tcp_client.hpp

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/*
 * Copyright 2025 Jinwoo Sung
 *
 * 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 <memory>
#include <optional>
#include <string>
#include <variant>
#include <vector>
 
#include "unilink/base/constants.hpp"
#include "unilink/base/platform.hpp"
#include "unilink/base/visibility.hpp"
#include "unilink/config/tcp_client_config.hpp"
#include "unilink/diagnostics/error_types.hpp"
#include "unilink/interface/channel.hpp"
#include "unilink/memory/memory_pool.hpp"
#include "unilink/transport/tcp_client/reconnect_policy.hpp"
 
// Forward declare boost components
namespace boost {
namespace asio {
class io_context;
}
}  // namespace boost
 
namespace unilink {
namespace transport {
 
using base::LinkState;
using config::TcpClientConfig;
using interface::Channel;
 
// Use static create() helpers to construct safely
class UNILINK_API TcpClient : public Channel, public std::enable_shared_from_this<TcpClient> {
 public:
  using BufferVariant =
      std::variant<memory::PooledBuffer, std::vector<uint8_t>, std::shared_ptr<const std::vector<uint8_t>>>;
 
  static std::shared_ptr<TcpClient> create(const TcpClientConfig& cfg);
  static std::shared_ptr<TcpClient> create(const TcpClientConfig& cfg, boost::asio::io_context& ioc);
  ~TcpClient();
 
  // Move semantics
  TcpClient(TcpClient&&) noexcept;
  TcpClient& operator=(TcpClient&&) noexcept;
 
  // Disable copy (should be already disabled by unique_ptr, but being explicit)
  TcpClient(const TcpClient&) = delete;
  TcpClient& operator=(const TcpClient&) = delete;
 
  void start() override;
  void stop() override;
  bool is_connected() const override;
 
  void async_write_copy(memory::ConstByteSpan data) override;
  void async_write_move(std::vector<uint8_t>&& data) override;
  void async_write_shared(std::shared_ptr<const std::vector<uint8_t>> data) override;
 
  // Callbacks must be configured before start() is invoked to avoid setter races.
  void on_bytes(OnBytes cb) override;
  void on_state(OnState cb) override;
  void on_backpressure(OnBackpressure cb) override;
 
  std::optional<diagnostics::ErrorInfo> last_error_info() const;
 
  // Dynamic configuration methods
  void set_retry_interval(unsigned interval_ms);
  void set_reconnect_policy(ReconnectPolicy policy);
 
 private:
  explicit TcpClient(const TcpClientConfig& cfg);
  explicit TcpClient(const TcpClientConfig& cfg, boost::asio::io_context& ioc);
 
  struct Impl;
  const Impl* get_impl() const { return impl_.get(); }
  Impl* get_impl() { return impl_.get(); }
  std::unique_ptr<Impl> impl_;
};
}  // namespace transport
}  // namespace unilink