QA: 편지 관련 수정사항 진행

app/(sub)/capsule-detail/[invite-code]/[id]/letters/_components/grid-layout/index.tsx

@@ -1,13 +1,21 @@
 import type { ImageUrl, Letter } from "@/shared/types/api/letter";
+import LoadingSpinner from "@/shared/ui/loading-spinner";
 import GridLetterCard from "../grid-letter-card";
 import * as styles from "./grid-layout.css";
 
 interface GridLayoutProps {
   letters: Letter[];
+  footerRef: (element: HTMLDivElement | null) => void;
   imageUrls: ImageUrl[];
+  isFetchingNextPage: boolean;
 }
 
-const GridLayout = ({ letters, imageUrls }: GridLayoutProps) => {
+const GridLayout = ({
+  letters,
+  footerRef,
+  imageUrls,
+  isFetchingNextPage,
+}: GridLayoutProps) => {
   return (
     <div className={styles.container}>
       <div className={styles.grid}>
@@ -24,6 +32,14 @@ const GridLayout = ({ letters, imageUrls }: GridLayoutProps) => {
           );
         })}
       </div>
+      <div style={{ minHeight: "1px", textAlign: "center" }} ref={footerRef}>
+        {isFetchingNextPage && (
+          <div style={{ padding: "20px" }}>
+            <LoadingSpinner loading={true} size={20} />
+            <div style={{ marginTop: "8px" }}>Loading more...</div>
+          </div>
+        )}
+      </div>
     </div>
   );
 };

app/(sub)/capsule-detail/[invite-code]/[id]/letters/_components/grid-letter-card/grid-letter-card.css.ts

@@ -1,6 +1,6 @@
 import { themeVars } from "@/shared/styles/base/theme.css";
 import { screen } from "@/shared/styles/tokens/screen";
-import { style } from "@vanilla-extract/css";
+import { keyframes, style } from "@vanilla-extract/css";
 
 export const card = style({
   position: "relative",
@@ -30,12 +30,26 @@ export const card = style({
   }),
 });
 
+const shimmer = keyframes({
+  "0%": { backgroundPosition: "-100% 0" },
+  "100%": { backgroundPosition: "100% 0" },
+});
+
 export const image = style({
   width: "100%",
   height: "100%",
   objectFit: "cover",
   borderRadius: "10px",
   overflow: "hidden",
+
+  selectors: {
+    '&[data-loaded="false"]': {
+      backgroundColor: themeVars.color.black["90_bg"],
+      backgroundImage: themeVars.color.gradient.darkgray_bg_horizontal,
+      backgroundSize: "200% 100%",
+      animation: `${shimmer} 4s  infinite`,
+    },
+  },
 });
 
 export const content = style({

app/(sub)/capsule-detail/[invite-code]/[id]/letters/_components/grid-letter-card/index.tsx

@@ -1,7 +1,7 @@
+import { useOverlay } from "@/shared/hooks/use-overlay";
 import type { Letter } from "@/shared/types/api/letter";
 import HoverMotion from "@/shared/ui/motion/hover-motion";
 import Image from "next/image";
-import { useOverlay } from "@/shared/hooks/use-overlay";
 import LetterDetailModal from "../letter-detail-modal";
 import * as styles from "./grid-letter-card.css";
 
@@ -34,6 +34,10 @@ const GridLetterCard = ({ letter, imageUrl }: LetterCardProps) => {
             className={styles.image}
             src={imageUrl}
             alt="편지 이미지"
+            data-loaded="false"
+            onLoad={(event) => {
+              event.currentTarget.setAttribute("data-loaded", "true");
+            }}
           />
         )}
         <div className={styles.content}>

app/(sub)/capsule-detail/[invite-code]/[id]/letters/_components/letter-detail-modal/index.tsx

@@ -23,6 +23,7 @@ const LetterDetailModal = ({
       overlayClassName={styles.modalOverlay}
       contentClassName={styles.modalContent}
       fullScreenOnMobile={false}
+      closeOnOverlayClick={true}
     >
       <section className={styles.container}>
         {imageUrl && (
@@ -32,6 +33,10 @@ const LetterDetailModal = ({
             width={300}
             height={300}
             className={styles.image}
+            data-loaded="false"
+            onLoad={(event) => {
+              event.currentTarget.setAttribute("data-loaded", "true");
+            }}
           />
         )}
         <div className={styles.contentWrapper}>

app/(sub)/capsule-detail/[invite-code]/[id]/letters/_components/letter-detail-modal/letter-detail-modal.css.ts

@@ -1,6 +1,6 @@
 import { themeVars } from "@/shared/styles/base/theme.css";
 import { screen } from "@/shared/styles/tokens/screen";
-import { style } from "@vanilla-extract/css";
+import { keyframes, style } from "@vanilla-extract/css";
 
 export const modalOverlay = style({
   alignItems: "center",
@@ -38,12 +38,27 @@ export const contentWrapper = style({
   flex: 1,
 });
 
+const shimmer = keyframes({
+  "0%": { backgroundPosition: "-100% 0" },
+  "100%": { backgroundPosition: "100% 0" },
+});
+
 export const image = style({
   flexShrink: 0,
   width: "100%",
   height: "auto",
   objectFit: "cover",
   borderRadius: "14px",
+
+  selectors: {
+    '&[data-loaded="false"]': {
+      backgroundColor: themeVars.color.black["90_bg"],
+      backgroundImage: themeVars.color.gradient.darkgray_bg_horizontal,
+      backgroundSize: "200% 100%",
+      animation: `${shimmer} 5s  infinite`,
+    },
+  },
+
   ...screen.md({
     width: "30rem",
     height: "30rem",

app/(sub)/capsule-detail/[invite-code]/[id]/letters/_components/stack-layout/index.tsx

@@ -3,6 +3,9 @@
 import Left from "@/shared/assets/icon/left.svg";
 import Right from "@/shared/assets/icon/right.svg";
 import type { Letter } from "@/shared/types/api/letter";
+import type {
+  InfiniteQueryObserverResult,
+} from "@tanstack/react-query";
 import { AnimatePresence, motion } from "motion/react";
 import { useEffect, useLayoutEffect, useRef, useState } from "react";
 import StackLetterCard from "../stack-letter-card";
@@ -25,30 +28,35 @@ interface ImageUrl {
 
 interface StackLayoutProps {
   letters: Letter[];
+  letterCount: number;
   imageUrls: ImageUrl[];
+  fetchNextPage: () => Promise<InfiniteQueryObserverResult<any, Error>>;
+  hasNextPage: boolean;
+  isFetchingNextPage: boolean;
 }
 
-const StackLayout = ({ letters, imageUrls }: StackLayoutProps) => {
+const StackLayout = ({
+  letters,
+  letterCount,
+  imageUrls,
+  fetchNextPage,
+  hasNextPage,
+  isFetchingNextPage,
+}: StackLayoutProps) => {
   const [currentIndex, setCurrentIndex] = useState(0);
+  const currentIndexRef = useRef(0);
   const [direction, setDirection] = useState(0);
   const [visibleLetters, setVisibleLetters] = useState<VisibleLetter[]>([]);
   const [isAnimating, setIsAnimating] = useState(false);
   const timerRef = useRef<NodeJS.Timeout | null>(null);
 
-  useEffect(() => {
-    return () => {
-      if (timerRef.current) {
-        clearTimeout(timerRef.current);
-      }
-    };
-  }, []);
-
   useLayoutEffect(() => {
     const maxCards = Math.min(3, letters.length - currentIndex);
     const newVisibleLetters: VisibleLetter[] = [];
 
     for (let i = 0; i < maxCards; i++) {
       const letterIndex = currentIndex + i;
+
       newVisibleLetters.push({
         letter: letters[letterIndex],
         stackIndex: i,
@@ -61,11 +69,38 @@ const StackLayout = ({ letters, imageUrls }: StackLayoutProps) => {
     setVisibleLetters(newVisibleLetters);
   }, [currentIndex, letters]);
 
+  useEffect(() => {
+    currentIndexRef.current = currentIndex;
+  }, [currentIndex]);
+
+  useEffect(() => {
+    if (!hasNextPage || isFetchingNextPage) return;
+
+    const shouldLoadNext =
+      currentIndexRef.current >= 8 && (currentIndexRef.current - 8) % 20 === 0;
+    if (shouldLoadNext) {
+      const timer = setTimeout(() => {
+        fetchNextPage();
+      }, 500);
+      return () => clearTimeout(timer);
+    }
+  }, [currentIndex, hasNextPage, isFetchingNextPage, fetchNextPage]);
+
+  useEffect(() => {
+    return () => {
+      if (timerRef.current) {
+        clearTimeout(timerRef.current);
+      }
+    };
+  }, []);
+
   const nextLetter = () => {
     if (currentIndex < letters.length - 1 && !isAnimating) {
       setIsAnimating(true);
       setDirection(1);
-      setCurrentIndex((prev) => prev + 1);
+      const nextIndex = currentIndex + 1;
+      setCurrentIndex(nextIndex);
+      currentIndexRef.current = nextIndex;
 
       timerRef.current = setTimeout(() => {
         setDirection(0);
@@ -102,7 +137,7 @@ const StackLayout = ({ letters, imageUrls }: StackLayoutProps) => {
       </button>
 
       <div className={styles.stackContainer}>
-        <AnimatePresence mode="popLayout">
+        <AnimatePresence mode="popLayout" initial={false}>
           {visibleLetters.map(({ letter, key }, index) => {
             const animationProps = createStackAnimations(
               direction,
@@ -123,7 +158,11 @@ const StackLayout = ({ letters, imageUrls }: StackLayoutProps) => {
                   left: 0,
                 }}
               >
-                <StackLetterCard letter={letter} imageUrl={imageUrl} />
+                <StackLetterCard
+                  letter={letter}
+                  imageUrl={imageUrl}
+                  disabled={isAnimating}
+                />
               </motion.div>
             );
           })}
@@ -144,7 +183,7 @@ const StackLayout = ({ letters, imageUrls }: StackLayoutProps) => {
 
       <div className={styles.pagination}>
         <span className={styles.paginationCurrent}>{currentIndex + 1}</span>
-        <span className={styles.paginationTotal}> / {letters.length}</span>
+        <span className={styles.paginationTotal}> / {letterCount}</span>
       </div>
     </div>
   );

app/(sub)/capsule-detail/[invite-code]/[id]/letters/_components/stack-letter-card/index.tsx

@@ -1,18 +1,24 @@
+import { useOverlay } from "@/shared/hooks/use-overlay";
 import type { Letter } from "@/shared/types/api/letter";
 import Image from "next/image";
-import { useOverlay } from "@/shared/hooks/use-overlay";
 import LetterDetailModal from "../letter-detail-modal";
 import * as styles from "./stack-letter-card.css";
 
 interface LetterCardProps {
   letter: Letter;
   imageUrl?: string | null;
+  disabled?: boolean;
 }
 
-const StackLetterCard = ({ letter, imageUrl }: LetterCardProps) => {
+const StackLetterCard = ({
+  letter,
+  imageUrl,
+  disabled = false,
+}: LetterCardProps) => {
   const { open } = useOverlay();
 
   const handleClick = () => {
+    if (disabled) return;
     open(({ isOpen, close }) => (
       <LetterDetailModal
         letter={letter}
@@ -28,13 +34,19 @@ const StackLetterCard = ({ letter, imageUrl }: LetterCardProps) => {
       <div className={styles.contentWrapper}>
         {imageUrl && (
           <Image
+            key={imageUrl}
             width={240}
             height={240}
             className={styles.image}
             src={imageUrl}
             alt="편지 이미지"
+            data-loaded="false"
+            onLoad={(event) => {
+              event.currentTarget.setAttribute("data-loaded", "true");
+            }}
           />
         )}
+
         <p
           className={
             imageUrl ? styles.contentWithImage : styles.contentWithoutImage

app/(sub)/capsule-detail/[invite-code]/[id]/letters/_components/stack-letter-card/stack-letter-card.css.ts

@@ -1,6 +1,6 @@
 import { themeVars } from "@/shared/styles/base/theme.css";
 import { screen } from "@/shared/styles/tokens/screen";
-import { style } from "@vanilla-extract/css";
+import { keyframes, style } from "@vanilla-extract/css";
 
 export const card = style({
   background: themeVars.color.gradient.darkgray_op,
@@ -34,13 +34,27 @@ export const contentWrapper = style({
   }),
 });
 
+const shimmer = keyframes({
+  "0%": { backgroundPosition: "-100% 0" },
+  "100%": { backgroundPosition: "100% 0" },
+});
+
 export const image = style({
   width: "16rem",
   height: "16rem",
   objectFit: "cover",
   borderRadius: "14px",
   overflow: "hidden",
 
+  selectors: {
+    '&[data-loaded="false"]': {
+      backgroundColor: themeVars.color.black["90_bg"],
+      backgroundImage: themeVars.color.gradient.darkgray_bg_horizontal,
+      backgroundSize: "200% 100%",
+      animation: `${shimmer} 5s  infinite`,
+    },
+  },
+
   ...screen.md({
     width: "24rem",
     height: "24rem",