From d5dad15d0a43cdb0004bd5dcedb55c8996fa8c5f Mon Sep 17 00:00:00 2001
From: BlackMark <me@blackmark.me>
Date: Thu, 9 Jul 2020 21:54:12 +0200
Subject: [PATCH] Implement log rotation

---
 AdaptiveBrightness/log_to_file.hpp | 46 ++++++++++++++++++++++++++++--
 1 file changed, 44 insertions(+), 2 deletions(-)

diff --git a/AdaptiveBrightness/log_to_file.hpp b/AdaptiveBrightness/log_to_file.hpp
index b8dd709..01abfd7 100644
--- a/AdaptiveBrightness/log_to_file.hpp
+++ b/AdaptiveBrightness/log_to_file.hpp
@@ -1,14 +1,50 @@
 #pragma once
 
+#include <filesystem>
+#include <string>
+#include <vector>
+
+#include <cstddef>
+
 #include <QDateTime>
 #include <QFile>
 #include <QMessageLogger>
 #include <QString>
 #include <QTextStream>
 
+static inline void rotateLog(const std::filesystem::path& logFileName, int numRotatingLogs)
+{
+    const auto generateRotateNames = [&]() {
+        std::vector<QString> rotateFileNames = {QString().fromStdString(logFileName.string())};
+
+        for(size_t i = 1; i < numRotatingLogs; ++i) {
+            auto rotateName = logFileName.stem();
+            rotateName += std::string(".") + std::to_string(i);
+            rotateName += logFileName.extension();
+            rotateFileNames.push_back(QString().fromStdString(rotateName.string()));
+        }
+
+        return rotateFileNames;
+    };
+
+    const auto rotateFileNames = generateRotateNames();
+
+    for(auto i = static_cast<int>(rotateFileNames.size()) - 2; i >= 0; --i) {
+        QFile file(rotateFileNames[i]);
+        QFile newFile(rotateFileNames[i + 1]);
+        if(file.exists()) {
+            newFile.remove();
+            file.rename(rotateFileNames[i + 1]);
+        }
+    }
+}
+
 void logToFile(QtMsgType msgType, [[maybe_unused]] const QMessageLogContext& msgContext, const QString& msg)
 {
-    constexpr auto LOG_FILE = "AdaptiveBrightness.log";
+    constexpr auto MAX_LOG_FILE_SIZE = 4 /*MiB*/ * 1024 * 1024;
+    constexpr auto NUM_ROTATING_LOGS = 4;
+
+    const auto logFileName = std::filesystem::path{"AdaptiveBrightness.log"};
 
     const auto dateTime = QDateTime::currentDateTime().toString("yyyy-MM-dd hh:mm:ss.zzz");
     QString formattedMsg = QString("[%1] ").arg(dateTime);
@@ -48,9 +84,15 @@ void logToFile(QtMsgType msgType, [[maybe_unused]] const QMessageLogContext& msg
 
     formattedMsg += QString("%1").arg(msg);
 
-    QFile logFile(LOG_FILE);
+    QFile logFile(QString().fromStdString(logFileName.string()));
     logFile.open(QIODevice::WriteOnly | QIODevice::Append);
 
+    if(logFile.size() > MAX_LOG_FILE_SIZE) {
+        logFile.close();
+        rotateLog(logFileName, NUM_ROTATING_LOGS);
+        logFile.open(QIODevice::WriteOnly | QIODevice::Append);
+    }
+
 #if QT_VERSION >= QT_VERSION_CHECK(5, 14, 0)
     constexpr auto qtEndl = Qt::endl;
 #else