Add base web app

matrixgw_frontend/src/widgets/AsyncWidget.tsx

@@ -0,0 +1,94 @@
+import { Alert, Box, Button, CircularProgress } from "@mui/material";
+import { useEffect, useRef, useState } from "react";
+
+const State = {
+  Loading: 0,
+  Ready: 1,
+  Error: 2,
+} as const;
+
+type State = keyof typeof State;
+
+export function AsyncWidget(p: {
+  loadKey: any;
+  load: () => Promise<void>;
+  errMsg: string;
+  build: () => React.ReactElement;
+  ready?: boolean;
+  errAdditionalElement?: () => React.ReactElement;
+}): React.ReactElement {
+  const [state, setState] = useState<number>(State.Loading);
+
+  const counter = useRef<any>(null);
+
+  const load = async () => {
+    try {
+      setState(State.Loading);
+      await p.load();
+      setState(State.Ready);
+    } catch (e) {
+      console.error(e);
+      setState(State.Error);
+    }
+  };
+
+  useEffect(() => {
+    if (counter.current === p.loadKey) return;
+    counter.current = p.loadKey;
+
+    load();
+  });
+
+  if (state === State.Error)
+    return (
+      <Box
+        component="div"
+        sx={{
+          display: "flex",
+          justifyContent: "center",
+          alignItems: "center",
+          height: "100%",
+          flex: "1",
+          flexDirection: "column",
+          backgroundColor: (theme) =>
+            theme.palette.mode === "light"
+              ? theme.palette.grey[100]
+              : theme.palette.grey[900],
+        }}
+      >
+        <Alert
+          variant="outlined"
+          severity="error"
+          style={{ margin: "0px 15px 15px 15px" }}
+        >
+          {p.errMsg}
+        </Alert>
+
+        <Button onClick={load}>Try again</Button>
+
+        {p.errAdditionalElement?.()}
+      </Box>
+    );
+
+  if (state === State.Loading || p.ready === false)
+    return (
+      <Box
+        component="div"
+        sx={{
+          display: "flex",
+          justifyContent: "center",
+          alignItems: "center",
+          height: "100%",
+          flex: "1",
+          backgroundColor: (theme) =>
+            theme.palette.mode === "light"
+              ? theme.palette.grey[100]
+              : theme.palette.grey[900],
+        }}
+      >
+        <CircularProgress />
+      </Box>
+    );
+
+  return p.build();
+}