Clean up generated text helpers

internal/generatedtext/json.go

@@ -0,0 +1,33 @@
+package generatedtext
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+)
+
+func decodeGeneratedText[T any](data []byte, name string) (T, error) {
+	var value T
+	decoder := json.NewDecoder(bytes.NewReader(data))
+	decoder.DisallowUnknownFields()
+	if err := decoder.Decode(&value); err != nil {
+		return value, fmt.Errorf("decode %s generated text: %w", name, err)
+	}
+	var extra any
+	if err := decoder.Decode(&extra); err != nil {
+		if err != io.EOF {
+			return value, fmt.Errorf("decode %s generated text: %w", name, err)
+		}
+		return value, nil
+	}
+	return value, fmt.Errorf("decode %s generated text: multiple JSON values", name)
+}
+
+func normalizeGeneratedText[T any](value T, name string) ([]byte, error) {
+	normalized, err := json.Marshal(value)
+	if err != nil {
+		return nil, fmt.Errorf("normalize %s generated text: %w", name, err)
+	}
+	return normalized, nil
+}