/*
 * This file is part of OpenTTD.
 * OpenTTD 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, version 2.
 * OpenTTD 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 OpenTTD. If not, see <https://www.gnu.org/licenses/old-licenses/gpl-2.0>.
 */

/** @file fluidsynth.cpp Playing music via the fluidsynth library. */

#include "../stdafx.h"

#include "fluidsynth.h"

#include <filesystem>
#include <fluidsynth.h>
#include <mutex>

#include "../debug.h"
#include "../mixer.h"
#include "midifile.hpp"

#include "../safeguards.h"

static struct {
	fluid_settings_t *settings; ///< FluidSynth settings handle
	fluid_synth_t *synth; ///< FluidSynth synthesizer handle
	fluid_player_t *player; ///< FluidSynth MIDI player handle
	std::mutex synth_mutex; ///< Guard mutex for synth access
	double max_gain; ///< Default max gain.
} _midi; ///< Metadata about the midi we're playing.

/** Factory for the FluidSynth driver. */
static FMusicDriver_FluidSynth iFMusicDriver_FluidSynth;

/** List of sound fonts to try by default. */
static const char *_default_soundfonts[] = {
	/* FluidSynth preferred */
	/* See: https://www.fluidsynth.org/api/settings_synth.html#settings_synth_default-soundfont */
	"/usr/share/soundfonts/default.sf2",

	/* Debian/Ubuntu preferred */
	/* See: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=929185 */
	"/usr/share/sounds/sf3/default-GM.sf3",

	/* OpenSUSE preferred */
	"/usr/share/sounds/sf2/FluidR3_GM.sf2",

	/* RedHat/Fedora/Arch preferred */
	"/usr/share/soundfonts/FluidR3_GM.sf2",

	/* Debian/Ubuntu/OpenSUSE alternatives */
	"/usr/share/sounds/sf2/TimGM6mb.sf2",
	"/usr/share/sounds/sf2/FluidR3_GS.sf2",
};

static void RenderMusicStream(int16_t *buffer, size_t samples)
{
	std::unique_lock<std::mutex> lock{_midi.synth_mutex, std::try_to_lock};

	if (!lock.owns_lock() || _midi.synth == nullptr || _midi.player == nullptr) return;
	fluid_synth_write_s16(_midi.synth, samples, buffer, 0, 2, buffer, 1, 2);
}

static void load_and_execute_config_file(fluid_cmd_handler_t *cmd_handler, const char *config_file)
{
	if (std::filesystem::exists(config_file)) {
		Debug(driver, 2, "Fluidsynth: Attempting to load config file '{}'", config_file);
		if (fluid_source(cmd_handler, config_file) < 0) {
			Debug(driver, 0, "Fluidsynth: Failed to execute command configuration file '{}'", config_file);
		}
	} else {
		Debug(driver, 1, "Fluidsynth: Failed to load config file '{}' - file doesn't exist", config_file);
	}
}

std::optional<std::string_view> MusicDriver_FluidSynth::Start(const StringList &param)
{
	std::lock_guard<std::mutex> lock{_midi.synth_mutex};

	auto sfont_name = GetDriverParam(param, "soundfont");
	int sfont_id;

	Debug(driver, 1, "Fluidsynth: sf {}", sfont_name.has_value() ? *sfont_name : "(null)");

	/* Create the settings. */
	_midi.settings = new_fluid_settings();
	if (_midi.settings == nullptr) return "Could not create midi settings";

	/* Read config file(s) */
	fluid_cmd_handler_t *cmd_handler = new_fluid_cmd_handler2(_midi.settings, nullptr, nullptr, nullptr);
	if (cmd_handler == NULL) return "Failed to create the early command handler";

	char buf[MAX_PATH] = {};
	const char *config_file = fluid_get_sysconf(buf, sizeof(buf)); // system-wide config file
	load_and_execute_config_file(cmd_handler, config_file);
	config_file = fluid_get_userconf(buf, sizeof(buf)); // user config file (potentially overrides system)
	load_and_execute_config_file(cmd_handler, config_file);

	delete_fluid_cmd_handler(cmd_handler);

	/* Don't try to lock sample data in memory, OTTD usually does not run with privileges allowing that */
	fluid_settings_setint(_midi.settings, "synth.lock-memory", 0);

	/* Install the music render routine and set up the samplerate */
	uint32_t samplerate = MxSetMusicSource(RenderMusicStream);
	fluid_settings_setnum(_midi.settings, "synth.sample-rate", samplerate);
	Debug(driver, 1, "Fluidsynth: samplerate {:.0f}", (float)samplerate);

	/* Create the synthesizer. */
	_midi.synth = new_fluid_synth(_midi.settings);
	if (_midi.synth == nullptr) return "Could not open synth";

	/* Load a SoundFont and reset presets (so that new instruments
	 * get used from the SoundFont) */
	if (!sfont_name.has_value()) {
		sfont_id = FLUID_FAILED;

		/* Try loading the default soundfont registered with FluidSynth. */
		char *default_soundfont = nullptr;
		fluid_settings_dupstr(_midi.settings, "synth.default-soundfont", &default_soundfont);
		if (default_soundfont != nullptr && std::filesystem::exists(default_soundfont) && fluid_is_soundfont(default_soundfont)) {
			sfont_id = fluid_synth_sfload(_midi.synth, default_soundfont, 1);
		}
		fluid_free(default_soundfont);

		/* If no default soundfont found, try our own list. */
		if (sfont_id == FLUID_FAILED) {
			for (const char *soundfont : _default_soundfonts) {
				if (!std::filesystem::exists(soundfont) || !fluid_is_soundfont(soundfont)) continue;
				sfont_id = fluid_synth_sfload(_midi.synth, soundfont, 1);
				if (sfont_id != FLUID_FAILED) break;
			}
		}
		if (sfont_id == FLUID_FAILED) return "Could not open any sound font";
	} else {
		std::string name{sfont_name.value()};
		sfont_id = fluid_synth_sfload(_midi.synth, name.c_str(), 1);
		if (sfont_id == FLUID_FAILED) return "Could not open sound font";
	}

	/* Treat a configured synth gain as the maximum gain to use. */
	if (fluid_settings_getnum(_midi.settings, "synth.gain", &_midi.max_gain) != FLUID_OK) {
		if (fluid_settings_getnum_default(_midi.settings, "synth.gain", &_midi.max_gain) != FLUID_OK) {
			/* No synth.gain value present for some reason, use FluidSynth's default value. */
			_midi.max_gain = 0.2;
		}
	}

	_midi.player = nullptr;

	return std::nullopt;
}

void MusicDriver_FluidSynth::Stop()
{
	MxSetMusicSource(nullptr);

	std::lock_guard<std::mutex> lock{_midi.synth_mutex};

	if (_midi.player != nullptr) delete_fluid_player(_midi.player);
	_midi.player = nullptr;

	if (_midi.synth != nullptr) delete_fluid_synth(_midi.synth);
	_midi.synth = nullptr;

	if (_midi.settings != nullptr) delete_fluid_settings(_midi.settings);
	_midi.settings = nullptr;
}

void MusicDriver_FluidSynth::PlaySong(const MusicSongInfo &song)
{
	std::string filename = MidiFile::GetSMFFile(song);

	this->StopSong();

	if (filename.empty()) {
		return;
	}

	std::lock_guard<std::mutex> lock{_midi.synth_mutex};

	_midi.player = new_fluid_player(_midi.synth);
	if (_midi.player == nullptr) {
		Debug(driver, 0, "Could not create midi player");
		return;
	}

	if (fluid_player_add(_midi.player, filename.c_str()) != FLUID_OK) {
		Debug(driver, 0, "Could not open music file");
		delete_fluid_player(_midi.player);
		_midi.player = nullptr;
		return;
	}
	if (fluid_player_play(_midi.player) != FLUID_OK) {
		Debug(driver, 0, "Could not start midi player");
		delete_fluid_player(_midi.player);
		_midi.player = nullptr;
		return;
	}
}

void MusicDriver_FluidSynth::StopSong()
{
	std::lock_guard<std::mutex> lock{_midi.synth_mutex};

	if (_midi.player == nullptr) return;

	fluid_player_stop(_midi.player);
	/* No fluid_player_join needed */
	delete_fluid_player(_midi.player);
	fluid_synth_system_reset(_midi.synth);
	fluid_synth_all_sounds_off(_midi.synth, -1);
	_midi.player = nullptr;
}

bool MusicDriver_FluidSynth::IsSongPlaying()
{
	std::lock_guard<std::mutex> lock{_midi.synth_mutex};
	if (_midi.player == nullptr) return false;

	return fluid_player_get_status(_midi.player) == FLUID_PLAYER_PLAYING;
}

void MusicDriver_FluidSynth::SetVolume(uint8_t vol)
{
	std::lock_guard<std::mutex> lock{_midi.synth_mutex};
	if (_midi.settings == nullptr) return;

	/* Set gain using OpenTTD's volume, as a number between 0 and max_gain. */
	double gain = (1.0 * vol) / 128.0 * _midi.max_gain;
	if (fluid_settings_setnum(_midi.settings, "synth.gain", gain) != FLUID_OK) {
		Debug(driver, 0, "Could not set volume");
	}
}
