Refactored, added comprehensive testing.

input/aggregate.go

@@ -0,0 +1,32 @@
+package input
+
+// AggregatePrompts combines prompt sources with stdin based on role.
+func AggregatePrompts(prompts []string, stdin string, role StdinRole) []string {
+	switch role {
+	case StdinAsPrompt:
+		if stdin != "" {
+			return []string{stdin}
+		}
+		return prompts
+
+	case StdinAsPrefixedContent:
+		if stdin != "" {
+			return append(prompts, stdin)
+		}
+		return prompts
+
+	case StdinAsFile:
+		return prompts
+
+	default:
+		return prompts
+	}
+}
+
+// AggregateFiles combines file sources with stdin based on role.
+func AggregateFiles(files []FileData, stdin string, role StdinRole) []FileData {
+	if role == StdinAsFile && stdin != "" {
+		return append([]FileData{{Path: "input", Content: stdin}}, files...)
+	}
+	return files
+}