add full WebSocket (RFC 6455) client/server support for zenhttp (#792)

* This branch adds full WebSocket (RFC 6455) support to the HTTP server layer, covering both transport backends, a client, and tests.

- **`websocket.h`** -- Core interfaces: `WebSocketOpcode`, `WebSocketMessage`, `WebSocketConnection` (ref-counted), and `IWebSocketHandler`. Services opt in to WebSocket support by implementing `IWebSocketHandler` alongside their existing `HttpService`.
- **`httpwsclient.h`** -- `HttpWsClient`: an ASIO-backed `ws://` client with both standalone (own thread) and shared `io_context` modes. Supports connect timeout and optional auth token injection via `IWsClientHandler` callbacks.

- **`wsasio.cpp/h`** -- `WsAsioConnection`: WebSocket over ASIO TCP. Takes over the socket after the HTTP 101 handshake and runs an async read/write loop with a queued write path (guarded by `RwLock`).
- **`wshttpsys.cpp/h`** -- `WsHttpSysConnection`: WebSocket over http.sys opaque-mode connections (Windows only). Uses `HttpReceiveRequestEntityBody` / `HttpSendResponseEntityBody` via IOCP, sharing the same threadpool as normal http.sys traffic. Self-ref lifetime management ensures graceful drain of outstanding async ops.
- **`httpsys_iocontext.h`** -- Tagged `OVERLAPPED` wrapper (`HttpSysIoContext`) used to distinguish normal HTTP transactions from WebSocket read/write completions in the single IOCP callback.

- **`wsframecodec.cpp/h`** -- `WsFrameCodec`: static helpers for parsing (unmasked and masked) and building (unmasked server frames and masked client frames) RFC 6455 frames across all three payload length encodings (7-bit, 16-bit, 64-bit). Also computes `Sec-WebSocket-Accept` keys.

- **`clients/httpwsclient.cpp`** -- `HttpWsClient::Impl`: ASIO-based client that performs the HTTP upgrade handshake, then hands off to the frame codec for the read loop. Manages its own `io_context` thread or plugs into an external one.

- **`httpasio.cpp`** -- ASIO server now detects `Upgrade: websocket` requests, checks the matching `HttpService` for `IWebSocketHandler` via `dynamic_cast`, performs the RFC 6455 handshake (101 response), and spins up a `WsAsioConnection`.
- **`httpsys.cpp`** -- Same upgrade detection and handshake logic for the http.sys backend, using `WsHttpSysConnection` and `HTTP_SEND_RESPONSE_FLAG_OPAQUE`.
- **`httpparser.cpp/h`** -- Extended to surface the `Upgrade` / `Connection` / `Sec-WebSocket-Key` headers needed by the handshake.
- **`httpcommon.h`** -- Minor additions (probably new header constants or response codes for the WS upgrade).
- **`httpserver.h`** -- Small interface changes to support WebSocket registration.
- **`zenhttp.cpp` / `xmake.lua`** -- New source files wired in; build config updated.

- **Unit tests** (`websocket.framecodec`): round-trip encode/decode for text, binary, close frames; all three payload sizes; masked and unmasked variants; RFC 6455 `Sec-WebSocket-Accept` test vector.
- **Integration tests** (`websocket.integration`): full ASIO server tests covering handshake (101), normal HTTP coexistence, echo, server-push broadcast, client close handshake, ping/pong auto-response, sequential messages, and rejection of upgrades on non-WS services.
- **Client tests** (`websocket.client`): `HttpWsClient` connect+echo+close, connection failure (bad port -> close code 1006), and server-initiated close.

* changed HttpRequestParser::ParseCurrentHeader to use switch instead of if/else chain

* remove spurious printf

---------

Co-authored-by: Stefan Boberg <[email protected]>

1 files changed, 74 insertions, 0 deletions

diff --git a/src/zenhttp/servers/wsframecodec.h b/src/zenhttp/servers/wsframecodec.h
new file mode 100644
index 000000000..2d90b6fa1
--- /dev/null
+++ b/src/zenhttp/servers/wsframecodec.h
@@ -0,0 +1,74 @@
+// Copyright Epic Games, Inc. All Rights Reserved.
+
+#pragma once
+
+#include <zenhttp/websocket.h>
+
+#include <cstddef>
+#include <cstdint>
+#include <optional>
+#include <span>
+#include <string>
+#include <string_view>
+#include <vector>
+
+namespace zen {
+
+/**
+ * Result of attempting to parse a single WebSocket frame from a byte buffer
+ */
+struct WsFrameParseResult
+{
+	bool				 IsValid	   = false;	 // true if a complete frame was successfully parsed
+	size_t				 BytesConsumed = 0;		 // number of bytes consumed from the input buffer
+	WebSocketOpcode		 Opcode		   = WebSocketOpcode::kText;
+	bool				 Fin		   = false;
+	std::vector<uint8_t> Payload;
+};
+
+/**
+ * RFC 6455 WebSocket frame codec
+ *
+ * Provides static helpers for parsing client-to-server frames (which are
+ * always masked) and building server-to-client frames (which are never masked).
+ */
+struct WsFrameCodec
+{
+	/**
+	 * Try to parse one complete frame from the front of the buffer.
+	 *
+	 * Returns a result with IsValid == false and BytesConsumed == 0 when
+	 * there is not enough data yet.  The caller should accumulate more data
+	 * and retry.
+	 */
+	static WsFrameParseResult TryParseFrame(const uint8_t* Data, size_t Size);
+
+	/**
+	 * Build a server-to-client frame (no masking)
+	 */
+	static std::vector<uint8_t> BuildFrame(WebSocketOpcode Opcode, std::span<const uint8_t> Payload);
+
+	/**
+	 * Build a close frame with a status code and optional reason string
+	 */
+	static std::vector<uint8_t> BuildCloseFrame(uint16_t Code, std::string_view Reason = {});
+
+	/**
+	 * Build a client-to-server frame (with masking per RFC 6455)
+	 */
+	static std::vector<uint8_t> BuildMaskedFrame(WebSocketOpcode Opcode, std::span<const uint8_t> Payload);
+
+	/**
+	 * Build a masked close frame with status code and optional reason
+	 */
+	static std::vector<uint8_t> BuildMaskedCloseFrame(uint16_t Code, std::string_view Reason = {});
+
+	/**
+	 * Compute the Sec-WebSocket-Accept value per RFC 6455 section 4.2.2
+	 *
+	 * accept = Base64(SHA1(clientKey + "258EAFA5-E914-47DA-95CA-C5AB0DC85B11"))
+	 */
+	static std::string ComputeAcceptKey(std::string_view ClientKey);
+};
+
+}  // namespace zen