//
//  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 <cstdarg>
#include <cmath>
#include <algorithm>
#include <cassert>

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, unsigned int vertical_sync_half_lines, bool should_alternate) {
	openGL_output_builder_.set_colour_format(colour_space, colour_cycle_numerator, colour_cycle_denominator);

	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_;
	cycles_per_line_ = cycles_per_line;
	unsigned int multiplied_cycles_per_line = cycles_per_line * time_multiplier_;

	// allow sync to be detected (and acted upon) a line earlier than the specified requirement,
	// as a simple way of avoiding not-quite-exact comparison issues while still being true enough to
	// the gist for simple debugging
	sync_capacitor_charge_threshold_ = ((vertical_sync_half_lines - 2) * cycles_per_line) >> 1;

	// 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, 5, true);	// i.e. 283.7516; 2.5 lines = vertical sync
			set_input_gamma(2.8f);
		break;

		case DisplayType::NTSC60:
			set_new_timing(cycles_per_line, 262, ColourSpace::YIQ, 455, 2, 6, false);	// i.e. 227.5, 3 lines = vertical sync
			set_input_gamma(2.2f);
		break;
	}
}

void CRT::set_composite_function_type(CompositeSourceType type, float offset_of_first_sample) {
	if(type == DiscreteFourSamplesPerCycle) {
		colour_burst_phase_adjustment_ = (uint8_t)(offset_of_first_sample * 256.0f) & 63;
	} else {
		colour_burst_phase_adjustment_ = 0xff;
	}
}

void CRT::set_input_gamma(float gamma) {
	input_gamma_ = gamma;
	update_gamma();
}

void CRT::set_output_gamma(float gamma) {
	output_gamma_ = gamma;
	update_gamma();
}

void CRT::update_gamma() {
	float gamma_ratio = input_gamma_ / output_gamma_;
	openGL_output_builder_.set_gamma(gamma_ratio);
}

CRT::CRT(unsigned int common_output_divisor, unsigned int buffer_depth) :
	is_receiving_sync_(false),
	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,
			unsigned int vertical_sync_half_lines,
			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, vertical_sync_half_lines, 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_output_run[OutputVertexOffsetOfHorizontal + 0])
#define output_x2()			(*(uint16_t *)&next_output_run[OutputVertexOffsetOfHorizontal + 2])
#define output_position_y()	(*(uint16_t *)&next_output_run[OutputVertexOffsetOfVertical + 0])
#define output_tex_y()		(*(uint16_t *)&next_output_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 + 1]

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()) {
			bool did_retain_source_data = openGL_output_builder_.texture_builder.retain_latest();
			if(did_retain_source_data) {
				next_run = openGL_output_builder_.array_builder.get_input_storage(SourceVertexSize);
				if(!next_run) {
					openGL_output_builder_.texture_builder.discard_latest();
				}
			}
		}

		if(next_run) {
			// output_y and texture locations will be written later; we won't necessarily know what they are
			// 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_output_run = openGL_output_builder_.array_builder.get_output_storage(OutputVertexSize);
					if(next_output_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(
						[=] (uint8_t *input_buffer, size_t input_size, uint8_t *output_buffer, size_t output_size) {
							openGL_output_builder_.texture_builder.flush(
								[=] (const std::vector<TextureBuilder::WriteArea> &write_areas, size_t number_of_write_areas) {
									assert(number_of_write_areas * SourceVertexSize == input_size);
									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) {
	// 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;

			if(colour_burst_phase_adjustment_ != 0xff)
				colour_burst_phase_ = (colour_burst_phase_ & ~63) + colour_burst_phase_adjustment_;
		}
	}
	// TODO: inspect raw data for potential colour burst if required; the DPLL and some zero crossing logic
	// will probably be sufficient but some test data would be helpful

	// sync logic: mark whether this is currently sync and check for a leading edge
	const bool this_is_sync = (scan->type == Scan::Type::Sync);
	const bool is_leading_edge = (!is_receiving_sync_ && this_is_sync);
	is_receiving_sync_ = this_is_sync;

	// horizontal sync is recognised on any leading edge that is not 'near' the expected vertical sync;
	// the second limb is to avoid slightly horizontal sync shifting from the common pattern of
	// equalisation pulses as the inverse of ordinary horizontal sync
	bool hsync_requested = is_leading_edge && !vertical_flywheel_->is_near_expected_sync();

	if(this_is_sync) {
		// if this is sync then either begin or continue a sync accumulation phase
		is_accumulating_sync_ = true;
		cycles_since_sync_ = 0;
	} else {
		// if this is not sync then check how long it has been since sync. If it's more than
		// half a line then end sync accumulation and zero out the accumulating count
		cycles_since_sync_ += scan->number_of_cycles;
		if(cycles_since_sync_ > (cycles_per_line_ >> 2)) {
			cycles_of_sync_ = 0;
			is_accumulating_sync_ = false;
			is_refusing_sync_ = false;
		}
	}

	unsigned int number_of_cycles = scan->number_of_cycles;
	bool vsync_requested = false;

	// if sync is being accumulated then accumulate it; if it crosses the vertical sync threshold then
	// divide this line at the crossing point and indicate vertical sync there
	if(is_accumulating_sync_ && !is_refusing_sync_) {
		cycles_of_sync_ += scan->number_of_cycles;

		if(this_is_sync && cycles_of_sync_ >= sync_capacitor_charge_threshold_) {
			unsigned int overshoot = std::min(cycles_of_sync_ - sync_capacitor_charge_threshold_, number_of_cycles);
			if(overshoot) {
				number_of_cycles -= overshoot;
				advance_cycles(number_of_cycles, hsync_requested, false, scan->type);
				hsync_requested = false;
				number_of_cycles = overshoot;
			}

			is_refusing_sync_ = true;
			vsync_requested = true;
		}
	}

	advance_cycles(number_of_cycles, hsync_requested, vsync_requested, scan->type);
}

/*
	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) {
	openGL_output_builder_.texture_builder.reduce_previous_allocation_to(1);
	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) {
	output_colour_burst(number_of_cycles, (uint8_t)((phase_numerator_ * 256) / phase_denominator_ + (is_alernate_line_ ? 128 : 0)));
}

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((unsigned int)first_cycle_after_sync < horizontal_retrace_period) first_cycle_after_sync = (int)horizontal_retrace_period;
	if((unsigned int)(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);
}
