feat: Sidebar에 스크롤 시 특정 offset에서 화면에 고정되는 sticky 기능을 추가합니다.

app/(home)/@tags/(tags)/layout.tsx

@@ -1,13 +1,22 @@
 import type { PropsWithChildren } from "react";
 
+import { Sidebar } from "components/shared/ui/sidebar";
+import { HEADER_HEIGHT } from "constants/header";
+
+const TAGS_TOP = 52;
+const TAGS_STICKY_OFFSET = TAGS_TOP + HEADER_HEIGHT;
+
 const TagsLayout = ({ children }: PropsWithChildren) => {
   return (
-    <div className="absolute left-[100%] top-[52px] pl-10">
-      <div className="w-56 rounded-md bg-zinc-100 px-3 py-2">
-        <p className="mb-3 text-base font-medium text-zinc-800">Popular Tags</p>
-        {children}
-      </div>
-    </div>
+    <Sidebar.Root align="right" top={TAGS_TOP}>
+      <Sidebar.Sticky offset={TAGS_STICKY_OFFSET}>
+        <Sidebar.Content>
+          <Sidebar.Title>Popular Tags</Sidebar.Title>
+
+          {children}
+        </Sidebar.Content>
+      </Sidebar.Sticky>
+    </Sidebar.Root>
   );
 };
 

components/shared/ui/sidebar/content.tsx

@@ -0,0 +1,14 @@
+import type { ComponentPropsWithoutRef } from "react";
+import { forwardRef } from "react";
+
+import { clsx } from "lib/clsx";
+
+type Props = ComponentPropsWithoutRef<"div">;
+
+export const Content = forwardRef<HTMLDivElement, Props>(({ children, className, ...rest }, ref) => {
+  return (
+    <div ref={ref} {...rest} className={clsx("w-56 rounded-md bg-zinc-100 px-3 py-2", className)}>
+      {children}
+    </div>
+  );
+});

components/shared/ui/sidebar/index.ts

@@ -0,0 +1,11 @@
+import { Content } from "./content";
+import { Root } from "./root";
+import { Sticky } from "./sticky";
+import { Title } from "./title";
+
+export const Sidebar = {
+  Root,
+  Content,
+  Title,
+  Sticky,
+};

components/shared/ui/sidebar/root.tsx

@@ -0,0 +1,35 @@
+import type { ComponentPropsWithoutRef } from "react";
+import { forwardRef } from "react";
+
+import { clsx } from "lib/clsx";
+import type { Override } from "types/utilities";
+
+const enum Align {
+  LEFT = "left",
+  RIGHT = "right",
+}
+
+type AlignValue = "left" | "right";
+
+type BaseProps = {
+  align: AlignValue;
+  top?: number;
+};
+
+type Props = Override<ComponentPropsWithoutRef<"div">, BaseProps>;
+
+export const Root = forwardRef<HTMLDivElement, Props>(({ children, className, align, top = 0, ...rest }, ref) => {
+  return (
+    <div ref={ref} style={{ top }} {...rest} className={clsx(styles.base, styles.align[align], className)}>
+      <div className="relative">{children}</div>
+    </div>
+  );
+});
+
+const styles = {
+  base: "absolute px-10",
+  align: {
+    [Align.LEFT]: "right-[100%]",
+    [Align.RIGHT]: "left-[100%]",
+  },
+} as const;

components/shared/ui/sidebar/sticky.tsx

@@ -0,0 +1,28 @@
+"use client";
+
+import type { ComponentPropsWithoutRef } from "react";
+import { forwardRef } from "react";
+
+import { useIsOverlap } from "hooks/use-is-overlap";
+import { clsx } from "lib/clsx";
+
+type Props = ComponentPropsWithoutRef<"div"> & {
+  offset: number;
+};
+
+export const Sticky = forwardRef<HTMLDivElement, Props>(({ children, className, offset, ...rest }, ref) => {
+  const [targetRef, isOverlap] = useIsOverlap<HTMLDivElement>(offset);
+
+  return (
+    <div ref={targetRef} className="absolute inset-0">
+      <div
+        ref={ref}
+        style={{ top: isOverlap ? offset : "auto" }}
+        {...rest}
+        className={clsx({ fixed: isOverlap }, className)}
+      >
+        {children}
+      </div>
+    </div>
+  );
+});

components/shared/ui/sidebar/title.tsx

@@ -0,0 +1,14 @@
+import type { ComponentPropsWithoutRef } from "react";
+import { forwardRef } from "react";
+
+import { clsx } from "lib/clsx";
+
+type Props = ComponentPropsWithoutRef<"h3">;
+
+export const Title = forwardRef<HTMLHeadingElement, Props>(({ children, className, ...rest }, ref) => {
+  return (
+    <h3 ref={ref} {...rest} className={clsx("mb-3 text-base font-medium text-zinc-800", className)}>
+      {children}
+    </h3>
+  );
+});

constants/header.ts

@@ -0,0 +1 @@
+export const HEADER_HEIGHT = 40;

hooks/use-is-overlap.ts

@@ -0,0 +1,24 @@
+import type { MutableRefObject } from "react";
+import { useCallback, useRef, useState } from "react";
+
+import { useWindowEventListener } from "hooks/use-window-event-listener";
+
+export const useIsOverlap = <T extends HTMLElement>(offset: number): [ref: MutableRefObject<T | null>, boolean] => {
+  const [isOverlap, setIsOverlap] = useState<boolean>(false);
+  const ref = useRef<T | null>(null);
+
+  const handleScroll = useCallback(() => {
+    if (ref.current === null) {
+      return;
+    }
+
+    const rect = ref.current.getBoundingClientRect();
+
+    setIsOverlap(rect.top <= offset);
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, []);
+
+  useWindowEventListener("scroll", handleScroll);
+
+  return [ref, isOverlap];
+};

hooks/use-window-event-listener.ts

@@ -0,0 +1,14 @@
+/* global WindowEventMap */
+
+import { useEffect } from "react";
+
+export const useWindowEventListener = <K extends keyof WindowEventMap>(
+  type: K,
+  listener: (ev: WindowEventMap[K]) => any,
+) => {
+  useEffect(() => {
+    window.addEventListener(type, listener);
+
+    return () => window.removeEventListener(type, listener);
+  }, [type, listener]);
+};