// Copyright (c) 2021-present The Bitcoin Core developers

// Distributed under the MIT software license, see the accompanying

// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#ifndef BITCOIN_IPC_PROTOCOL_H

#define BITCOIN_IPC_PROTOCOL_H

#include <interfaces/init.h>

#include <ipc/util.h>

#include <cstddef>

#include <functional>

#include <memory>

#include <optional>

#include <typeindex>

namespace ipc {

struct Context;

//! IPC protocol interface for calling IPC methods over sockets.

//!

//! There may be different implementations of this interface for different IPC

//! protocols (e.g. Cap'n Proto, gRPC, JSON-RPC, or custom protocols).

class Protocol

{

public:

    virtual ~Protocol() = default;

    //! Return Init interface that forwards requests over given connection

    //! stream. Socket communication is handled on a background thread.

    //!

    //! @note It could be potentially useful in the future to add

    //! std::function<void()> on_disconnect callback argument here. But there

    //! isn't an immediate need, because the protocol implementation can clean

    //! up its own state (calling ProxyServer destructors, etc) on disconnect,

    //! and any client calls will just throw ipc::Exception errors after a

    //! disconnect.

    virtual std::unique_ptr<interfaces::Init> connect(mp::Stream stream) = 0;

    //! Listen for connections on provided socket id, accept them, and handle

    //! requests on accepted connections. This method doesn't block, and

    //! performs I/O on a background thread.

    virtual void listen(mp::SocketId listen_fd, interfaces::Init& init, std::optional<size_t> max_connections = std::nullopt) = 0;

    //! Handle requests from a stream provided by the make_stream callback,

    //! forwarding them to the provided Init interface. Socket communication is

    //! handled on the current thread, and this call blocks until the socket is

    //! closed. A callback is used to specify the stream because this method

    //! initializes the event loop and it may not be possible to create the

    //! stream before the event loop is initialized.

    //!

    //! @note: If this method is called, it needs to be called before connect()

    //! or listen() methods, because for ease of implementation this method is

    //! inflexible and always runs the event loop in the foreground thread. It

    //! can share its event loop with the other methods but can't share an event

    //! loop that was created by them. This isn't a problem because serve() is

    //! only called by spawned child processes that call it immediately to

    //! communicate back with parent processes.

    virtual void serve(interfaces::Init& init, const std::function<mp::Stream()>& make_stream) = 0;

    //! Make stream object from socket id.

    virtual mp::Stream makeStream(mp::SocketId socket) = 0;

    //! Disconnect any incoming connections that are still connected.

    virtual void disconnectIncoming() = 0;

    //! Add cleanup callback to interface that will run when the interface is

    //! deleted.

    virtual void addCleanup(std::type_index type, void* iface, std::function<void()> cleanup) = 0;

    //! Context accessor.

    virtual Context& context() = 0;

};

} // namespace ipc

#endif // BITCOIN_IPC_PROTOCOL_H