Extract layer rename planning

src/app_core/document_layer.h

@@ -0,0 +1,48 @@
+#pragma once
+
+#include "foundation/result.h"
+
+#include <cstddef>
+#include <string>
+#include <string_view>
+#include <utility>
+
+namespace pp::app {
+
+inline constexpr std::size_t document_layer_name_max_length = 128;
+
+enum class DocumentLayerRenameAction {
+    no_op_same_name,
+    rename_and_record_undo,
+};
+
+struct DocumentLayerRenamePlan {
+    std::string old_name;
+    std::string new_name;
+    DocumentLayerRenameAction action = DocumentLayerRenameAction::no_op_same_name;
+};
+
+[[nodiscard]] inline pp::foundation::Result<DocumentLayerRenamePlan> plan_document_layer_rename(
+    std::string_view old_name,
+    std::string_view requested_name)
+{
+    if (requested_name.empty()) {
+        return pp::foundation::Result<DocumentLayerRenamePlan>::failure(
+            pp::foundation::Status::invalid_argument("layer name must not be empty"));
+    }
+
+    if (requested_name.size() > document_layer_name_max_length) {
+        return pp::foundation::Result<DocumentLayerRenamePlan>::failure(
+            pp::foundation::Status::out_of_range("layer name length exceeds the configured limit"));
+    }
+
+    DocumentLayerRenamePlan plan;
+    plan.old_name = std::string(old_name);
+    plan.new_name = std::string(requested_name);
+    plan.action = old_name == requested_name
+        ? DocumentLayerRenameAction::no_op_same_name
+        : DocumentLayerRenameAction::rename_and_record_undo;
+    return pp::foundation::Result<DocumentLayerRenamePlan>::success(std::move(plan));
+}
+
+}