refactor(internal): move core implementation headers to internal

Move non-deprecated core headers from include/kcenon/network/core/ to
src/internal/core/ to reduce public API surface and hide implementation
details.

Changes:
- Move 26 core implementation headers to src/internal/core/
- Create deprecated redirect headers for backward compatibility
- Update include paths in source files
- Preserve public interfaces through facade classes

This change reduces the public header count by ~26 files while
maintaining full backward compatibility for existing users.

Closes #632

Author: kcenon

include/kcenon/network/core/callback_indices.h

@@ -1,7 +1,7 @@
 /*****************************************************************************
 BSD 3-Clause License
 
-Copyright (c) 2024, 🍀☀🌕🌥 🌊
+Copyright (c) 2024, kcenon
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
@@ -32,165 +32,17 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #pragma once
 
-#include <cstddef>
-#include <type_traits>
-
-namespace kcenon::network {
-
-/**
- * \brief Callback indices for messaging_client and secure_messaging_client.
- *
- * These clients use callbacks for: receive, connected, disconnected, error.
- */
-enum class tcp_client_callback : std::size_t {
-	receive = 0,
-	connected = 1,
-	disconnected = 2,
-	error = 3
-};
-
-/**
- * \brief Callback indices for messaging_server and secure_messaging_server.
- *
- * These servers use callbacks for: connection, disconnection, receive, error.
- */
-enum class tcp_server_callback : std::size_t {
-	connection = 0,
-	disconnection = 1,
-	receive = 2,
-	error = 3
-};
-
-/**
- * \brief Callback indices for messaging_udp_client.
- *
- * UDP client uses callbacks for: receive, error.
- */
-enum class udp_client_callback : std::size_t {
-	receive = 0,
-	error = 1
-};
-
-/**
- * \brief Callback indices for secure_messaging_udp_client.
- *
- * Secure UDP client uses callbacks for: receive, connected, disconnected, error.
- */
-enum class secure_udp_client_callback : std::size_t {
-	receive = 0,
-	connected = 1,
-	disconnected = 2,
-	error = 3
-};
-
-/**
- * \brief Callback indices for messaging_udp_server.
- *
- * UDP server uses callbacks for: receive, error.
- */
-enum class udp_server_callback : std::size_t {
-	receive = 0,
-	error = 1
-};
-
-/**
- * \brief Callback indices for unified_udp_messaging_client.
- *
- * Unified UDP client uses callbacks for: receive, connected, disconnected, error.
- * The connected/disconnected callbacks are used for DTLS handshake completion.
- * For plain UDP, connected is called immediately after start.
- */
-enum class unified_udp_client_callback : std::size_t {
-	receive = 0,
-	connected = 1,
-	disconnected = 2,
-	error = 3
-};
-
-/**
- * \brief Callback indices for unified_udp_messaging_server.
- *
- * Unified UDP server uses callbacks for: receive, client_connected,
- * client_disconnected, error.
- * The client_connected/client_disconnected callbacks are used for DTLS sessions.
- * For plain UDP, only receive and error are meaningful.
- */
-enum class unified_udp_server_callback : std::size_t {
-	receive = 0,
-	client_connected = 1,
-	client_disconnected = 2,
-	error = 3
-};
-
-/**
- * \brief Callback indices for messaging_ws_client.
- *
- * WebSocket client uses callbacks for: message, text_message, binary_message,
- * connected, disconnected, error.
- */
-enum class ws_client_callback : std::size_t {
-	message = 0,
-	text_message = 1,
-	binary_message = 2,
-	connected = 3,
-	disconnected = 4,
-	error = 5
-};
-
-/**
- * \brief Callback indices for messaging_ws_server.
- *
- * WebSocket server uses callbacks for: connection, disconnection, message,
- * text_message, binary_message, error.
- */
-enum class ws_server_callback : std::size_t {
-	connection = 0,
-	disconnection = 1,
-	message = 2,
-	text_message = 3,
-	binary_message = 4,
-	error = 5
-};
-
-/**
- * \brief Callback indices for messaging_quic_client.
- *
- * QUIC client uses callbacks for: receive, stream_receive, connected,
- * disconnected, error.
- */
-enum class quic_client_callback : std::size_t {
-	receive = 0,
-	stream_receive = 1,
-	connected = 2,
-	disconnected = 3,
-	error = 4
-};
-
-/**
- * \brief Callback indices for messaging_quic_server.
- *
- * QUIC server uses callbacks for: connection, disconnection, receive,
- * stream_receive, error.
- */
-enum class quic_server_callback : std::size_t {
-	connection = 0,
-	disconnection = 1,
-	receive = 2,
-	stream_receive = 3,
-	error = 4
-};
-
-/**
- * \brief Helper to convert enum to std::size_t for callback_manager access.
- * \tparam E The enum type.
- * \param e The enum value.
- * \return The underlying std::size_t value.
- */
-template <typename E>
-constexpr auto to_index(E e) noexcept -> std::size_t
-{
-	static_assert(std::is_enum_v<E>, "to_index requires an enum type");
-	return static_cast<std::size_t>(e);
-}
-
-} // namespace kcenon::network
+// DEPRECATED: This header location is deprecated.
+// Please use facade headers for new code.
+#ifndef NETWORK_SYSTEM_SUPPRESS_DEPRECATION_WARNINGS
+#if defined(__GNUC__) || defined(__clang__)
+#pragma message("DEPRECATED: include path 'kcenon/network/core/callback_indices.h' is deprecated. " \
+                "Use facade headers instead.")
+#elif defined(_MSC_VER)
+#pragma message("DEPRECATED: include path 'kcenon/network/core/callback_indices.h' is deprecated. " \
+                "Use facade headers instead.")
+#endif
+#endif
+
+// Include internal header for backward compatibility
+#include "internal/core/callback_indices.h"

include/kcenon/network/core/connection_pool.h

@@ -1,7 +1,7 @@
 /*****************************************************************************
 BSD 3-Clause License
 
-Copyright (c) 2024, 🍀☀🌕🌥 🌊
+Copyright (c) 2024, kcenon
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
@@ -32,128 +32,17 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #pragma once
 
-#include <atomic>
-#include <condition_variable>
-#include <memory>
-#include <mutex>
-#include <queue>
-#include <string>
-
-#include "kcenon/network/core/messaging_client.h"
-#include "kcenon/network/utils/result_types.h"
-
-namespace kcenon::network::core
-{
-
-	/*!
-	 * \class connection_pool
-	 * \brief Manages a pool of reusable client connections to reduce
-	 *        connection overhead and improve performance.
-	 *
-	 * ### Key Features
-	 * - Pre-creates a fixed number of connections at initialization
-	 * - Provides thread-safe acquire/release semantics for borrowing connections
-	 * - Blocks when all connections are in use until one becomes available
-	 * - Automatically reconnects clients if connection is lost
-	 * - Tracks active connection count for monitoring
-	 *
-	 * ### Thread Safety
-	 * - All public methods are thread-safe
-	 * - Uses mutex and condition variable for synchronization
-	 * - Multiple threads can safely acquire/release connections concurrently
-	 *
-	 * ### Usage Example
-	 * \code
-	 * auto pool = std::make_shared<connection_pool>("localhost", 5555, 10);
-	 * auto result = pool->initialize();
-	 * if (!result) {
-	 *     std::cerr << "Failed to initialize pool\n";
-	 *     return;
-	 * }
-	 *
-	 * // Acquire a connection
-	 * auto client = pool->acquire();
-	 * client->send_packet(data);
-	 *
-	 * // Release back to pool when done
-	 * pool->release(std::move(client));
-	 * \endcode
-	 */
-	class connection_pool
-	{
-	public:
-		/*!
-		 * \brief Constructs a connection pool.
-		 * \param host The remote host to connect to
-		 * \param port The remote port to connect to
-		 * \param pool_size Number of connections to maintain in the pool (default: 10)
-		 */
-		connection_pool(std::string host, unsigned short port,
-						size_t pool_size = 10);
-
-		/*!
-		 * \brief Destructor. Stops all connections and cleans up resources.
-		 */
-		~connection_pool() noexcept;
-
-		/*!
-		 * \brief Initializes the pool by creating and connecting all clients.
-		 * \return Result<void> - Success if all connections established, or error
-		 *
-		 * This method should be called after construction and before using the pool.
-		 * It pre-creates all connections to avoid latency on first use.
-		 */
-		auto initialize() -> VoidResult;
-
-		/*!
-		 * \brief Acquires a connection from the pool.
-		 * \return A unique_ptr to messaging_client
-		 *
-		 * This method blocks if no connections are available until one is released.
-		 * The acquired connection is guaranteed to be connected and ready to use.
-		 */
-		auto acquire() -> std::unique_ptr<messaging_client>;
-
-		/*!
-		 * \brief Releases a connection back to the pool.
-		 * \param client The client to return to the pool
-		 *
-		 * The client is checked for connectivity and reconnected if necessary
-		 * before being returned to the available queue.
-		 */
-		auto release(std::unique_ptr<messaging_client> client) -> void;
-
-		/*!
-		 * \brief Gets the number of active (borrowed) connections.
-		 * \return Number of connections currently in use
-		 */
-		[[nodiscard]] auto active_count() const noexcept -> size_t
-		{
-			return active_count_.load(std::memory_order_relaxed);
-		}
-
-		/*!
-		 * \brief Gets the total pool size.
-		 * \return Total number of connections in the pool
-		 */
-		[[nodiscard]] auto pool_size() const noexcept -> size_t
-		{
-			return pool_size_;
-		}
-
-	private:
-		std::string host_;              /*!< Remote host to connect to */
-		unsigned short port_;           /*!< Remote port to connect to */
-		size_t pool_size_;              /*!< Total number of connections */
-
-		std::queue<std::unique_ptr<messaging_client>> available_;
-													/*!< Available connections */
-		std::atomic<size_t> active_count_{0};
-													/*!< Active connection count */
-		std::mutex mutex_;              /*!< Protects available_ queue */
-		std::condition_variable cv_;    /*!< Signals when connection available */
-		std::atomic<bool> is_shutdown_{false};
-													/*!< Shutdown flag */
-	};
-
-} // namespace kcenon::network::core
+// DEPRECATED: This header location is deprecated.
+// Please use facade headers for new code.
+#ifndef NETWORK_SYSTEM_SUPPRESS_DEPRECATION_WARNINGS
+#if defined(__GNUC__) || defined(__clang__)
+#pragma message("DEPRECATED: include path 'kcenon/network/core/connection_pool.h' is deprecated. " \
+                "Use facade headers instead.")
+#elif defined(_MSC_VER)
+#pragma message("DEPRECATED: include path 'kcenon/network/core/connection_pool.h' is deprecated. " \
+                "Use facade headers instead.")
+#endif
+#endif
+
+// Include internal header for backward compatibility
+#include "internal/core/connection_pool.h"