/**

 * DJM-Fix

 * Copyright © 2025 František Kučera (Frantovo.cz, GlobalCode.info)

 *

 * 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, version 3 of the License.

 *

 * 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/>.

 */

#include <memory>

#include <iostream>

#include <chrono>

#include <thread>

#include <csignal>

#include <atomic>

#include "DJMFix.h"

#include "AlsaBridge.h"

#include "Logger.h"

static std::atomic<bool> run{true};

void interrupt(int signal) {

	run = false;

}

/**

 * The support for Pioneer DJ DJM-250MK2 (an external  USB  sound  card / mixer)

 * was added to the Linux (kernel) by these patches:

 *

 * https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/...

 *   - ...sound/usb?id=73d8c94084341e2895169a0462dbc18167f01683 (playback)

 *   - ...sound/usb?id=14335d8b9e1a2bf006f9d969a103f9731cabb210 (recording)

 *   - ...sound/usb?id=cdc01a1558dedcee3daee7e1802d0349a07edb87 (mixer setup)

 *

 * These patches are enough for playback and for recording from post CH  faders.

 *

 * However this mixer is somehow incapacitated and if we want to record the  raw

 * signal  from the PHONO or LINE channels, we only get silence. This feature is

 * important for DVS (Digital Vinyl Systems) setups where  the  timecode  signal

 * from  special  control  vinyls  flows  from mixer to the computer where it is

 * interpreted in a software like MIXXX and used for controlling the playback of

 * files on our computer. The signal (usually music) from these files flows back

 * to the mixer and then to speakers and headphones.

 *

 * To make this work and enjoy all the features of the device we have bought, we

 * need  to  tell  the mixer that we want the signal instead of silence on given

 * channels. And this is the purpose of the djm-fix utility and it  is  done  by

 * sending some magic packet to the mixer.

 *

 * Implementation of this magic in the DJMFix.cpp file is based on  publicly

 * available documentation that can be found at:

 *   - https://swiftb0y.github.io/CDJHidProtocol/hid-analysis/handshake.html

 *   - https://mixb.me/CDJHidProtocol/hid-analysis/handshake.html (formerly).

 * This page pointed me to the proper hash function (according to the constants,

 * it  is bit uncommon but publicly known Fowler–Noll–Vo hash function, FNV) and

 * some magic bits. I wrote this standalone C++  program  that  talks  with  the

 * mixer over MIDI SysEx messages and does the magic.

 *

 * When this program is started, it finds the mixer and makes it fully  working.

 * It needs to be running all the time, otherwise we will get silence

 * on the PHONO/LINE channels again.

 *

 * Install dependencies:

 *   apt install mercurial make pkg-config g++ libasound2-dev

 * (in Debian or Ubuntu - it will be similar in other distributions)

 *

 * Download djm-fix:

 *   hg clone https://hg.frantovo.cz/midi/djm-fix/        # primary source

 *   hg clone https://hg.globalcode.info/midi/djm-fix/    # mirror

 *

 * Compile:

 *   make                                                 # can be skipped

 *

 * Run:

 *   make run                                             # in most cases

 *   build/djm-fix 'Pioneer DJ.*'                         # with custom name

 *                 ^ regular expression to select desired card

 *

 * Stop:

 *   press Ctrl+C

 * 

 * Look for updates in the Mercurial repositories and at:

 *   - https://blog.frantovo.cz/c/387/

 *   - https://blog.frantovo.cz/c/396/

 */

int main(int argc, char**argv) {

	using L = djmfix::logging::Level;

	std::unique_ptr<djmfix::logging::Logger>

			logger(djmfix::logging::create(std::cerr, L::INFO));

	try {

		logger->log(L::INFO, "DJM-Fix started.");

		std::string cardNamePattern = argc == 2

				? argv[1]

				: "(Pioneer DJ|AlphaTheta).*";

		signal(SIGINT, interrupt);

		std::unique_ptr<djmfix::DJMFix> djmFix(djmfix::create(logger.get()));

		std::unique_ptr<djmfix::alsa::AlsaBridge> alsaBridge(

				djmfix::alsa::create(djmFix.get(),

				cardNamePattern,

				logger.get()));

		alsaBridge->start();

		while (run) std::this_thread::sleep_for(std::chrono::milliseconds(100));

		std::cerr << std::endl;

		logger->log(L::INFO, "DJM-Fix stopping.");

		alsaBridge->stop();

		return 0;

	} catch (const std::exception& e) {

		logger->log(L::SEVERE, e.what());

	}

}