/**
 * 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 <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>;

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(std::chrono::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& midiMessage) override {
		logger->log(L::FINE, "Received a message: size = " + std::to_string(midiMessage.size()) + " data = " + toString(midiMessage));
		std::lock_guard<std::recursive_mutex> lock(midiMutex);


		if (midiMessage.size() == 12 && midiMessage[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 (midiMessage.size() == 54 && midiMessage[9] == 0x13 && midiMessage[33] == 0x04 && midiMessage[43] == 0x03) {
			Bytes hash1(midiMessage.begin() + 35, midiMessage.begin() + 35 + 8);
			seed2 = Bytes(midiMessage.begin() + 45, midiMessage.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(midiMessage)
						<< " 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 (midiMessage.size() == 12 && midiMessage[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);
}

}