/* ScummVM - Graphic Adventure Engine
 *
 * ScummVM is the legal property of its developers, whose names
 * are too numerous to list here. Please refer to the COPYRIGHT
 * file distributed with this source distribution.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

#ifndef AUDIO_SOFTSYNTH_EMUMIDI_H
#define AUDIO_SOFTSYNTH_EMUMIDI_H

#include "audio/audiostream.h"
#include "audio/mididrv.h"
#include "audio/mixer.h"

class MidiDriver_Emulated : public Audio::AudioStream, public MidiDriver {
protected:
	bool _isOpen;
	Audio::Mixer *_mixer;
	Audio::SoundHandle _mixerSoundHandle;

private:
	Common::TimerManager::TimerProc _timerProc;
	void *_timerParam;

	enum {
		FIXP_SHIFT = 16
	};

	int _nextTick;
	int _samplesPerTick;

protected:
	int _baseFreq;

	virtual void generateSamples(int16 *buf, int len) = 0;
	virtual void onTimer() {}

public:
	MidiDriver_Emulated(Audio::Mixer *mixer) :
		_mixer(mixer),
		_isOpen(false),
		_timerProc(0),
		_timerParam(0),
		_nextTick(0),
		_samplesPerTick(0),
		_baseFreq(250) {
	}

	// MidiDriver API
	virtual int open() {
		_isOpen = true;

		int d = getRate() / _baseFreq;
		int r = getRate() % _baseFreq;

		// This is equivalent to (getRate() << FIXP_SHIFT) / BASE_FREQ
		// but less prone to arithmetic overflow.

		_samplesPerTick = (d << FIXP_SHIFT) + (r << FIXP_SHIFT) / _baseFreq;

		return 0;
	}

	bool isOpen() const { return _isOpen; }

	virtual void setTimerCallback(void *timer_param, Common::TimerManager::TimerProc timer_proc) {
		_timerProc = timer_proc;
		_timerParam = timer_param;
	}

	virtual uint32 getBaseTempo() {
		return 1000000 / _baseFreq;
	}

	// AudioStream API
	virtual int readBuffer(int16 *data, const int numSamples) {
		const int stereoFactor = isStereo() ? 2 : 1;
		int len = numSamples / stereoFactor;
		int step;

		do {
			step = len;
			if (step > (_nextTick >> FIXP_SHIFT))
				step = (_nextTick >> FIXP_SHIFT);

			generateSamples(data, step);

			_nextTick -= step << FIXP_SHIFT;
			if (!(_nextTick >> FIXP_SHIFT)) {
				if (_timerProc)
					(*_timerProc)(_timerParam);

				onTimer();

				_nextTick += _samplesPerTick;
			}

			data += step * stereoFactor;
			len -= step;
		} while (len);

		return numSamples;
	}

	virtual bool endOfData() const {
		return false;
	}
};

#endif
