CLK/Activity/Observer.hpp

//
//  ActivityObserver.h
//  Clock Signal
//
//  Created by Thomas Harte on 07/05/2018.
//  Copyright 2018 Thomas Harte. All rights reserved.
//

#pragma once

#include <cstdint>
#include <string>

namespace Activity {

/*!
	Provides a purely virtual base class for anybody that wants to receive notifications of
	'activity': any feedback from an emulated system which a user could perceive other than
	through the machine's native audio and video outputs.

	So: status LEDs, drive activity, etc. A receiver may choose to make appropriate noises
	and/or to show or unshow status indicators.
*/
class Observer {
public:
	virtual ~Observer() = default;

	/// Provides hints as to the sort of information presented on an LED.
	enum LEDPresentation: uint8_t {
		/// This LED informs the user of some sort of persistent state, e.g. scroll lock.
		/// If this flag is absent then the LED describes an ephemeral state, such as media access.
		Persistent = (1 << 0),
	};

	/// Announces to the receiver that there is an LED of name @c name.
	virtual void register_led([[maybe_unused]] const std::string &name, [[maybe_unused]] uint8_t presentation = 0) {}

	/// Announces to the receiver that there is a drive of name @c name.
	///
	/// If a drive has the same name as an LED, that LED goes with this drive.
	virtual void register_drive([[maybe_unused]] const std::string &name) {}

	/// Informs the receiver of the new state of the LED with name @c name.
	virtual void set_led_status([[maybe_unused]] const std::string &name, [[maybe_unused]] bool lit) {}

	enum class DriveEvent {
		StepNormal,
		StepBelowZero,
		StepBeyondMaximum
	};

	/// Informs the receiver that the named event just occurred for the drive with name @c name.
	virtual void announce_drive_event([[maybe_unused]] const std::string &name, [[maybe_unused]] DriveEvent event) {}

	/// Informs the receiver of the motor-on status of the drive with name @c name.
	virtual void set_drive_motor_status([[maybe_unused]] const std::string &name, [[maybe_unused]] bool is_on) {}
};

}