Services: Add a WebSocket service

The WebSocket service isolates communication with a WebSocket to its
own isolated process. Similar to other isolating services, it has its
own user and group.

Userland/Libraries/LibProtocol/WebSocket.h

@@ -0,0 +1,78 @@
+/*
+ * Copyright (c) 2021, Dex♪ <dexes.ttp@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Badge.h>
+#include <AK/ByteBuffer.h>
+#include <AK/Function.h>
+#include <AK/RefCounted.h>
+#include <AK/String.h>
+#include <AK/WeakPtr.h>
+#include <LibCore/Notifier.h>
+#include <LibIPC/Forward.h>
+
+namespace Protocol {
+
+class WebSocketClient;
+
+class WebSocket : public RefCounted<WebSocket> {
+public:
+    struct CertificateAndKey {
+        String certificate;
+        String key;
+    };
+
+    struct Message {
+        ByteBuffer data;
+        bool is_text { false };
+    };
+
+    enum class Error {
+        CouldNotEstablishConnection,
+        ConnectionUpgradeFailed,
+        ServerClosedSocket,
+    };
+
+    enum class ReadyState {
+        Connecting = 0,
+        Open = 1,
+        Closing = 2,
+        Closed = 3,
+    };
+
+    static NonnullRefPtr<WebSocket> create_from_id(Badge<WebSocketClient>, WebSocketClient& client, i32 connection_id)
+    {
+        return adopt_ref(*new WebSocket(client, connection_id));
+    }
+
+    int id() const { return m_connection_id; }
+
+    ReadyState ready_state();
+
+    void send(ByteBuffer binary_or_text_message, bool is_text);
+    void send(StringView text_message);
+    void close(u16 code = 1005, String reason = {});
+
+    Function<void()> on_open;
+    Function<void(Message)> on_message;
+    Function<void(Error)> on_error;
+    Function<void(u16 code, String reason, bool was_clean)> on_close;
+    Function<CertificateAndKey()> on_certificate_requested;
+
+    void did_open(Badge<WebSocketClient>);
+    void did_receive(Badge<WebSocketClient>, ByteBuffer, bool);
+    void did_error(Badge<WebSocketClient>, i32);
+    void did_close(Badge<WebSocketClient>, u16, String, bool);
+    void did_request_certificates(Badge<WebSocketClient>);
+
+private:
+    explicit WebSocket(WebSocketClient&, i32 connection_id);
+    WeakPtr<WebSocketClient> m_client;
+    int m_connection_id { -1 };
+};
+
+}