slogutil: imp code

logutil/slogutil/jsonhybrid.go

@@ -26,7 +26,7 @@ import (
 //	{"severity":"NORMAL","message":"time=2024-10-22T12:09:59.525+03:00 level=INFO msg=listening prefix=websvc server=http://127.0.0.1:8181"}
 type JSONHybridHandler struct {
 	level       slog.Leveler
-	writer      io.Writer
+	encoder     *json.Encoder
 	bufTextPool *syncutil.Pool[bufferedTextHandler]
 	mu          *sync.Mutex
 	textAttrs   []slog.Attr
@@ -39,14 +39,17 @@ const initLineLenEst = 256
 // NewJSONHybridHandler creates a new properly initialized *JSONHybridHandler.
 // opts are used for the underlying text handler.
 func NewJSONHybridHandler(w io.Writer, opts *slog.HandlerOptions) (h *JSONHybridHandler) {
+	enc := json.NewEncoder(w)
+	enc.SetEscapeHTML(false)
+
 	lvl := slog.LevelInfo
 	if opts != nil && opts.Level != nil {
 		lvl = opts.Level.Level()
 	}
 
 	return &JSONHybridHandler{
-		level:  lvl,
-		writer: w,
+		level:   lvl,
+		encoder: enc,
 		bufTextPool: syncutil.NewPool(func() (bufTextHdlr *bufferedTextHandler) {
 			return newBufferedTextHandler(initLineLenEst, opts)
 		}),
@@ -74,43 +77,47 @@ func (h *JSONHybridHandler) Handle(ctx context.Context, r slog.Record) (err erro
 
 	err = bufTextHdlr.handler.Handle(ctx, r)
 	if err != nil {
-		return fmt.Errorf("handling text for msg: %w", err)
+		return fmt.Errorf("handling text for data: %w", err)
 	}
 
-	msgForJSON := bufTextHdlr.buffer.String()
+	msg := bufTextHdlr.buffer.String()
 
 	// Remove newline.
-	msgForJSON = msgForJSON[:len(msgForJSON)-1]
+	msg = msg[:len(msg)-1]
+	data := newJSONHybridMessage(r.Level, msg)
+
+	h.mu.Lock()
+	defer h.mu.Unlock()
+
+	return h.encoder.Encode(data)
+}
 
+// jsonHybridMessage represents the data structure for *JSONHybridHandler.
+type jsonHybridMessage = struct {
+	Severity string `json:"severity"`
+	Message  string `json:"message"`
+}
+
+// newJSONHybridMessage returns new properly initialized message.
+func newJSONHybridMessage(lvl slog.Level, msg string) (m *jsonHybridMessage) {
 	var severity string
-	if r.Level < slog.LevelError {
+	if lvl < slog.LevelError {
 		severity = "NORMAL"
 	} else {
 		severity = "ERROR"
 	}
 
-	data := struct {
-		Severity string `json:"severity"`
-		Message  string `json:"message"`
-	}{
+	return &jsonHybridMessage{
 		Severity: severity,
-		Message:  msgForJSON,
+		Message:  msg,
 	}
-
-	enc := json.NewEncoder(h.writer)
-	enc.SetEscapeHTML(false)
-
-	h.mu.Lock()
-	defer h.mu.Unlock()
-
-	return enc.Encode(data)
 }
 
 // WithAttrs implements the [slog.Handler] interface for *JSONHybridHandler.
 func (h *JSONHybridHandler) WithAttrs(attrs []slog.Attr) (res slog.Handler) {
 	return &JSONHybridHandler{
 		level:       h.level,
-		writer:      h.writer,
+		encoder:     h.encoder,
 		bufTextPool: h.bufTextPool,
 		mu:          h.mu,
 		textAttrs:   append(slices.Clip(h.textAttrs), attrs...),