Add support of showing confirmation when leaving settings page with unsaved changes

frontend/src/pages/Settings/components/Layout.tsx

@@ -3,9 +3,10 @@ import { Toolbox } from "@/components";
 import { LoadingProvider } from "@/contexts";
 import { useOnValueChange } from "@/utilities";
 import { LOG } from "@/utilities/console";
+import { usePrompt } from "@/utilities/routers";
 import { useUpdateLocalStorage } from "@/utilities/storage";
 import { faSave } from "@fortawesome/free-solid-svg-icons";
-import { Container, Group, LoadingOverlay } from "@mantine/core";
+import { Badge, Container, Group, LoadingOverlay } from "@mantine/core";
 import { useDocumentTitle, useForm } from "@mantine/hooks";
 import { FunctionComponent, ReactNode, useCallback, useMemo } from "react";
 import { enabledLanguageKey, languageProfileKey } from "../keys";
@@ -84,6 +85,11 @@ const Layout: FunctionComponent<Props> = (props) => {
     return Object.keys(object).length;
   }, [form.values.settings, form.values.storages]);
 
+  usePrompt(
+    totalStagedCount > 0,
+    `You have ${totalStagedCount} unsaved changes, are you sure you want to leave?`
+  );
+
   useDocumentTitle(`${name} - Bazarr (Settings)`);
 
   if (settings === undefined) {
@@ -101,6 +107,11 @@ const Layout: FunctionComponent<Props> = (props) => {
                 icon={faSave}
                 loading={isMutating}
                 disabled={totalStagedCount === 0}
+                rightIcon={
+                  <Badge size="xs" radius="sm" hidden={totalStagedCount === 0}>
+                    {totalStagedCount}
+                  </Badge>
+                }
               >
                 Save
               </Toolbox.Button>

frontend/src/utilities/routers.ts

@@ -0,0 +1,40 @@
+// A workaround of built-in hooks in React-Router v6
+// https://gist.github.com/rmorse/426ffcc579922a82749934826fa9f743
+
+import type { Blocker, History, Transition } from "history";
+import { useContext, useEffect } from "react";
+import { UNSAFE_NavigationContext } from "react-router-dom";
+
+export function useBlocker(blocker: Blocker, when = true) {
+  const navigator = useContext(UNSAFE_NavigationContext).navigator as History;
+
+  useEffect(() => {
+    if (!when) return;
+
+    const unblock = navigator.block((tx: Transition) => {
+      const autoUnblockingTx = {
+        ...tx,
+        retry() {
+          // Automatically unblock the transition so it can play all the way
+          // through before retrying it. TODO: Figure out how to re-enable
+          // this block if the transition is cancelled for some reason.
+          unblock();
+          tx.retry();
+        },
+      };
+
+      blocker(autoUnblockingTx);
+    });
+
+    return unblock;
+  }, [navigator, blocker, when]);
+}
+
+// TODO: Replace with Mantine's confirmation modal
+export function usePrompt(when: boolean, message: string) {
+  useBlocker((tx) => {
+    if (window.confirm(message)) {
+      tx.retry();
+    }
+  }, when);
+}