import type { CellComplex, CellGroup } from './cell-complex.js';
/** Which boundary facet a cell lies on, and which way that facet faces. */
export interface CellFacetN {
    /** Ambient axis held constant across the cell. */
    readonly axis: number;
    /** `+1` at the complex's maximum along `axis`, `-1` at its minimum. */
    readonly sign: 1 | -1;
    /** The constant coordinate itself, in source units. */
    readonly coordinate: number;
}
/**
 * Names the boundary facet a cuboid cell lies on, recovered from positions.
 *
 * A facet-dimensional cuboid cell spans every ambient axis but one, so the
 * remaining axis is constant across its corners and identifies the facet. This
 * reads that axis off the geometry, because the cell carries no such metadata:
 * `CellGroup` is positions plus indices, and a construction like
 * `createHypercube` emits no per-cell record of which side it came from.
 *
 * Callers reconstruct this constantly and get it wrong in the same two ways.
 * Comparing coordinates against a literal `±1` assumes a particular `size`, and
 * taking `Math.sign` of the coordinate assumes the complex is centred on the
 * origin. Both are silent: they return a confident wrong facet for a rescaled
 * or translated complex rather than failing. Orientation here is resolved
 * against the complex's own extent along the axis, so it survives both.
 *
 * @param complex - Complex owning the positions.
 * @param group - Cuboid group of dimension `complex.ambientDim - 1`.
 * @param cell - Cell ordinal within `group`.
 * @param tolerance - Absolute slack for treating coordinates as equal.
 * @returns The facet, or `null` if the cell lies on none — a group of the wrong
 * dimension, a cell whose corners share no axis, or one whose constant axis
 * sits strictly inside the body.
 *
 * @example
 * Name every facet of a tesseract without assuming its size or centre:
 * ```ts
 * const tesseract = createHypercube({ dim: 4, size: 2, maxCellDimension: 3 });
 * const cubes = tesseract.cellsOfDim(3).find((group) => group.kind === 'cuboid');
 * if (!cubes) throw new Error('no cuboid 3-cells; raise maxCellDimension');
 *
 * // A group carries no cell count; derive it from the index buffer.
 * const cellCount = cubes.indices.length / cubes.verticesPerCell;
 *
 * const facets = [];
 * for (let cell = 0; cell < cellCount; cell += 1) {
 *   // CellFacetN, or null for a cell that is not on the boundary.
 *   const facet = cuboidCellFacetN(tesseract, cubes, cell);
 *   facets.push(facet === null ? 'none' : `${facet.axis}:${facet.sign > 0 ? '+' : '-'}`);
 * }
 * log(facets.join(' ')); // 3:- 3:+ 2:- 2:+ 1:- 1:+ 0:- 0:+
 * ```
 */
export declare function cuboidCellFacetN(complex: CellComplex, group: CellGroup, cell: number, tolerance?: number): CellFacetN | null;
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