LibWebSocket: Add a new websocket library

This library currently contains a basic WebSocket client that can
handle both standard TCP websockets and TLS websockets.

Userland/Libraries/LibWebSocket/WebSocket.h

@@ -0,0 +1,130 @@
+/*
+ * Copyright (c) 2021, The SerenityOS developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/Span.h>
+#include <LibCore/Object.h>
+#include <LibWebSocket/ConnectionInfo.h>
+#include <LibWebSocket/Impl/AbstractWebSocketImpl.h>
+#include <LibWebSocket/Message.h>
+
+namespace WebSocket {
+
+enum class ReadyState {
+    Connecting = 0,
+    Open = 1,
+    Closing = 2,
+    Closed = 3,
+};
+
+class WebSocket final : public Core::Object {
+    C_OBJECT(WebSocket)
+public:
+    static NonnullRefPtr<WebSocket> create(ConnectionInfo);
+    virtual ~WebSocket() override;
+
+    URL const& url() const { return m_connection.url(); }
+
+    ReadyState ready_state();
+
+    // Call this to start the WebSocket connection.
+    void start();
+
+    // This can only be used if the `ready_state` is `ReadyState::Open`
+    void send(Message);
+
+    // This can only be used if the `ready_state` is `ReadyState::Open`
+    void close(u16 code = 1005, String reason = {});
+
+    Function<void()> on_open;
+    Function<void(u16 code, String reason, bool was_clean)> on_close;
+    Function<void(Message message)> on_message;
+
+    enum class Error {
+        CouldNotEstablishConnection,
+        ConnectionUpgradeFailed,
+        ServerClosedSocket,
+    };
+
+    Function<void(Error)> on_error;
+
+private:
+    explicit WebSocket(ConnectionInfo);
+
+    // As defined in section 5.2
+    enum class OpCode : u8 {
+        Continuation = 0x0,
+        Text = 0x1,
+        Binary = 0x2,
+        ConnectionClose = 0x8,
+        Ping = 0x9,
+        Pong = 0xA,
+    };
+
+    void drain_read();
+
+    void send_client_handshake();
+    void read_server_handshake();
+
+    void read_frame();
+    void send_frame(OpCode, ReadonlyBytes, bool is_final);
+
+    void notify_open();
+    void notify_close(u16 code, String reason, bool was_clean);
+    void notify_error(Error);
+    void notify_message(Message);
+
+    void fatal_error(Error);
+    void discard_connection();
+
+    enum class InternalState {
+        NotStarted,
+        EstablishingProtocolConnection,
+        SendingClientHandshake,
+        WaitingForServerHandshake,
+        Open,
+        Closing,
+        Closed,
+        Errored,
+    };
+
+    InternalState m_state { InternalState::NotStarted };
+
+    String m_websocket_key;
+    bool m_has_read_server_handshake_first_line { false };
+    bool m_has_read_server_handshake_upgrade { false };
+    bool m_has_read_server_handshake_connection { false };
+    bool m_has_read_server_handshake_accept { false };
+
+    u16 m_last_close_code { 1005 };
+    String m_last_close_message;
+
+    ConnectionInfo m_connection;
+    RefPtr<AbstractWebSocketImpl> m_impl;
+};
+
+}