feat(logger): slog 结构化日志封装（text/json + 级别解析）

internal/logger/logger.go

@@ -0,0 +1,70 @@
+// Package logger provides the project-wide structured logging facade built on
+// log/slog. All modules must use this package instead of creating their own
+// logger instances. Development builds render human-friendly TextHandler output;
+// production builds render JSON for machine parsing.
+package logger
+
+import (
+	"io"
+	"log/slog"
+	"os"
+	"strings"
+)
+
+// Format selects the structured log output encoding.
+type Format string
+
+const (
+	// FormatText is the human-readable development format.
+	FormatText Format = "text"
+	// FormatJSON is the machine-parseable production format.
+	FormatJSON Format = "json"
+)
+
+// Options configures a Logger.
+type Options struct {
+	// Level is the minimum level to record, one of debug, info, warn, error.
+	// Unknown values fall back to info.
+	Level string
+	// Format is the output encoding, one of text, json. Unknown values fall
+	// back to text.
+	Format string
+	// Out is the destination writer. Defaults to os.Stderr when nil.
+	Out io.Writer
+}
+
+// New builds a slog.Logger from opts.
+func New(opts Options) *slog.Logger {
+	level := ParseLevel(opts.Level)
+	out := opts.Out
+	if out == nil {
+		out = os.Stderr
+	}
+
+	handlerOpts := &slog.HandlerOptions{Level: level}
+	var handler slog.Handler
+	if Format(opts.Format) == FormatJSON {
+		handler = slog.NewJSONHandler(out, handlerOpts)
+	} else {
+		handler = slog.NewTextHandler(out, handlerOpts)
+	}
+
+	return slog.New(handler)
+}
+
+// ParseLevel maps a string level name to a slog.Level. Unknown or empty values
+// produce slog.LevelInfo.
+func ParseLevel(s string) slog.Level {
+	switch strings.ToLower(strings.TrimSpace(s)) {
+	case "debug":
+		return slog.LevelDebug
+	case "info":
+		return slog.LevelInfo
+	case "warn", "warning":
+		return slog.LevelWarn
+	case "error":
+		return slog.LevelError
+	default:
+		return slog.LevelInfo
+	}
+}