CLK/Components/6560/6560.hpp

//
//  6560.hpp
//  Clock Signal
//
//  Created by Thomas Harte on 05/06/2016.
//  Copyright 2016 Thomas Harte. All rights reserved.
//

#pragma once

#include "../../ClockReceiver/ClockReceiver.hpp"
#include "../../Concurrency/AsyncTaskQueue.hpp"
#include "../../Outputs/CRT/CRT.hpp"
#include "../../Outputs/Speaker/Implementation/LowpassSpeaker.hpp"
#include "../../Outputs/Speaker/Implementation/BufferSource.hpp"

namespace MOS::MOS6560 {

// audio state
class AudioGenerator: public Outputs::Speaker::BufferSource<AudioGenerator, false> {
public:
	AudioGenerator(Concurrency::AsyncTaskQueue<false> &audio_queue);

	void set_volume(uint8_t);
	void set_control(int channel, uint8_t value);

	// For ::SampleSource.
	template <Outputs::Speaker::Action action>
		void apply_samples(std::size_t number_of_samples, Outputs::Speaker::MonoSample *target);
	void set_sample_volume_range(std::int16_t);

private:
	Concurrency::AsyncTaskQueue<false> &audio_queue_;

	unsigned int counters_[4] = {2, 1, 0, 0};	// create a slight phase offset for the three channels
	unsigned int shift_registers_[4] = {0, 0, 0, 0};
	uint8_t control_registers_[4] = {0, 0, 0, 0};
	int16_t volume_ = 0;
	int16_t dc_offset_ = 0;
	int16_t range_multiplier_ = 1;
};

struct BusHandler {
	void perform_read(uint16_t, uint8_t *const pixel_data, uint8_t *const colour_data) {
		*pixel_data = 0xff;
		*colour_data = 0xff;
	}
};

enum class OutputMode {
	PAL, NTSC
};

/*!
	The 6560 Video Interface Chip ('VIC') is a video and audio output chip; it therefore vends both a @c CRT and a @c Speaker.

	To run the VIC for a cycle, the caller should call @c get_address, make the requested bus access
	and call @c set_graphics_value with the result.

	@c write and @c read provide register access.
*/
template <class BusHandler> class MOS6560 {
public:
	MOS6560(BusHandler &bus_handler) :
			bus_handler_(bus_handler),
			crt_(65*4, 1, Outputs::Display::Type::NTSC60, Outputs::Display::InputDataType::Luminance8Phase8),
			audio_generator_(audio_queue_),
			speaker_(audio_generator_)
	{
		// default to s-video output
		crt_.set_display_type(Outputs::Display::DisplayType::SVideo);

		// default to NTSC
		set_output_mode(OutputMode::NTSC);
	}

	~MOS6560() {
		audio_queue_.flush();
	}

	void set_clock_rate(const double clock_rate) {
		speaker_.set_input_rate(float(clock_rate / 4.0));
	}

	void set_scan_target(Outputs::Display::ScanTarget *const scan_target) {
		crt_.set_scan_target(scan_target);
	}
	Outputs::Display::ScanStatus get_scaled_scan_status() const {
		return crt_.get_scaled_scan_status() / 4.0f;
	}
	void set_display_type(const Outputs::Display::DisplayType display_type) {
		crt_.set_display_type(display_type);
	}
	Outputs::Display::DisplayType get_display_type() const {
		return crt_.get_display_type();
	}
	Outputs::Speaker::Speaker *get_speaker() {
		return &speaker_;
	}

	void set_high_frequency_cutoff(const float cutoff) {
		speaker_.set_high_frequency_cutoff(cutoff);
	}

	/*!
		Sets the output mode to either PAL or NTSC.
	*/
	void set_output_mode(const OutputMode output_mode) {
		output_mode_ = output_mode;

		// Luminances are encoded trivially: on a 0-255 scale.
		const uint8_t luminances[16] = {
			0,		255,	64,		192,
			128,	128,	64,		192,
			128,	192,	128,	255,
			192,	192,	128,	255
		};

		// Chrominances are encoded such that 0-128 is a complete revolution of phase;
		// anything above 191 disables the colour subcarrier. Phase is relative to the
		// colour burst, so 0 is green (NTSC) or blue/violet (PAL).
		const uint8_t pal_chrominances[16] = {
			255,	255,	90,		20,
			96,		42,		8,		72,
			84,		90,		90,		20,
			96,		42,		8,		72,
		};
		const uint8_t ntsc_chrominances[16] = {
			255,	255,	121,	57,
			103,	42,		80,		16,
			0,		9,		121,	57,
			103,	42,		80,		16,
		};
		const uint8_t *chrominances;
		Outputs::Display::Type display_type;

		switch(output_mode) {
			default:
				chrominances = pal_chrominances;
				display_type = Outputs::Display::Type::PAL50;
				timing_.cycles_per_line = 71;
				timing_.line_counter_increment_offset = 4;
				timing_.final_line_increment_position =
					timing_.cycles_per_line - timing_.line_counter_increment_offset;
				timing_.lines_per_progressive_field = 312;
				timing_.supports_interlacing = false;
			break;

			case OutputMode::NTSC:
				chrominances = ntsc_chrominances;
				display_type = Outputs::Display::Type::NTSC60;
				timing_.cycles_per_line = 65;
				timing_.line_counter_increment_offset = 40;
				timing_.final_line_increment_position = 58;
				timing_.lines_per_progressive_field = 261;
				timing_.supports_interlacing = true;
			break;
		}

		crt_.set_new_display_type(timing_.cycles_per_line*4, display_type);

		switch(output_mode) {
			case OutputMode::PAL:
				crt_.set_visible_area(Outputs::Display::Rect(0.1f, 0.07f, 0.9f, 0.9f));
			break;
			case OutputMode::NTSC:
				crt_.set_visible_area(Outputs::Display::Rect(0.05f, 0.05f, 0.9f, 0.9f));
			break;
		}

		for(int c = 0; c < 16; c++) {
			uint8_t *colour = reinterpret_cast<uint8_t *>(&colours_[c]);
			colour[0] = luminances[c];
			colour[1] = chrominances[c];
		}
	}

	/*!
		Runs for cycles. Derr.
	*/
	inline void run_for(const Cycles cycles) {
		// keep track of the amount of time since the speaker was updated; lazy updates are applied
		cycles_since_speaker_update_ += cycles;

		auto number_of_cycles = cycles.as_integral();
		while(number_of_cycles--) {
			// keep an old copy of the vertical count because that test is a cycle later than the actual changes
			int previous_vertical_counter = vertical_counter_;

			// keep track of internal time relative to this scanline
			++horizontal_counter_;
			if(horizontal_counter_ == timing_.cycles_per_line) {
				if(horizontal_drawing_latch_) {
					++current_character_row_;
					if(
						(current_character_row_ == 16) ||
						(current_character_row_ == 8 && !registers_.tall_characters)
					) {
						current_character_row_ = 0;
						++current_row_;
					}

					pixel_line_cycle_ = -1;
					columns_this_line_ = -1;
					column_counter_ = -1;
				}

				horizontal_counter_ = 0;
				if(output_mode_ == OutputMode::PAL) is_odd_line_ ^= true;
				horizontal_drawing_latch_ = false;

				++vertical_counter_;
				if(vertical_counter_ == lines_this_field()) {
					vertical_counter_ = 0;

					if(output_mode_ == OutputMode::NTSC) is_odd_frame_ ^= true;
					current_row_ = 0;
					rows_this_field_ = -1;
					vertical_drawing_latch_ = false;
					base_video_matrix_address_counter_ = 0;
					current_character_row_ = 0;
				}
			}

			// check for vertical starting events
			vertical_drawing_latch_ |= registers_.first_row_location == (previous_vertical_counter >> 1);
			horizontal_drawing_latch_ |=
				vertical_drawing_latch_ && (horizontal_counter_ == registers_.first_column_location);

			if(pixel_line_cycle_ >= 0) ++pixel_line_cycle_;
			switch(pixel_line_cycle_) {
				case -1:
					if(horizontal_drawing_latch_) {
						pixel_line_cycle_ = 0;
						video_matrix_address_counter_ = base_video_matrix_address_counter_;
					}
				break;
				case 1:	columns_this_line_ = registers_.number_of_columns;	break;
				case 2:	if(rows_this_field_ < 0) rows_this_field_ = registers_.number_of_rows;	break;
				case 3: if(current_row_ < rows_this_field_) column_counter_ = 0;	break;
			}

			uint16_t fetch_address = 0x1c;
			if(column_counter_ >= 0 && column_counter_ < columns_this_line_*2) {
				if(column_counter_&1) {
					fetch_address =
						registers_.character_cell_start_address +
						(character_code_*(registers_.tall_characters ? 16 : 8)) +
						current_character_row_;
				} else {
					fetch_address = uint16_t(registers_.video_matrix_start_address + video_matrix_address_counter_);
					++video_matrix_address_counter_;
					if(
						(current_character_row_ == 15) ||
						(current_character_row_ == 7 && !registers_.tall_characters)
					) {
						base_video_matrix_address_counter_ = video_matrix_address_counter_;
					}
				}
			}

			fetch_address &= 0x3fff;

			uint8_t pixel_data;
			uint8_t colour_data;
			bus_handler_.perform_read(fetch_address, &pixel_data, &colour_data);

			// TODO: there should be a further two-cycle delay on pixels being output; the reverse bit should
			// divide the byte it is set for 3:1 and then continue as usual.

			// determine output state; colour burst and sync timing are currently a guess
			State this_state;
			if(horizontal_counter_ > timing_.cycles_per_line-4) this_state = State::ColourBurst;
			else if(horizontal_counter_ > timing_.cycles_per_line-7) this_state = State::Sync;
			else {
				this_state = (column_counter_ >= 0 && column_counter_ < columns_this_line_*2) ?
					State::Pixels : State::Border;
			}

			// apply vertical sync
			if(
				(vertical_counter_ < 3 && is_odd_frame()) ||
				(registers_.interlaced &&
					(
						(vertical_counter_ == 0 && horizontal_counter_ > 32) ||
						(vertical_counter_ == 1) || (vertical_counter_ == 2) ||
						(vertical_counter_ == 3 && horizontal_counter_ <= 32)
					)
				))
				this_state = State::Sync;

			// update the CRT
			if(this_state != output_state_) {
				switch(output_state_) {
					case State::Sync:
						crt_.output_sync(cycles_in_state_ * 4);
					break;
					case State::ColourBurst:
						crt_.output_colour_burst(cycles_in_state_ * 4, (is_odd_frame_ || is_odd_line_) ? 128 : 0);
					break;
					case State::Border:
						crt_.output_level<uint16_t>(cycles_in_state_ * 4, registers_.border_colour);
					break;
					case State::Pixels:
						crt_.output_data(cycles_in_state_ * 4);
					break;
				}
				output_state_ = this_state;
				cycles_in_state_ = 0;

				pixel_pointer = nullptr;
				if(output_state_ == State::Pixels) {
					pixel_pointer = reinterpret_cast<uint16_t *>(crt_.begin_data(260));
				}
			}
			++cycles_in_state_;

			if(output_state_ == State::Pixels) {
				// TODO: palette changes can happen within half-characters; the below needs to be divided.
				// Also: a perfect opportunity to rearrange this inner loop for no longer needing to be
				// two parts with a cooperative owner?
				if(column_counter_&1) {
					character_value_ = pixel_data;

					if(pixel_pointer) {
						const uint16_t cell_colour = colours_[character_colour_ & 0x7];
						if(!(character_colour_&0x8)) {
							uint16_t colours[2];
							if(registers_.invertedCells) {
								colours[0] = cell_colour;
								colours[1] = registers_.background_colour;
							} else {
								colours[0] = registers_.background_colour;
								colours[1] = cell_colour;
							}
							pixel_pointer[0] = colours[(character_value_ >> 7)&1];
							pixel_pointer[1] = colours[(character_value_ >> 6)&1];
							pixel_pointer[2] = colours[(character_value_ >> 5)&1];
							pixel_pointer[3] = colours[(character_value_ >> 4)&1];
							pixel_pointer[4] = colours[(character_value_ >> 3)&1];
							pixel_pointer[5] = colours[(character_value_ >> 2)&1];
							pixel_pointer[6] = colours[(character_value_ >> 1)&1];
							pixel_pointer[7] = colours[(character_value_ >> 0)&1];
						} else {
							const uint16_t colours[4] = {
								registers_.background_colour,
								registers_.border_colour,
								cell_colour,
								registers_.auxiliary_colour
							};
							pixel_pointer[0] =
							pixel_pointer[1] = colours[(character_value_ >> 6)&3];
							pixel_pointer[2] =
							pixel_pointer[3] = colours[(character_value_ >> 4)&3];
							pixel_pointer[4] =
							pixel_pointer[5] = colours[(character_value_ >> 2)&3];
							pixel_pointer[6] =
							pixel_pointer[7] = colours[(character_value_ >> 0)&3];
						}

						pixel_pointer += 8;
					}
				} else {
					character_code_ = pixel_data;
					character_colour_ = colour_data;
				}
			}

			// Keep counting columns even if sync or the colour burst have interceded.
			if(column_counter_ >= 0 && column_counter_ < columns_this_line_*2) {
				++column_counter_;
			}
		}
	}

	/*!
		Causes the 6560 to flush as much pending CRT and speaker communications as possible.
	*/
	inline void flush() {
		update_audio();
		audio_queue_.perform();
	}

	/*!
		Writes to a 6560 register.
	*/
	void write(int address, const uint8_t value) {
		address &= 0xf;
		registers_.direct_values[address] = value;
		switch(address) {
			case 0x0:
				registers_.interlaced = !!(value&0x80) && timing_.supports_interlacing;
				registers_.first_column_location = value & 0x7f;
			break;

			case 0x1:
				registers_.first_row_location = value;
			break;

			case 0x2:
				registers_.number_of_columns = value & 0x7f;
				registers_.video_matrix_start_address = uint16_t(
					(registers_.video_matrix_start_address & 0x3c00) | ((value & 0x80) << 2)
				);
			break;

			case 0x3:
				registers_.number_of_rows = (value >> 1)&0x3f;
				registers_.tall_characters = !!(value&0x01);
			break;

			case 0x5:
				registers_.character_cell_start_address = uint16_t((value & 0x0f) << 10);
				registers_.video_matrix_start_address = uint16_t(
					(registers_.video_matrix_start_address & 0x0200) | ((value & 0xf0) << 6)
				);
			break;

			case 0xa:
			case 0xb:
			case 0xc:
			case 0xd:
				update_audio();
				audio_generator_.set_control(address - 0xa, value);
			break;

			case 0xe:
				update_audio();
				registers_.auxiliary_colour = colours_[value >> 4];
				audio_generator_.set_volume(value & 0xf);
			break;

			case 0xf: {
				const uint16_t new_border_colour = colours_[value & 0x07];
				if(new_border_colour != registers_.border_colour) {
					if(output_state_ == State::Border) {
						crt_.output_level<uint16_t>(cycles_in_state_ * 4, registers_.border_colour);
						cycles_in_state_ = 0;
					}
					registers_.border_colour = new_border_colour;
				}
				registers_.invertedCells = !((value >> 3)&1);
				registers_.background_colour = colours_[value >> 4];
			}
			break;

			// TODO: the lightpen, etc

			default:
			break;
		}
	}

	/*
		Reads from a 6560 register.
	*/
	uint8_t read(int address) const {
		address &= 0xf;
		switch(address) {
			default: return registers_.direct_values[address];
			case 0x03: return uint8_t(raster_value() << 7) | (registers_.direct_values[3] & 0x7f);
			case 0x04: return (raster_value() >> 1) & 0xff;
		}
	}

private:
	BusHandler &bus_handler_;
	Outputs::CRT::CRT crt_;

	Concurrency::AsyncTaskQueue<false> audio_queue_;
	AudioGenerator audio_generator_;
	Outputs::Speaker::PullLowpass<AudioGenerator> speaker_;

	Cycles cycles_since_speaker_update_;
	void update_audio() {
		speaker_.run_for(audio_queue_, Cycles(cycles_since_speaker_update_.divide(Cycles(4))));
	}

	// register state
	struct {
		bool interlaced = false, tall_characters = false;
		uint8_t first_column_location = 0, first_row_location = 0;
		uint8_t number_of_columns = 0, number_of_rows = 0;
		uint16_t character_cell_start_address = 0, video_matrix_start_address = 0;
		uint16_t border_colour = 0;
		uint16_t background_colour = 0;
		uint16_t auxiliary_colour = 0;
		bool invertedCells = false;

		uint8_t direct_values[16]{};
	} registers_;

	// output state
	enum State {
		Sync, ColourBurst, Border, Pixels
	} output_state_ = State::Sync;
	int cycles_in_state_ = 0;

	// counters that cover an entire field
	int horizontal_counter_ = 0, vertical_counter_ = 0;
	int lines_this_field() const {
		// Necessary knowledge here: only the NTSC 6560 supports interlaced video.
		return registers_.interlaced ? (is_odd_frame_ ? 262 : 263) : timing_.lines_per_progressive_field;
	}
	int raster_value() const {
		const int bonus_line = (horizontal_counter_ + timing_.line_counter_increment_offset) / timing_.cycles_per_line;
		const int line = vertical_counter_ + bonus_line;
		const int final_line = lines_this_field();

		if(line < final_line)
			return line;

		if(is_odd_frame()) {
			return (horizontal_counter_ >= timing_.final_line_increment_position) ? 0 : final_line - 1;
		} else {
			return line % final_line;
		}
		// Cf. http://www.sleepingelephant.com/ipw-web/bulletin/bb/viewtopic.php?f=14&t=7237&start=15#p80737
	}
	bool is_odd_frame() const {
		return is_odd_frame_ || !registers_.interlaced;
	}

	// latches dictating start and length of drawing
	bool vertical_drawing_latch_ = false, horizontal_drawing_latch_ = false;
	int rows_this_field_ = 0, columns_this_line_ = 0;

	// current drawing position counter
	int pixel_line_cycle_ = 0, column_counter_ = 0;
	int current_row_ = 0;
	uint16_t current_character_row_ = 0;
	uint16_t video_matrix_address_counter_ = 0, base_video_matrix_address_counter_ = 0;

	// data latched from the bus
	uint8_t character_code_ = 0, character_colour_ = 0, character_value_ = 0;

	bool is_odd_frame_ = false, is_odd_line_ = false;

	// lookup table from 6560 colour index to appropriate PAL/NTSC value
	uint16_t colours_[16] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };

	uint16_t *pixel_pointer = nullptr;

	struct {
		int cycles_per_line = 0;
		int line_counter_increment_offset = 0;
		int final_line_increment_position = 0;
		int lines_per_progressive_field = 0;
		bool supports_interlacing = 0;
	} timing_;
	OutputMode output_mode_ = OutputMode::NTSC;
};

}