Plan cloud upload decisions in app core

src/app_cloud.cpp

@@ -1,19 +1,29 @@
 #include "pch.h"
 #include "app.h"
+#include "app_core/document_cloud.h"
 #include "util.h"
 #include "node_progress_bar.h"
 #include "node_dialog_cloud.h"
 
 void App::cloud_upload()
 {
-    if (!canvas)
+    const bool has_canvas = canvas != nullptr;
+    const auto plan = pp::app::plan_cloud_upload(
+        has_canvas,
+        has_canvas && Canvas::I->m_newdoc,
+        has_canvas && Canvas::I->m_unsaved);
+
+    switch (plan.action)
+    {
+    case pp::app::CloudUploadAction::unavailable_no_canvas:
         return;
-    if (Canvas::I->m_newdoc)
-    {
+    case pp::app::CloudUploadAction::show_save_required_warning:
         message_box("Warning", "This document needs to be saved before upload.");
+        return;
+    case pp::app::CloudUploadAction::prompt_publish:
+        break;
     }
-    else
-    {
+
         auto upload_thread = [this] {
             BT_SetTerminate();
 
@@ -42,7 +52,6 @@ void App::cloud_upload()
         m->btn_cancel->on_click = [this, m, upload_thread](Node*) {
             m->destroy();
         };
-    }
 }
 
 void App::cloud_upload_all()