/**
 * Pattern detection + extrapolation for the cell-range fill handle.
 *
 * Recognized patterns, in priority order:
 *
 *   1. Known sequences (case-insensitive): days of the week (Monday /
 *      Mon), months (January / Jan), quarters (Q1..Q4). When source
 *      values match a sequence and form an arithmetic progression of
 *      indices into it, we extrapolate by stepping through the sequence
 *      with wrap-around. Output case is matched to the source - UPPER,
 *      lower, or Title.
 *
 *   2. Prefix-number-suffix patterns: "Item 1", "Item 2" → "Item 3";
 *      "2024-Q1", "2024-Q2" → "2024-Q3". The shared prefix + suffix is
 *      preserved and the number is extrapolated.
 *
 *   3. Pure numeric arithmetic progression: 1, 2, 3 → 4, 5, 6; or
 *      100, 200, 300 → 400, 500, 600.
 *
 *   4. Fallback: cycle the source values across the new cells.
 *
 * A single source value falls through to the cycle case (repeats), which
 * matches Excel's default fill behavior.
 */
/**
 * Compute the values to write into `targetCount` new cells given the
 * `sourceValues` already in the selection. See module header for the
 * pattern-detection rules.
 */
export declare function buildFillPattern(sourceValues: ReadonlyArray<unknown>, targetCount: number): unknown[];