// Copyright (c) Facebook, Inc. and its affiliates.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#pragma once

#include <folly/Optional.h>

#include "rsocket/DuplexConnection.h"

namespace folly {
class EventBase;
}

namespace rsocket {

using OnDuplexConnectionAccept = std::function<
    void(std::unique_ptr<rsocket::DuplexConnection>, folly::EventBase&)>;

/**
 * Common interface for a server that accepts connections and turns them into
 * DuplexConnection.
 *
 * This is primarily used with RSocket::createServer(ConnectionAcceptor)
 *
 * Built-in implementations can be found in rsocket/transports/, such as
 * rsocket/transports/TcpConnectionAcceptor.h
 */
class ConnectionAcceptor {
 public:
  ConnectionAcceptor() = default;
  virtual ~ConnectionAcceptor() = default;

  ConnectionAcceptor(const ConnectionAcceptor&) = delete;
  ConnectionAcceptor(ConnectionAcceptor&&) = delete;

  ConnectionAcceptor& operator=(const ConnectionAcceptor&) = delete;
  ConnectionAcceptor& operator=(ConnectionAcceptor&&) = delete;

  /**
   * Allocate/start required resources (threads, sockets, etc) and begin
   * listening for new connections.  Must be synchronous.
   *
   * This can only be called once.
   */
  virtual void start(OnDuplexConnectionAccept) = 0;

  /**
   * Stop listening for new connections.
   *
   * This can only be called once.  Must be called in or before
   * the implementation's destructor.  Must be synchronous.
   */
  virtual void stop() = 0;

  /**
   * Get the port the acceptor is listening on.  Returns folly::none when the
   * acceptor is not listening.
   */
  virtual folly::Optional<uint16_t> listeningPort() const = 0;
};
} // namespace rsocket