/**

 * 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/>.

 */

#include <string>

#include <cstring>

#include <unistd.h>

#include <stdexcept>

#include <arpa/inet.h>

#include <sys/types.h>

#include <sys/socket.h>

#include <sys/un.h>

#include <netinet/in.h>

#include <vector>

#include <memory>

#include <regex>

#include <iostream>

#include <netdb.h>

#include "Socket.h"

namespace relpipe {

namespace in {

namespace socket {

using namespace relpipe::in::socket::options;

static const std::string findOption(SocketOptions options, std::string name, bool required = false, const std::string defaultValue = "") {

	for (auto o : options) if (o.name == name) return o.value;

	if (required) throw std::invalid_argument("Option " + name + " is required but was not found");

	else return defaultValue;

}

class FD {

private:

	int fd;

public:

	FD(int fd) : fd(fd) {

	};

	virtual ~FD() {

		close(fd);

	}

	int getFD() {

		return fd;

	}

};

static void check(int result, std::string message) {

	if (result == 0); // OK

	else throw std::logic_error("Got error result: " + message + ": " + strerror(errno) + " (result=" + std::to_string(result) + ", errno=" + std::to_string(errno) + ")");

}

class AddressInfos {

private:

	std::shared_ptr<addrinfo> addrInfo;

	AddressInfos(addrinfo* addrInfo) : addrInfo(std::shared_ptr<addrinfo>(addrInfo, freeaddrinfo)) {

	}

public:

	virtual ~AddressInfos() {

	}

	class AddressInfo {

	private:

		std::shared_ptr<addrinfo> parent; // to avoid premature deletion of the whole structure

	public:

		const addrinfo * const ai;

		AddressInfo(const addrinfo * const ai, std::shared_ptr<addrinfo> parent) : ai(ai), parent(parent) {

		}

		const std::string toString() const {

			char buffer[INET6_ADDRSTRLEN] = {0};

			if (ai->ai_family == AF_INET) return inet_ntop(ai->ai_family, &((sockaddr_in const *) ai->ai_addr)->sin_addr, buffer, sizeof (buffer)); // TODO: check 0 result

			else if (ai->ai_family == AF_INET6) return inet_ntop(ai->ai_family, &((sockaddr_in6 const *) ai->ai_addr)->sin6_addr, buffer, sizeof (buffer)); // TODO: check 0 result

			else return "unknown address family: " + std::to_string(ai->ai_family);

		}

	};

	static AddressInfos getAddressInfos(const std::string& host, const std::string& port, int socketType = SOCK_STREAM, int protocol = IPPROTO_TCP) {

		struct addrinfo query;

		memset(&query, sizeof (query), 0);

		query.ai_family = AF_UNSPEC;

		query.ai_socktype = socketType;

		query.ai_protocol = protocol;

		query.ai_flags = AI_ALL;

		struct addrinfo* addrInfo;

		check(getaddrinfo(host.c_str(), port.c_str(), &query, &addrInfo), "getaddrinfo");

		return AddressInfos(addrInfo);

	}

	const std::size_t size() const {

		std::size_t size = 0;

		for (addrinfo* ai = addrInfo.get(); ai; ai = ai->ai_next) size++;

		return size;

	}

	const AddressInfo operator[](std::size_t index) const {

		for (addrinfo* ai = addrInfo.get(); ai; index--) {

			if (index == 0) return AddressInfo(ai, addrInfo);

			else ai = ai->ai_next;

		}

		throw std::out_of_range("invalid index for AddressInfo: " + std::to_string(index));

	}

};

template<class SocketClass, class... MoreArgs> static std::shared_ptr<SocketClass> openClientSocket(const SocketOptions& options, int socketType, int protocol, MoreArgs... moreArgs) {

	AddressInfos remoteAddresses = AddressInfos::getAddressInfos(

			findOption(options, OPTION_HOST, true),

			findOption(options, OPTION_PORT, true),

			socketType,

			protocol);

	return std::shared_ptr<SocketClass>(new SocketClass(remoteAddresses[0], moreArgs...));

}

/**

 * abstract class for sockets that use sendmsg() / recvmsg()

 */

class MSGSocket : public Socket {

protected:

	FD socket;

	void sendmsg(const std::string& message) {

		iovec iov[1];

		msghdr msg = {};

		msg.msg_iov = iov;

		msg.msg_iov[0].iov_base = (void*) message.c_str();

		msg.msg_iov[0].iov_len = message.size();

		msg.msg_iovlen = sizeof (iov) / sizeof (iov[0]);

		ssize_t written = ::sendmsg(socket.getFD(), &msg, 0);

		if (written != message.size()) throw std::logic_error("writing to the socket failed");

	}

public:

	MSGSocket(int socket) : socket(socket) {

	}

	void send(const OutgoingMessage& message) {

		sendmsg(message.data);

	}

};

class UDPClientSocket : public Socket {

private:

	AddressInfos::AddressInfo remoteAddress;

	useconds_t delay = 0;

	FD socket;

public:

	UDPClientSocket(AddressInfos::AddressInfo remoteAddress) : remoteAddress(remoteAddress), socket(::socket(remoteAddress.ai->ai_family, remoteAddress.ai->ai_socktype, remoteAddress.ai->ai_protocol)) {

	}

	static std::shared_ptr<Socket> open(const SocketOptions& options) {

		auto socket = openClientSocket<UDPClientSocket>(options, SOCK_DGRAM, IPPROTO_UDP);

		socket->delay = std::stol(findOption(options, OPTION_DELAY, false, "0")); // TODO: Move to SocketHandler? Or delete.

		return socket;

	}

	void send(const OutgoingMessage& message) override {

		auto ai = remoteAddress.ai;

		sendto(socket.getFD(), message.data.c_str(), message.data.size(), 0, ai->ai_addr, ai->ai_addrlen);

		if (delay) usleep(delay);

	}

	const IncomingMessage receive() override {

		// TODO: UDP receive()

		return IncomingMessage("TODO: receive() a message");

	}

};

class UDPServerSocket : public Socket {

private:

	AddressInfos::AddressInfo localAddress;

	sockaddr_in6 remoteAddressForSending = {};

	useconds_t delay = 0;

	FD socket;

public:

	UDPServerSocket(AddressInfos::AddressInfo remoteAddress) : localAddress(remoteAddress), socket(::socket(remoteAddress.ai->ai_family, remoteAddress.ai->ai_socktype, remoteAddress.ai->ai_protocol)) {

	}

	static std::shared_ptr<Socket> open(const SocketOptions& options) {

		auto socket = openClientSocket<UDPServerSocket>(options, SOCK_DGRAM, IPPROTO_UDP);

		auto ai = socket->localAddress.ai;

		int reuseAddr = true;

		check(::setsockopt(socket->socket.getFD(), SOL_SOCKET, SO_REUSEADDR, &reuseAddr, sizeof (reuseAddr)), "setsockopt SO_REUSEADDR");

		check(::bind(socket->socket.getFD(), ai->ai_addr, ai->ai_addrlen), "bind");

		return socket;

	}

	void send(const OutgoingMessage& message) override {

		// receive a message first to get a remote address:

		char buffer[8192];

		memset((char *) &remoteAddressForSending, 0, sizeof (remoteAddressForSending));

		socklen_t remoteAddressSize = sizeof (remoteAddressForSending);

		ssize_t msgSize = recvfrom(socket.getFD(), buffer, sizeof (buffer), 0, (sockaddr*) & remoteAddressForSending, &remoteAddressSize);

		// respond with our messsage:

		sendto(socket.getFD(), message.data.c_str(), message.data.size(), 0, (sockaddr*) & remoteAddressForSending, remoteAddressSize);

	}

	const IncomingMessage receive() override {

		char buffer[8192];

		sockaddr_in6 remoteAddress;

		memset((char *) &remoteAddress, 0, sizeof (remoteAddress));

		socklen_t remoteAddressSize = sizeof (remoteAddress);

		ssize_t msgSize = recvfrom(socket.getFD(), buffer, sizeof (buffer), 0, (sockaddr*) & remoteAddress, &remoteAddressSize);

		check(msgSize < 0, "recvfrom");

		IncomingMessage message(std::string(buffer, std::min(sizeof (buffer), (size_t) msgSize)));

		// TODO: move to a common method

		char hostBuffer[INET6_ADDRSTRLEN] = {0};

		if (remoteAddress.sin6_family == AF_INET) {

			sockaddr_in* remoteAddress4 = (sockaddr_in*) & remoteAddress;

			message.remoteHost = inet_ntop(remoteAddress4->sin_family, &remoteAddress4->sin_addr, hostBuffer, sizeof (hostBuffer)); // TODO: check 0 result

			message.remotePort = remoteAddress4->sin_port;

		} else if (remoteAddress.sin6_family == AF_INET6) {

			message.remoteHost = inet_ntop(remoteAddress.sin6_family, &remoteAddress.sin6_addr, hostBuffer, sizeof (hostBuffer)); // TODO: check 0 result

			message.remotePort = remoteAddress.sin6_port;

		}

		return message;

	}

};

class TCPClientSocket : public Socket {

private:

	AddressInfos::AddressInfo remoteAddress;

public:

	TCPClientSocket(AddressInfos::AddressInfo remoteAddress) : remoteAddress(remoteAddress) {

	}

	static std::shared_ptr<Socket> open(const SocketOptions& options) {

		return openClientSocket<TCPClientSocket>(options, SOCK_STREAM, IPPROTO_TCP);

	}

	void send(const OutgoingMessage& message) override {

		auto ai = remoteAddress.ai;

		FD s(::socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol));

		check(::connect(s.getFD(), ai->ai_addr, ai->ai_addrlen), "connect socket");

		ssize_t written = ::write(s.getFD(), message.data.c_str(), message.data.size());

		if (written != message.data.size()) throw std::logic_error("writing to the socket failed");

		// TODO: partial writes, repeat

	}

	const IncomingMessage receive() override {

		// TODO: TCP receive()

		return IncomingMessage("TODO: receive() a message");

	}

};

class TCPServerSocket : public Socket {

private:

	AddressInfos::AddressInfo localAddress;

	FD socket;

public:

	TCPServerSocket(AddressInfos::AddressInfo localAddress) : localAddress(localAddress), socket(::socket(localAddress.ai->ai_family, localAddress.ai->ai_socktype, localAddress.ai->ai_protocol)) {

	}

	static std::shared_ptr<Socket> open(const SocketOptions& options) {

		auto socket = openClientSocket<TCPServerSocket>(options, SOCK_STREAM, IPPROTO_TCP);

		auto ai = socket->localAddress.ai;

		int reuseAddr = true;

		check(::setsockopt(socket->socket.getFD(), SOL_SOCKET, SO_REUSEADDR, &reuseAddr, sizeof (reuseAddr)), "setsockopt SO_REUSEADDR");

		check(::bind(socket->socket.getFD(), ai->ai_addr, ai->ai_addrlen), "bind");

		check(::listen(socket->socket.getFD(), 10), "listen"); // TODO: configurable backlog connection count?

		return socket;

	}

	void send(const OutgoingMessage& message) override {

		FD clientSocket(accept(socket.getFD(), nullptr, 0));

		ssize_t written = ::write(clientSocket.getFD(), message.data.c_str(), message.data.size());

		if (written != message.data.size()) throw std::logic_error("writing to the socket failed");

		// TODO: partial writes, repeat

	}

	const IncomingMessage receive() override {

		// TODO: TCP receive()

		return IncomingMessage("TODO: receive() a message");

	}

};

class SCTPClientSocket : public MSGSocket {

private:

	AddressInfos::AddressInfo remoteAddress;

public:

	SCTPClientSocket(AddressInfos::AddressInfo remoteAddress) : remoteAddress(remoteAddress), MSGSocket(::socket(remoteAddress.ai->ai_family, remoteAddress.ai->ai_socktype, remoteAddress.ai->ai_protocol)) {

	}

	static std::shared_ptr<Socket> open(const SocketOptions& options) {

		auto socket = openClientSocket<SCTPClientSocket>(options, SOCK_STREAM, IPPROTO_SCTP);

		check(::connect(socket->socket.getFD(), socket->remoteAddress.ai->ai_addr, socket->remoteAddress.ai->ai_addrlen), "connect socket");

		return socket;

	}

	const IncomingMessage receive() override {

		// TODO: SCTP receive()

		return IncomingMessage("TODO: receive() a message");

	}

};

class UDSClientSocket : public MSGSocket {

public:

	UDSClientSocket(int fd) : MSGSocket(fd) {

	}

	static std::shared_ptr<Socket> open(const SocketOptions& options) {

		struct sockaddr_un address;

		std::string path = findOption(options, OPTION_PATH);

		memset(&address, 0x00, sizeof (address));

		address.sun_family = AF_UNIX;

		strncpy(address.sun_path, path.c_str(), path.size());

		int fd = ::socket(AF_UNIX, SOCK_STREAM, 0);

		auto socket = std::make_shared<UDSClientSocket>(fd);

		check(::connect(socket->socket.getFD(), (const sockaddr*) &address, sizeof (address)), "connect socket");

		if (findOption(options, "debug") == "true") { // TODO: undocumented feature → standardize or remove

			struct ucred credentials;

			socklen_t credentialsLength = sizeof (credentials);

			memset(&credentials, 0x00, credentialsLength);

			getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &credentials, &credentialsLength);

			printf("uds.fd = %d\n", fd);

			printf("uds.path = %s\n", address.sun_path);

			printf("uds.server.pid = %d\n", credentials.pid);

			printf("uds.server.uid = %d\n", credentials.uid);

			printf("uds.server.gid = %d\n", credentials.gid);

		}

		return socket;

	}

	const IncomingMessage receive() override {

		// TODO: UDS receive()

		return IncomingMessage("TODO: receive() a message");

	}

};

template<const char* protocol, const char* role, const char* mode, typename SocketClass>

class TemplateSocketFactory : public SocketFactory {

public:

	bool canHandle(const SocketOptions& options) override {

		return findOption(options, OPTION_PROTOCOL) == protocol

				&& findOption(options, OPTION_ROLE) == role

				&& findOption(options, OPTION_MODE) == mode;

	}

	std::shared_ptr<Socket> open(const SocketOptions& options) override {

		return SocketClass::open(options);

	}

};

static std::vector<std::shared_ptr<SocketFactory>> factories

{

	std::make_shared<TemplateSocketFactory<PROTOCOL_TCP, ROLE_CLIENT, MODE_STREAM, TCPClientSocket >> (),

	std::make_shared<TemplateSocketFactory<PROTOCOL_TCP, ROLE_SERVER, MODE_STREAM, TCPServerSocket >> (),

	std::make_shared<TemplateSocketFactory<PROTOCOL_UDP, ROLE_CLIENT, MODE_DATAGRAM, UDPClientSocket >> (),

	std::make_shared<TemplateSocketFactory<PROTOCOL_UDP, ROLE_SERVER, MODE_DATAGRAM, UDPServerSocket >> (),

	std::make_shared<TemplateSocketFactory<PROTOCOL_SCTP, ROLE_CLIENT, MODE_STREAM, SCTPClientSocket >> (),

	std::make_shared<TemplateSocketFactory<PROTOCOL_SCTP, ROLE_SERVER, MODE_STREAM, UDPClientSocket >> (), // TODO: correct class

	std::make_shared<TemplateSocketFactory<PROTOCOL_UDS, ROLE_CLIENT, MODE_STREAM, UDSClientSocket >> (),

	std::make_shared<TemplateSocketFactory<PROTOCOL_UDS, ROLE_CLIENT, MODE_DATAGRAM, UDSClientSocket >> (), // TODO: correct class

	std::make_shared<TemplateSocketFactory<PROTOCOL_UDS, ROLE_SERVER, MODE_STREAM, UDSClientSocket >> (), // TODO: correct class

	std::make_shared<TemplateSocketFactory<PROTOCOL_UDS, ROLE_SERVER, MODE_DATAGRAM, UDSClientSocket >> (), // TODO: correct class

};

std::shared_ptr<SocketFactory> SocketFactory::find(const SocketOptions& options) {

	for (auto f : factories) if (f->canHandle(options)) return f;

	throw std::logic_error("Unable to find a SocketFactory"); // TODO: add relevant options?

}

}

}

}