//
//  CRT.cpp
//  Clock Signal
//
//  Created by Thomas Harte on 19/07/2015.
//  Copyright © 2015 Thomas Harte. All rights reserved.
//

#include "CRT.hpp"
#include "CRTOpenGL.hpp"
#include <stdarg.h>
#include <math.h>
#include <algorithm>

using namespace Outputs::CRT;

void CRT::set_new_timing(unsigned int cycles_per_line, unsigned int height_of_display, ColourSpace colour_space, unsigned int colour_cycle_numerator, unsigned int colour_cycle_denominator, bool should_alternate)
{
	openGL_output_builder_.set_colour_format(colour_space, colour_cycle_numerator, colour_cycle_denominator);

	const unsigned int syncCapacityLineChargeThreshold = 2;
	const unsigned int millisecondsHorizontalRetraceTime = 7;	// source: Dictionary of Video and Television Technology, p. 234
	const unsigned int scanlinesVerticalRetraceTime = 10;		// source: ibid

																// To quote:
																//
																//	"retrace interval; The interval of time for the return of the blanked scanning beam of
																//	a TV picture tube or camera tube to the starting point of a line or field. It is about 7 µs
																//	for horizontal retrace and 500 to 750 µs for vertical retrace in NTSC and PAL TV."

	time_multiplier_ = IntermediateBufferWidth / cycles_per_line;
	phase_denominator_ = cycles_per_line * colour_cycle_denominator * time_multiplier_;
	phase_numerator_ = 0;
	colour_cycle_numerator_ = colour_cycle_numerator;
	phase_alternates_ = should_alternate;
	is_alernate_line_ &= phase_alternates_;
	unsigned int multiplied_cycles_per_line = cycles_per_line * time_multiplier_;

	// generate timing values implied by the given arbuments
	sync_capacitor_charge_threshold_ = ((int)(syncCapacityLineChargeThreshold * cycles_per_line) * 3) / 4;

	// create the two flywheels
	horizontal_flywheel_.reset(new Flywheel(multiplied_cycles_per_line, (millisecondsHorizontalRetraceTime * multiplied_cycles_per_line) >> 6, multiplied_cycles_per_line >> 6));
	vertical_flywheel_.reset(new Flywheel(multiplied_cycles_per_line * height_of_display, scanlinesVerticalRetraceTime * multiplied_cycles_per_line, (multiplied_cycles_per_line * height_of_display) >> 3));

	// figure out the divisor necessary to get the horizontal flywheel into a 16-bit range
	unsigned int real_clock_scan_period = (multiplied_cycles_per_line * height_of_display) / (time_multiplier_ * common_output_divisor_);
	vertical_flywheel_output_divider_ = (uint16_t)(ceilf(real_clock_scan_period / 65536.0f) * (time_multiplier_ * common_output_divisor_));

	openGL_output_builder_.set_timing(cycles_per_line, multiplied_cycles_per_line, height_of_display, horizontal_flywheel_->get_scan_period(), vertical_flywheel_->get_scan_period(), vertical_flywheel_output_divider_);
}

void CRT::set_new_display_type(unsigned int cycles_per_line, DisplayType displayType)
{
	switch(displayType)
	{
		case DisplayType::PAL50:
			set_new_timing(cycles_per_line, 312, ColourSpace::YUV, 709379, 2500, true);	// i.e. 283.7516
		break;

		case DisplayType::NTSC60:
			set_new_timing(cycles_per_line, 262, ColourSpace::YIQ, 455, 2, false);	// i.e. 227.5
		break;
	}
}

CRT::CRT(unsigned int common_output_divisor, unsigned int buffer_depth) :
	sync_capacitor_charge_level_(0),
	is_receiving_sync_(false),
	sync_period_(0),
	common_output_divisor_(common_output_divisor),
	is_writing_composite_run_(false),
	delegate_(nullptr),
	frames_since_last_delegate_call_(0),
	openGL_output_builder_(buffer_depth),
	is_alernate_line_(false) {}

CRT::CRT(unsigned int cycles_per_line, unsigned int common_output_divisor, unsigned int height_of_display, ColourSpace colour_space, unsigned int colour_cycle_numerator, unsigned int colour_cycle_denominator, bool should_alternate, unsigned int buffer_depth) :
	CRT(common_output_divisor, buffer_depth)
{
	set_new_timing(cycles_per_line, height_of_display, colour_space, colour_cycle_numerator, colour_cycle_denominator, should_alternate);
}

CRT::CRT(unsigned int cycles_per_line, unsigned int common_output_divisor, DisplayType displayType, unsigned int buffer_depth) :
	CRT(common_output_divisor, buffer_depth)
{
	set_new_display_type(cycles_per_line, displayType);
}

#pragma mark - Sync loop

Flywheel::SyncEvent CRT::get_next_vertical_sync_event(bool vsync_is_requested, unsigned int cycles_to_run_for, unsigned int *cycles_advanced)
{
	return vertical_flywheel_->get_next_event_in_period(vsync_is_requested, cycles_to_run_for, cycles_advanced);
}

Flywheel::SyncEvent CRT::get_next_horizontal_sync_event(bool hsync_is_requested, unsigned int cycles_to_run_for, unsigned int *cycles_advanced)
{
	return horizontal_flywheel_->get_next_event_in_period(hsync_is_requested, cycles_to_run_for, cycles_advanced);
}

#define output_x1()			(*(uint16_t *)&next_run[OutputVertexOffsetOfHorizontal + 0])
#define output_x2()			(*(uint16_t *)&next_run[OutputVertexOffsetOfHorizontal + 2])
#define output_position_y()	(*(uint16_t *)&next_run[OutputVertexOffsetOfVertical + 0])
#define output_tex_y()		(*(uint16_t *)&next_run[OutputVertexOffsetOfVertical + 2])

#define source_input_position_x1()	(*(uint16_t *)&next_run[SourceVertexOffsetOfInputStart + 0])
#define source_input_position_y()	(*(uint16_t *)&next_run[SourceVertexOffsetOfInputStart + 2])
#define source_input_position_x2()	(*(uint16_t *)&next_run[SourceVertexOffsetOfEnds + 0])
#define source_output_position_x1()	(*(uint16_t *)&next_run[SourceVertexOffsetOfOutputStart + 0])
#define source_output_position_y()	(*(uint16_t *)&next_run[SourceVertexOffsetOfOutputStart + 2])
#define source_output_position_x2()	(*(uint16_t *)&next_run[SourceVertexOffsetOfEnds + 2])
#define source_phase()				next_run[SourceVertexOffsetOfPhaseTimeAndAmplitude + 0]
#define source_amplitude()			next_run[SourceVertexOffsetOfPhaseTimeAndAmplitude + 2]

void CRT::advance_cycles(unsigned int number_of_cycles, bool hsync_requested, bool vsync_requested, const Scan::Type type)
{
	std::unique_lock<std::mutex> output_lock = openGL_output_builder_.get_output_lock();
	number_of_cycles *= time_multiplier_;

	bool is_output_run = ((type == Scan::Type::Level) || (type == Scan::Type::Data));

	while(number_of_cycles) {

		unsigned int time_until_vertical_sync_event, time_until_horizontal_sync_event;
		Flywheel::SyncEvent next_vertical_sync_event = get_next_vertical_sync_event(vsync_requested, number_of_cycles, &time_until_vertical_sync_event);
		Flywheel::SyncEvent next_horizontal_sync_event = get_next_horizontal_sync_event(hsync_requested, time_until_vertical_sync_event, &time_until_horizontal_sync_event);

		// get the next sync event and its timing; hsync request is instantaneous (being edge triggered) so
		// set it to false for the next run through this loop (if any)
		unsigned int next_run_length = std::min(time_until_vertical_sync_event, time_until_horizontal_sync_event);
		phase_numerator_ += next_run_length * colour_cycle_numerator_;
		phase_numerator_ %= phase_denominator_;

		hsync_requested = false;
		vsync_requested = false;

		bool is_output_segment = ((is_output_run && next_run_length) && !horizontal_flywheel_->is_in_retrace() && !vertical_flywheel_->is_in_retrace());
		uint8_t *next_run = nullptr;
		if(is_output_segment && !openGL_output_builder_.composite_output_buffer_is_full())
		{
			next_run = openGL_output_builder_.array_builder.get_input_storage(SourceVertexSize);
		}

		if(next_run)
		{
			// output_y and texture locations will be written later; we won't necessarily know what it is outside of the locked region
			source_output_position_x1() = (uint16_t)horizontal_flywheel_->get_current_output_position();
			source_phase() = colour_burst_phase_;
			source_amplitude() = colour_burst_amplitude_;
		}

		// decrement the number of cycles left to run for and increment the
		// horizontal counter appropriately
		number_of_cycles -= next_run_length;

		// react to the incoming event...
		horizontal_flywheel_->apply_event(next_run_length, (next_run_length == time_until_horizontal_sync_event) ? next_horizontal_sync_event : Flywheel::SyncEvent::None);
		vertical_flywheel_->apply_event(next_run_length, (next_run_length == time_until_vertical_sync_event) ? next_vertical_sync_event : Flywheel::SyncEvent::None);

		if(next_run)
		{
			source_output_position_x2() = (uint16_t)horizontal_flywheel_->get_current_output_position();
		}

		// if this is horizontal retrace then advance the output line counter and bookend an output run
		Flywheel::SyncEvent honoured_event = Flywheel::SyncEvent::None;
		if(next_run_length == time_until_vertical_sync_event && next_vertical_sync_event != Flywheel::SyncEvent::None) honoured_event = next_vertical_sync_event;
		if(next_run_length == time_until_horizontal_sync_event && next_horizontal_sync_event != Flywheel::SyncEvent::None) honoured_event = next_horizontal_sync_event;
		bool needs_endpoint =
			(honoured_event == Flywheel::SyncEvent::StartRetrace && is_writing_composite_run_) ||
			(honoured_event == Flywheel::SyncEvent::EndRetrace && !horizontal_flywheel_->is_in_retrace() && !vertical_flywheel_->is_in_retrace());

		if(next_run_length == time_until_horizontal_sync_event && next_horizontal_sync_event == Flywheel::SyncEvent::StartRetrace) is_alernate_line_ ^= phase_alternates_;

		if(needs_endpoint)
		{
			if(
				!openGL_output_builder_.array_builder.is_full() &&
				!openGL_output_builder_.composite_output_buffer_is_full())
			{
				if(!is_writing_composite_run_)
				{
					output_run_.x1 = (uint16_t)horizontal_flywheel_->get_current_output_position();
					output_run_.y = (uint16_t)(vertical_flywheel_->get_current_output_position() / vertical_flywheel_output_divider_);
				}
				else
				{
					// Get and write all those previously unwritten output ys
					const uint16_t output_y = openGL_output_builder_.get_composite_output_y();

					// Construct the output run
					uint8_t *next_run = openGL_output_builder_.array_builder.get_output_storage(OutputVertexSize);
					if(next_run)
					{
						output_x1() = output_run_.x1;
						output_position_y() = output_run_.y;
						output_tex_y() = output_y;
						output_x2() = (uint16_t)horizontal_flywheel_->get_current_output_position();
					}
					openGL_output_builder_.array_builder.flush(
						[output_y, this] (uint8_t *input_buffer, size_t input_size, uint8_t *output_buffer, size_t output_size)
						{
							openGL_output_builder_.texture_builder.flush(
								[output_y, input_buffer] (const std::vector<TextureBuilder::WriteArea> &write_areas, size_t number_of_write_areas)
								{
									for(size_t run = 0; run < number_of_write_areas; run++)
									{
										*(uint16_t *)&input_buffer[run * SourceVertexSize + SourceVertexOffsetOfInputStart + 0] = write_areas[run].x;
										*(uint16_t *)&input_buffer[run * SourceVertexSize + SourceVertexOffsetOfInputStart + 2] = write_areas[run].y;
										*(uint16_t *)&input_buffer[run * SourceVertexSize + SourceVertexOffsetOfEnds + 0] = write_areas[run].x + write_areas[run].length;
									}
								});
							for(size_t position = 0; position < input_size; position += SourceVertexSize)
							{
								(*(uint16_t *)&input_buffer[position + SourceVertexOffsetOfOutputStart + 2]) = output_y;
							}
						});
					colour_burst_amplitude_ = 0;
				}
				is_writing_composite_run_ ^= true;
			}
		}

		if(next_run_length == time_until_horizontal_sync_event && next_horizontal_sync_event == Flywheel::SyncEvent::StartRetrace)
		{
			openGL_output_builder_.increment_composite_output_y();
		}

		// if this is vertical retrace then adcance a field
		if(next_run_length == time_until_vertical_sync_event && next_vertical_sync_event == Flywheel::SyncEvent::EndRetrace)
		{
			if(delegate_)
			{
				frames_since_last_delegate_call_++;
				if(frames_since_last_delegate_call_ == 20)
				{
					output_lock.unlock();
					delegate_->crt_did_end_batch_of_frames(this, frames_since_last_delegate_call_, vertical_flywheel_->get_and_reset_number_of_surprises());
					output_lock.lock();
					frames_since_last_delegate_call_ = 0;
				}
			}
		}
	}
}

#undef output_x1
#undef output_x2
#undef output_position_y
#undef output_tex_y

#undef source_input_position_x1
#undef source_input_position_y
#undef source_input_position_x2
#undef source_output_position_x1
#undef source_output_position_y
#undef source_output_position_x2
#undef source_phase
#undef source_amplitude
#undef source_phase_time

#pragma mark - stream feeding methods

void CRT::output_scan(const Scan *const scan)
{
	const bool this_is_sync = (scan->type == Scan::Type::Sync);
	const bool is_trailing_edge = (is_receiving_sync_ && !this_is_sync);
	const bool is_leading_edge = (!is_receiving_sync_ && this_is_sync);
	is_receiving_sync_ = this_is_sync;

	// This introduces a blackout period close to the expected vertical sync point in which horizontal syncs are not
	// recognised, effectively causing the horizontal flywheel to freewheel during that period. This attempts to seek
	// the problem that vertical sync otherwise often starts halfway through a scanline, which confuses the horizontal
	// flywheel. I'm currently unclear whether this is an accurate solution to this problem.
	const bool hsync_requested = is_leading_edge && !vertical_flywheel_->is_near_expected_sync();
	const bool vsync_requested = is_trailing_edge && (sync_capacitor_charge_level_ >= sync_capacitor_charge_threshold_);

	// simplified colour burst logic: if it's within the back porch we'll take it
	if(scan->type == Scan::Type::ColourBurst)
	{
		if(!colour_burst_amplitude_ && horizontal_flywheel_->get_current_time() < (horizontal_flywheel_->get_standard_period() * 12) >> 6)
		{
			unsigned int position_phase = (horizontal_flywheel_->get_current_time() * colour_cycle_numerator_ * 256) / phase_denominator_;
			colour_burst_phase_ = (position_phase + scan->phase) & 255;
			colour_burst_amplitude_ = scan->amplitude;

			colour_burst_phase_ = (colour_burst_phase_ & ~63) + 32;
		}
	}

	// TODO: inspect raw data for potential colour burst if required

	sync_period_ = is_receiving_sync_ ? (sync_period_ + scan->number_of_cycles) : 0;
	advance_cycles(scan->number_of_cycles, hsync_requested, vsync_requested, scan->type);

	// either charge or deplete the vertical retrace capacitor (making sure it stops at 0)
	if(this_is_sync)
		sync_capacitor_charge_level_ += scan->number_of_cycles;
	else
		sync_capacitor_charge_level_ = std::max(sync_capacitor_charge_level_ - (int)scan->number_of_cycles, 0);
}

/*
	These all merely channel into advance_cycles, supplying appropriate arguments
*/
void CRT::output_sync(unsigned int number_of_cycles)
{
	Scan scan{
		.type = Scan::Type::Sync,
		.number_of_cycles = number_of_cycles
	};
	output_scan(&scan);
}

void CRT::output_blank(unsigned int number_of_cycles)
{
	Scan scan {
		.type = Scan::Type::Blank,
		.number_of_cycles = number_of_cycles
	};
	output_scan(&scan);
}

void CRT::output_level(unsigned int number_of_cycles)
{
	Scan scan {
		.type = Scan::Type::Level,
		.number_of_cycles = number_of_cycles,
	};
	output_scan(&scan);
}

void CRT::output_colour_burst(unsigned int number_of_cycles, uint8_t phase, uint8_t amplitude)
{
	Scan scan {
		.type = Scan::Type::ColourBurst,
		.number_of_cycles = number_of_cycles,
		.phase = phase,
		.amplitude = amplitude
	};
	output_scan(&scan);
}

void CRT::output_default_colour_burst(unsigned int number_of_cycles)
{
	Scan scan {
		.type = Scan::Type::ColourBurst,
		.number_of_cycles = number_of_cycles,
		.phase = (uint8_t)((phase_numerator_ * 256) / phase_denominator_ + (is_alernate_line_ ? 128 : 0)),
		.amplitude = 32
	};
	output_scan(&scan);
}

void CRT::output_data(unsigned int number_of_cycles, unsigned int source_divider)
{
	openGL_output_builder_.texture_builder.reduce_previous_allocation_to(number_of_cycles / source_divider);
	Scan scan {
		.type = Scan::Type::Data,
		.number_of_cycles = number_of_cycles,
	};
	output_scan(&scan);
}

Outputs::CRT::Rect CRT::get_rect_for_area(int first_line_after_sync, int number_of_lines, int first_cycle_after_sync, int number_of_cycles, float aspect_ratio)
{
	first_cycle_after_sync *= time_multiplier_;
	number_of_cycles *= time_multiplier_;

	first_line_after_sync -= 2;
	number_of_lines += 4;

	// determine prima facie x extent
	unsigned int horizontal_period = horizontal_flywheel_->get_standard_period();
	unsigned int horizontal_scan_period = horizontal_flywheel_->get_scan_period();
	unsigned int horizontal_retrace_period = horizontal_period - horizontal_scan_period;

	// make sure that the requested range is visible
	if(first_cycle_after_sync < horizontal_retrace_period) first_cycle_after_sync = (int)horizontal_retrace_period;
	if(first_cycle_after_sync + number_of_cycles > horizontal_scan_period) number_of_cycles = (int)(horizontal_scan_period - (unsigned)first_cycle_after_sync);

	float start_x = (float)((unsigned)first_cycle_after_sync - horizontal_retrace_period) / (float)horizontal_scan_period;
	float width = (float)number_of_cycles / (float)horizontal_scan_period;

	// determine prima facie y extent
	unsigned int vertical_period = vertical_flywheel_->get_standard_period();
	unsigned int vertical_scan_period = vertical_flywheel_->get_scan_period();
	unsigned int vertical_retrace_period = vertical_period - vertical_scan_period;

	// make sure that the requested range is visible
//	if((unsigned)first_line_after_sync * horizontal_period < vertical_retrace_period)
//		first_line_after_sync = (vertical_retrace_period + horizontal_period - 1) / horizontal_period;
//	if((first_line_after_sync + number_of_lines) * horizontal_period > vertical_scan_period)
//		number_of_lines = (int)(horizontal_scan_period - (unsigned)first_cycle_after_sync);

	float start_y = (float)(((unsigned)first_line_after_sync * horizontal_period) - vertical_retrace_period) / (float)vertical_scan_period;
	float height = (float)((unsigned)number_of_lines * horizontal_period) / vertical_scan_period;

	// adjust to ensure aspect ratio is correct
	float adjusted_aspect_ratio = (3.0f*aspect_ratio / 4.0f);
	float ideal_width = height * adjusted_aspect_ratio;
	if(ideal_width > width)
	{
		start_x -= (ideal_width - width) * 0.5f;
		width = ideal_width;
	}
	else
	{
		float ideal_height = width / adjusted_aspect_ratio;
		start_y -= (ideal_height - height) * 0.5f;
		height = ideal_height;
	}

	return Rect(start_x, start_y, width, height);
}