From b60fbd8092ee421b430235ee994fb73259a19455 Mon Sep 17 00:00:00 2001
From: Tautvydas Derzinskas <tautvydasuk@gmail.com>
Date: Fri, 11 Sep 2026 22:31:35 +0200
Subject: [PATCH] feat: back to top button

---
 frontend/src/components/Layout/AppLayout.tsx  |  2 +
 .../src/components/Layout/BackToTopButton.tsx | 58 +++++++++++++++++++
 frontend/src/i18n/locales/en.json             |  1 +
 frontend/src/i18n/locales/lt.json             |  1 +
 4 files changed, 62 insertions(+)
 create mode 100644 frontend/src/components/Layout/BackToTopButton.tsx

diff --git a/frontend/src/components/Layout/AppLayout.tsx b/frontend/src/components/Layout/AppLayout.tsx
index 41b9c2e..a938d1d 100644
--- a/frontend/src/components/Layout/AppLayout.tsx
+++ b/frontend/src/components/Layout/AppLayout.tsx
@@ -8,6 +8,7 @@ import Alert from "@mui/material/Alert";
 import Sidebar from "./Sidebar";
 import TopBar from "./TopBar";
 import ImportProgressBar from "./ImportProgressBar";
+import BackToTopButton from "./BackToTopButton";
 import { ConfirmProvider } from "../ConfirmProvider";
 import { ToastProvider } from "../ToastProvider";
 import { PageHeaderContext, type PageHeader } from "./PageHeaderContext";
@@ -176,6 +177,7 @@ function AppLayoutShell({
         </Box>
       </Box>
       <ImportProgressBar />
+      <BackToTopButton />
     </ImportJobProvider>
   );
 }
diff --git a/frontend/src/components/Layout/BackToTopButton.tsx b/frontend/src/components/Layout/BackToTopButton.tsx
new file mode 100644
index 0000000..66ca11a
--- /dev/null
+++ b/frontend/src/components/Layout/BackToTopButton.tsx
@@ -0,0 +1,58 @@
+import { useEffect, useState } from "react";
+import { useTranslation } from "react-i18next";
+import Box from "@mui/material/Box";
+import Fab from "@mui/material/Fab";
+import Tooltip from "@mui/material/Tooltip";
+import Zoom from "@mui/material/Zoom";
+import KeyboardArrowUpIcon from "@mui/icons-material/KeyboardArrowUp";
+import { useImportJob } from "./ImportJobContext";
+
+// Appears once enough of the page has scrolled past that "a bit down" reads as true, not on the
+// first pixel of scroll -- matches the threshold feel of most scroll-to-top buttons.
+const SCROLL_SHOW_THRESHOLD = 300;
+
+function scrollToTop() {
+  window.scrollTo({ top: 0, behavior: "smooth" });
+}
+
+/** Fixed bottom-right "back to top" FAB, shown app-wide (mounted once in AppLayout) -- the app
+ *  scrolls at the window level (see AppLayout's own comment on why `main` has no overflow of its
+ *  own), so a single `window.scroll` listener here covers every route. Zoom in/out on the
+ *  visibility flip for the "pop" MUI's own back-to-top example uses, rather than an instant
+ *  show/hide. Shifts up while ImportProgressBar is showing (also fixed to the bottom, full-width)
+ *  so the two don't overlap. */
+export default function BackToTopButton() {
+  const { t } = useTranslation("app");
+  const [visible, setVisible] = useState(false);
+  const { activeJob } = useImportJob();
+
+  useEffect(() => {
+    const onScroll = () => setVisible(window.scrollY > SCROLL_SHOW_THRESHOLD);
+    onScroll();
+    window.addEventListener("scroll", onScroll, { passive: true });
+    return () => window.removeEventListener("scroll", onScroll);
+  }, []);
+
+  const label = t("shell.backToTop");
+
+  return (
+    <Zoom in={visible}>
+      <Box
+        onClick={scrollToTop}
+        sx={{
+          position: "fixed",
+          right: 24,
+          bottom: activeJob ? 88 : 24,
+          zIndex: (theme) => theme.zIndex.fab,
+          transition: (theme) => theme.transitions.create("bottom"),
+        }}
+      >
+        <Tooltip title={label}>
+          <Fab color="primary" aria-label={label ?? undefined} size="medium">
+            <KeyboardArrowUpIcon />
+          </Fab>
+        </Tooltip>
+      </Box>
+    </Zoom>
+  );
+}
diff --git a/frontend/src/i18n/locales/en.json b/frontend/src/i18n/locales/en.json
index 6b9f00e..aaebde9 100644
--- a/frontend/src/i18n/locales/en.json
+++ b/frontend/src/i18n/locales/en.json
@@ -3,6 +3,7 @@
     "shell": {
       "apiUnreachable": "API unreachable. Ensure the API container is running and reachable.",
       "backToLibrary": "Back to library",
+      "backToTop": "Back to top",
       "sessionExpired": "Your session has expired. Please sign in again."
     },
     "auth": {
diff --git a/frontend/src/i18n/locales/lt.json b/frontend/src/i18n/locales/lt.json
index 96f5e94..b83448c 100644
--- a/frontend/src/i18n/locales/lt.json
+++ b/frontend/src/i18n/locales/lt.json
@@ -3,6 +3,7 @@
     "shell": {
       "apiUnreachable": "API nepasiekiamas. Įsitikinkite, kad API konteineris veikia ir pasiekiamas.",
       "backToLibrary": "Grįžti į biblioteką",
+      "backToTop": "Grįžti į viršų",
       "sessionExpired": "Jūsų sesija baigėsi. Prašome prisijungti iš naujo."
     },
     "auth": {