refactor: better project structure (#35)

This project is starting to grow, and I've seen flaws in the initial
project structure design
I think I'll restructure the entire project directory for better
scalability and also cleaner

internal/logger/logger.go

@@ -0,0 +1,116 @@
+package logger
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"sync"
+	"time"
+)
+
+type Level int
+
+const (
+	LevelDebug Level = iota
+	LevelInfo
+	LevelWarn
+	LevelError
+)
+
+var (
+	mu         sync.Mutex
+	logFile    *os.File
+	currentLvl = LevelInfo
+)
+
+// Init initializes the logger writing to logFilePath
+func Init(logFilePath string, debug bool) {
+	mu.Lock()
+	defer mu.Unlock()
+
+	if logFile != nil {
+		_ = logFile.Close()
+		logFile = nil
+	}
+
+	// get log level from env
+	lvlEnv := strings.ToLower(os.Getenv("IRIS_LOG_LEVEL"))
+	switch lvlEnv {
+	case "debug":
+		currentLvl = LevelDebug
+	case "info":
+		currentLvl = LevelInfo
+	case "warn":
+		currentLvl = LevelWarn
+	case "error":
+		currentLvl = LevelError
+	default:
+		if debug {
+			currentLvl = LevelDebug
+		} else {
+			currentLvl = LevelInfo
+		}
+	}
+
+	// rotate if log file is larger than 5MB
+	if info, err := os.Stat(logFilePath); err == nil && info.Size() > 5*1024*1024 {
+		_ = os.Rename(logFilePath, logFilePath+".old")
+	}
+
+	_ = os.MkdirAll(filepath.Dir(logFilePath), 0755)
+	f, err := os.OpenFile(logFilePath, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0644)
+	if err == nil {
+		logFile = f
+	}
+}
+
+// Close closes the underlying log file
+func Close() {
+	mu.Lock()
+	defer mu.Unlock()
+	if logFile != nil {
+		_ = logFile.Close()
+		logFile = nil
+	}
+}
+
+func logmsg(lvl Level, lvlStr string, format string, a ...any) {
+	mu.Lock()
+	defer mu.Unlock()
+
+	if logFile == nil || lvl < currentLvl {
+		return
+	}
+
+	// get caller information to append file:line
+	caller := "unknown:0"
+	if _, file, line, ok := runtime.Caller(2); ok {
+		caller = fmt.Sprintf("%s:%d", filepath.Base(file), line)
+	}
+
+	tStr := time.Now().Format("2006-01-02T15:04:05.000Z07:00")
+	msg := fmt.Sprintf(format, a...)
+	_, _ = fmt.Fprintf(logFile, "%s [%s] [%s] %s\n", tStr, lvlStr, caller, msg)
+}
+
+// Debugf writes a debug log message
+func Debugf(format string, a ...any) {
+	logmsg(LevelDebug, "DEBUG", format, a...)
+}
+
+// Infof writes an info log message
+func Infof(format string, a ...any) {
+	logmsg(LevelInfo, "INFO", format, a...)
+}
+
+// Warnf writes a warning log message
+func Warnf(format string, a ...any) {
+	logmsg(LevelWarn, "WARN", format, a...)
+}
+
+// Errorf writes an error log message
+func Errorf(format string, a ...any) {
+	logmsg(LevelError, "ERROR", format, a...)
+}