Added progress indicator to map data loading

src/contexts/MapLoadingContext.js

@@ -1,4 +1,5 @@
 import React, { useState } from "react";
+import { omit, isEmpty } from "../helpers/shared";
 
 const MapLoadingContext = React.createContext();
 
@@ -13,12 +14,36 @@ export function MapLoadingProvider({ children }) {
     setLoadingAssetCount((prevLoadingAssets) => prevLoadingAssets - 1);
   }
 
+  const [assetProgress, setAssetProgress] = useState({});
+  function assetProgressUpdate({ id, count, total }) {
+    if (count === total) {
+      setAssetProgress(omit(assetProgress, [id]));
+    } else {
+      setAssetProgress((prevAssetProgress) => ({
+        ...prevAssetProgress,
+        [id]: { count, total },
+      }));
+    }
+  }
+
   const isLoading = loadingAssetCount > 0;
+  let loadingProgress = null;
+  if (!isEmpty(assetProgress)) {
+    let total = 0;
+    let count = 0;
+    for (let progress of Object.values(assetProgress)) {
+      total += progress.total;
+      count += progress.count;
+    }
+    loadingProgress = count / total;
+  }
 
   const value = {
     assetLoadStart,
     assetLoadFinish,
     isLoading,
+    assetProgressUpdate,
+    loadingProgress,
   };
 
   return (