/*
 *  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 P2P_BASE_STUN_PORT_H_
#define P2P_BASE_STUN_PORT_H_

#include <cstddef>
#include <cstdint>
#include <functional>
#include <map>
#include <memory>
#include <optional>
#include <span>

#include "absl/memory/memory.h"
#include "absl/strings/string_view.h"
#include "api/async_dns_resolver.h"
#include "api/candidate.h"
#include "api/field_trials_view.h"
#include "api/packet_socket_factory.h"
#include "api/units/time_delta.h"
#include "p2p/base/connection.h"
#include "p2p/base/port.h"
#include "p2p/base/port_interface.h"
#include "p2p/base/stun_request.h"
#include "rtc_base/async_packet_socket.h"
#include "rtc_base/dscp.h"
#include "rtc_base/net_helper.h"
#include "rtc_base/network/received_packet.h"
#include "rtc_base/network/sent_packet.h"
#include "rtc_base/network_constants.h"
#include "rtc_base/socket.h"
#include "rtc_base/socket_address.h"
#include "rtc_base/system/rtc_export.h"

namespace webrtc {

// Lifetime for STUN ports on high-cost networks: 2 minutes
inline constexpr TimeDelta kHighCostPortKeepaliveLifetime =
    TimeDelta::Seconds(2 * 60);

// Communicates using the address on the outside of a NAT.
class RTC_EXPORT UDPPort : public Port {
 public:
  static std::unique_ptr<UDPPort> Create(
      const PortParametersRef& args,
      AsyncPacketSocket* socket,
      bool emit_local_for_anyaddress,
      std::optional<TimeDelta> stun_keepalive_interval) {
    // Using `new` to access a non-public constructor.
    auto port = absl::WrapUnique(new UDPPort(
        args, IceCandidateType::kHost, socket, emit_local_for_anyaddress));
    port->set_stun_keepalive_delay(stun_keepalive_interval);
    if (!port->Init()) {
      return nullptr;
    }
    return port;
  }

  static std::unique_ptr<UDPPort> Create(
      const PortParametersRef& args,
      uint16_t min_port,
      uint16_t max_port,
      bool emit_local_for_anyaddress,
      std::optional<TimeDelta> stun_keepalive_interval) {
    // Using `new` to access a non-public constructor.
    auto port =
        absl::WrapUnique(new UDPPort(args, IceCandidateType::kHost, min_port,
                                     max_port, emit_local_for_anyaddress));
    port->set_stun_keepalive_delay(stun_keepalive_interval);
    if (!port->Init()) {
      return nullptr;
    }
    return port;
  }

  ~UDPPort() override;

  SocketAddress GetLocalAddress() const { return socket_->GetLocalAddress(); }

  const ServerAddresses& server_addresses() const { return server_addresses_; }
  void set_server_addresses(const ServerAddresses& addresses) {
    server_addresses_ = addresses;
  }

  void PrepareAddress() override;

  Connection* CreateConnection(const Candidate& address,
                               CandidateOrigin origin) override;
  int SetOption(Socket::Option opt, int value) override;
  int GetOption(Socket::Option opt, int* value) override;
  int GetError() override;

  bool HandleIncomingPacket(AsyncPacketSocket* socket,
                            const ReceivedIpPacket& packet) override;

  bool SupportsProtocol(absl::string_view protocol) const override;
  ProtocolType GetProtocol() const override;

  void GetStunStats(std::optional<StunStats>* stats) override;

  void set_stun_keepalive_delay(const std::optional<TimeDelta>& delay);
  TimeDelta stun_keepalive_delay() const { return stun_keepalive_delay_; }

  // Visible for testing.
  TimeDelta stun_keepalive_lifetime() const { return stun_keepalive_lifetime_; }
  void set_stun_keepalive_lifetime(TimeDelta lifetime) {
    stun_keepalive_lifetime_ = lifetime;
  }

  StunRequestManager& request_manager() { return request_manager_; }

 protected:
  UDPPort(const PortParametersRef& args,
          IceCandidateType type,
          AsyncPacketSocket* socket,
          bool emit_local_for_anyaddress);
  UDPPort(const PortParametersRef& args,
          IceCandidateType type,
          uint16_t min_port,
          uint16_t max_port,
          bool emit_local_for_anyaddress);
  bool Init();

  int SendTo(std::span<const uint8_t> data,
             const SocketAddress& addr,
             const AsyncSocketPacketOptions& options,
             bool payload) override;
  void UpdateNetworkCost() override;
  DiffServCodePoint StunDscpValue() const override;

  void OnLocalAddressReady(AsyncPacketSocket* socket,
                           const SocketAddress& address);

  void PostAddAddress(bool is_final) override;

  void OnReadPacket(AsyncPacketSocket* socket, const ReceivedIpPacket& packet);

  void OnSentPacket(AsyncPacketSocket* socket,
                    const SentPacketInfo& sent_packet) override;

  void OnReadyToSend(AsyncPacketSocket* socket);

  // This method will send STUN binding request if STUN server address is set.
  void MaybePrepareStunCandidate();

  void SendStunBindingRequests();

  // Helper function which will set `addr`'s IP to the default local address if
  // `addr` is the "any" address and `emit_local_for_anyaddress_` is true. When
  // returning false, it indicates that the operation has failed and the
  // address shouldn't be used by any candidate.
  bool MaybeSetDefaultLocalAddress(SocketAddress* addr) const;

 private:
  // A helper class which can be called repeatedly to resolve multiple
  // addresses, as opposed to AsyncDnsResolverInterface, which can only
  // resolve one address per instance.
  class AddressResolver {
   public:
    explicit AddressResolver(
        PacketSocketFactory* factory,
        std::function<void(const SocketAddress&, int)> done_callback);

    void Resolve(const SocketAddress& address,
                 int family,
                 const FieldTrialsView& field_trials);
    bool GetResolvedAddress(const SocketAddress& input,
                            int family,
                            SocketAddress* output) const;

   private:
    typedef std::map<SocketAddress, std::unique_ptr<AsyncDnsResolverInterface>>
        ResolverMap;

    PacketSocketFactory* socket_factory_;
    // The function is called when resolving the specified address is finished.
    // The first argument is the input address, the second argument is the error
    // or 0 if it succeeded.
    std::function<void(const SocketAddress&, int)> done_;
    // Resolver may fire callbacks that refer to done_, so ensure
    // that all resolvers are destroyed first.
    ResolverMap resolvers_;
  };

  // DNS resolution of the STUN server.
  void ResolveStunAddress(const SocketAddress& stun_addr);
  void OnResolveResult(const SocketAddress& input, int error);

  // Send a STUN binding request to the given address. Calling this method may
  // cause the set of known server addresses to be modified, eg. by replacing an
  // unresolved server address with a resolved address.
  void SendStunBindingRequest(const SocketAddress& stun_addr);

  // Below methods handles binding request responses.
  void OnStunBindingRequestSucceeded(TimeDelta rtt,
                                     const SocketAddress& stun_server_addr,
                                     const SocketAddress& stun_reflected_addr);
  void OnStunBindingOrResolveRequestFailed(
      const SocketAddress& stun_server_addr,
      int error_code,
      absl::string_view reason);

  // Sends STUN requests to the server.
  void SendStunRequest(std::span<const uint8_t> data, StunRequest* req);

  // TODO(mallinaht): Move this up to Port when SignalAddressReady is
  // changed to SignalPortReady.
  void MaybeSetPortCompleteOrError();

  bool HasStunCandidateWithAddress(const SocketAddress& addr) const;

  // If this is a low-cost network, it will keep on sending STUN binding
  // requests indefinitely to keep the NAT binding alive. Otherwise, stop
  // sending STUN binding requests after kHighCostPortKeepaliveLifetime.
  TimeDelta GetStunKeepaliveLifetime() {
    return (network_cost() >= kNetworkCostHigh) ? kHighCostPortKeepaliveLifetime
                                                : TimeDelta::PlusInfinity();
  }

  ServerAddresses server_addresses_;
  ServerAddresses bind_request_succeeded_servers_;
  ServerAddresses bind_request_failed_servers_;
  StunRequestManager request_manager_;

  AsyncPacketSocket* socket_;
  std::unique_ptr<AsyncPacketSocket> owned_socket_;
  int error_;
  int send_error_count_ = 0;
  std::unique_ptr<AddressResolver> resolver_;
  bool ready_;
  TimeDelta stun_keepalive_delay_;
  TimeDelta stun_keepalive_lifetime_ = TimeDelta::PlusInfinity();
  DiffServCodePoint dscp_;

  StunStats stats_;

  // This is true by default and false when
  // PORTALLOCATOR_DISABLE_DEFAULT_LOCAL_CANDIDATE is specified.
  bool emit_local_for_anyaddress_;

  friend class StunBindingRequest;
};

class StunPort : public UDPPort {
 public:
  static std::unique_ptr<StunPort> Create(
      const PortParametersRef& args,
      uint16_t min_port,
      uint16_t max_port,
      const ServerAddresses& servers,
      std::optional<TimeDelta> stun_keepalive_interval);

  void PrepareAddress() override;

 protected:
  StunPort(const PortParametersRef& args,
           uint16_t min_port,
           uint16_t max_port,
           const ServerAddresses& servers);
};

}  //  namespace webrtc


#endif  // P2P_BASE_STUN_PORT_H_