Route collection export targets through platform policy

src/app_core/document_export.h

@@ -26,6 +26,11 @@ struct DocumentExportSuggestedName {
     std::string name;
 };
 
+enum class DocumentExportCollectionDestination {
+    work_directory_collection,
+    picked_directory_stem,
+};
+
 enum class DocumentExportStartDecision {
     start_now,
     show_license_disabled,
@@ -72,6 +77,12 @@ struct DocumentExportMenuPlan {
     bool opens_dialog = true;
 };
 
+struct DocumentExportCollectionTargetPlan {
+    DocumentExportCollectionKind kind = DocumentExportCollectionKind::layers;
+    DocumentExportCollectionDestination destination = DocumentExportCollectionDestination::picked_directory_stem;
+    std::string_view suffix;
+};
+
 class DocumentExportMenuServices {
 public:
     virtual ~DocumentExportMenuServices() = default;
@@ -193,6 +204,32 @@ public:
     return plan;
 }
 
+[[nodiscard]] constexpr std::string_view document_export_collection_suffix(
+    DocumentExportCollectionKind kind) noexcept
+{
+    switch (kind) {
+    case DocumentExportCollectionKind::layers:
+        return "_layers";
+    case DocumentExportCollectionKind::animation_frames:
+        return "_frames";
+    }
+
+    return {};
+}
+
+[[nodiscard]] constexpr DocumentExportCollectionTargetPlan plan_document_export_collection_target(
+    DocumentExportCollectionKind kind,
+    bool use_work_directory_collection) noexcept
+{
+    return {
+        kind,
+        use_work_directory_collection
+            ? DocumentExportCollectionDestination::work_directory_collection
+            : DocumentExportCollectionDestination::picked_directory_stem,
+        document_export_collection_suffix(kind),
+    };
+}
+
 [[nodiscard]] inline pp::foundation::Result<DocumentExportFileTarget> make_document_export_file_target(
     std::string_view work_directory,
     std::string_view document_name,