//SPDX-License-Identifier: LGPL-3.0-only
//SPDX-FileCopyrightText: Copyright (C) 2026 Catcrafts®

module;

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <sys/uio.h>
#include <sys/time.h>
#include <sys/wait.h>
#include <sys/ioctl.h>
#include <netdb.h>
#include <strings.h>
#include <cerrno>
#include <fcntl.h>
#include <netinet/tcp.h>
#include <poll.h>

module Crafter.Network:ClientTCP_impl;
import :ClientTCP;
import Crafter.Thread;
import std;

using namespace Crafter;

namespace {
    // recv, retried when a signal interrupts it: a receive waits on through
    // a signal rather than failing.
    ssize_t RecieveRetrying(int socketid, void* buffer, std::size_t size) {
        ssize_t read;
        do {
            read = recv(socketid, buffer, size, 0);
        } while (read < 0 && errno == EINTR);
        return read;
    }

    // A failed recv. EAGAIN is the receive timeout (SO_RCVTIMEO) running out;
    // anything else carries its errno, under the message a receive always
    // threw.
    [[noreturn]] void ThrowRecieveError() {
        const int failure = errno;
        if (failure == EAGAIN || failure == EWOULDBLOCK) throw SocketTimeoutException();
        throw SocketErrorException(SocketErrorKind::System, failure, std::strerror(failure));
    }

    // One connect attempt to one address: a connected, blocking socket, or a
    // throw that leaves nothing open.
    int ConnectTo(const sockaddr* address, socklen_t length, std::chrono::milliseconds timeout) {
        const int fd = socket(address->sa_family, SOCK_STREAM, 0);
        if (fd == -1) {
            // An address family the host cannot open — IPv6 switched off,
            // say — fails this address alone; the caller moves on.
            const int failure = errno;
            throw SocketErrorException(SocketErrorKind::System, failure, std::string("Could not open socket: ") + std::strerror(failure));
        }

        // With a timeout the connect runs non-blocking, so poll can bound the
        // wait; the socket is made blocking again once it is connected.
        const bool bounded = timeout > std::chrono::milliseconds::zero();
        const int flags = fcntl(fd, F_GETFL, 0);
        if (bounded) {
            fcntl(fd, F_SETFL, flags | O_NONBLOCK);
        }
        int failure = 0;
        if (connect(fd, address, length) == -1) {
            failure = errno;
            if (failure == EINPROGRESS) {
                pollfd connecting { .fd = fd, .events = POLLOUT, .revents = 0 };
                const int waitMs = static_cast<int>(std::min<std::chrono::milliseconds::rep>(timeout.count(), std::numeric_limits<int>::max()));
                int ready;
                do {
                    ready = poll(&connecting, 1, waitMs);
                } while (ready == -1 && errno == EINTR);
                if (ready == 0) {
                    close(fd);
                    throw SocketTimeoutException();
                }
                if (ready == -1) {
                    failure = errno;
                } else {
                    // The connect's own result.
                    socklen_t size = sizeof(failure);
                    getsockopt(fd, SOL_SOCKET, SO_ERROR, &failure, &size);
                }
            }
        }
        if (failure != 0) {
            // Report the failure instead of handing back a socket that is not
            // connected to anything — every later send/recv on it would fail
            // with a far less obvious error.
            close(fd);
            throw SocketErrorException(SocketErrorKind::System, failure, std::string("Could not connect to server: ") + std::strerror(failure));
        }
        if (bounded) {
            fcntl(fd, F_SETFL, flags);
        }
        return fd;
    }
}

ClientTCP::ClientTCP(int socketid) : socketid(socketid)
{

}

ClientTCP::ClientTCP(const char* hostName, std::uint16_t port, std::chrono::milliseconds connectTimeout)
{
	// getaddrinfo rather than gethostbyname: the latter is not thread safe,
	// and it signals failure by returning null — which was then dereferenced
	// straight into a crash on any unresolvable host.
	//
	// AF_UNSPEC, and every result kept: `localhost` resolves to ::1 and
	// 127.0.0.1, and a server may listen on either one alone. Asking for
	// AF_INET only, as this used to, made a server bound to ::1 unreachable
	// by name. No AI_ADDRCONFIG, as Python's create_connection passes none
	// either: it hides ::1 on a host whose only IPv6 address is loopback.
	addrinfo hints{};
	hints.ai_family = AF_UNSPEC;
	hints.ai_socktype = SOCK_STREAM;
	addrinfo* resolved = nullptr;
	const std::string service = std::to_string(port);
	const int status = getaddrinfo(hostName, service.c_str(), &hints, &resolved);
	if (status != 0 || resolved == nullptr) {
		throw SocketErrorException(SocketErrorKind::Resolver, status,
		                           std::string("Could not resolve host '") + hostName + "': " + gai_strerror(status));
	}
	for (const addrinfo* entry = resolved; entry != nullptr; entry = entry->ai_next) {
		Address address {};
		std::memcpy(&address.storage, entry->ai_addr, entry->ai_addrlen);
		address.length = entry->ai_addrlen;
		addresses.push_back(address);
	}
	freeaddrinfo(resolved);

    Connect(connectTimeout);
}

ClientTCP::ClientTCP(std::string hostName, std::uint16_t port, std::chrono::milliseconds connectTimeout): ClientTCP(hostName.c_str(), port, connectTimeout)
{

}

// The moved-from object gives up ownership; the socket itself stays open —
// closing it here (as this used to) meant moving a ClientTCP silently
// dropped the connection it was carrying.
ClientTCP::ClientTCP(ClientTCP&& other) noexcept : socketid(other.socketid), addresses(std::move(other.addresses)) {
    other.socketid = -1;
}

ClientTCP::~ClientTCP()
{
    if(socketid != -1) {
        shutdown(socketid, SHUT_RDWR);
	    close(socketid);
    }
}

void ClientTCP::Connect(std::chrono::milliseconds timeout) {
    if (addresses.empty()) {
        throw std::logic_error("ClientTCP::Connect: no address to connect to; a socket handed over by accept() cannot connect again");
    }
    // Each address in turn, in the order getaddrinfo ranked them; when none
    // connects, the caller sees what the last one failed with, as with
    // Python's create_connection.
    std::exception_ptr last;
    for (const Address& address : addresses) {
        try {
            socketid = ConnectTo(reinterpret_cast<const sockaddr*>(&address.storage), address.length, timeout);
            return;
        } catch (...) {
            last = std::current_exception();
        }
    }
    socketid = -1;
    std::rethrow_exception(last);
}

void ClientTCP::Stop() {
    shutdown(socketid, SHUT_RDWR);
	close(socketid);
    socketid = -1;
}

void ClientTCP::SetNoDelay(bool enabled) {
    const int value = enabled ? 1 : 0;
    if (setsockopt(socketid, IPPROTO_TCP, TCP_NODELAY, &value, sizeof(value)) == -1) {
        throw std::runtime_error(std::string("Could not set TCP_NODELAY: ") + std::strerror(errno));
    }
}

void ClientTCP::SetReceiveTimeout(std::chrono::milliseconds timeout) {
    const auto seconds = std::chrono::duration_cast<std::chrono::seconds>(timeout);
    timeval value {};
    value.tv_sec = static_cast<time_t>(seconds.count());
    value.tv_usec = static_cast<suseconds_t>(std::chrono::duration_cast<std::chrono::microseconds>(timeout - seconds).count());
    if (setsockopt(socketid, SOL_SOCKET, SO_RCVTIMEO, &value, sizeof(value)) == -1) {
        throw std::runtime_error(std::string("Could not set the receive timeout: ") + std::strerror(errno));
    }
}

void ClientTCP::Send(const void* buffer, std::uint32_t size) const {
    // send() is free to accept less than it was offered, and does so
    // routinely once a buffer outgrows the socket's send buffer — a
    // multi-megabyte HTTP body, say. Loop until it is all handed over.
    const char* data = reinterpret_cast<const char*>(buffer);
    std::uint32_t sent = 0;
    while (sent < size) {
        const auto status = send(socketid, data + sent, size - sent, MSG_NOSIGNAL);
        if (status == 0) {
            throw SocketClosedException();
        } else if (status < 0) {
            if (errno == EINTR) continue;
            const int failure = errno;
            throw SocketErrorException(SocketErrorKind::System, failure, std::strerror(failure));
        }
        sent += static_cast<std::uint32_t>(status);
    }
}
std::vector<char> ClientTCP::RecieveSync(std::uint32_t bufferSize) const {
    // recv's 0 means a closed peer, but not for a receive of no bytes.
    if (bufferSize == 0) return {};
    std::vector<char> buffer(bufferSize);
    const ssize_t read = RecieveRetrying(socketid, buffer.data(), bufferSize);
    if (read < 0) ThrowRecieveError();
    if (read == 0) throw SocketClosedException();
    buffer.resize(static_cast<std::size_t>(read));
    return buffer;
}
std::uint32_t ClientTCP::RecieveSync(std::uint32_t bufferSize, void* buffer) const {
    if (bufferSize == 0) return 0;
    const ssize_t read = RecieveRetrying(socketid, buffer, bufferSize);
    if (read < 0) ThrowRecieveError();
    if (read == 0) throw SocketClosedException();
    return static_cast<std::uint32_t>(read);
}

std::vector<char> ClientTCP::RecieveSync() const {
    int count = 0;
    ioctl(socketid, FIONREAD, &count);
    if (count <= 0) {
        count = 1024;
    }
    std::vector<char> buffer(static_cast<std::size_t>(count));
    const ssize_t read = RecieveRetrying(socketid, buffer.data(), buffer.size());
    if (read < 0) ThrowRecieveError();
    if (read == 0) throw SocketClosedException();
    buffer.resize(static_cast<std::size_t>(read));
    return buffer;
}

std::vector<char> ClientTCP::RecieveUntilCloseSync() const {
    std::vector<char> buffer;
    while (true) {
        int count = 0;
        ioctl(socketid, FIONREAD, &count);
        if (count <= 0) {
            count = 1024;
        }
        const std::size_t oldSize = buffer.size();
        buffer.resize(oldSize + static_cast<std::size_t>(count));
        const ssize_t read = RecieveRetrying(socketid, buffer.data() + oldSize, static_cast<std::size_t>(count));
        if (read < 0) ThrowRecieveError();
        buffer.resize(oldSize + static_cast<std::size_t>(read));
        if (read == 0) {
            // A peer that closes before sending anything is reported the
            // way the other receives report it.
            if (buffer.empty()) throw SocketClosedException();
            return buffer;
        }
    }
}

std::vector<char> ClientTCP::RecieveUntilFullSync(std::uint32_t bufferSize) const {
    std::vector<char> buffer(bufferSize);
    std::size_t read = 0;
    while (read < bufferSize) {
        const ssize_t newRead = RecieveRetrying(socketid, buffer.data() + read, bufferSize - read);
        if (newRead < 0) ThrowRecieveError();
        if (newRead == 0) throw SocketClosedException();
        read += static_cast<std::size_t>(newRead);
    }
    return buffer;
}

namespace {
    // Runs `receive` on the ThreadPool and hands its result to `onReceived`,
    // or what it threw to `onError` (dropped without one): a pool task must
    // not let an exception escape, or it ends the program. The callback runs
    // outside the try, so its own exceptions aren't taken for a failed
    // receive.
    template <typename Result>
    void EnqueueReceive(std::function<Result()> receive, std::function<void(Result)> onReceived, std::function<void(std::exception_ptr)> onError) {
        ThreadPool::Enqueue([receive = std::move(receive), onReceived = std::move(onReceived), onError = std::move(onError)]() {
            std::optional<Result> result;
            try {
                result = receive();
            } catch (...) {
                if (onError) onError(std::current_exception());
                return;
            }
            onReceived(std::move(*result));
        });
    }
}

void ClientTCP::RecieveAsync(std::uint32_t bufferSize, std::function<void(std::vector<char>)> recieveCallback, std::function<void(std::exception_ptr)> onError) const {
    EnqueueReceive<std::vector<char>>([this, bufferSize] { return RecieveSync(bufferSize); }, std::move(recieveCallback), std::move(onError));
}

void ClientTCP::RecieveAsync(std::uint32_t bufferSize, std::function<void(std::uint32_t)> recieveCallback, char* buffer, std::function<void(std::exception_ptr)> onError) const {
    EnqueueReceive<std::uint32_t>([this, bufferSize, buffer] { return RecieveSync(bufferSize, buffer); }, std::move(recieveCallback), std::move(onError));
}

void ClientTCP::RecieveUntilFullAsync(std::uint32_t bufferSize, std::function<void(std::vector<char>)> recieveCallback, std::function<void(std::exception_ptr)> onError) const {
    EnqueueReceive<std::vector<char>>([this, bufferSize] { return RecieveUntilFullSync(bufferSize); }, std::move(recieveCallback), std::move(onError));
}

void ClientTCP::RecieveAsync(std::function<void(std::vector<char>)> recieveCallback, std::function<void(std::exception_ptr)> onError) const {
    EnqueueReceive<std::vector<char>>([this] { return RecieveSync(); }, std::move(recieveCallback), std::move(onError));
}

void ClientTCP::RecieveUntilCloseAsync(std::function<void(std::vector<char>)> recieveCallback, std::function<void(std::exception_ptr)> onError) const {
    EnqueueReceive<std::vector<char>>([this] { return RecieveUntilCloseSync(); }, std::move(recieveCallback), std::move(onError));
}