/**
 * Parent-child relationships between two levels of geometry.
 *
 * Drilling from states into counties is only a map swap if the child level is
 * also *restricted* to the parent that was clicked. Showing all 3,231 US counties
 * after clicking California is not a drilldown, it is a zoom, and the reader has
 * to find California again themselves.
 *
 * Which counties belong to California is a question about the data, and published
 * hierarchical geometry nearly always answers it in one of two ways:
 *
 * 1. **A property naming the parent.** TIGER counties carry `state_abbr` and
 *    `state_fips`, Eurostat NUTS carries `cntr_code`, Natural Earth admin-1
 *    carries `adm0_a3`. Detecting the field beats asking for it, because the
 *    caller would have to know the internals of a pack they never opened.
 * 2. **A key prefix.** County FIPS `06037` sits under state FIPS `06`, and NUTS
 *    `DE12` under `DE1`, because both code systems are hierarchical by design.
 *
 * Property detection runs first because it is exact: a prefix test can only be
 * as good as the code system, while a property either equals the parent key or
 * does not. Prefix is the fallback, and it is what carries NUTS below level 1,
 * where `cntr_code` stops distinguishing the levels.
 *
 * Both are checked against real features rather than assumed, so a pack that does
 * neither reports that it does neither instead of quietly drawing an empty map.
 *
 * @module data/Hierarchy
 */
import type { DrilldownOptions, NormalizedFeature, NormalizedGeo } from '../types';
/** How a set of child features was matched to its parent. */
export type ScopeMethod = 'property' | 'keyPrefix' | 'all' | 'none';
export interface ScopeResult {
    /** Child geometry restricted to the parent, with feature indices renumbered. */
    geo: NormalizedGeo;
    method: ScopeMethod;
    /** Property that matched, for `method: 'property'`. */
    field?: string;
    count: number;
    /** Dev-mode explanation of what was matched and how. */
    note: string;
}
/**
 * Find a child property whose value is the parent's key.
 *
 * Scores every candidate by how many children it matches and takes the winner,
 * rather than the first hit: one county whose `name` happens to equal a state
 * abbreviation must not beat the `state_abbr` field that matches all fifty-eight.
 *
 * @returns The field name, or null when no property matches any child.
 */
export declare function detectParentField(features: readonly NormalizedFeature[], parentKey: string): string | null;
/**
 * Restrict child geometry to the descendants of one parent key.
 *
 * Returns the whole child level unchanged when `scope: 'all'`, and reports
 * `method: 'none'` when a restriction was wanted but nothing matched, which the
 * caller must treat as a refusal: a drilldown that lands on an empty map is worse
 * than one that does not happen.
 */
export declare function scopeToParent(geo: NormalizedGeo, parentKey: string, options?: Pick<DrilldownOptions, 'scope' | 'parentField'>): ScopeResult;
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