Add infinite scroll to reader

src/modules/reader/utils/ReaderPager.utils.tsx

@@ -505,6 +505,29 @@ export const isSpreadPage = (image: HTMLImageElement): boolean => {
     return aspectRatio < 1;
 };
 
+const MIN_PREVIOUS_NEXT_CHAPTER_IMAGE_LOAD_AMOUNT = 0;
+const MAX_PREVIOUS_NEXT_CHAPTER_IMAGE_LOAD_AMOUNT = 1;
+const getImagePreLoadAmount = (
+    isCurrentChapter: boolean,
+    isPreviousChapter: boolean,
+    isNextChapter: boolean,
+    imagePreLoadAmount: number,
+): number => {
+    if (isCurrentChapter) {
+        return imagePreLoadAmount;
+    }
+
+    if (isPreviousChapter || isNextChapter) {
+        return coerceIn(
+            MAX_PREVIOUS_NEXT_CHAPTER_IMAGE_LOAD_AMOUNT,
+            MIN_PREVIOUS_NEXT_CHAPTER_IMAGE_LOAD_AMOUNT,
+            imagePreLoadAmount,
+        );
+    }
+
+    return 0;
+};
+
 const PREVIOUS_IMAGE_LOAD_AMOUNT = 2;
 export const getPageIndexesToLoad = (
     currentPageIndex: number,
@@ -512,20 +535,33 @@ export const getPageIndexesToLoad = (
     previousCurrentPageIndex: number,
     imagePreLoadAmount: number,
     readingMode: ReadingMode,
+    isCurrentChapter: boolean,
+    isPreviousChapter: boolean,
+    isNextChapter: boolean,
 ): number[] => {
-    const currentPagesIndex = getPage(currentPageIndex, pages).pagesIndex;
+    if (!isCurrentChapter && !isPreviousChapter && !isNextChapter) {
+        return [];
+    }
 
-    const directionInvert = previousCurrentPageIndex <= currentPageIndex ? 1 : -1;
+    const currentPagesIndex = getPage(currentPageIndex, pages).pagesIndex;
+    const finalImagePreLoadAmount = getImagePreLoadAmount(
+        isCurrentChapter,
+        isPreviousChapter,
+        isNextChapter,
+        imagePreLoadAmount,
+    );
+
+    const directionInvert = previousCurrentPageIndex <= currentPageIndex && !isPreviousChapter ? 1 : -1;
     // load at most PREVIOUS_IMAGE_LOAD_AMOUNT of the previous pages to ensure that you do not have to wait too long
     // when going back to the previous pages
     const startPagesIndexTrailingIncluded = Math.max(
         0,
-        currentPagesIndex - Math.min(PREVIOUS_IMAGE_LOAD_AMOUNT, imagePreLoadAmount) * directionInvert,
+        currentPagesIndex - Math.min(PREVIOUS_IMAGE_LOAD_AMOUNT, finalImagePreLoadAmount) * directionInvert,
     );
     // do not load previous pages for continuous pagers to prevent layout shifts due to leading pages getting loaded
     const startPagesIndex = !isContinuousReadingMode(readingMode) ? startPagesIndexTrailingIncluded : currentPageIndex;
-    const endPagesIndex = currentPagesIndex + imagePreLoadAmount * directionInvert;
-    const pagesToRenderLength = Math.abs(endPagesIndex - startPagesIndex) + 1;
+    const endPagesIndex = currentPagesIndex + finalImagePreLoadAmount * directionInvert;
+    const pagesToRenderLength = Math.max(1, Math.abs(endPagesIndex - startPagesIndex));
 
     return Array(pagesToRenderLength)
         .fill(1)