signalling.h

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/*
 * Copyright 2026 The A11 Authors
 *
 * 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.
 */
 
#ifndef A11_NET_SIGNALLING_H_
#define A11_NET_SIGNALLING_H_
 
#include <functional>
#include <memory>
#include <string>
#include <string_view>
#include <vector>
 
#include <absl/status/status.h>
#include <absl/status/statusor.h>
 
#include "a11/concurrency/future.h"
 
namespace a11::net {
 
enum class SignallingMessageType {
  kDescription,
  kCandidate,
  kError,
};
 
struct SignallingMessage {
  SignallingMessageType type =
      SignallingMessageType::kDescription;  
  std::string sender = {};            
  std::string recipient;              
  std::string description = {};       
  std::string description_type = {};  
  std::string candidate = {};         
  std::string mid = {};     
  absl::Status error = {};  
  std::vector<std::string> capabilities = {};
 
  absl::Status Validate() const;
  absl::StatusOr<std::string> ToJson() const;
  static absl::StatusOr<SignallingMessage> FromJson(std::string_view json);
};
 
class SignallingService;
 
using OnSignallingMessage = std::function<a11::Task(SignallingMessage message)>;
 
class SignallingTransport {
 public:
  virtual ~SignallingTransport() = default;
  virtual absl::Status Send(SignallingMessage message) = 0;
  virtual absl::Status SetOnMessage(OnSignallingMessage on_message) = 0;
  virtual absl::Status Close() = 0;
  [[nodiscard]] virtual std::string identity() const = 0;
  [[nodiscard]] virtual bool connected() const = 0;
  [[nodiscard]] virtual absl::Status GetStatus() const = 0;
};
 
class SignallingEndpoint
    : public SignallingTransport,
      public std::enable_shared_from_this<SignallingEndpoint> {
 public:
  ~SignallingEndpoint();
 
  absl::Status Send(SignallingMessage message) override;
  absl::Status SetOnMessage(OnSignallingMessage on_message) override;
  absl::Status Close() override;
  [[nodiscard]] std::string identity() const override;
  [[nodiscard]] bool connected() const override;
  [[nodiscard]] absl::Status GetStatus() const override;
 
 private:
  struct State;
 
  explicit SignallingEndpoint(std::shared_ptr<State> state)
      : state_(std::move(state)) {}
 
  std::shared_ptr<State> state_;
 
  friend class SignallingService;
};
 
class SignallingService
    : public std::enable_shared_from_this<SignallingService> {
 public:
  static std::shared_ptr<SignallingService> Create();
  ~SignallingService();
 
  absl::StatusOr<std::shared_ptr<SignallingEndpoint>> Connect(
      std::string identity, OnSignallingMessage on_message);
  absl::Status Deliver(SignallingMessage message);
  [[nodiscard]] bool Contains(std::string_view identity) const;
  [[nodiscard]] std::vector<std::string> Identities() const;
  absl::Status Stop();
 
 private:
  struct State;
 
  explicit SignallingService(std::shared_ptr<State> state)
      : state_(std::move(state)) {}
 
  absl::Status Route(const std::shared_ptr<SignallingEndpoint::State>& sender,
                     SignallingMessage message);
  void Disconnect(const std::shared_ptr<SignallingEndpoint::State>& endpoint,
                  absl::Status status);
  static void Pump(const std::shared_ptr<SignallingEndpoint::State>& endpoint);
 
  std::shared_ptr<State> state_;
 
  friend class SignallingEndpoint;
};
 
}  // namespace a11::net
 
#endif  // A11_NET_SIGNALLING_H_