// Pure helper for reflecting a reader's personal progress on a manga's
// chapter list. Kept UI-free so the read/unread logic is unit-testable
// without rendering the detail page.

/**
 * A chapter counts as read once its number is at or before the reader's
 * last-read chapter number. An unknown last-read position (guest, never
 * opened, or a deleted chapter) marks nothing — we never guess.
 */
export function isChapterRead(chapterNumber: number, lastReadNumber: number | null): boolean {
    return lastReadNumber != null && chapterNumber <= lastReadNumber;
}

// Note: the "new since last read" *count* is computed server-side
// (distinct chapter numbers over ALL chapters — see
// repo::read_progress) and delivered on the read-progress payloads, so it
// isn't recomputed here over the detail page's paginated chapter list.