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

module;
#include <poll.h>
#include <fcntl.h>
#include <sys/socket.h>
#include <cerrno>

module Crafter.Network:Stream_impl;
import :Stream;
import std;

using namespace Crafter;

void Crafter::SetNonBlocking(int descriptor) {
    const int flags = fcntl(descriptor, F_GETFL, 0);
    if (flags == -1 || fcntl(descriptor, F_SETFL, flags | O_NONBLOCK) == -1) {
        throw std::runtime_error(std::string("could not make the socket non-blocking: ")
                                 + std::strerror(errno));
    }
}

bool Crafter::PollDescriptor(int descriptor, short events,
                             std::chrono::steady_clock::time_point deadline) {
    for (;;) {
        const auto left = std::chrono::duration_cast<std::chrono::milliseconds>(
            deadline - std::chrono::steady_clock::now());
        // A deadline already in the past still gets one non-blocking look, so
        // a zero timeout means "is it ready right now" rather than "give up".
        const int wait = left.count() > 0 ? static_cast<int>(left.count()) : 0;

        pollfd descriptors{ .fd = descriptor, .events = events, .revents = 0 };
        const int ready = poll(&descriptors, 1, wait);
        if (ready < 0) {
            if (errno == EINTR) continue;
            throw std::runtime_error(std::string("poll failed: ") + std::strerror(errno));
        }
        if (ready == 0) return false;
        return true;
    }
}

PlainStream::PlainStream(int descriptor) : descriptor(descriptor) {
    SetNonBlocking(descriptor);
}

StreamStatus PlainStream::ReadSome(char* buffer, std::size_t size,
                                   std::chrono::milliseconds timeout,
                                   std::size_t& read) {
    read = 0;
    const auto deadline = std::chrono::steady_clock::now() + timeout;
    for (;;) {
        const auto got = recv(descriptor, buffer, size, 0);
        if (got > 0) {
            read = static_cast<std::size_t>(got);
            return StreamStatus::Data;
        }
        if (got == 0) return StreamStatus::Closed;
        if (errno == EINTR) continue;
        if (errno == EAGAIN || errno == EWOULDBLOCK) {
            if (!PollDescriptor(descriptor, POLLIN, deadline)) return StreamStatus::TimedOut;
            continue;
        }
        // A reset is how a peer that stopped caring shows up; it is an end of
        // connection rather than something worth a diagnostic.
        if (errno == ECONNRESET) return StreamStatus::Closed;
        throw std::runtime_error(std::string("recv failed: ") + std::strerror(errno));
    }
}

void PlainStream::Write(const void* buffer, std::size_t size,
                        std::chrono::milliseconds timeout) {
    const auto deadline = std::chrono::steady_clock::now() + timeout;
    const char* data = reinterpret_cast<const char*>(buffer);
    std::size_t sent = 0;
    while (sent < size) {
        // MSG_NOSIGNAL: a peer that closed early must surface as EPIPE here,
        // not as a SIGPIPE that takes the process down.
        const auto wrote = send(descriptor, data + sent, size - sent, MSG_NOSIGNAL);
        if (wrote > 0) {
            sent += static_cast<std::size_t>(wrote);
            continue;
        }
        if (wrote == 0) throw std::runtime_error("the peer closed the connection");
        if (errno == EINTR) continue;
        if (errno == EAGAIN || errno == EWOULDBLOCK) {
            if (!PollDescriptor(descriptor, POLLOUT, deadline)) {
                throw std::runtime_error("timed out writing to the peer");
            }
            continue;
        }
        throw std::runtime_error(std::string("send failed: ") + std::strerror(errno));
    }
}

void PlainStream::Shutdown() noexcept {
    shutdown(descriptor, SHUT_WR);
}