rendering engines receive a context containing the username

lib/render.go

@@ -20,4 +20,6 @@
 
 const LogRenderBatchSize = 1000
 
+type contextKey int
+
 var (
@@ -23,5 +25,6 @@
 var (
-	ErrInvalidInput = errors.New("invalid input")
+	userNameContextKey contextKey = 1
+	ErrInvalidInput               = errors.New("invalid input")
 
 	renderPipelineDuration = prometheus.NewSummaryVec(
 		prometheus.SummaryOpts{
@@ -228,7 +231,8 @@
 			reader := rendering.NewDocumentReader(document)
 			writer := rendering.NewDocumentWriter(&output)
 
-			if err := pipeline.Render(ctx, writer, reader); err != nil {
+			userContext := SetUsername(ctx, username)
+			if err := pipeline.Render(userContext, writer, reader); err != nil {
 				return nil, err
 			}
 
@@ -262,6 +266,28 @@
 	return result, nil
 }
 
+// GetUsername allows to extract the username from a context
+// this is intended to be used by engines to extract the username
+// info.
+func GetUsername(ctx context.Context) string {
+	v := ctx.Value(userNameContextKey)
+	if v == nil {
+		return ""
+	}
+	res, ok := v.(string)
+	if !ok {
+		panic("could not type assert on the userName from context")
+	}
+
+	return res
+}
+
+// SetUsername set the given username in the given context and returns
+// a derived context.
+func SetUsername(ctx context.Context, username string) context.Context {
+	return context.WithValue(ctx, userNameContextKey, username)
+}
+
 func init() {
 	prometheus.MustRegister(renderPipelineDuration)
 }