LibJS: Implement ConsoleClient

Now, you can optionally specify a ConsoleClient, to customise the
behaviour of the LibJS Console.

To customise the console, create a new ConsoleClient class that inherits
from JS::ConsoleClient and override all the abstract methods.

When Console::log() is called, if Console has a ConsoleClient,
ConsoleClient::log() is called instead.

These abstract methods are Value(void) functions: you can return a Value
which will be returned by the JavaScript function which calls that
method, in JavaScript.

Libraries/LibJS/Console.cpp

@@ -39,42 +39,63 @@ Console::Console(Interpreter& interpreter)
 
 Value Console::debug()
 {
+    if (m_client)
+        return m_client->debug();
+
     dbg() << "debug: " << m_interpreter.join_arguments();
     return js_undefined();
 }
 
 Value Console::error()
 {
+    if (m_client)
+        return m_client->error();
+
     dbg() << "error: " << m_interpreter.join_arguments();
     return js_undefined();
 }
 
 Value Console::info()
 {
+    if (m_client)
+        return m_client->info();
+
     dbg() << "info: " << m_interpreter.join_arguments();
     return js_undefined();
 }
 
 Value Console::log()
 {
+    if (m_client)
+        return m_client->log();
+
     dbg() << "log: " << m_interpreter.join_arguments();
     return js_undefined();
 }
 
 Value Console::warn()
 {
+    if (m_client)
+        return m_client->warn();
+
     dbg() << "warn: " << m_interpreter.join_arguments();
     return js_undefined();
 }
 
 Value Console::clear()
 {
+    if (m_client)
+        return m_client->clear();
+
     dbg() << "clear:";
     return js_undefined();
 }
 
 Value Console::trace()
 {
+    if (m_client)
+        return m_client->trace();
+
     StringBuilder message_text;
     message_text.append(m_interpreter.join_arguments());
 
@@ -92,6 +113,9 @@ Value Console::trace()
 
 Value Console::count()
 {
+    if (m_client)
+        return m_client->count();
+
     auto label = m_interpreter.argument_count() ? m_interpreter.argument(0).to_string() : "default";
 
     auto counter_value = counter_increment(label);
@@ -102,6 +126,9 @@ Value Console::count()
 
 Value Console::count_reset()
 {
+    if (m_client)
+        return m_client->count_reset();
+
     auto label = m_interpreter.argument_count() ? m_interpreter.argument(0).to_string() : "default";
 
     if (counter_reset(label))

Libraries/LibJS/Console.h

@@ -33,6 +33,8 @@
 
 namespace JS {
 
+class ConsoleClient;
+
 class Console {
     AK_MAKE_NONCOPYABLE(Console);
     AK_MAKE_NONMOVABLE(Console);
@@ -40,6 +42,8 @@ class Console {
 public:
     Console(Interpreter&);
 
+    void set_client(ConsoleClient& client) { m_client = &client; }
+
     Interpreter& interpreter() { return m_interpreter; }
     const Interpreter& interpreter() const { return m_interpreter; }
 
@@ -64,8 +68,33 @@ public:
 
 private:
     Interpreter& m_interpreter;
+    ConsoleClient* m_client { nullptr };
 
     HashMap<String, unsigned> m_counters;
 };
 
+class ConsoleClient {
+public:
+    ConsoleClient(Console& console)
+        : m_console(console)
+    {
+    }
+
+    virtual Value debug() = 0;
+    virtual Value error() = 0;
+    virtual Value info() = 0;
+    virtual Value log() = 0;
+    virtual Value warn() = 0;
+    virtual Value clear() = 0;
+    virtual Value trace() = 0;
+    virtual Value count() = 0;
+    virtual Value count_reset() = 0;
+
+protected:
+    Interpreter& interpreter() { return m_console.interpreter(); }
+    const Interpreter& interpreter() const { return m_console.interpreter(); }
+
+    Console& m_console;
+};
+
 }