/**

 * 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 <regex>

#include "DJMFix.h"

#include "MessageCodec.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;

	MessageCodec codec;

	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};

	/**

	 * Device (V10) may send multiple greeting messages.

	 * It works even if we respond multiple times. But one response is enough.

	 */

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

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

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

	Bytes seed2;

	Bytes seed3;

	Bytes name1 = {0x50, 0x69, 0x6f, 0x6e, 0x65, 0x65, 0x72, 0x44, 0x4a};

	Bytes name2 = {0x72, 0x65, 0x6b, 0x6f, 0x72, 0x64, 0x62, 0x6f, 0x78};

	Bytes hash1;

	Bytes hash2;

	uint8_t version = 0x17;

	void run() {

		while (!stopped) {

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

			if (sendKeepAlive) send({

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

					0x00, 0x00, 0x00, version,

					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 Message& msg) {

		logger->log(L::FINE, "<!-- Sent message: -->" + msg.toString());

		send(codec.encode(msg));

	}

	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 setDeviceName(std::string name) override {

		logger->log(L::FINE, "DJMFixImpl::setDeviceName(" + name + ")");

		std::regex djm250pattern("Pioneer DJ Corporation DJM-250MK2.*");

		std::regex djm450pattern(".*450.*"); // TODO: correct pattern

		if (std::regex_match(name, djm250pattern)) {

			// DJM-250MK2:

			version = 0x17;

			seed3 = {

				0x59, 0xb5, 0x4b, 0xfe, 0xe4,

				0x4a, 0x5a, 0xc8, 0xe4, 0xc5

			};

			logger->log(L::FINE, "Switched to DJM-250MK2 mode");

		} else if (std::regex_match(name, djm450pattern)) {

			// DJM-450:

			// DJM-450 - not tested yet:

			version = 0x13;

			seed0 = {0x8c, 0x5b, 0x3f, 0x5d};

			seed3 = {

				0x08, 0xef, 0x3f, 0x2f, 0x1e,

				0x7a, 0x90, 0x17, 0xf6, 0xaf

			};

			logger->log(L::FINE, "Switched to DJM-450 mode");

		} else {

			// DJM-V10:

			version = 0x34;

			seed3 = {

				0x70, 0x01, 0x4d, 0x05, 0xbe,

				0xf2, 0xe4, 0xde, 0x60, 0xd6

			};

			logger->log(L::FINE, "Switched to DJM-V10 mode");

		}

	}

	void setMidiSender(MidiSender* midiSender) override {

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

		this->midiSender = midiSender;

	}

	virtual void receive(const MidiMessage& msg) override {

		// TODO: remove try/catch - there should be no unknown messages

		try {

			receive0(msg);

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

			logger->log(L::SEVERE,

					std::string("Message receiving failed: ") + e.what());

		}

	}

	virtual void receive0(const MidiMessage& msg) {

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

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

				"data = " + toString(msg));

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

		Message msgIn = codec.decode(msg);

		logger->log(L::FINE, "<!-- Received message: -->" + msgIn.toString());

		if (msgIn.type == MessageType::D11_GREETING && !greetingReceived) {

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

			Message msgOut(MessageType::H12_SEED1, version,{

				{FieldType::F01, name1},

				{FieldType::F02, name2},

				{FieldType::F03, denormalize(seed1)}

			});

			send(msgOut);

			greetingReceived = true;

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

		} else if (msgIn.type == MessageType::D13_HASH1_SEED2) {

			std::vector<Field> hash1F = msgIn.findFields(FieldType::F04);

			std::vector<Field> seed2F = msgIn.findFields(FieldType::F03);

			if (hash1F.empty()) throw std::logic_error("hash1 not found");

			if (seed2F.empty()) throw std::logic_error("seed2 not found");

			hash1 = normalize(hash1F[0].data);

			seed2 = normalize(seed2F[0].data);

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

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

					"seed2 = " + toString(seed2));

			Bytes hash1check =

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

			if (equals(hash1, hash1check)) {

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

				hash2 = toBytes(fnv32hash(concat(seed2, xOR(seed0, seed2))));

				Message msgOut(MessageType::H14_HASH2, version,{

					{FieldType::F01, name1},

					{FieldType::F02, name2},

					{FieldType::F04, denormalize(hash2)},

					{FieldType::F05, denormalize(seed3)}

				});

				send(msgOut);

				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 (msgIn.type == MessageType::D15_CONFIRMATION) {

			sendKeepAlive = true;

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

					"Started sending keep-alive messages. "

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

		} else {

			logger->log(L::SEVERE, "Received unexpected message type.");

		}

	}

	void start() override {

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

		if (midiSender == nullptr)

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

		send({

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

			0x00, 0x00, 0x00, version,

			0x00, 0x50, 0x01, 0xf7

		});

		// TODO: check whether this second message is neccessary for V10:

		send({

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

			0x00, 0x00, 0x00, version,

			0x00, 0x03, 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);

}

}