CLK/Machines/AppleII/AppleII.cpp

//
//  AppleII.cpp
//  Clock Signal
//
//  Created by Thomas Harte on 14/04/2018.
//  Copyright © 2018 Thomas Harte. All rights reserved.
//

#include "AppleII.hpp"

#include "../CRTMachine.hpp"
#include "../KeyboardMachine.hpp"
#include "../Utility/MemoryFuzzer.hpp"

#include "../../Processors/6502/6502.hpp"
#include "../../Components/AudioToggle/AudioToggle.hpp"

#include "../../Outputs/Speaker/Implementation/LowpassSpeaker.hpp"

#include "Video.hpp"

#include <memory>

namespace {

class ConcreteMachine:
	public CRTMachine::Machine,
	public KeyboardMachine::Machine,
	public CPU::MOS6502::BusHandler,
	public Inputs::Keyboard,
	public AppleII::Machine {
	private:
		struct VideoBusHandler : public AppleII::Video::BusHandler {
			public:
				VideoBusHandler(uint8_t *ram) : ram_(ram) {}

				uint8_t perform_read(uint16_t address) {
					return ram_[address];
				}

			private:
				uint8_t *ram_;
		};

		CPU::MOS6502::Processor<ConcreteMachine, false> m6502_;
		VideoBusHandler video_bus_handler_;
		std::unique_ptr<AppleII::Video::Video<VideoBusHandler>> video_;
		int cycles_into_current_line_ = 0;
		Cycles cycles_since_video_update_;

		void update_video() {
			video_->run_for(cycles_since_video_update_.flush());
		}
		void update_audio() {
			speaker_.run_for(cycles_since_audio_update_.divide(Cycles(16)));
		}

		uint8_t ram_[48*1024];
		std::vector<uint8_t> rom_;
		std::vector<uint8_t> character_rom_;
		uint16_t rom_start_address_;
		uint8_t keyboard_input_ = 0x00;

		Concurrency::DeferringAsyncTaskQueue audio_queue_;
		Audio::Toggle audio_toggle_;
		Outputs::Speaker::LowpassSpeaker<Audio::Toggle> speaker_;
		Cycles cycles_since_audio_update_;

	public:
		ConcreteMachine():
		 	m6502_(*this),
		 	video_bus_handler_(ram_),
		 	audio_toggle_(audio_queue_),
		 	speaker_(audio_toggle_) {
		 	// The system's master clock rate.
		 	const float master_clock = 14318180.0;

		 	// This is where things get slightly convoluted: establish the machine as having a clock rate
		 	// equal to the number of cycles of work the 6502 will actually achieve. Which is less than
		 	// the master clock rate divided by 14 because every 65th cycle is extended by one seventh.
			set_clock_rate((master_clock / 14.0) * 65.0 / (65.0 + 1.0 / 7.0));

			// The speaker, however, should think it is clocked at half the master clock, per a general
			// decision to sample it at seven times the CPU clock (plus stretches).
			speaker_.set_input_rate(static_cast<float>(master_clock / (2.0 * 16.0)));

			// Also, start with randomised memory contents.
			Memory::Fuzz(ram_, sizeof(ram_));
		}

		void setup_output(float aspect_ratio) override {
			video_.reset(new AppleII::Video::Video<VideoBusHandler>(video_bus_handler_));
			video_->set_character_rom(character_rom_);
		}

		void close_output() override {
			video_.reset();
		}

		Outputs::CRT::CRT *get_crt() override {
			return video_->get_crt();
		}

		Outputs::Speaker::Speaker *get_speaker() override {
			return &speaker_;
		}

		Cycles perform_bus_operation(CPU::MOS6502::BusOperation operation, uint16_t address, uint8_t *value) {
			++ cycles_since_video_update_;
			cycles_since_audio_update_ += Cycles(7);

			switch(address) {
				default:
					if(isReadOperation(operation)) {
						if(address < sizeof(ram_)) {
							*value = ram_[address];
						} else if(address >= rom_start_address_) {
							*value = rom_[address - rom_start_address_];
						} else {
							switch(address) {
								default:
//									printf("Unknown access to %04x\n", address);
									*value = 0xff;
								break;
								case 0xc000:
									*value = keyboard_input_;
								break;
							}
						}
					} else {
						if(address < sizeof(ram_)) {
							if(address >= 0x400) {
								// TODO: be more selective.
								update_video();
							}
							ram_[address] = *value;
						}
					}
				break;

				case 0xc050:	update_video();		video_->set_graphics_mode();	break;
				case 0xc051:	update_video();		video_->set_text_mode();		break;
				case 0xc052:	update_video();		video_->set_mixed_mode(false);	break;
				case 0xc053:	update_video();		video_->set_mixed_mode(true);	break;
				case 0xc054:	update_video();		video_->set_video_page(0);		break;
				case 0xc055:	update_video();		video_->set_video_page(1);		break;
				case 0xc056:	update_video();		video_->set_low_resolution();	break;
				case 0xc057:	update_video();		video_->set_high_resolution();	break;

				case 0xc010:
					keyboard_input_ &= 0x7f;
				break;

				case 0xc030:
					update_audio();
					audio_toggle_.set_output(!audio_toggle_.get_output());
				break;
			}

			// The Apple II has a slightly weird timing pattern: every 65th CPU cycle is stretched
			// by an extra 1/7th. That's because one cycle lasts 3.5 NTSC colour clocks, so after
			// 65 cycles a full line of 227.5 colour clocks have passed. But the high-rate binary
			// signal approximation that produces colour needs to be in phase, so a stretch of exactly
			// 0.5 further colour cycles is added. The video class handles that implicitly, but it
			// needs to be accumulated here for the audio.
			cycles_into_current_line_ = (cycles_into_current_line_ + 1) % 65;
			if(!cycles_into_current_line_) {
				++ cycles_since_audio_update_;
			}

			return Cycles(1);
		}

		void flush() {
			update_video();
			update_audio();
			audio_queue_.perform();
		}

		bool set_rom_fetcher(const std::function<std::vector<std::unique_ptr<std::vector<uint8_t>>>(const std::string &machine, const std::vector<std::string> &names)> &roms_with_names) override {
			auto roms = roms_with_names(
				"AppleII",
				{
					"apple2o.rom",
					"apple2-character.rom"
				});

			if(!roms[0] || !roms[1]) return false;
			rom_ = std::move(*roms[0]);
			rom_start_address_ = static_cast<uint16_t>(0x10000 - rom_.size());

			character_rom_ = std::move(*roms[1]);

			return true;
		}

		void run_for(const Cycles cycles) override {
			m6502_.run_for(cycles);
		}

		void set_key_pressed(Key key, char value, bool is_pressed) override {
			if(is_pressed) {
				// If no ASCII value is supplied, look for a few special cases.
				if(!value) {
					switch(key) {
						case Key::Left:		value = 8;	break;
						case Key::Right:	value = 21;	break;
						case Key::Down:		value = 10;	break;
						default: break;
					}
				}

				keyboard_input_ = static_cast<uint8_t>(value | 0x80);
			}
		}

		Inputs::Keyboard &get_keyboard() override {
			return *this;
		}
};

}

using namespace AppleII;

Machine *Machine::AppleII() {
	return new ConcreteMachine;
}

Machine::~Machine() {}