/**
 * 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 out {
namespace socket {

using namespace relpipe::out::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...));
}

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

		// respond with our messsage:
		sendto(socket.getFD(), message.data.c_str(), message.data.size(), 0, (sockaddr*) & remoteAddress, remoteAddressSize);
	}

	const IncomingMessage receive() override {
		// TODO: UDP receive()
		return IncomingMessage("TODO: receive() a 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?
}


}
}
}