From fe62ddf7a9d4700b4103992e17c4a927f6abaca9 Mon Sep 17 00:00:00 2001
From: Jun <jun@udongein.xyz>
Date: Sun, 18 Sep 2022 16:11:59 -0300
Subject: [PATCH] Initial logging utility implementation

- Add basic Application logging
---
 src/application/shared/application/log.h | 57 ++++++++++++++++++++++++
 src/application/src/application.cpp      |  9 ++++
 src/application/src/log.cpp              | 26 +++++++++++
 3 files changed, 92 insertions(+)
 create mode 100644 src/application/shared/application/log.h
 create mode 100644 src/application/src/log.cpp

diff --git a/src/application/shared/application/log.h b/src/application/shared/application/log.h
new file mode 100644
index 0000000..d3725a0
--- /dev/null
+++ b/src/application/shared/application/log.h
@@ -0,0 +1,57 @@
+#pragma once
+
+#include <string>
+
+/**
+ * @brief Basic logging class
+ *
+ * Defines helper functions for logging facility. Configured in Application::init()
+ * 
+ */
+class Log
+{
+public:
+    enum LogLevel
+    {
+        FATAL,
+        ERROR,
+        WARN,
+        INFO,
+        DEBUG,
+    };
+
+    LogLevel level = WARN; ///< Default logging level
+
+    /**
+     * @brief Prints message to stdout
+     *
+     * TODO: write to configurable stream, be it stdout, stderr or even a file
+     * 
+     * @param level the message level
+     * @param fmt the message format
+     * @param ... variable parameters
+     */
+    void log(LogLevel level, const std::string &fmt, ...);
+    
+private:
+    inline std::string _getLabel(LogLevel level)
+    {
+        switch (level)
+        {
+            case DEBUG: return "DEBUG";
+            case INFO:  return "INFO ";
+            case WARN:  return "WARN ";
+            case ERROR: return "ERROR";
+            case FATAL: return "FATAL";
+            default:    return "UNK  ";
+        }
+    }
+};
+
+extern Log LOG; /// Global variable :(
+
+#define INFO(fmt, ...) LOG.log(Log::INFO, fmt, ##__VA_ARGS__)
+#define WARN(fmt, ...) LOG.log(Log::WARN, fmt, ##__VA_ARGS__)
+#define ERROR(fmt, ...) LOG.log(Log::ERROR, fmt, ##__VA_ARGS__)
+#define FATAL(fmt, ...) LOG.log(Log::FATAL, fmt, ##__VA_ARGS__)
+#define DEBUG(fmt, ...) LOG.log(Log::DEBUG, fmt, ##__VA_ARGS__)
diff --git a/src/application/src/application.cpp b/src/application/src/application.cpp
index 337559b..da11ffb 100644
--- a/src/application/src/application.cpp
+++ b/src/application/src/application.cpp
@@ -1,4 +1,5 @@
 #include "application/application.h"
+#include "application/log.h"
 #include "core/gameevent.h"
 #include "core/editor.h"
 
@@ -9,8 +10,13 @@
 
 #include "classicmode/classicfactory.h"
 
+Log LOG;
+
 bool Application::init()
 {
+    LOG.level = Log::DEBUG;
+    DEBUG("Initializing Application");
+
     if (!_core_factory)
         return false;
 
@@ -48,6 +54,8 @@ void Application::update(const kku::microsec& dt)
 
 void Application::pushState(GUIState::Tag new_state)
 {
+    DEBUG("Pushing state %d", new_state);
+
     if (!_state_stack.empty())
         _state_stack.back()->leave();
 
@@ -57,6 +65,7 @@ void Application::pushState(GUIState::Tag new_state)
 
 void Application::popState()
 {
+    DEBUG("Popping state");
     _state_stack.back()->leave();
     _state_stack.pop_back();
     _state_stack.back()->enter();
diff --git a/src/application/src/log.cpp b/src/application/src/log.cpp
new file mode 100644
index 0000000..aada004
--- /dev/null
+++ b/src/application/src/log.cpp
@@ -0,0 +1,26 @@
+#include <cstdarg>
+#include <iostream>
+#include <vector>
+
+#include "application/log.h"
+
+void Log::log(LogLevel level, const std::string &fmt, ...) {
+    if (level > this->level)
+        return;
+
+    va_list args;
+
+    // First va_start: count how many characters are needed for formatting
+    va_start(args, fmt);
+    size_t len = std::vsnprintf(NULL, 0, fmt.c_str(), args);
+    va_end(args);
+
+    std::vector<char> buf(len + 1);
+
+    // Second va_start: actually write formatted message to buffer
+    va_start(args, fmt);
+    std::vsnprintf(&buf[0], len + 1, fmt.c_str(), args);
+    va_end(args);
+
+    std::cout << this->_getLabel(level) << " " << &buf[0] << std::endl;
+}
\ No newline at end of file