_uint(4));
		m_linespace_bounces[Effect::eTransmission] = static_cast<uint8_t>(ls_thresholds_child.find_child_by_attribute("item", "name", "transmission").attribute("value").as_uint(4));
		m_linespace_bounces[Effect::eEmission] = static_cast<uint8_t>(ls_thresholds_child.find_child_by_attribute("item", "name", "emission").attribute("value").as_uint(8));
		m_linespace_distance = ls_thresholds_child.find_child_by_attribute("item", "name", "distance").attribute("value").as_float(10.f);

		m_linespace_accuracy = ls_thresholds_child.find_child_by_attribute("item", "name", "accuracy").attribute("value").as_float(0.5f);
		m_linespace_shadow = ls_thresholds_child.find_child_by_attribute("item", "name", "shadow").attribute("value").as_float(0.5f);

		m_clamp_direct = pt_child.find_child_by_attribute("item", "name", "clamp-direct").attribute("value").as_float(8);
		m_clamp_indirect = pt_child.find_child_by_attribute("item", "name", "clamp-indirect").attribute("value").as_float(8);
	}

	void Pathtracer::reset()
	{
		m_samples_current = 0;

		m_collector->apply(*m_render_shader);

		m_render_shader->uniform("u_render_config.num_bounces", m_bounce_count);
		m_render_shader->uniform("u_render_config.clamp_direct", m_clamp_direct);
		m_render_shader->uniform("u_render_config.clamp_indirect", m_clamp_indirect);
		m_render_shader->uniform("u_render_config.bounce_thresholds", uint32_t(m_bounce_thresholds));

		m_render_shader->uniform("u_linespace_properties.accuracy_quality", m_linespace_accuracy);
		m_render_shader->uniform("u_linespace_properties.shadow_quality", m_linespace_shadow);
		m_render_shader->uniform("u_linespace_properties.distance_threshold", m_linespace_distance);
		m_render_shader->uniform("u_linespace_properties.bounce_thresholds", uint32_t(m_linespace_bounces));

		m_render_shader->bindSubroutine(gl::ShaderType::eCompute, "u_light_sample[0]", "samplePoint");
		m_render_shader->bindSubroutine(gl::ShaderType::eCompute, "u_light_sample[1]", "sampleSpot");
		m_render_shader->bindSubroutine(gl::ShaderType::eCompute, "u_light_sample[2]", "sampleDirectional");
		m_render_shader->bindSubroutine(gl::ShaderType::eCompute, "u_light_sample[3]", "sampleAmbient");
	}

	const core::Texture &Pathtracer::render(uint32_t width, uint32_t height)
	{
		if (width != m_width || height != m_height) {
			m_width = width;
			m_height = height;

			m_trace_buffer.reserve<Trace>(width * height, gl::BufferUsage::eDynamicCopy);

			m_render_target->set(core::Texture::SubTarget::e2D, core::Image<float>({ static_cast<int>(width), static_cast<int>(height) }, 4));
			m_color_storage->set(core::Texture::SubTarget::e2D, core::Image<float>({ static_cast<int>(width), static_cast<int>(height) }, 4));

			m_render_shader->uniform("u_render_target", m_render_target->imageAddress(gl::Access::eReadWrite));
			m_render_shader->uniform("u_color_store", m_color_storage->imageAddress(gl::Access::eReadWrite));
			m_render_shader->storageBuffer("trace_buffer", m_trace_buffer);

			m_samples_current = 0;
		}

		if (m_samples_current == 0)
		{
			m_collector->collect();
			gl::clearTextureImage(m_color_storage->id(), 0, gl::TextureFormat::eRGBA, gl::Type::eFloat, glm::value_ptr(glm::vec4(0)));
		}

		for (unsigned sample = 0; sample < m_samples_per_frame; sample++) {

			if (m_samples_current >= m_samples_max)
				return *m_render_target;

			const static std::unique_ptr<RayGenerator> ray_generator = std::make_unique<RayGenerator>();

			{
				LogTime("Generate Primary Rays", m_debug_times);
				ray_generator->generate(*this);
			}

			{
				LogTime("Trace and Bounce", m_debug_times);
				m_render_shader->use();
				m_render_shader->uniform("u_render_config.current_sample", m_samples_current);
				m_render_shader->uniform("random_seed", ray_generator->randomSeed());
				m_render_shader->dispatch2d(width, 16, height, 16);
			}

			++m_samples_current;
		}

		return *m_render_target;
	}

	void Pathtracer::draw(std::shared_ptr<core::SceneNode> node)
	{
		// If it's not manually initialized via the GUI button, initialize the Pathtracer here.
		if (!m_collector)
			reload(node);

		static const std::shared_ptr<core::TextureRenderer> texture_renderer = core::DefaultTextureRenderers::makeSimpleRenderer();
		texture_renderer->draw(render(core::Context::current().window().getWidth(), core::Context::current().window().getHeight()));
	}

	void Pathtracer::saveRender(const fs::path& target) const
	{
		if (target.extension() == ".hdr")
		{
			m_render_target->get<float>().save(target);
		}
		else
		{
			m_render_target->get<uint8_t>().save(target);
		}
	}

	Pathtracer::EffectArray::operator unsigned()
	{
		return *reinterpret_cast<uint32_t*>(m_data.data());
	}

	uint8_t& Pathtracer::EffectArray::operator[](Effect effect)
	{
		return m_data[static_cast<size_t>(effect)];
	}

	const uint8_t& Pathtracer::EffectArray::operator[](Effect effect) const
	{
		return m_data[static_cast<size_t>(effect)];
	}

	Pathtracer::LogTime::LogTime(std::string label, bool enabled): m_label(std::move(label)), m_enabled(enabled)
	{
		core::ClockGL::instance().start();
	}

	Pathtracer::LogTime::~LogTime()
	{
		if (m_enabled)
		Log_Hint << "Log Time for label=\"" << m_label << "\": " << core::ClockGL::instance().end() << " ns";
	}

	void Pathtracer::initialize(std::shared_ptr<SceneCollector> collector)
	{
		assert(collector != nullptr);

		m_collector = collector;
		reset();
	}

	void Pathtracer::reload(std::shared_ptr<core::SceneNode> graph_root)
	{
		assert(graph_root != nullptr);

		if (!m_collector)
			m_collector = std::make_shared<SceneCollector>();

		m_collector->setDirty(DirtyFlags::eAll);
		m_collector->collect(graph_root);
		reset();
	}

	void Pathtracer::onNotify(msg::id_type id, msg::message_type message)
	{
		switch (id)
		{
		case tags::scene:
			reset();
			break;
		default: break;
		}
	}

	const core::Program& Pathtracer::shader() const
	{
		return *m_render_shader;
	}

	uint32_t Pathtracer::width() const
	{
		return m_width;
	}

	uint32_t Pathtracer::height() const
	{
		return m_height;
	}

	core::Buffer& Pathtracer::traceBuffer()
	{
		return m_trace_buffer;
	}

	const core::Texture& Pathtracer::renderTarget() const
	{
		return *m_render_target;
	}

	std::shared_ptr<SceneCollector> Pathtracer::collector() const
	{
		return m_collector;
	}
}