CLK/Storage/Tape/Tape.hpp

//
//  Tape.hpp
//  Clock Signal
//
//  Created by Thomas Harte on 18/01/2016.
//  Copyright 2016 Thomas Harte. All rights reserved.
//

#pragma once

#include <memory>

#include "../../ClockReceiver/ClockReceiver.hpp"
#include "../../ClockReceiver/ClockingHintSource.hpp"

#include "../TimedEventLoop.hpp"

#include "../../Activity/Source.hpp"

namespace Storage::Tape {

/*!
	Models a tape as a sequence of pulses, each pulse being of arbitrary length and described
	by their relationship with zero:
		- high pulses exit from zero upward before returning to it;
		- low pulses exit from zero downward before returning to it;
		- zero pulses run along zero.

	Subclasses should implement at least @c get_next_pulse and @c reset to provide a serial feeding
	of pulses and the ability to return to the start of the feed. They may also implement @c seek if
	a better implementation than a linear search from the @c reset time can be implemented.
*/
class Tape {
public:
	struct Pulse {
		enum Type {
			High, Low, Zero
		} type;
		Time length;

		Pulse(Type type, Time length) : type(type), length(length) {}
		Pulse() = default;
	};

	/*!
		If at the start of the tape returns the first stored pulse. Otherwise advances past
		the last-returned pulse and returns the next.

		@returns the pulse that begins at the current cursor position.
	*/
	Pulse get_next_pulse();

	/// Returns the tape to the beginning.
	void reset();

	/// @returns @c true if the tape has progressed beyond all recorded content; @c false otherwise.
	virtual bool is_at_end() const = 0;

	/*!
		Returns a numerical representation of progression into the tape. Precision is arbitrary but
		required to be at least to the whole pulse. Greater numbers are later than earlier numbers,
		but not necessarily continuous.
	*/
	virtual uint64_t get_offset() const;

	/*!
		Moves the tape to the first time at which the specified offset would be returned by get_offset.
	*/
	virtual void set_offset(uint64_t);

	/*!
		Calculates and returns the amount of time that has elapsed since the time began. Potentially expensive.
	*/
	virtual Time get_current_time();

	/*!
		Seeks to @c time. Potentially expensive.
	*/
	virtual void seek(Time &time);

	virtual ~Tape() = default;

private:
	uint64_t offset_;
	Tape::Pulse pulse_;

	virtual Pulse virtual_get_next_pulse() = 0;
	virtual void virtual_reset() = 0;
};

/*!
	Provides a helper for: (i) retaining a reference to a tape; and (ii) running the tape at a certain
	input clock rate.

	Will call @c process_input_pulse instantaneously upon reaching *the end* of a pulse. Therefore a subclass
	can decode pulses into data within process_input_pulse, using the supplied pulse's @c length and @c type.
*/
class TapePlayer: public TimedEventLoop, public ClockingHint::Source {
public:
	TapePlayer(int input_clock_rate);
	virtual ~TapePlayer() = default;

	void set_tape(std::shared_ptr<Storage::Tape::Tape> tape);
	bool has_tape();
	std::shared_ptr<Storage::Tape::Tape> get_tape();

	void run_for(const Cycles cycles);

	void run_for_input_pulse();

	ClockingHint::Preference preferred_clocking() const override;

	Tape::Pulse get_current_pulse();
	void complete_pulse();

protected:
	virtual void process_next_event() override;
	virtual void process_input_pulse(const Tape::Pulse &pulse) = 0;

private:
	inline void get_next_pulse();

	std::shared_ptr<Storage::Tape::Tape> tape_;
	Tape::Pulse current_pulse_;
};

/*!
	A specific subclass of the tape player for machines that sample such as to report only either a
	high or a low current input level.

	Such machines can use @c get_input() to get the current level of the input.

	They can also provide a delegate to be notified upon any change in the input level.
*/
class BinaryTapePlayer : public TapePlayer {
public:
	BinaryTapePlayer(int input_clock_rate);
	void set_motor_control(bool enabled);
	bool get_motor_control() const;

	void set_tape_output(bool set);
	bool get_input() const;

	void run_for(const Cycles cycles);

	struct Delegate {
		virtual void tape_did_change_input(BinaryTapePlayer *tape_player) = 0;
	};
	void set_delegate(Delegate *delegate);

	ClockingHint::Preference preferred_clocking() const final;

	void set_activity_observer(Activity::Observer *observer);

protected:
	Delegate *delegate_ = nullptr;
	void process_input_pulse(const Storage::Tape::Tape::Pulse &pulse) final;
	bool input_level_ = false;
	bool motor_is_running_ = false;

	Activity::Observer *observer_ = nullptr;
};

}