From 1c2fe8076b880bd26179e432cf7b2ca0d36179c3 Mon Sep 17 00:00:00 2001
From: Praveen Ravichandran <me@pravinba9495.dev>
Date: Thu, 19 May 2022 10:03:24 -0400
Subject: [PATCH] Enable log rotation

---
 logger.go | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 types.go  |  5 +++--
 2 files changed, 51 insertions(+), 2 deletions(-)

diff --git a/logger.go b/logger.go
index e1ecc7e..e435b6a 100644
--- a/logger.go
+++ b/logger.go
@@ -6,6 +6,7 @@ import (
 	"log"
 	"os"
 	"runtime"
+	"time"
 
 	"github.com/fatih/color"
 )
@@ -13,6 +14,7 @@ import (
 var (
 	currentLogLevel LogLevel = LevelError
 	logFilePath     string   = "logfile.txt"
+	maxSizeInBytes  int64    = 5 * 1024 * 1024
 )
 
 // Init initializes a logger
@@ -24,6 +26,9 @@ func Init(opts *LoggerOptions) (func(), error) {
 		if opts.LogFilePath != "" {
 			logFilePath = opts.LogFilePath
 		}
+		if opts.LogFileMaxSize > 0 {
+			maxSizeInBytes = opts.LogFileMaxSize
+		}
 	}
 	f, err := os.OpenFile(logFilePath, os.O_APPEND|os.O_RDWR|os.O_CREATE, 0755)
 	if err != nil {
@@ -31,6 +36,36 @@ func Init(opts *LoggerOptions) (func(), error) {
 	}
 	mw := io.MultiWriter(os.Stdout, f)
 	log.SetOutput(mw)
+
+	go func() {
+		for {
+			size, err := GetFileSize()
+			if err != nil {
+				panic(err)
+			}
+			if size >= maxSizeInBytes {
+				source, err := os.Open(logFilePath)
+				if err != nil {
+					panic(err)
+				}
+				destination, err := os.Create(logFilePath + "-" + time.Now().Format("20060102150405"))
+				if err != nil {
+					panic(err)
+				}
+				_, err = io.Copy(destination, source)
+				if err != nil {
+					panic(err)
+				}
+				source.Close()
+				destination.Close()
+				if err := os.Truncate(logFilePath, 0); err != nil {
+					panic(err)
+				}
+			}
+			time.Sleep(10 * time.Second)
+		}
+	}()
+
 	return func() {
 		defer f.Close()
 	}, nil
@@ -98,3 +133,16 @@ func Error(s string) {
 	str := color.RedString("%s", s)
 	log.Print("[" + filename + ":" + fmt.Sprint(line) + "] " + str)
 }
+
+// GetFileSize returns the log file size
+func GetFileSize() (int64, error) {
+	info, err := os.Stat(logFilePath)
+	if err != nil {
+		return 0, err
+	}
+	if !info.Mode().IsRegular() {
+		return 0, fmt.Errorf("%s is not a regular file", logFilePath)
+	}
+	bytes := info.Size()
+	return bytes, nil
+}
diff --git a/types.go b/types.go
index 1f3eeee..7d77a2f 100644
--- a/types.go
+++ b/types.go
@@ -5,6 +5,7 @@ type LogLevel string
 
 // LoggerOptions to pass to the logger instance
 type LoggerOptions struct {
-	LogLevel    LogLevel
-	LogFilePath string
+	LogLevel       LogLevel
+	LogFilePath    string
+	LogFileMaxSize int64
 }