// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef REMOTING_HOST_CHROMOTING_HOST_H_
#define REMOTING_HOST_CHROMOTING_HOST_H_

#include <list>
#include <string>

#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "base/memory/scoped_ptr.h"
#include "base/memory/scoped_vector.h"
#include "base/memory/weak_ptr.h"
#include "base/observer_list.h"
#include "base/threading/non_thread_safe.h"
#include "base/threading/thread.h"
#include "net/base/backoff_entry.h"
#include "remoting/host/client_session.h"
#include "remoting/host/host_extension.h"
#include "remoting/host/host_status_monitor.h"
#include "remoting/host/host_status_observer.h"
#include "remoting/protocol/authenticator.h"
#include "remoting/protocol/connection_to_client.h"
#include "remoting/protocol/pairing_registry.h"
#include "remoting/protocol/session_manager.h"

namespace base {
class SingleThreadTaskRunner;
}  // namespace base

namespace remoting {

namespace protocol {
class InputStub;
class TransportContext;
}  // namespace protocol

class DesktopEnvironmentFactory;

// A class to implement the functionality of a host process.
//
// Here's the work flow of this class:
// 1. We should load the saved GAIA ID token or if this is the first
//    time the host process runs we should prompt user for the
//    credential. We will use this token or credentials to authenicate
//    and register the host.
//
// 2. We listen for incoming connection using libjingle. We will create
//    a ConnectionToClient object that wraps around linjingle for transport.
//    A VideoFramePump is created with an Encoder and a webrtc::DesktopCapturer.
//    A ConnectionToClient is added to the ScreenRecorder for transporting
//    the screen captures. An InputStub is created and registered with the
//    ConnectionToClient to receive mouse / keyboard events from the remote
//    client.
//    After we have done all the initialization we'll start the ScreenRecorder.
//    We'll then enter the running state of the host process.
//
// 3. When the user is disconnected, we will pause the ScreenRecorder
//    and try to terminate the threads we have created. This will allow
//    all pending tasks to complete. After all of that completed we
//    return to the idle state. We then go to step (2) if there a new
//    incoming connection.
class ChromotingHost : public base::NonThreadSafe,
                       public ClientSession::EventHandler,
                       public HostStatusMonitor {
 public:
  // |desktop_environment_factory| must outlive this object.
  ChromotingHost(
      DesktopEnvironmentFactory* desktop_environment_factory,
      scoped_ptr<protocol::SessionManager> session_manager,
      scoped_refptr<protocol::TransportContext> transport_context,
      scoped_refptr<base::SingleThreadTaskRunner> audio_task_runner,
      scoped_refptr<base::SingleThreadTaskRunner> video_encode_task_runner);
  ~ChromotingHost() override;

  // Asynchronously starts the host.
  //
  // After this is invoked, the host process will connect to the talk
  // network and start listening for incoming connections.
  //
  // This method can only be called once during the lifetime of this object.
  void Start(const std::string& host_owner);

  // HostStatusMonitor interface.
  void AddStatusObserver(HostStatusObserver* observer) override;
  void RemoveStatusObserver(HostStatusObserver* observer) override;

  // Registers a host extension.
  void AddExtension(scoped_ptr<HostExtension> extension);

  // Sets the authenticator factory to use for incoming
  // connections. Incoming connections are rejected until
  // authenticator factory is set. Must be called on the network
  // thread after the host is started. Must not be called more than
  // once per host instance because it may not be safe to delete
  // factory before all authenticators it created are deleted.
  void SetAuthenticatorFactory(
      scoped_ptr<protocol::AuthenticatorFactory> authenticator_factory);

  // Enables/disables curtaining when one or more clients are connected.
  // Takes immediate effect if clients are already connected.
  void SetEnableCurtaining(bool enable);

  // Sets the maximum duration of any session. By default, a session has no
  // maximum duration.
  void SetMaximumSessionDuration(const base::TimeDelta& max_session_duration);

  ////////////////////////////////////////////////////////////////////////////
  // ClientSession::EventHandler implementation.
  void OnSessionAuthenticating(ClientSession* client) override;
  void OnSessionAuthenticated(ClientSession* client) override;
  void OnSessionChannelsConnected(ClientSession* client) override;
  void OnSessionAuthenticationFailed(ClientSession* client) override;
  void OnSessionClosed(ClientSession* session) override;
  void OnSessionRouteChange(ClientSession* session,
                            const std::string& channel_name,
                            const protocol::TransportRoute& route) override;

  // Callback for SessionManager to accept incoming sessions.
  void OnIncomingSession(
      protocol::Session* session,
      protocol::SessionManager::IncomingSessionResponse* response);

  // The host uses a pairing registry to generate and store pairing information
  // for clients for PIN-less authentication.
  scoped_refptr<protocol::PairingRegistry> pairing_registry() const {
    return pairing_registry_;
  }
  void set_pairing_registry(
      scoped_refptr<protocol::PairingRegistry> pairing_registry) {
    pairing_registry_ = pairing_registry;
  }

  base::WeakPtr<ChromotingHost> AsWeakPtr() {
    return weak_factory_.GetWeakPtr();
  }

 private:
  friend class ChromotingHostTest;

  typedef std::list<ClientSession*> ClientList;
  typedef ScopedVector<HostExtension> HostExtensionList;

  // Immediately disconnects all active clients. Host-internal components may
  // shutdown asynchronously, but the caller is guaranteed not to receive
  // callbacks for disconnected clients after this call returns.
  void DisconnectAllClients();

  // Unless specified otherwise all members of this class must be
  // used on the network thread only.

  // Parameters specified when the host was created.
  DesktopEnvironmentFactory* desktop_environment_factory_;
  scoped_ptr<protocol::SessionManager> session_manager_;
  scoped_refptr<protocol::TransportContext> transport_context_;
  scoped_refptr<base::SingleThreadTaskRunner> audio_task_runner_;
  scoped_refptr<base::SingleThreadTaskRunner> video_encode_task_runner_;

  // Must be used on the network thread only.
  base::ObserverList<HostStatusObserver> status_observers_;

  // The connections to remote clients.
  ClientList clients_;

  // True if the host has been started.
  bool started_;

  // Login backoff state.
  net::BackoffEntry login_backoff_;

  // True if the curtain mode is enabled.
  bool enable_curtaining_;

  // The maximum duration of any session.
  base::TimeDelta max_session_duration_;

  // The pairing registry for PIN-less authentication.
  scoped_refptr<protocol::PairingRegistry> pairing_registry_;

  // List of host extensions.
  HostExtensionList extensions_;

  base::WeakPtrFactory<ChromotingHost> weak_factory_;

  DISALLOW_COPY_AND_ASSIGN(ChromotingHost);
};

}  // namespace remoting

#endif  // REMOTING_HOST_CHROMOTING_HOST_H_