feat: better debugger (#13)

- create centralized structured logger with rotation
(https://github.com/versenilvis/IRIS/commit/96ad7c95ef0f7a9957b1bbf70bb6c8da3ce28b2e)
- update core lookup and utils to use new logger
(https://github.com/versenilvis/IRIS/commit/8b74b5a9cdc1828cff8c6d0bdaaccbe31da7a00a)
- add log startup metadata and propagate reload flags
(https://github.com/versenilvis/IRIS/commit/31208aa91a58e9e09abbf5497c314f5c961a58e2)
- add log key interceptions and pty events
(https://github.com/versenilvis/IRIS/commit/91ccb92835dd16ee70bf630fe0f267aad93c9db0)
- add test for logger 221a40c893b75e6215787163cd751a4c1cb6c1d8
- secure reload arguments file path to prevent symlink attacks
(https://github.com/versenilvis/IRIS/pull/13/commits/c3eabfda451230e52cb71f0c2a556687f839bd3f)
- close log file on reinitialization to prevent descriptor leak
(https://github.com/versenilvis/IRIS/pull/13/commits/a57d2c9be107a8c6200cf7046cc85b2f58667dce)

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...)
+}