/*
 *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

#ifndef WEBRTC_BASE_VIRTUALSOCKETSERVER_H_
#define WEBRTC_BASE_VIRTUALSOCKETSERVER_H_

#include <assert.h>

#include <deque>
#include <map>

#include "webrtc/base/messagequeue.h"
#include "webrtc/base/socketserver.h"

namespace rtc {

class Packet;
class VirtualSocket;
class SocketAddressPair;

// Simulates a network in the same manner as a loopback interface.  The
// interface can create as many addresses as you want.  All of the sockets
// created by this network will be able to communicate with one another, unless
// they are bound to addresses from incompatible families.
class VirtualSocketServer : public SocketServer, public sigslot::has_slots<> {
 public:
  // TODO: Add "owned" parameter.
  // If "owned" is set, the supplied socketserver will be deleted later.
  explicit VirtualSocketServer(SocketServer* ss);
  ~VirtualSocketServer() override;

  SocketServer* socketserver() { return server_; }

  // Limits the network bandwidth (maximum bytes per second).  Zero means that
  // all sends occur instantly.  Defaults to 0.
  uint32 bandwidth() const { return bandwidth_; }
  void set_bandwidth(uint32 bandwidth) { bandwidth_ = bandwidth; }

  // Limits the amount of data which can be in flight on the network without
  // packet loss (on a per sender basis).  Defaults to 64 KB.
  uint32 network_capacity() const { return network_capacity_; }
  void set_network_capacity(uint32 capacity) {
    network_capacity_ = capacity;
  }

  // The amount of data which can be buffered by tcp on the sender's side
  uint32 send_buffer_capacity() const { return send_buffer_capacity_; }
  void set_send_buffer_capacity(uint32 capacity) {
    send_buffer_capacity_ = capacity;
  }

  // The amount of data which can be buffered by tcp on the receiver's side
  uint32 recv_buffer_capacity() const { return recv_buffer_capacity_; }
  void set_recv_buffer_capacity(uint32 capacity) {
    recv_buffer_capacity_ = capacity;
  }

  // Controls the (transit) delay for packets sent in the network.  This does
  // not inclue the time required to sit in the send queue.  Both of these
  // values are measured in milliseconds.  Defaults to no delay.
  uint32 delay_mean() const { return delay_mean_; }
  uint32 delay_stddev() const { return delay_stddev_; }
  uint32 delay_samples() const { return delay_samples_; }
  void set_delay_mean(uint32 delay_mean) { delay_mean_ = delay_mean; }
  void set_delay_stddev(uint32 delay_stddev) {
    delay_stddev_ = delay_stddev;
  }
  void set_delay_samples(uint32 delay_samples) {
    delay_samples_ = delay_samples;
  }

  // If the (transit) delay parameters are modified, this method should be
  // called to recompute the new distribution.
  void UpdateDelayDistribution();

  // Controls the (uniform) probability that any sent packet is dropped.  This
  // is separate from calculations to drop based on queue size.
  double drop_probability() { return drop_prob_; }
  void set_drop_probability(double drop_prob) {
    assert((0 <= drop_prob) && (drop_prob <= 1));
    drop_prob_ = drop_prob;
  }

  // SocketFactory:
  Socket* CreateSocket(int type) override;
  Socket* CreateSocket(int family, int type) override;

  AsyncSocket* CreateAsyncSocket(int type) override;
  AsyncSocket* CreateAsyncSocket(int family, int type) override;

  // SocketServer:
  void SetMessageQueue(MessageQueue* queue) override;
  bool Wait(int cms, bool process_io) override;
  void WakeUp() override;

  typedef std::pair<double, double> Point;
  typedef std::vector<Point> Function;

  static Function* CreateDistribution(uint32 mean, uint32 stddev,
                                      uint32 samples);

  // Similar to Thread::ProcessMessages, but it only processes messages until
  // there are no immediate messages or pending network traffic.  Returns false
  // if Thread::Stop() was called.
  bool ProcessMessagesUntilIdle();

  // Sets the next port number to use for testing.
  void SetNextPortForTesting(uint16 port);

 protected:
  // Returns a new IP not used before in this network.
  IPAddress GetNextIP(int family);
  uint16 GetNextPort();

  VirtualSocket* CreateSocketInternal(int family, int type);

  // Binds the given socket to addr, assigning and IP and Port if necessary
  int Bind(VirtualSocket* socket, SocketAddress* addr);

  // Binds the given socket to the given (fully-defined) address.
  int Bind(VirtualSocket* socket, const SocketAddress& addr);

  // Find the socket bound to the given address
  VirtualSocket* LookupBinding(const SocketAddress& addr);

  int Unbind(const SocketAddress& addr, VirtualSocket* socket);

  // Adds a mapping between this socket pair and the socket.
  void AddConnection(const SocketAddress& client,
                     const SocketAddress& server,
                     VirtualSocket* socket);

  // Find the socket pair corresponding to this server address.
  VirtualSocket* LookupConnection(const SocketAddress& client,
                                  const SocketAddress& server);

  void RemoveConnection(const SocketAddress& client,
                        const SocketAddress& server);

  // Connects the given socket to the socket at the given address
  int Connect(VirtualSocket* socket, const SocketAddress& remote_addr,
              bool use_delay);

  // Sends a disconnect message to the socket at the given address
  bool Disconnect(VirtualSocket* socket);

  // Sends the given packet to the socket at the given address (if one exists).
  int SendUdp(VirtualSocket* socket, const char* data, size_t data_size,
              const SocketAddress& remote_addr);

  // Moves as much data as possible from the sender's buffer to the network
  void SendTcp(VirtualSocket* socket);

  // Places a packet on the network.
  void AddPacketToNetwork(VirtualSocket* socket, VirtualSocket* recipient,
                          uint32 cur_time, const char* data, size_t data_size,
                          size_t header_size, bool ordered);

  // Removes stale packets from the network
  void PurgeNetworkPackets(VirtualSocket* socket, uint32 cur_time);

  // Computes the number of milliseconds required to send a packet of this size.
  uint32 SendDelay(uint32 size);

  // Returns a random transit delay chosen from the appropriate distribution.
  uint32 GetRandomTransitDelay();

  // Basic operations on functions.  Those that return a function also take
  // ownership of the function given (and hence, may modify or delete it).
  static Function* Accumulate(Function* f);
  static Function* Invert(Function* f);
  static Function* Resample(Function* f, double x1, double x2, uint32 samples);
  static double Evaluate(Function* f, double x);

  // NULL out our message queue if it goes away. Necessary in the case where
  // our lifetime is greater than that of the thread we are using, since we
  // try to send Close messages for all connected sockets when we shutdown.
  void OnMessageQueueDestroyed() { msg_queue_ = NULL; }

  // Determine if two sockets should be able to communicate.
  // We don't (currently) specify an address family for sockets; instead,
  // the currently bound address is used to infer the address family.
  // Any socket that is not explicitly bound to an IPv4 address is assumed to be
  // dual-stack capable.
  // This function tests if two addresses can communicate, as well as the
  // sockets to which they may be bound (the addresses may or may not yet be
  // bound to the sockets).
  // First the addresses are tested (after normalization):
  // If both have the same family, then communication is OK.
  // If only one is IPv4 then false, unless the other is bound to ::.
  // This applies even if the IPv4 address is 0.0.0.0.
  // The socket arguments are optional; the sockets are checked to see if they
  // were explicitly bound to IPv6-any ('::'), and if so communication is
  // permitted.
  // NB: This scheme doesn't permit non-dualstack IPv6 sockets.
  static bool CanInteractWith(VirtualSocket* local, VirtualSocket* remote);

 private:
  friend class VirtualSocket;

  typedef std::map<SocketAddress, VirtualSocket*> AddressMap;
  typedef std::map<SocketAddressPair, VirtualSocket*> ConnectionMap;

  SocketServer* server_;
  bool server_owned_;
  MessageQueue* msg_queue_;
  bool stop_on_idle_;
  uint32 network_delay_;
  in_addr next_ipv4_;
  in6_addr next_ipv6_;
  uint16 next_port_;
  AddressMap* bindings_;
  ConnectionMap* connections_;

  uint32 bandwidth_;
  uint32 network_capacity_;
  uint32 send_buffer_capacity_;
  uint32 recv_buffer_capacity_;
  uint32 delay_mean_;
  uint32 delay_stddev_;
  uint32 delay_samples_;
  Function* delay_dist_;
  CriticalSection delay_crit_;

  double drop_prob_;
  DISALLOW_EVIL_CONSTRUCTORS(VirtualSocketServer);
};

// Implements the socket interface using the virtual network.  Packets are
// passed as messages using the message queue of the socket server.
class VirtualSocket : public AsyncSocket, public MessageHandler {
 public:
  VirtualSocket(VirtualSocketServer* server, int family, int type, bool async);
  ~VirtualSocket() override;

  SocketAddress GetLocalAddress() const override;
  SocketAddress GetRemoteAddress() const override;

  // Used by server sockets to set the local address without binding.
  void SetLocalAddress(const SocketAddress& addr);

  // Used by TurnPortTest to mimic a case where proxy returns local host address
  // instead of the original one TurnPort was bound against. Please see WebRTC
  // issue 3927 for more detail.
  void SetAlternativeLocalAddress(const SocketAddress& addr);

  int Bind(const SocketAddress& addr) override;
  int Connect(const SocketAddress& addr) override;
  int Close() override;
  int Send(const void* pv, size_t cb) override;
  int SendTo(const void* pv, size_t cb, const SocketAddress& addr) override;
  int Recv(void* pv, size_t cb) override;
  int RecvFrom(void* pv, size_t cb, SocketAddress* paddr) override;
  int Listen(int backlog) override;
  VirtualSocket* Accept(SocketAddress* paddr) override;

  int GetError() const override;
  void SetError(int error) override;
  ConnState GetState() const override;
  int GetOption(Option opt, int* value) override;
  int SetOption(Option opt, int value) override;
  int EstimateMTU(uint16* mtu) override;
  void OnMessage(Message* pmsg) override;

  bool was_any() { return was_any_; }
  void set_was_any(bool was_any) { was_any_ = was_any; }

  // For testing purpose only. Fired when client socket is bound to an address.
  sigslot::signal2<VirtualSocket*, const SocketAddress&> SignalAddressReady;

 private:
  struct NetworkEntry {
    size_t size;
    uint32 done_time;
  };

  typedef std::deque<SocketAddress> ListenQueue;
  typedef std::deque<NetworkEntry> NetworkQueue;
  typedef std::vector<char> SendBuffer;
  typedef std::list<Packet*> RecvBuffer;
  typedef std::map<Option, int> OptionsMap;

  int InitiateConnect(const SocketAddress& addr, bool use_delay);
  void CompleteConnect(const SocketAddress& addr, bool notify);
  int SendUdp(const void* pv, size_t cb, const SocketAddress& addr);
  int SendTcp(const void* pv, size_t cb);

  VirtualSocketServer* server_;
  int family_;
  int type_;
  bool async_;
  ConnState state_;
  int error_;
  SocketAddress local_addr_;
  SocketAddress alternative_local_addr_;
  SocketAddress remote_addr_;

  // Pending sockets which can be Accepted
  ListenQueue* listen_queue_;

  // Data which tcp has buffered for sending
  SendBuffer send_buffer_;
  bool write_enabled_;

  // Critical section to protect the recv_buffer and queue_
  CriticalSection crit_;

  // Network model that enforces bandwidth and capacity constraints
  NetworkQueue network_;
  size_t network_size_;

  // Data which has been received from the network
  RecvBuffer recv_buffer_;
  // The amount of data which is in flight or in recv_buffer_
  size_t recv_buffer_size_;

  // Is this socket bound?
  bool bound_;

  // When we bind a socket to Any, VSS's Bind gives it another address. For
  // dual-stack sockets, we want to distinguish between sockets that were
  // explicitly given a particular address and sockets that had one picked
  // for them by VSS.
  bool was_any_;

  // Store the options that are set
  OptionsMap options_map_;

  friend class VirtualSocketServer;
};

}  // namespace rtc

#endif  // WEBRTC_BASE_VIRTUALSOCKETSERVER_H_
