//
//  MFP68901.hpp
//  Clock Signal
//
//  Created by Thomas Harte on 06/10/2019.
//  Copyright © 2019 Thomas Harte. All rights reserved.
//

#ifndef MFP68901_hpp
#define MFP68901_hpp

#include <cstdint>
#include "../../ClockReceiver/ClockReceiver.hpp"

namespace Motorola {
namespace MFP68901 {

class PortHandler {
	public:
		// TODO: announce changes in output.
};

class MFP68901 {
	public:
		uint8_t read(int address);
		void write(int address, uint8_t value);

		void run_for(HalfCycles);
		HalfCycles get_next_sequence_point();

		void set_timer_event_input(int channel, bool value);

		void set_port_handler(PortHandler *);
		void set_port_input(uint8_t);
		uint8_t get_port_output();

		bool get_interrupt_line();
		uint8_t acknowledge_interrupt();

		struct InterruptDelegate {
			virtual void mfp68901_did_change_interrupt_status(MFP68901 *) = 0;
		};
		void set_interrupt_delegate(InterruptDelegate *delegate);

	private:
		// MARK: - Timers
		enum class TimerMode {
			Stopped, EventCount, Delay, PulseWidth
		};
		void set_timer_mode(int timer, TimerMode, int prescale, bool reset_timer);
		void set_timer_data(int timer, uint8_t);
		uint8_t get_timer_data(int timer);
		void decrement_timer(int timer);

		struct Timer {
			TimerMode mode = TimerMode::Stopped;
			uint8_t value = 0;
			uint8_t reload_value = 0;
			int prescale = 1;
			int divisor = 0;
			bool event_input = false;
		} timers_[4];

		HalfCycles cycles_left_;

		// MARK: - GPIP
		uint8_t gpip_input_ = 0;
		uint8_t gpip_output_ = 0;
		uint8_t gpip_active_edge_ = 0;
		uint8_t gpip_direction_ = 0;
		uint8_t gpip_interrupt_state_ = 0;

		void reevaluate_gpip_interrupts();

		// MARK: - Interrupts

		InterruptDelegate *interrupt_delegate_ = nullptr;

		// Ad hoc documentation: there seems to be a four-stage process here.
		// This is my current understanding:
		//
		// Interrupt in-service refers to whether the signal that would cause an
		// interrupt is active.
		//
		// If the interrupt is in-service and enabled, it will be listed as pending.
		//
		// If a pending interrupt is enabled in the interrupt mask, it will generate
		// a processor interrupt.
		//
		// So, the designers seem to have wanted to allow for polling and interrupts,
		// and then also decided to have some interrupts be able to be completely
		// disabled, so that don't even show up for polling.
		int interrupt_in_service_ = 0;
		int interrupt_enable_ = 0;
		int interrupt_pending_ = 0;
		int interrupt_mask_ = 0;
		bool interrupt_line_ = false;
		uint8_t interrupt_vector_ = 0;

		enum Interrupt {
			GPIP0				= (1 << 0),
			GPIP1				= (1 << 1),
			GPIP2				= (1 << 2),
			GPIP3				= (1 << 3),
			TimerD				= (1 << 4),
			TimerC				= (1 << 5),
			GPIP4				= (1 << 6),
			GPIP5				= (1 << 7),

			TimerB				= (1 << 8),
			TransmitError		= (1 << 9),
			TransmitBufferEmpty	= (1 << 10),
			ReceiveError		= (1 << 11),
			ReceiveBufferFull	= (1 << 12),
			TimerA				= (1 << 13),
			GPIP6				= (1 << 14),
			GPIP7				= (1 << 15),
		};
		void begin_interrupts(int interrupt);
		void end_interrupts(int interrupt);
		void update_interrupts();
};

}
}

#endif /* MFP68901_hpp */