feat: scroll to top (#4244)

web/src/components/PagedMemoList/PagedMemoList.tsx

 import { Button } from "@usememos/mui";
 import { ArrowDownIcon, LoaderIcon } from "lucide-react";
-import { useEffect, useState } from "react";
+import { useEffect, useRef, useState, useMemo } from "react";
+import { useLocation } from "react-router-dom";
 import PullToRefresh from "react-simple-pull-to-refresh";
+import ScrollToTop from "@/components/ScrollToTop";
 import { DEFAULT_LIST_MEMOS_PAGE_SIZE } from "@/helpers/consts";
 import useResponsiveWidth from "@/hooks/useResponsiveWidth";
+import { Routes } from "@/router";
 import { useMemoList, useMemoStore } from "@/store/v1";
 import { Memo } from "@/types/proto/api/v1/memo_service";
 import { useTranslate } from "@/utils/i18n";
@@ -26,11 +29,33 @@ const PagedMemoList = (props: Props) => {
   const { md } = useResponsiveWidth();
   const memoStore = useMemoStore();
   const memoList = useMemoList();
+  const containerRef = useRef<HTMLDivElement>(null);
+  const [containerRightOffset, setContainerRightOffset] = useState(0);
   const [state, setState] = useState<State>({
     isRequesting: true, // Initial request
     nextPageToken: "",
   });
   const sortedMemoList = props.listSort ? props.listSort(memoList.value) : memoList.value;
+  const location = useLocation();
+
+  const shouldShowScrollToTop = useMemo(
+    () => [Routes.ROOT, Routes.EXPLORE, Routes.ARCHIVED].includes(location.pathname as Routes) || location.pathname.startsWith("/u/"),
+    [location.pathname],
+  );
+
+  useEffect(() => {
+    const updateOffset = () => {
+      if (containerRef.current) {
+        const rect = containerRef.current.getBoundingClientRect();
+        const offset = window.innerWidth - rect.right;
+        setContainerRightOffset(offset);
+      }
+    };
+
+    updateOffset();
+    window.addEventListener("resize", updateOffset);
+    return () => window.removeEventListener("resize", updateOffset);
+  }, []);
 
   const fetchMoreMemos = async (nextPageToken: string) => {
     setState((state) => ({ ...state, isRequesting: true }));
@@ -56,7 +81,7 @@ const PagedMemoList = (props: Props) => {
   }, [props.filter, props.pageSize]);
 
   const children = (
-    <>
+    <div ref={containerRef} className="flex flex-col justify-start items-start w-full max-w-full">
       {sortedMemoList.map((memo) => props.renderer(memo))}
       {state.isRequesting && (
         <div className="w-full flex flex-row justify-center items-center my-4">
@@ -77,7 +102,8 @@ const PagedMemoList = (props: Props) => {
           <p className="mt-2 text-gray-600 dark:text-gray-400">{t("message.no-data")}</p>
         </div>
       )}
-    </>
+      <ScrollToTop enabled={shouldShowScrollToTop} className="fixed bottom-6" style={{ right: `calc(1rem + ${containerRightOffset}px)` }} />
+    </div>
   );
 
   // In case of md screen, we don't need pull to refresh.

web/src/components/ScrollToTop.tsx

+import clsx from "clsx";
+import { ArrowUpIcon } from "lucide-react";
+import { useEffect, useState } from "react";
+
+interface ScrollToTopProps {
+  className?: string;
+  style?: React.CSSProperties;
+  enabled?: boolean;
+}
+
+const ScrollToTop = ({ className, style, enabled = true }: ScrollToTopProps) => {
+  const [isVisible, setIsVisible] = useState(false);
+  const [shouldRender, setShouldRender] = useState(false);
+
+  useEffect(() => {
+    const handleScroll = () => {
+      const shouldBeVisible = window.scrollY > 400;
+      if (shouldBeVisible !== isVisible) {
+        if (shouldBeVisible) {
+          setShouldRender(true);
+          setTimeout(() => setIsVisible(true), 50);
+        } else {
+          setIsVisible(false);
+          setTimeout(() => setShouldRender(false), 200);
+        }
+      }
+    };
+
+    if (enabled) {
+      window.addEventListener("scroll", handleScroll);
+      return () => window.removeEventListener("scroll", handleScroll);
+    }
+  }, [enabled, isVisible]);
+
+  const scrollToTop = () => {
+    window.scrollTo({
+      top: 0,
+      behavior: "smooth",
+    });
+  };
+
+  if (!enabled || !shouldRender) {
+    return null;
+  }
+
+  return (
+    <button
+      onClick={scrollToTop}
+      className={clsx(
+        "p-3 bg-primary dark:bg-primary-dark hover:bg-primary-darker dark:hover:bg-primary-darker rounded-full shadow-lg",
+        "transition-all duration-200",
+        "opacity-0 scale-95",
+        isVisible && "opacity-100 scale-100",
+        className,
+      )}
+      style={style}
+      aria-label="Scroll to top"
+    >
+      <ArrowUpIcon className="w-5 h-5 text-white" />
+    </button>
+  );
+};
+
+export default ScrollToTop;