feat(skel): slog logger factory with text|json format and level parsing

internal/logging/logging.go

@@ -0,0 +1,42 @@
+package logging
+
+import (
+	"fmt"
+	"io"
+	"log/slog"
+	"strings"
+)
+
+func New(w io.Writer, level, format string) (*slog.Logger, error) {
+	lvl, err := parseLevel(level)
+	if err != nil {
+		return nil, err
+	}
+	opts := &slog.HandlerOptions{Level: lvl}
+
+	var h slog.Handler
+	switch strings.ToLower(format) {
+	case "", "text":
+		h = slog.NewTextHandler(w, opts)
+	case "json":
+		h = slog.NewJSONHandler(w, opts)
+	default:
+		return nil, fmt.Errorf("unknown log format %q (want text|json)", format)
+	}
+	return slog.New(h), nil
+}
+
+func parseLevel(s string) (slog.Level, error) {
+	switch strings.ToLower(strings.TrimSpace(s)) {
+	case "", "info":
+		return slog.LevelInfo, nil
+	case "debug":
+		return slog.LevelDebug, nil
+	case "warn", "warning":
+		return slog.LevelWarn, nil
+	case "error":
+		return slog.LevelError, nil
+	default:
+		return 0, fmt.Errorf("unknown log level %q", s)
+	}
+}