Provide script download suggestions async (#986)

src/main/java/carpet/script/utils/AppStoreManager.java

@@ -38,6 +38,7 @@ import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.concurrent.CountDownLatch;
 import java.util.stream.Collectors;
 
 /**
@@ -81,6 +82,7 @@ public class AppStoreManager
         public Map<String, StoreNode> children;
         public boolean sealed;
         public String value;
+        private CountDownLatch childrenProgress;
         public static StoreNode folder(StoreNode parent, String name)
         {
             StoreNode node = new StoreNode(parent, name);
@@ -126,6 +128,20 @@ public class AppStoreManager
         {
             if (sealed) return;
             if (scarpetRepoLink == null) throw new IOException("Accessing scarpet app repo is disabled");
+            try
+            {
+                if (childrenProgress != null)
+                {
+                    childrenProgress.await();
+                    if (sealed) return;
+                    else throw new IOException("Problems fetching suggestions. Check more details in previous exceptions.");
+                }
+            }
+            catch (InterruptedException e)
+            {
+                throw new IOException("Suggestion provider thread was interrupted, unexpected!", e);
+            }
+            childrenProgress = new CountDownLatch(1);
 
             String queryPath = scarpetRepoLink + getPath();
             String response;
@@ -135,7 +151,9 @@ public class AppStoreManager
             }
             catch (IOException e)
             {
-                throw new IOException("Problems fetching "+queryPath+": "+e);
+                childrenProgress.countDown();
+                childrenProgress = null; // Reset to allow retrying
+                throw new IOException("Problems fetching " + queryPath, e);
             }
             JsonArray files = new JsonParser().parse(response).getAsJsonArray();
             for(JsonElement je : files)
@@ -153,6 +171,7 @@ public class AppStoreManager
                 }
             }
             sealed = true;
+            childrenProgress.countDown();
         }
 
         /**