/**

  * 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 <iostream>

 #include <sstream>

 #include <iomanip>

 #include <thread>

 #include <mutex>

 #include <atomic>

 #include <chrono>

 #include <stdexcept>

 #include <vector>

 #include "DJMFix.h"

 namespace djmfix {

 using L = djmfix::logging::Level;

 using Bytes = std::vector<uint8_t>;

 namespace chro = std::chrono;

 class DJMFixImpl : public DJMFix {

 private:

 	MidiSender* midiSender;

 	djmfix::logging::Logger* logger;

 	const int keepAliveInterval = 200;

 	int keepAliveCounter = 0;

 	std::thread keepAliveThread;

 	std::recursive_mutex midiMutex;

 	std::atomic<bool> running{false};

 	std::atomic<bool> stopped{false};

 	std::atomic<bool> sendKeepAlive{false};

 	Bytes seed2;

 	void run() {

 		while (!stopped) {

 			logger->log(L::FINE, "DJMFixImpl::run()");

 			if (sendKeepAlive) send({

 					0xf0, 0x00, 0x40, 0x05,

 					0x00, 0x00, 0x00, 0x17,

 					0x00, 0x50, 0x01, 0xf7

 				});

 			std::this_thread::sleep_for(chro::milliseconds(keepAliveInterval));

 			keepAliveCounter++;

 			if (keepAliveCounter % (60 * 1000 / keepAliveInterval) == 0)

 				logger->log(L::INFO,

 					"Still sending periodic keep-alive messages "

 					"(each " + std::to_string(keepAliveInterval) + " ms).");

 		}

 	}

 	void send(const MidiMessage& midiMessage) {

 		std::lock_guard<std::recursive_mutex> lock(midiMutex);

 		midiSender->send(midiMessage);

 	}

 	std::string toString(const Bytes& midiMessage) {

 		std::stringstream result;

 		for (uint8_t b : midiMessage)

 			result << std::hex << std::setw(2) << std::setfill('0') << (int) b;

 		return result.str();

 	}

 	Bytes normalize(const Bytes& data) {

 		if (data.size() % 2) throw std::invalid_argument(

 				"Data before normalization must have even number of bytes.");

 		Bytes result;

 		result.reserve(data.size() / 2);

 		for (size_t i = 0; i < data.size() / 2; i++) result.push_back(

 				(data[i * 2] & 0x0F) << 4 | (data[i * 2 + 1] & 0x0F));

 		return result;

 	}

 	Bytes denormalize(const Bytes& data) {

 		Bytes result;

 		result.reserve(data.size()*2);

 		for (size_t i = 0; i < data.size(); i++) {

 			result.push_back(data[i] >> 4);

 			result.push_back(data[i] & 0x0F);

 		}

 		return result;

 	}

 	uint32_t fnv32hash(const Bytes& buff) {

 		uint32_t hash = 0x811c9dc5;

 		for (uint8_t b : buff) hash = ((b^hash) * 0x1000193);

 		return hash;

 	}

 	Bytes toBytes(const uint32_t value) {

 		Bytes result;

 		result.reserve(4);

 		result.push_back(value >> 24);

 		result.push_back(value >> 16);

 		result.push_back(value >> 8);

 		result.push_back(value >> 0);

 		return result;

 	}

 	bool equals(Bytes a, Bytes b) {

 		if (a.size() != b.size()) return false;

 		for (size_t i = 0; i < a.size(); i++) if (a[i] != b[i]) return false;

 		return true;

 	}

 	template<typename T> std::vector<T> concat(

 			const std::vector<T>& a,

 			const std::vector<T>& b,

 			const std::vector<T>& c = {}) //

 	{

 		std::vector<T> result;

 		result.reserve(a.size() + b.size() + c.size());

 		for (size_t i = 0; i < a.size(); i++) result.push_back(a[i]);

 		for (size_t i = 0; i < b.size(); i++) result.push_back(b[i]);

 		for (size_t i = 0; i < c.size(); i++) result.push_back(c[i]);

 		return result;

 	}

 	template<typename T>

 	std::vector<T> xOR(const std::vector<T>& a, const std::vector<T>& b) {

 		if (a.size() != b.size()) throw std::invalid_argument(

 				"Both must be the same length when doing XOR.");

 		std::vector<T> result;

 		result.reserve(a.size());

 		for (size_t i = 0; i < a.size(); i++) result.push_back(a[i] ^ b[i]);

 		return result;

 	}

 public:

 	DJMFixImpl(djmfix::logging::Logger* logger)

 	: logger(logger ? logger : djmfix::logging::blackhole()) {

 	}

 	virtual ~DJMFixImpl() override {

 		logger->log(L::FINER, "~DJMFixImpl()");

 		if (running) stop();

 	}

 	void setMidiSender(MidiSender* midiSender) {

 		logger->log(L::FINER, "DJMFixImpl::setMidiSender()");

 		this->midiSender = midiSender;

 	}

 	virtual void receive(const MidiMessage& msg) override {

 		logger->log(L::FINE, "Received a message: "

 				"size = " + std::to_string(msg.size()) + " "

 				"data = " + toString(msg));

 		std::lock_guard<std::recursive_mutex> lock(midiMutex);

 		if (msg.size() == 12 && msg[9] == 0x11) {

 			logger->log(L::INFO, "Received greeting message.");

 			send({

 				0xf0, 0x00, 0x40, 0x05,

 				0x00, 0x00, 0x00, 0x17,

 				0x00, 0x12, 0x2a, 0x01,

 				0x0b, 0x50, 0x69, 0x6f,

 				0x6e, 0x65, 0x65, 0x72,

 				0x44, 0x4a, 0x02, 0x0b,

 				0x72, 0x65, 0x6b, 0x6f,

 				0x72, 0x64, 0x62, 0x6f,

 				0x78, 0x03, 0x12, 0x02,

 				0x09, 0x00, 0x00, 0x00,

 				0x00, 0x00, 0x00, 0x02,

 				0x03, 0x04, 0x08, 0x00,

 				0x00, 0x00, 0x00, 0xf7

 			});

 			logger->log(L::INFO, "Sent message with seed1.");

 		} else if (msg.size() == 54

 				&& msg[9] == 0x13

 				&& msg[33] == 0x04

 				&& msg[43] == 0x03) //

 		{

 			Bytes hash1(msg.begin() + 35, msg.begin() + 35 + 8);

 			seed2 = Bytes(msg.begin() + 45, msg.begin() + 45 + 8);

 			hash1 = normalize(hash1);

 			seed2 = normalize(seed2);

 			logger->log(L::INFO, "Received message with "

 					"hash1 = " + toString(hash1) + " and "

 					"seed2 = " + toString(seed2));

 			Bytes seed0 = {0x68, 0x01, 0x31, 0xFB};

 			Bytes seed1 = {0x29, 0x00, 0x00, 0x00, 0x23, 0x48, 0x00, 0x00};

 			Bytes hash1check =

 					toBytes(fnv32hash(concat(seed1, xOR(seed0, seed2))));

 			if (equals(hash1, hash1check)) {

 				logger->log(L::INFO, "Verification of hash1 was successful.");

 				Bytes hash2 =

 						toBytes(fnv32hash(concat(seed2, xOR(seed0, seed2))));

 				send(concat({

 					0xf0, 0x00, 0x40, 0x05,

 					0x00, 0x00, 0x00, 0x17,

 					0x00, 0x14, 0x38, 0x01,

 					0x0b, 0x50, 0x69, 0x6f,

 					0x6e, 0x65, 0x65, 0x72,

 					0x44, 0x4a, 0x02, 0x0b,

 					0x72, 0x65, 0x6b, 0x6f,

 					0x72, 0x64, 0x62, 0x6f,

 					0x78, 0x04, 0x0a

 				}, concat(denormalize(hash2),{

 					0x05, 0x16, 0x05, 0x09,

 					0x0b, 0x05, 0x04, 0x0b,

 					0x0f, 0x0e, 0x0e, 0x04,

 					0x04, 0x0a, 0x05, 0x0a,

 					0x0c, 0x08, 0x0e, 0x04,

 					0x0c, 0x05, 0xf7

 				})));

 				logger->log(L::INFO, "Sent message with hash2.");

 			} else {

 				std::stringstream logMessage;

 				logMessage

 						<< "Verification of hash1 failed: "

 						<< " midiMessage = " << toString(msg)

 						<< " seed0 = " << toString(seed0)

 						<< " seed1 = " << toString(seed1)

 						<< " seed2 = " << toString(seed2)

 						<< " hash1 = " << toString(hash1)

 						<< " hash1check = " << toString(hash1check);

 				logger->log(L::SEVERE, logMessage.str());

 				// TODO: graceful death

 			}

 		} else if (msg.size() == 12 && msg[9] == 0x15) {

 			sendKeepAlive = true;

 			logger->log(L::INFO, "Received acknowledgment message. "

 					"Started sending keep-alive messages. "

 					"LINE/PHONO channels should work now.");

 		}

 	}

 	void start() override {

 		logger->log(L::FINE, "DJMFixImpl::start()");

 		if (midiSender == nullptr)

 			throw std::logic_error("Need a midiSender when starting DJMFix");

 		// TODO: methods for parsing and constructing messages from parts (TLV)

 		send({

 			0xf0, 0x00, 0x40, 0x05,

 			0x00, 0x00, 0x00, 0x17,

 			0x00, 0x50, 0x01, 0xf7

 		});

 		logger->log(L::INFO, "Sent greeting message.");

 		keepAliveThread = std::thread(&DJMFixImpl::run, this);

 		running = true;

 	}

 	void stop() override {

 		stopped = true;

 		keepAliveThread.join();

 		running = false;

 		logger->log(L::FINE, "DJMFixImpl::stop()");

 	}

 };

 DJMFix* create(djmfix::logging::Logger* logger) {

 	return new DJMFixImpl(logger);

 }

 }