/** A fixed-size 2D board of cells, row-major from the top-left; `null` is an empty cell. Plain data, so it serializes and restores as-is. */
export interface CellGrid<T> {
    readonly width: number;
    readonly height: number;
    readonly cells: readonly (T | null)[];
}
/** A straight line of matching cells found by {@link findRuns}. */
export interface CellRun<T> {
    readonly value: T;
    readonly cells: readonly {
        readonly x: number;
        readonly y: number;
    }[];
    readonly direction: "row" | "column";
}
/**
 * An empty `width` × `height` board. Every helper here returns a new grid, so a store slot can hold it
 * and undo, replay, and save/restore work without copying.
 * @capability cell-grid immutable 2D board of cells with row clears, gravity collapse, and match runs
 */
export declare function createCellGrid<T>(width: number, height: number): CellGrid<T>;
/** Whether `(x, y)` lies on the board. */
export declare function inGridBounds<T>(grid: CellGrid<T>, x: number, y: number): boolean;
/** The value at `(x, y)`, or `null` when empty or off the board. */
export declare function cellAt<T>(grid: CellGrid<T>, x: number, y: number): T | null;
/** A copy with `(x, y)` set to `value`; off-board writes return the grid unchanged. */
export declare function withCell<T>(grid: CellGrid<T>, x: number, y: number, value: T | null): CellGrid<T>;
/** A copy with every in-bounds entry written; one allocation for a whole piece or stamp. */
export declare function withCells<T>(grid: CellGrid<T>, entries: readonly {
    readonly x: number;
    readonly y: number;
    readonly value: T | null;
}[]): CellGrid<T>;
/** Indices of rows with no empty cell, top to bottom. */
export declare function fullRows<T>(grid: CellGrid<T>): number[];
/** A copy with `rows` removed and the rows above shifted down, refilling empty rows at the top. */
export declare function clearRows<T>(grid: CellGrid<T>, rows: readonly number[]): CellGrid<T>;
/** A copy where every column's cells fall to the bottom, keeping their order. */
export declare function collapseColumns<T>(grid: CellGrid<T>): CellGrid<T>;
/** Horizontal and vertical runs of at least `minLength` cells whose values `matches` (default `===`). */
export declare function findRuns<T>(grid: CellGrid<T>, minLength: number, matches?: (a: T, b: T) => boolean): CellRun<T>[];