/**

  * 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());

 	}

 }