/**
 * Relational pipes
 * Copyright © 2022 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/>.
 */
#pragma once

#include <memory>
#include <string>
#include <vector>
#include <iostream>
#include <sstream>
#include <locale>
#include <codecvt>
#include <random>
#include <regex>

#include <mosquittopp.h>

#include <relpipe/common/type/typedefs.h>
#include <relpipe/reader/TypeId.h>
#include <relpipe/reader/handlers/RelationalReaderStringHandler.h>
#include <relpipe/reader/handlers/AttributeMetadata.h>

#include "Configuration.h"
#include "Hex.h"

namespace relpipe {
namespace out {
namespace mqtt {

class MQTTHandler : public relpipe::reader::handlers::RelationalReaderStringHandler {
private:
	std::wstring_convert<codecvt_utf8<wchar_t>> convertor; // TODO: support also other encodings.
	Configuration configuration;
	std::shared_ptr<mosqpp::mosquittopp> mq = std::make_shared<mosqpp::mosquittopp>(generateClientID().c_str());

	/**
	 * @return unique (random) client ID for MQTT to allow multiple simultaneous connections
	 */
	static std::string generateClientID() {
		std::stringstream result;
		std::string symbols("0123456789abcdef");

		std::random_device dev;
		std::mt19937 rng(dev());
		std::uniform_int_distribution<std::mt19937::result_type> dist(0, symbols.size());

		for (int i = 0; i < 8; i++) result << symbols[dist(rng)];

		return result.str();
	}

	struct CurrentRelation {
		relpipe::common::type::StringX name;
		std::vector<relpipe::reader::handlers::AttributeMetadata> attributes;
		relpipe::common::type::Integer attributeIndex = 0;
		std::string currentValue;
	} currentRelation;

	static void parseConnectionString(const std::string& connectionString, std::string& hostname, int& port) {
		std::regex pattern("mqtt:(//)?([^:]+)(:([0-9]+))?");
		std::smatch match;
		if (std::regex_match(connectionString, match, pattern)) {
			hostname = match[2];
			port = stoi(match[4]);
		} else {
			throw std::invalid_argument("Invalid connection string format. Expecting something like: mqtt://localhost:1883");
		}
	}

	static void check(std::string operation, int result) {
		if (result) throw std::logic_error("mosquitto operation failed: " + operation + " = " + std::to_string(result));
	}

public:

	static MQTTHandler* create(Configuration configuration) {
		MQTTHandler* h = new MQTTHandler();

		std::string connectionString = h->convertor.to_bytes(configuration.connectionString);
		std::string username;
		std::string password;
		std::string hostname;
		int port;

		parseConnectionString(connectionString, hostname, port);

		for (auto o : configuration.connectionOptions) {
			if (o.name == L"username") username = h->convertor.to_bytes(o.value);
			else if (o.name == L"password") password = h->convertor.to_bytes(o.value);
			else throw std::invalid_argument("Unsupported connection option: " + h->convertor.to_bytes(o.name));
		}

		if (username.size()) check("set credentials", h->mq->username_pw_set(username.c_str(), password.c_str()));

		check("connect", h->mq->connect(hostname.c_str(), port));

		return h;
	}

	void startRelation(relpipe::common::type::StringX name, std::vector<relpipe::reader::handlers::AttributeMetadata> attributes) override {
		// TODO: check relation name according to the configuration
		currentRelation = CurrentRelation{name, attributes};
	}

	void attribute(const relpipe::common::type::StringX& value) override {

		auto attributeName = currentRelation.attributes[currentRelation.attributeIndex].getAttributeName();
		if (attributeName == L"text" && value.size()) currentRelation.currentValue = convertor.to_bytes(value);
		else if (attributeName == L"data" && value.size()) currentRelation.currentValue = Hex::fromHex(value).str();
		else if (attributeName == L"text"); // keep empty or value from 'data'
		else if (attributeName == L"data"); // keep empty or value from 'text'

		currentRelation.attributeIndex++;
		if (currentRelation.attributeIndex == currentRelation.attributes.size()) {
			currentRelation.attributeIndex = 0;
			int mid = -1;
			check("publish", mq->publish(&mid, convertor.to_bytes(configuration.stream).c_str(), currentRelation.currentValue.size(), currentRelation.currentValue.c_str()));
			// std::cerr << "MQTT message enqueued: " << mid << std::endl;
		}

	}

	void endOfPipe() {
		check("disconnect", mq->disconnect());
	}

};

}
}
}