Initial commit

internal/log/log.go

@@ -0,0 +1,80 @@
+package log
+
+import (
+	"fmt"
+	"io"
+	stdlog "log"
+	"strings"
+)
+
+type Level int
+
+const (
+	LevelDebug Level = iota
+	LevelInfo
+	LevelWarn
+	LevelError
+)
+
+var levelLabels = map[Level]string{
+	LevelDebug: "[DEBUG]",
+	LevelInfo:  "[INFO]",
+	LevelWarn:  "[WARN]",
+	LevelError: "[ERROR]",
+}
+
+type Logger struct {
+	level  Level
+	logger *stdlog.Logger
+}
+
+// New returns a Logger that writes to the given output. Messages below the
+// configured level are silently dropped.
+func New(level Level, output io.Writer) *Logger {
+	return &Logger{
+		level:  level,
+		logger: stdlog.New(output, "", stdlog.LstdFlags),
+	}
+}
+
+func (l *Logger) Debug(format string, args ...any) {
+	l.log(LevelDebug, format, args...)
+}
+
+func (l *Logger) Info(format string, args ...any) {
+	l.log(LevelInfo, format, args...)
+}
+
+func (l *Logger) Warn(format string, args ...any) {
+	l.log(LevelWarn, format, args...)
+}
+
+func (l *Logger) Error(format string, args ...any) {
+	l.log(LevelError, format, args...)
+}
+
+func (l *Logger) log(level Level, format string, args ...any) {
+	if level < l.level {
+		return
+	}
+	label := levelLabels[level]
+	msg := fmt.Sprintf(format, args...)
+	l.logger.Printf("%s %s", label, msg)
+}
+
+// ParseLevel converts a string to a Level. Input is case-insensitive.
+// Valid values: "debug", "info", "warn", "error".
+func ParseLevel(s string) (Level, error) {
+	switch strings.ToLower(strings.TrimSpace(s)) {
+	case "debug":
+		return LevelDebug, nil
+	case "info":
+		return LevelInfo, nil
+	case "warn":
+		return LevelWarn, nil
+	case "error":
+		return LevelError, nil
+	default:
+		return LevelInfo, fmt.Errorf("unrecognized log level %q; valid values: debug, info, warn, error", s)
+	}
+}