//  CRTOpenGL.cpp
//  Clock Signal
//
//  Created by Thomas Harte on 03/02/2016.
//  Copyright © 2016 Thomas Harte. All rights reserved.
//

#include "CRT.hpp"
#include <stdlib.h>
#include <math.h>

#include "CRTOpenGL.hpp"
#include "../../../SignalProcessing/FIRFilter.hpp"
#include "Shaders/OutputShader.hpp"

static const GLint internalFormatForDepth(size_t depth)
{
	switch(depth)
	{
		default: return GL_FALSE;
		case 1: return GL_R8UI;
		case 2: return GL_RG8UI;
		case 3: return GL_RGB8UI;
		case 4: return GL_RGBA8UI;
	}
}

static const GLenum formatForDepth(size_t depth)
{
	switch(depth)
	{
		default: return GL_FALSE;
		case 1: return GL_RED_INTEGER;
		case 2: return GL_RG_INTEGER;
		case 3: return GL_RGB_INTEGER;
		case 4: return GL_RGBA_INTEGER;
	}
}

struct Range {
	GLsizei location, length;
};

static int getCircularRanges(GLsizei *start_pointer, GLsizei *end_pointer, GLsizei buffer_length, GLsizei granularity, GLsizei offset, Range *ranges)
{
	GLsizei start = *start_pointer;
	GLsizei end = *end_pointer;

	*end_pointer %= buffer_length;
	*start_pointer = *end_pointer;

	start += offset;
	end += offset;
	start -= start%granularity;
	end -= end%granularity;

	GLsizei length = end - start;
	if(!length) return 0;
	if(length >= buffer_length)
	{
		ranges[0].location = 0;
		ranges[0].length = buffer_length;
		return 1;
	}
	else
	{
		ranges[0].location = start % buffer_length;
		if(ranges[0].location + length <= buffer_length)
		{
			ranges[0].length = length;
			return 1;
		}
		else
		{
			ranges[0].length = buffer_length - ranges[0].location;
			ranges[1].location = 0;
			ranges[1].length = length - ranges[0].length;
			return 2;
		}
	}
}

static GLsizei submitArrayData(GLuint buffer, uint8_t *source, GLsizei *length_pointer)
{
	GLsizei length = *length_pointer;

	glBindBuffer(GL_ARRAY_BUFFER, buffer);
	uint8_t *data = (uint8_t *)glMapBufferRange(GL_ARRAY_BUFFER, 0, length, GL_MAP_WRITE_BIT | GL_MAP_UNSYNCHRONIZED_BIT | GL_MAP_FLUSH_EXPLICIT_BIT);
	memcpy(data, source, (size_t)length);
	glFlushMappedBufferRange(GL_ARRAY_BUFFER, 0, length);
	glUnmapBuffer(GL_ARRAY_BUFFER);

	*length_pointer = 0;

	return length;
}

using namespace Outputs::CRT;

namespace {
	static const GLenum composite_texture_unit			= GL_TEXTURE0;
	static const GLenum separated_texture_unit			= GL_TEXTURE1;
	static const GLenum filtered_y_texture_unit			= GL_TEXTURE2;
	static const GLenum filtered_texture_unit			= GL_TEXTURE3;
	static const GLenum source_data_texture_unit		= GL_TEXTURE4;
	static const GLenum pixel_accumulation_texture_unit	= GL_TEXTURE5;
}

OpenGLOutputBuilder::OpenGLOutputBuilder(unsigned int buffer_depth) :
	_output_mutex(new std::mutex),
	_visible_area(Rect(0, 0, 1, 1)),
	_composite_src_output_y(0),
	_cleared_composite_output_y(0),
	_composite_shader(nullptr),
	_rgb_shader(nullptr),
	_output_buffer_data(new uint8_t[OutputVertexBufferDataSize]),
	_source_buffer_data(new uint8_t[SourceVertexBufferDataSize]),
	_output_buffer_data_pointer(0),
	_source_buffer_data_pointer(0),
	_last_output_width(0),
	_last_output_height(0),
	_fence(nullptr)
{
	_buffer_builder = std::unique_ptr<CRTInputBufferBuilder>(new CRTInputBufferBuilder(buffer_depth));

	glBlendFunc(GL_SRC_ALPHA, GL_CONSTANT_COLOR);
	glBlendColor(0.6f, 0.6f, 0.6f, 1.0f);

	// Create intermediate textures and bind to slots 0, 1 and 2
	compositeTexture	= std::unique_ptr<OpenGL::TextureTarget>(new OpenGL::TextureTarget(IntermediateBufferWidth, IntermediateBufferHeight, composite_texture_unit));
	separatedTexture	= std::unique_ptr<OpenGL::TextureTarget>(new OpenGL::TextureTarget(IntermediateBufferWidth, IntermediateBufferHeight, separated_texture_unit));
	filteredYTexture	= std::unique_ptr<OpenGL::TextureTarget>(new OpenGL::TextureTarget(IntermediateBufferWidth, IntermediateBufferHeight, filtered_y_texture_unit));
	filteredTexture		= std::unique_ptr<OpenGL::TextureTarget>(new OpenGL::TextureTarget(IntermediateBufferWidth, IntermediateBufferHeight, filtered_texture_unit));

	// create the surce texture
	glGenTextures(1, &textureName);
	glActiveTexture(source_data_texture_unit);
	glBindTexture(GL_TEXTURE_2D, textureName);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
	glTexImage2D(GL_TEXTURE_2D, 0, internalFormatForDepth(_buffer_builder->get_bytes_per_pixel()), InputBufferBuilderWidth, InputBufferBuilderHeight, 0, formatForDepth(_buffer_builder->get_bytes_per_pixel()), GL_UNSIGNED_BYTE, nullptr);

	// create the output vertex array
	glGenVertexArrays(1, &output_vertex_array);

	// create a buffer for output vertex attributes
	glGenBuffers(1, &output_array_buffer);
	glBindBuffer(GL_ARRAY_BUFFER, output_array_buffer);
	glBufferData(GL_ARRAY_BUFFER, OutputVertexBufferDataSize, NULL, GL_STREAM_DRAW);

	// create the source vertex array
	glGenVertexArrays(1, &source_vertex_array);

	// create a buffer for source vertex attributes
	glGenBuffers(1, &source_array_buffer);
	glBindBuffer(GL_ARRAY_BUFFER, source_array_buffer);
	glBufferData(GL_ARRAY_BUFFER, SourceVertexBufferDataSize, NULL, GL_STREAM_DRAW);
}

OpenGLOutputBuilder::~OpenGLOutputBuilder()
{
	glDeleteTextures(1, &textureName);
	glDeleteBuffers(1, &output_array_buffer);
	glDeleteBuffers(1, &source_array_buffer);
	glDeleteVertexArrays(1, &output_vertex_array);

	free(_composite_shader);
	free(_rgb_shader);
}

void OpenGLOutputBuilder::draw_frame(unsigned int output_width, unsigned int output_height, bool only_if_dirty)
{
	// lock down any further work on the current frame
	_output_mutex->lock();

	// establish essentials
	if(!output_shader_program)
	{
		prepare_composite_input_shaders();
		prepare_rgb_input_shaders();
		prepare_source_vertex_array();

		prepare_output_shader();
		prepare_output_vertex_array();

		set_timing_uniforms();
		set_colour_space_uniforms();
	}

	if(_fence != nullptr)
	{
		glClientWaitSync(_fence, GL_SYNC_FLUSH_COMMANDS_BIT, GL_TIMEOUT_IGNORED);
		glDeleteSync(_fence);
	}

	// release the mapping, giving up on trying to draw if data has been lost
	GLsizei submitted_output_data = submitArrayData(output_array_buffer, _output_buffer_data.get(), &_output_buffer_data_pointer);

	// bind and flush the source array buffer
	GLsizei submitted_source_data = submitArrayData(source_array_buffer, _source_buffer_data.get(), &_source_buffer_data_pointer);

	// determine how many lines are newly reclaimed; they'll need to be cleared
	Range clearing_zones[2];

	// the clearing zones for the composite output Y are calculated with a fixed offset of '1' which has the effect of clearing
	// one ahead of the expected drawing area this frame; that's because the current _composite_src_output_y may or may not have been
	// written to during the last update, so we want it to have been cleared during the last update.
	int number_of_clearing_zones	= getCircularRanges(&_cleared_composite_output_y, &_composite_src_output_y, IntermediateBufferHeight, 1, 1, clearing_zones);
	uint16_t completed_texture_y	= _buffer_builder->get_and_finalise_current_line();

	// make sure there's a target to draw to
	if(!framebuffer || framebuffer->get_height() != output_height || framebuffer->get_width() != output_width)
	{
		std::unique_ptr<OpenGL::TextureTarget> new_framebuffer = std::unique_ptr<OpenGL::TextureTarget>(new OpenGL::TextureTarget((GLsizei)output_width, (GLsizei)output_height, pixel_accumulation_texture_unit));
		if(framebuffer)
		{
			new_framebuffer->bind_framebuffer();
			glClear(GL_COLOR_BUFFER_BIT);

			glActiveTexture(pixel_accumulation_texture_unit);
			framebuffer->bind_texture();
			framebuffer->draw((float)output_width / (float)output_height);

			new_framebuffer->bind_texture();
		}
		framebuffer = std::move(new_framebuffer);
	}

	// upload new source pixels
	if(completed_texture_y)
	{
		glActiveTexture(source_data_texture_unit);
		glTexSubImage2D(	GL_TEXTURE_2D, 0,
							0, 0,
							InputBufferBuilderWidth, completed_texture_y,
							formatForDepth(_buffer_builder->get_bytes_per_pixel()), GL_UNSIGNED_BYTE,
							_buffer_builder->get_image_pointer());
	}

	struct RenderStage {
		OpenGL::TextureTarget *const target;
		OpenGL::Shader *const shader;
		float clear_colour[3];
	};

	RenderStage composite_render_stages[] =
	{
		{compositeTexture.get(),	composite_input_shader_program.get(),				{0.0, 0.0, 0.0}},
		{separatedTexture.get(),	composite_separation_filter_program.get(),			{0.0, 0.5, 0.5}},
		{filteredYTexture.get(),	composite_y_filter_shader_program.get(),			{0.0, 0.5, 0.5}},
		{filteredTexture.get(),		composite_chrominance_filter_shader_program.get(),	{0.0, 0.0, 0.0}},
		{nullptr}
	};

	RenderStage rgb_render_stages[] =
	{
		{compositeTexture.get(),	rgb_input_shader_program.get(),		{0.0, 0.0, 0.0}},
		{filteredTexture.get(),		rgb_filter_shader_program.get(),	{0.0, 0.0, 0.0}},
		{nullptr}
	};

	RenderStage *active_pipeline = (_output_device == Television || !rgb_input_shader_program) ? composite_render_stages : rgb_render_stages;

	// for television, update intermediate buffers and then draw; for a monitor, just draw
	if(submitted_source_data)
	{
		// all drawing will be from the source vertex array and without blending
		glBindVertexArray(source_vertex_array);
		glDisable(GL_BLEND);

		while(active_pipeline->target)
		{
			// switch to the initial texture
			active_pipeline->target->bind_framebuffer();
			active_pipeline->shader->bind();

			// clear as desired
			if(number_of_clearing_zones)
			{
				glEnable(GL_SCISSOR_TEST);
				glClearColor(active_pipeline->clear_colour[0], active_pipeline->clear_colour[1], active_pipeline->clear_colour[2], 1.0);
				for(int c = 0; c < number_of_clearing_zones; c++)
				{
					glScissor(0, clearing_zones[c].location, IntermediateBufferWidth, clearing_zones[c].length);
					glClear(GL_COLOR_BUFFER_BIT);
				}
				glDisable(GL_SCISSOR_TEST);
			}

			// draw as desired
			glDrawArraysInstanced(GL_LINES, 0, 2, submitted_source_data / SourceVertexSize);

			active_pipeline++;
		}
	}

	// transfer to framebuffer
	framebuffer->bind_framebuffer();

	if(submitted_output_data)
	{
		glEnable(GL_BLEND);

		// Ensure we're back on the output framebuffer, drawing from the output array buffer
		glBindVertexArray(output_vertex_array);

		// update uniforms (implicitly binding the shader)
		if(_last_output_width != output_width || _last_output_height != output_height)
		{
			output_shader_program->set_output_size(output_width, output_height, _visible_area);
			_last_output_width = output_width;
			_last_output_height = output_height;
		}
		output_shader_program->bind();

		// draw
		glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, submitted_output_data / OutputVertexSize);
	}

	// copy framebuffer to the intended place
	glDisable(GL_BLEND);
	glBindFramebuffer(GL_FRAMEBUFFER, 0);
	glViewport(0, 0, (GLsizei)output_width, (GLsizei)output_height);
	glClear(GL_COLOR_BUFFER_BIT);

	glActiveTexture(pixel_accumulation_texture_unit);
	framebuffer->bind_texture();
	framebuffer->draw((float)output_width / (float)output_height);

	_fence = glFenceSync(GL_SYNC_GPU_COMMANDS_COMPLETE, 0);
	_output_mutex->unlock();
}

void OpenGLOutputBuilder::reset_all_OpenGL_state()
{
	composite_input_shader_program = nullptr;
	composite_separation_filter_program = nullptr;
	composite_y_filter_shader_program = nullptr;
	composite_chrominance_filter_shader_program = nullptr;
	rgb_input_shader_program = nullptr;
	rgb_filter_shader_program = nullptr;
	output_shader_program = nullptr;
	framebuffer = nullptr;
	_last_output_width = _last_output_height = 0;
}

void OpenGLOutputBuilder::set_openGL_context_will_change(bool should_delete_resources)
{
	_output_mutex->lock();
	reset_all_OpenGL_state();
	_output_mutex->unlock();
}

void OpenGLOutputBuilder::set_composite_sampling_function(const char *shader)
{
	_output_mutex->lock();
	_composite_shader = strdup(shader);
	reset_all_OpenGL_state();
	_output_mutex->unlock();
}

void OpenGLOutputBuilder::set_rgb_sampling_function(const char *shader)
{
	_output_mutex->lock();
	_rgb_shader = strdup(shader);
	reset_all_OpenGL_state();
	_output_mutex->unlock();
}

#pragma mark - Program compilation

void OpenGLOutputBuilder::prepare_composite_input_shaders()
{
	composite_input_shader_program = OpenGL::IntermediateShader::make_source_conversion_shader(_composite_shader, _rgb_shader);
	composite_input_shader_program->set_source_texture_unit(source_data_texture_unit);
	composite_input_shader_program->set_output_size(IntermediateBufferWidth, IntermediateBufferHeight);

	composite_separation_filter_program = OpenGL::IntermediateShader::make_chroma_luma_separation_shader();
	composite_separation_filter_program->set_source_texture_unit(composite_texture_unit);
	composite_separation_filter_program->set_output_size(IntermediateBufferWidth, IntermediateBufferHeight);

	composite_y_filter_shader_program = OpenGL::IntermediateShader::make_luma_filter_shader();
	composite_y_filter_shader_program->set_source_texture_unit(separated_texture_unit);
	composite_y_filter_shader_program->set_output_size(IntermediateBufferWidth, IntermediateBufferHeight);

	composite_chrominance_filter_shader_program = OpenGL::IntermediateShader::make_chroma_filter_shader();
	composite_chrominance_filter_shader_program->set_source_texture_unit(filtered_y_texture_unit);
	composite_chrominance_filter_shader_program->set_output_size(IntermediateBufferWidth, IntermediateBufferHeight);
}

void OpenGLOutputBuilder::prepare_rgb_input_shaders()
{
	if(_rgb_shader)
	{
		rgb_input_shader_program = OpenGL::IntermediateShader::make_rgb_source_shader(_rgb_shader);
		rgb_input_shader_program->set_source_texture_unit(source_data_texture_unit);
		rgb_input_shader_program->set_output_size(IntermediateBufferWidth, IntermediateBufferHeight);

		rgb_filter_shader_program = OpenGL::IntermediateShader::make_rgb_filter_shader();
		rgb_filter_shader_program->set_source_texture_unit(composite_texture_unit);
		rgb_filter_shader_program->set_output_size(IntermediateBufferWidth, IntermediateBufferHeight);
	}
}

void OpenGLOutputBuilder::prepare_source_vertex_array()
{
	if(composite_input_shader_program)
	{
		glBindVertexArray(source_vertex_array);
		glBindBuffer(GL_ARRAY_BUFFER, source_array_buffer);

		composite_input_shader_program->enable_vertex_attribute_with_pointer("inputStart", 2, GL_UNSIGNED_SHORT, GL_FALSE, SourceVertexSize, (void *)SourceVertexOffsetOfInputStart, 1);
		composite_input_shader_program->enable_vertex_attribute_with_pointer("outputStart", 2, GL_UNSIGNED_SHORT, GL_FALSE, SourceVertexSize, (void *)SourceVertexOffsetOfOutputStart, 1);
		composite_input_shader_program->enable_vertex_attribute_with_pointer("ends", 2, GL_UNSIGNED_SHORT, GL_FALSE, SourceVertexSize, (void *)SourceVertexOffsetOfEnds, 1);
		composite_input_shader_program->enable_vertex_attribute_with_pointer("phaseTimeAndAmplitude", 3, GL_UNSIGNED_BYTE, GL_FALSE, SourceVertexSize, (void *)SourceVertexOffsetOfPhaseTimeAndAmplitude, 1);
	}
}

void OpenGLOutputBuilder::prepare_output_shader()
{
	output_shader_program = OpenGL::OutputShader::make_shader("", "texture(texID, srcCoordinatesVarying).rgb", false);
	output_shader_program->set_source_texture_unit(filtered_texture_unit);
}

void OpenGLOutputBuilder::prepare_output_vertex_array()
{
	if(output_shader_program)
	{
		glBindVertexArray(output_vertex_array);
		glBindBuffer(GL_ARRAY_BUFFER, output_array_buffer);
		output_shader_program->enable_vertex_attribute_with_pointer("horizontal", 2, GL_UNSIGNED_SHORT, GL_FALSE, OutputVertexSize, (void *)OutputVertexOffsetOfHorizontal, 1);
		output_shader_program->enable_vertex_attribute_with_pointer("vertical", 2, GL_UNSIGNED_SHORT, GL_FALSE, OutputVertexSize, (void *)OutputVertexOffsetOfVertical, 1);
	}
}

#pragma mark - Public Configuration

void OpenGLOutputBuilder::set_output_device(OutputDevice output_device)
{
	if(_output_device != output_device)
	{
		_output_device = output_device;
		_composite_src_output_y = 0;
		_last_output_width = 0;
		_last_output_height = 0;
	}
}

void OpenGLOutputBuilder::set_timing(unsigned int input_frequency, unsigned int cycles_per_line, unsigned int height_of_display, unsigned int horizontal_scan_period, unsigned int vertical_scan_period, unsigned int vertical_period_divider)
{
	_output_mutex->lock();
	_input_frequency = input_frequency;
	_cycles_per_line = cycles_per_line;
	_height_of_display = height_of_display;
	_horizontal_scan_period = horizontal_scan_period;
	_vertical_scan_period = vertical_scan_period;
	_vertical_period_divider = vertical_period_divider;

	set_timing_uniforms();
	_output_mutex->unlock();
}

#pragma mark - Internal Configuration

void OpenGLOutputBuilder::set_colour_space_uniforms()
{
	GLfloat rgbToYUV[] = {0.299f, -0.14713f, 0.615f, 0.587f, -0.28886f, -0.51499f, 0.114f, 0.436f, -0.10001f};
	GLfloat yuvToRGB[] = {1.0f, 1.0f, 1.0f, 0.0f, -0.39465f, 2.03211f, 1.13983f, -0.58060f, 0.0f};

	GLfloat rgbToYIQ[] = {0.299f, 0.596f, 0.211f, 0.587f, -0.274f, -0.523f, 0.114f, -0.322f, 0.312f};
	GLfloat yiqToRGB[] = {1.0f, 1.0f, 1.0f, 0.956f, -0.272f, -1.106f, 0.621f, -0.647f, 1.703f};

	GLfloat *fromRGB, *toRGB;

	switch(_colour_space)
	{
		case ColourSpace::YIQ:
			fromRGB = rgbToYIQ;
			toRGB = yiqToRGB;
		break;

		case ColourSpace::YUV:
			fromRGB = rgbToYUV;
			toRGB = yuvToRGB;
		break;
	}

	if(composite_input_shader_program)				composite_input_shader_program->set_colour_conversion_matrices(fromRGB, toRGB);
	if(composite_chrominance_filter_shader_program) composite_chrominance_filter_shader_program->set_colour_conversion_matrices(fromRGB, toRGB);
}

void OpenGLOutputBuilder::set_timing_uniforms()
{
	OpenGL::IntermediateShader *intermediate_shaders[] = {
		composite_input_shader_program.get(),
		composite_separation_filter_program.get(),
		composite_y_filter_shader_program.get(),
		composite_chrominance_filter_shader_program.get()
	};
	bool extends = false;
	float phaseCyclesPerTick = (float)_colour_cycle_numerator / (float)(_colour_cycle_denominator * _cycles_per_line);
	for(int c = 0; c < 3; c++)
	{
		if(intermediate_shaders[c]) intermediate_shaders[c]->set_phase_cycles_per_sample(phaseCyclesPerTick, extends);
		extends = true;
	}

	if(output_shader_program) output_shader_program->set_timing(_height_of_display, _cycles_per_line, _horizontal_scan_period, _vertical_scan_period, _vertical_period_divider);

	float colour_subcarrier_frequency = (float)_colour_cycle_numerator / (float)_colour_cycle_denominator;
	if(composite_separation_filter_program)			composite_separation_filter_program->set_separation_frequency(_cycles_per_line, colour_subcarrier_frequency);
	if(composite_y_filter_shader_program)			composite_y_filter_shader_program->set_filter_coefficients(_cycles_per_line, colour_subcarrier_frequency * 0.66f);
	if(composite_chrominance_filter_shader_program)	composite_chrominance_filter_shader_program->set_filter_coefficients(_cycles_per_line, colour_subcarrier_frequency * 0.5f);
	if(rgb_filter_shader_program)					rgb_filter_shader_program->set_filter_coefficients(_cycles_per_line, (float)_input_frequency * 0.5f);
}