/*
 * Copyright (c) 2024, Andrew Kaster <andrew@ladybird.org>
 * Copyright (c) 2025, Aliaksandr Kalenik <kalenik.aliaksandr@gmail.com>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#pragma once

#include <AK/MemoryStream.h>
#include <AK/Queue.h>
#include <LibCore/Socket.h>
#include <LibIPC/AutoCloseFileDescriptor.h>
#include <LibIPC/File.h>
#include <LibThreading/ConditionVariable.h>
#include <LibThreading/Forward.h>
#include <LibThreading/MutexProtected.h>
#include <LibThreading/RWLock.h>

namespace IPC {

class SendQueue : public AtomicRefCounted<SendQueue> {
public:
    void enqueue_message(Vector<u8>&& bytes, Vector<int>&& fds);
    struct BytesAndFds {
        Vector<u8> bytes;
        Vector<int> fds;
    };
    BytesAndFds peek(size_t max_bytes);
    void discard(size_t bytes_count, size_t fds_count);

private:
    AllocatingMemoryStream m_stream;
    Vector<int> m_fds;
    Threading::Mutex m_mutex;
};

class TransportSocket {
    AK_MAKE_NONCOPYABLE(TransportSocket);
    AK_MAKE_NONMOVABLE(TransportSocket);

public:
    static constexpr socklen_t SOCKET_BUFFER_SIZE = 128 * KiB;

    explicit TransportSocket(NonnullOwnPtr<Core::LocalSocket> socket);
    ~TransportSocket();

    void set_up_read_hook(Function<void()>);
    bool is_open() const;

    void close();
    void close_after_sending_all_pending_messages();

    void wait_until_readable();

    void post_message(Vector<u8> const&, Vector<NonnullRefPtr<AutoCloseFileDescriptor>> const&);

    enum class ShouldShutdown {
        No,
        Yes,
    };
    struct Message {
        Vector<u8> bytes;
        Queue<File> fds;
    };
    ShouldShutdown read_as_many_messages_as_possible_without_blocking(Function<void(Message&&)>&&);

    // Obnoxious name to make it clear that this is a dangerous operation.
    ErrorOr<int> release_underlying_transport_for_transfer();

    ErrorOr<IPC::File> clone_for_transfer();

private:
    enum class TransferState {
        Continue,
        SocketClosed,
    };
    [[nodiscard]] TransferState transfer_data(ReadonlyBytes& bytes, Vector<int>& fds);

    static ErrorOr<void> send_message(Core::LocalSocket&, ReadonlyBytes& bytes, Vector<int>& unowned_fds);

    enum class IOThreadState {
        Running,
        SendPendingMessagesAndStop,
        Stopped,
    };
    intptr_t io_thread_loop();
    void stop_io_thread(IOThreadState desired_state);
    void wake_io_thread();
    void read_incoming_messages();

    NonnullOwnPtr<Core::LocalSocket> m_socket;

    // After file descriptor is sent, it is moved to the wait queue until an acknowledgement is received from the peer.
    // This is necessary to handle a specific behavior of the macOS kernel, which may prematurely garbage-collect the file
    // descriptor contained in the message before the peer receives it. https://openradar.me/9477351
    Queue<NonnullRefPtr<AutoCloseFileDescriptor>> m_fds_retained_until_received_by_peer;
    Threading::Mutex m_fds_retained_until_received_by_peer_mutex;

    RefPtr<Threading::Thread> m_io_thread;
    RefPtr<SendQueue> m_send_queue;
    Atomic<IOThreadState> m_io_thread_state { IOThreadState::Running };
    Atomic<bool> m_peer_eof { false };
    ByteBuffer m_unprocessed_bytes;
    Queue<File> m_unprocessed_fds;
    Threading::Mutex m_incoming_mutex;
    Threading::ConditionVariable m_incoming_cv { m_incoming_mutex };
    Vector<NonnullOwnPtr<Message>> m_incoming_messages;

    RefPtr<AutoCloseFileDescriptor> m_wakeup_io_thread_read_fd;
    RefPtr<AutoCloseFileDescriptor> m_wakeup_io_thread_write_fd;

    RefPtr<AutoCloseFileDescriptor> m_notify_hook_read_fd;
    RefPtr<AutoCloseFileDescriptor> m_notify_hook_write_fd;
    RefPtr<Core::Notifier> m_read_hook_notifier;
    Function<void()> m_on_read_hook;
};

}