/*
 * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <AK/StringView.h>
#include <Kernel/API/POSIX/errno.h>
#include <Kernel/Debug.h>
#include <Kernel/FileSystem/OpenFileDescription.h>
#include <Kernel/Net/IP/Socket.h>
#include <Kernel/Net/LocalSocket.h>
#include <Kernel/Net/NetworkingManagement.h>
#include <Kernel/Net/Socket.h>
#include <Kernel/Tasks/Process.h>
#include <Kernel/UnixTypes.h>

namespace Kernel {

ErrorOr<NonnullRefPtr<Socket>> Socket::create(int domain, int type, int protocol)
{
    switch (domain) {
    case AF_LOCAL:
        return TRY(LocalSocket::try_create(type & SOCK_TYPE_MASK));
    case AF_INET:
        return IPv4Socket::create(type & SOCK_TYPE_MASK, protocol);
    default:
        return EAFNOSUPPORT;
    }
}

Socket::Socket(int domain, int type, int protocol)
    : m_domain(domain)
    , m_type(type)
    , m_protocol(protocol)
{
    set_origin(Process::current());
}

Socket::~Socket() = default;

void Socket::set_setup_state(SetupState new_setup_state)
{
    dbgln_if(SOCKET_DEBUG, "Socket({}) setup state moving from {} to {}", this, to_string(m_setup_state), to_string(new_setup_state));
    m_setup_state = new_setup_state;
    evaluate_block_conditions();
}

RefPtr<Socket> Socket::accept()
{
    MutexLocker locker(mutex());
    if (m_pending.is_empty())
        return nullptr;
    dbgln_if(SOCKET_DEBUG, "Socket({}) de-queueing connection", this);
    auto client = m_pending.take_first();
    VERIFY(!client->is_connected());
    auto& process = Process::current();
    client->set_acceptor(process);
    client->m_connected = true;
    client->set_role(Role::Accepted);
    if (!m_pending.is_empty())
        evaluate_block_conditions();
    return client;
}

ErrorOr<void> Socket::queue_connection_from(NonnullRefPtr<Socket> peer)
{
    dbgln_if(SOCKET_DEBUG, "Socket({}) queueing connection", this);
    MutexLocker locker(mutex());
    if (m_pending.size() >= m_backlog)
        return set_so_error(ECONNREFUSED);
    SOCKET_TRY(m_pending.try_append(move(peer)));
    evaluate_block_conditions();
    return {};
}

ErrorOr<void> Socket::setsockopt(int level, int option, Userspace<void const*> user_value, socklen_t user_value_size)
{
    MutexLocker locker(mutex());

    if (level != SOL_SOCKET)
        return ENOPROTOOPT;
    VERIFY(level == SOL_SOCKET);
    switch (option) {
    case SO_SNDTIMEO:
        if (user_value_size != sizeof(timeval))
            return EINVAL;
        m_send_timeout = TRY(copy_time_from_user(static_ptr_cast<timeval const*>(user_value)));
        return {};
    case SO_RCVTIMEO:
        if (user_value_size != sizeof(timeval))
            return EINVAL;
        m_receive_timeout = TRY(copy_time_from_user(static_ptr_cast<timeval const*>(user_value)));
        return {};
    case SO_BINDTODEVICE: {
        if (user_value_size != IFNAMSIZ)
            return EINVAL;
        auto user_string = static_ptr_cast<char const*>(user_value);
        auto ifname = TRY(Process::get_syscall_name_string_fixed_buffer<IFNAMSIZ>(user_string, user_value_size));
        auto device = NetworkingManagement::the().lookup_by_name(ifname.representable_view());
        if (!device)
            return ENODEV;
        m_bound_interface.with([&device](auto& bound_device) {
            bound_device = move(device);
        });
        return {};
    }
    case SO_DEBUG:
        // NOTE: This is supposed to toggle collection of debugging information on/off, we don't have any right now, so this is a no-op.
        return {};
    case SO_KEEPALIVE:
        // FIXME: Obviously, this is not a real keepalive.
        return {};
    case SO_TIMESTAMP:
        if (user_value_size != sizeof(int))
            return EINVAL;
        m_timestamp = TRY(copy_typed_from_user(static_ptr_cast<int const*>(user_value)));
        if (m_timestamp != 0 && (domain() != AF_INET || type() == SOCK_STREAM)) {
            // FIXME: Support SO_TIMESTAMP for more protocols?
            m_timestamp = 0;
            return ENOTSUP;
        }
        return {};
    case SO_DONTROUTE: {
        if (user_value_size != sizeof(int))
            return EINVAL;
        m_routing_disabled = TRY(copy_typed_from_user(static_ptr_cast<int const*>(user_value))) != 0;
        return {};
    }
    case SO_REUSEADDR:
        dbgln("FIXME: SO_REUSEADDR requested, but not implemented.");
        return {};
    case SO_BROADCAST: {
        if (user_value_size != sizeof(int))
            return EINVAL;
        m_broadcast_allowed = TRY(copy_typed_from_user(static_ptr_cast<int const*>(user_value))) != 0;
        return {};
    }
    default:
        dbgln("setsockopt({}) at SOL_SOCKET not implemented.", option);
        return ENOPROTOOPT;
    }
}

ErrorOr<void> Socket::getsockopt(OpenFileDescription&, int level, int option, Userspace<void*> value, Userspace<socklen_t*> value_size)
{
    MutexLocker locker(mutex());

    socklen_t size;
    TRY(copy_from_user(&size, value_size.unsafe_userspace_ptr()));

    // FIXME: Add TCP_NODELAY, IPPROTO_TCP and IPPROTO_IP (used in OpenSSH)
    if (level != SOL_SOCKET) {
        // Not sure if this is the correct error code, but it's only temporary until other levels are implemented.
        return ENOPROTOOPT;
    }

    switch (option) {
    case SO_SNDTIMEO:
        if (size < sizeof(timeval))
            return EINVAL;
        {
            timeval tv = m_send_timeout.to_timeval();
            TRY(copy_to_user(static_ptr_cast<timeval*>(value), &tv));
        }
        size = sizeof(timeval);
        return copy_to_user(value_size, &size);
    case SO_RCVTIMEO:
        if (size < sizeof(timeval))
            return EINVAL;
        {
            timeval tv = m_receive_timeout.to_timeval();
            TRY(copy_to_user(static_ptr_cast<timeval*>(value), &tv));
        }
        size = sizeof(timeval);
        return copy_to_user(value_size, &size);
    case SO_ERROR: {
        if (size < sizeof(int))
            return EINVAL;
        return so_error().with([&size, value, value_size](auto& error) -> ErrorOr<void> {
            int errno = 0;
            if (error.has_value())
                errno = error.value();
            TRY(copy_to_user(static_ptr_cast<int*>(value), &errno));
            size = sizeof(int);
            TRY(copy_to_user(value_size, &size));
            error = {};
            return {};
        });
    }
    case SO_BINDTODEVICE:
        if (size < IFNAMSIZ)
            return EINVAL;
        return m_bound_interface.with([&](auto& bound_device) -> ErrorOr<void> {
            if (bound_device) {
                auto name = bound_device->name();
                auto length = name.length() + 1;
                auto characters = name.characters_without_null_termination();
                TRY(copy_to_user(static_ptr_cast<char*>(value), characters, length));
                size = length;
                return copy_to_user(value_size, &size);
            } else {
                size = 0;
                TRY(copy_to_user(value_size, &size));
                // FIXME: This return value looks suspicious.
                return EFAULT;
            }
        });
    case SO_TIMESTAMP:
        if (size < sizeof(int))
            return EINVAL;
        TRY(copy_to_user(static_ptr_cast<int*>(value), &m_timestamp));
        size = sizeof(int);
        return copy_to_user(value_size, &size);
    case SO_TYPE:
        if (size < sizeof(int))
            return EINVAL;
        TRY(copy_to_user(static_ptr_cast<int*>(value), &m_type));
        size = sizeof(int);
        return copy_to_user(value_size, &size);
    case SO_DEBUG:
        // NOTE: This is supposed to toggle collection of debugging information on/off, we don't have any right now, so we just claim it's always off.
        if (size < sizeof(int))
            return EINVAL;
        TRY(memset_user(value.unsafe_userspace_ptr(), 0, sizeof(int)));
        size = sizeof(int);
        return copy_to_user(value_size, &size);
    case SO_ACCEPTCONN: {
        int accepting_connections = (m_role == Role::Listener) ? 1 : 0;
        if (size < sizeof(accepting_connections))
            return EINVAL;
        TRY(copy_to_user(static_ptr_cast<int*>(value), &accepting_connections));
        size = sizeof(accepting_connections);
        return copy_to_user(value_size, &size);
    }
    case SO_DONTROUTE: {
        int routing_disabled = m_routing_disabled ? 1 : 0;
        if (size < sizeof(routing_disabled))
            return EINVAL;
        TRY(copy_to_user(static_ptr_cast<int*>(value), &routing_disabled));
        size = sizeof(routing_disabled);
        return copy_to_user(value_size, &size);
    }
    case SO_REUSEADDR: {
        int reuse_address = 0;
        if (size < sizeof(reuse_address))
            return EINVAL;
        TRY(copy_to_user(static_ptr_cast<int*>(value), &reuse_address));
        size = sizeof(reuse_address);
        return copy_to_user(value_size, &size);
    }
    case SO_BROADCAST: {
        int broadcast_allowed = m_broadcast_allowed ? 1 : 0;
        if (size < sizeof(broadcast_allowed))
            return EINVAL;
        TRY(copy_to_user(static_ptr_cast<int*>(value), &broadcast_allowed));
        size = sizeof(broadcast_allowed);
        return copy_to_user(value_size, &size);
    }
    default:
        dbgln("getsockopt({}) at SOL_SOCKET not implemented.", option);
        return ENOPROTOOPT;
    }
}

ErrorOr<size_t> Socket::read(OpenFileDescription& description, u64, UserOrKernelBuffer& buffer, size_t size)
{
    if (is_shut_down_for_reading())
        return 0;
    UnixDateTime t {};
    return recvfrom(description, buffer, size, 0, {}, 0, t, description.is_blocking());
}

ErrorOr<size_t> Socket::write(OpenFileDescription& description, u64, UserOrKernelBuffer const& data, size_t size)
{
    if (is_shut_down_for_writing())
        return set_so_error(EPIPE);
    return sendto(description, data, size, 0, {}, 0);
}

ErrorOr<void> Socket::shutdown(int how)
{
    MutexLocker locker(mutex());
    if (type() == SOCK_STREAM && !is_connected())
        return set_so_error(ENOTCONN);
    if (m_role == Role::Listener)
        return set_so_error(ENOTCONN);
    if (!m_shut_down_for_writing && (how == SHUT_WR || how == SHUT_RDWR)) {
        shut_down_for_writing();
        m_shut_down_for_writing = true;
    }
    if (!m_shut_down_for_reading && (how == SHUT_RD || how == SHUT_RDWR)) {
        shut_down_for_reading();
        m_shut_down_for_reading = true;
    }
    return {};
}

ErrorOr<struct stat> Socket::stat() const
{
    struct stat st = {};
    st.st_mode = S_IFSOCK;
    return st;
}

void Socket::set_connected(bool connected)
{
    MutexLocker locker(mutex());
    if (m_connected == connected)
        return;
    m_connected = connected;
    evaluate_block_conditions();
}

void Socket::set_origin(Process const& process)
{
    auto credentials = process.credentials();
    m_origin = { process.pid().value(), credentials->uid().value(), credentials->gid().value() };
}

void Socket::set_acceptor(Process const& process)
{
    auto credentials = process.credentials();
    m_acceptor = { process.pid().value(), credentials->uid().value(), credentials->gid().value() };
}

}