LibJS: Add ConsoleMessage concept

A ConsoleMessage is a struct cointaining:
 * AK::String text;         represents the text of the message sent
                             to the console.
 * ConsoleMessageKind kind; represents the kind of JS `console` function
                             from which the message was sent.

Now, Javascript `console` functions only send a ConsoleMessage to the
Interpreter's Console instead of printing text directly to stdout.
The Console then stores the recived ConsoleMessage in
Console::m_messages; the Console does not print to stdout by default.

You can set Console::on_new_message to a void(ConsoleMessage&); this
function will get call everytime a new message is added to the Console's
messages and can be used, for example, to print ConsoleMessages to
stdout or to color the output based on the kind of ConsoleMessage.

In this patch, I also:
  * Re-implement all the previously implemented functions in the
     JavaScript ConsoleObject, as wrappers around Console functions
     that add new message to the Console.
  * Implement console.clear() like so:
    - m_messages get cleared;
    - a new_message with kind set ConsoleMessageKind::Clear gets added
       to m_messages, its text is an empty AK::String;
  * Give credit to linusg in Console.cpp since I used his
     console.trace() algorithm in Console::trace().

I think that having this abstration will help us in the implementation
of a browser console or a JS debugger. We could also add more MetaData
to ConsoleMessage, e.g. Object IDs of the arguments passed to console
functions in order to make hyperlinks, Timestamps, ecc.; which could be
interesting to see.

This will also help in implementing a `/bin/js` option to make, for
example, return a ConsoleMessageWrapper to console functions instead of
undefined. This will be useful to make tests for functions like
console.count() and console.countClear(). :^)

4 files changed, 116 insertions, 29 deletions

diff --git a/Libraries/LibJS/Console.cpp b/Libraries/LibJS/Console.cpp
index 1a62a453eb..986268d0b6 100644
--- a/Libraries/LibJS/Console.cpp
+++ b/Libraries/LibJS/Console.cpp
@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2020, Emanuele Torre <torreemanuele6@gmail.com>
+ * Copyright (c) 2020, Linus Groh <mail@linusgroh.de>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -25,8 +26,9 @@
  */
 
 #include <AK/String.h>
+#include <AK/StringBuilder.h>
 #include <LibJS/Console.h>
-#include <stdio.h>
+#include <LibJS/Interpreter.h>
 
 namespace JS {
 
@@ -35,17 +37,75 @@ Console::Console(Interpreter& interpreter)
 {
 }
 
+void Console::add_message(ConsoleMessageKind kind, String text)
+{
+    ConsoleMessage message = { kind, text };
+    m_messages.append(message);
+
+    if (on_new_message)
+        on_new_message(message);
+}
+
+void Console::debug(String text)
+{
+    add_message(ConsoleMessageKind::Debug, text);
+}
+
+void Console::error(String text)
+{
+    add_message(ConsoleMessageKind::Error, text);
+}
+
+void Console::info(String text)
+{
+    add_message(ConsoleMessageKind::Info, text);
+}
+
+void Console::log(String text)
+{
+    add_message(ConsoleMessageKind::Log, text);
+}
+
+void Console::warn(String text)
+{
+    add_message(ConsoleMessageKind::Warn, text);
+}
+
+void Console::clear()
+{
+    m_messages.clear();
+    add_message(ConsoleMessageKind::Clear, {});
+}
+
+void Console::trace(String title)
+{
+    StringBuilder message_text;
+    message_text.append(title);
+
+    auto call_stack = m_interpreter.call_stack();
+    // -2 to skip the console.trace() call frame
+    for (ssize_t i = call_stack.size() - 2; i >= 0; --i) {
+        auto function_name = call_stack[i].function_name;
+        message_text.append("\n\t");
+        if (String(function_name).is_empty())
+            function_name = "<anonymous>";
+        message_text.append(function_name);
+    }
+
+    add_message(ConsoleMessageKind::Trace, message_text.build());
+}
+
 unsigned Console::count(String label)
 {
     auto counter_value = m_counters.get(label);
     if (!counter_value.has_value()) {
-        printf("%s: 1\n", label.characters());
+        add_message(ConsoleMessageKind::Count, String::format("%s: 1", label.characters()));
         m_counters.set(label, 1);
         return 1;
     }
 
     auto new_counter_value = counter_value.value() + 1;
-    printf("%s: %d\n", label.characters(), new_counter_value);
+    add_message(ConsoleMessageKind::Count, String::format("%s: %u", label.characters(), new_counter_value));
     m_counters.set(label, new_counter_value);
     return new_counter_value;
 }
@@ -56,7 +116,7 @@ bool Console::count_reset(String label)
         return false;
 
     m_counters.remove(label);
-    printf("%s: 0\n", label.characters());
+    add_message(ConsoleMessageKind::Count, String::format("%s: 0", label.characters()));
     return true;
 }
 
diff --git a/Libraries/LibJS/Console.h b/Libraries/LibJS/Console.h
index 3d4ef371d5..1ae6120b37 100644
--- a/Libraries/LibJS/Console.h
+++ b/Libraries/LibJS/Console.h
@@ -26,12 +26,29 @@
 
 #pragma once
 
+#include <AK/Function.h>
 #include <AK/HashMap.h>
 #include <AK/Noncopyable.h>
 #include <LibJS/Forward.h>
 
 namespace JS {
 
+enum class ConsoleMessageKind {
+    Clear,
+    Count,
+    Debug,
+    Error,
+    Info,
+    Log,
+    Trace,
+    Warn,
+};
+
+struct ConsoleMessage {
+    ConsoleMessageKind kind;
+    String text;
+};
+
 class Console {
     AK_MAKE_NONCOPYABLE(Console);
     AK_MAKE_NONMOVABLE(Console);
@@ -43,12 +60,27 @@ public:
 
     HashMap<String, unsigned>& counters() { return m_counters; }
 
+    void debug(String text);
+    void error(String text);
+    void info(String text);
+    void log(String text);
+    void warn(String text);
+
+    void clear();
+
+    void trace(String title);
+
     unsigned count(String label = "default");
     bool count_reset(String label = "default");
 
+    void add_message(ConsoleMessageKind, String text);
+
+    AK::Function<void(ConsoleMessage&)> on_new_message;
+
 private:
     Interpreter& m_interpreter;
 
+    Vector<ConsoleMessage> m_messages;
     HashMap<String, unsigned> m_counters;
 };
 
diff --git a/Libraries/LibJS/Runtime/ConsoleObject.cpp b/Libraries/LibJS/Runtime/ConsoleObject.cpp
index c4d2be4fa3..b6a5eb81ad 100644
--- a/Libraries/LibJS/Runtime/ConsoleObject.cpp
+++ b/Libraries/LibJS/Runtime/ConsoleObject.cpp
@@ -28,22 +28,23 @@
 
 #include <AK/FlyString.h>
 #include <AK/Function.h>
+#include <AK/StringBuilder.h>
 #include <LibJS/Console.h>
 #include <LibJS/Interpreter.h>
 #include <LibJS/Runtime/ConsoleObject.h>
 #include <LibJS/Runtime/GlobalObject.h>
-#include <stdio.h>
 
 namespace JS {
 
-static void print_args(Interpreter& interpreter)
+static String join_args(Interpreter& interpreter)
 {
+    StringBuilder joined_arguments;
     for (size_t i = 0; i < interpreter.argument_count(); ++i) {
-        printf("%s", interpreter.argument(i).to_string().characters());
+        joined_arguments.append(interpreter.argument(i).to_string().characters());
         if (i != interpreter.argument_count() - 1)
-            putchar(' ');
+            joined_arguments.append(' ');
     }
-    putchar('\n');
+    return joined_arguments.build();
 }
 
 ConsoleObject::ConsoleObject()
@@ -57,6 +58,7 @@ ConsoleObject::ConsoleObject()
     put_native_function("trace", trace);
     put_native_function("count", count);
     put_native_function("countReset", count_reset);
+    put_native_function("clear", clear);
 }
 
 ConsoleObject::~ConsoleObject()
@@ -65,51 +67,37 @@ ConsoleObject::~ConsoleObject()
 
 Value ConsoleObject::log(Interpreter& interpreter)
 {
-    print_args(interpreter);
+    interpreter.console().log(join_args(interpreter));
     return js_undefined();
 }
 
 Value ConsoleObject::debug(Interpreter& interpreter)
 {
-    printf("\033[36;1m");
-    print_args(interpreter);
-    printf("\033[0m");
+    interpreter.console().debug(join_args(interpreter));
     return js_undefined();
 }
 
 Value ConsoleObject::info(Interpreter& interpreter)
 {
-    print_args(interpreter);
+    interpreter.console().info(join_args(interpreter));
     return js_undefined();
 }
 
 Value ConsoleObject::warn(Interpreter& interpreter)
 {
-    printf("\033[33;1m");
-    print_args(interpreter);
-    printf("\033[0m");
+    interpreter.console().warn(join_args(interpreter));
     return js_undefined();
 }
 
 Value ConsoleObject::error(Interpreter& interpreter)
 {
-    printf("\033[31;1m");
-    print_args(interpreter);
-    printf("\033[0m");
+    interpreter.console().error(join_args(interpreter));
     return js_undefined();
 }
 
 Value ConsoleObject::trace(Interpreter& interpreter)
 {
-    print_args(interpreter);
-    auto call_stack = interpreter.call_stack();
-    // -2 to skip the console.trace() call frame
-    for (ssize_t i = call_stack.size() - 2; i >= 0; --i) {
-        auto function_name = call_stack[i].function_name;
-        if (String(function_name).is_empty())
-            function_name = "<anonymous>";
-        printf("%s\n", function_name.characters());
-    }
+    interpreter.console().trace(join_args(interpreter));
     return js_undefined();
 }
 
@@ -131,4 +119,10 @@ Value ConsoleObject::count_reset(Interpreter& interpreter)
     return js_undefined();
 }
 
+Value ConsoleObject::clear(Interpreter& interpreter)
+{
+    interpreter.console().clear();
+    return js_undefined();
+}
+
 }
diff --git a/Libraries/LibJS/Runtime/ConsoleObject.h b/Libraries/LibJS/Runtime/ConsoleObject.h
index eff99da621..eb5fedf84e 100644
--- a/Libraries/LibJS/Runtime/ConsoleObject.h
+++ b/Libraries/LibJS/Runtime/ConsoleObject.h
@@ -46,6 +46,7 @@ private:
     static Value trace(Interpreter&);
     static Value count(Interpreter&);
     static Value count_reset(Interpreter&);
+    static Value clear(Interpreter&);
 };
 
 }