/**

 * 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);

}

}