/**
 * A position within a single chapter, expressed as a paragraph index and a
 * Unicode code point offset into that paragraph's `text`.
 *
 * Code point offsets are stable under reflow (font / size / line-width changes),
 * which is what makes them suitable for cross-device reading-position resume.
 */
interface InChapterAnchor {
    /** Zero-based paragraph index within the chapter. */
    paragraph: number;
    /** Unicode code point offset into the paragraph's `text`. */
    charIndex: number;
}
/**
 * A full reading position across an entire book — a chapter index combined
 * with an {@link InChapterAnchor}.
 *
 * Persist this struct (e.g. via `useReadingPosition`) to restore the user's
 * exact position even after a layout change that invalidates spread indices.
 */
interface ReadingAnchor extends InChapterAnchor {
    /** Zero-based chapter index. */
    chapter: number;
}
/**
 * Layout location for an in-chapter anchor, identified by spread + page + line.
 */
interface AnchorLocation {
    /** Zero-based spread index. */
    spreadIdx: number;
    /** Zero-based page index (= spreadIdx*2 + 0 for right, +1 for left). */
    pageIdx: number;
    /**
     * Zero-based line index across the chapter's flattened line list (i.e. the
     * same index used by {@link LineMetricsResult.metrics}). Equal to
     * `paraLineStarts[paragraph] + inParagraphLine`.
     */
    lineIdx: number;
    /** Side of the spread the anchor falls on. */
    side: 'right' | 'left';
}
/**
 * A pair of in-chapter anchors that delimits a contiguous range of text.
 *
 * The range is half-open: `start` is included, `end` is the position *after*
 * the last included character. If `start` and `end` are equal the range is
 * empty (a caret position). The order of `start` / `end` is not enforced —
 * callers may pass them in either direction; consuming methods normalize.
 */
interface AnchorRange {
    /** Start anchor (inclusive). */
    start: InChapterAnchor;
    /** End anchor (exclusive). */
    end: InChapterAnchor;
}
/**
 * Pixel rectangle of a single character in spread-local coordinates.
 *
 * Origin is the top-left of the **right page's content area** (matching
 * {@link BookImage} convention). The right page's content area spans
 * `x in [0, contentWidth]`; the left page's content area spans
 * `x in [-contentWidth, 0]`. `y` runs top-to-bottom along the inline
 * direction (text flow in vertical-rl) and covers `[0, lineWidth]`.
 *
 * `width` is the column block-direction pitch and `height` is the character's
 * inline-direction advance. The character bounding box is
 * `(x, y) ‒ (x + width, y + height)`.
 */
interface AnchorRect {
    /** Zero-based spread index. */
    spreadIdx: number;
    /** Zero-based page index. */
    pageIdx: number;
    /** Side of the spread the character falls on. */
    side: 'right' | 'left';
    /** Top-left x of the character bounding box (spread-local, content frame). */
    x: number;
    /** Top-left y of the character bounding box (spread-local, content frame). */
    y: number;
    /** Block-direction width (column pitch) in pixels. */
    width: number;
    /** Inline-direction length (character advance) in pixels. */
    height: number;
}

export type { AnchorLocation as A, InChapterAnchor as I, ReadingAnchor as R, AnchorRect as a, AnchorRange as b };