Dispatch cube export writes through app core

src/app_core/document_export.h

@@ -6,6 +6,7 @@
 
 #include <array>
 #include <cstddef>
+#include <span>
 #include <string>
 #include <string_view>
 #include <utility>
@@ -36,6 +37,10 @@ struct DocumentCubeFaceExportTarget {
     std::size_t face_count = 0;
 };
 
+struct DocumentCubeFaceExportPayload {
+    std::span<const std::byte> bytes;
+};
+
 struct DocumentExportSuggestedName {
     std::string name;
 };
@@ -175,6 +180,16 @@ public:
     virtual void show_timelapse_export_success(std::string_view path) = 0;
 };
 
+class DocumentCubeFaceExportWriteServices {
+public:
+    virtual ~DocumentCubeFaceExportWriteServices() = default;
+
+    virtual pp::foundation::Status write_binary_file(
+        std::string_view path,
+        std::span<const std::byte> bytes) = 0;
+    virtual void publish_exported_image(std::string_view path) = 0;
+};
+
 [[nodiscard]] constexpr DocumentExportStartDecision plan_document_export_start(
     bool requires_license,
     bool license_valid,
@@ -609,6 +624,38 @@ document_cube_face_export_names() noexcept
     return pp::foundation::Result<DocumentExportSuggestedName>::success(std::move(target));
 }
 
+[[nodiscard]] inline pp::foundation::Status execute_document_cube_face_export_write(
+    const DocumentCubeFaceExportTarget& target,
+    std::span<const DocumentCubeFaceExportPayload> face_payloads,
+    DocumentCubeFaceExportWriteServices& services)
+{
+    if (target.face_count != pp::document::cube_face_count) {
+        return pp::foundation::Status::invalid_argument("cube face export target must contain all cube faces");
+    }
+
+    if (face_payloads.size() != target.face_count) {
+        return pp::foundation::Status::invalid_argument("cube face export payload count must match target face count");
+    }
+
+    for (std::size_t face_index = 0; face_index < target.face_count; ++face_index) {
+        const auto& face = target.faces[face_index];
+        if (face.path.empty()) {
+            return pp::foundation::Status::invalid_argument("cube face export path must not be empty");
+        }
+        if (face_payloads[face_index].bytes.empty()) {
+            return pp::foundation::Status::invalid_argument("cube face export payload must not be empty");
+        }
+
+        const auto write_status = services.write_binary_file(face.path, face_payloads[face_index].bytes);
+        if (!write_status.ok()) {
+            return write_status;
+        }
+        services.publish_exported_image(face.path);
+    }
+
+    return pp::foundation::Status::success();
+}
+
 [[nodiscard]] inline pp::foundation::Status execute_document_export_file(
     const DocumentExportFileTarget& target,
     DocumentExportServices& services)