/**
 * DJM-Fix
 * Copyright © 2020 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"

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

void interrupt(int signal) {
	run = false;
	std::cerr << "interrupt()" << std::endl; // TODO: do not mess STDIO
}

/**
 * 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)
 *  - https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/sound/usb?id=14335d8b9e1a2bf006f9d969a103f9731cabb210 (recording)
 *  - https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/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 AlsaBridge.cpp file is based on publicly available documentation
 * that can be found at <https://mixb.me/CDJHidProtocol/hid-analysis/handshake.html>.
 * 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/           # or we can use this mirror
 *
 * Compile:
 *   make                                                        # we can skip this step, it will be compiled on the first run
 *
 * Run:
 *   make run                                                    # in most cases
 *   build/djm-fix 'Pioneer DJ.*'                                # or provide custom name pattern (regular expression) to select the proper card
 *
 * Stop:
 *   press Ctrl+C
 * 
 * Look for updates in the Mercurial repositories and at <https://blog.frantovo.cz/c/387/>.
 */

int main(int argc, char**argv) {
	try {
		std::string cardNamePattern = argc == 2 ? argv[1] : "Pioneer DJ.*";

		signal(SIGINT, interrupt);
		std::unique_ptr<djmfix::DJMFix> djmFix(djmfix::create());
		std::unique_ptr<djmfix::alsa::AlsaBridge> alsaBridge(djmfix::alsa::create(djmFix.get(), cardNamePattern));

		alsaBridge->start();
		while (run) std::this_thread::sleep_for(std::chrono::milliseconds(100));
		alsaBridge->stop();

		return 0;
	} catch (const std::exception& e) {
		std::cerr << "ERROR: " << e.what() << std::endl; // TODO: do not mess STDIO
	}
}