/**
 * The aggregates in code-land — the handful of reductions an island reaches for
 * by name, over core's ONE numeric reduce ({@link reduceNumeric}).
 *
 * They no longer build expression SOURCE and hand it to an evaluator. They
 * used to, because `$expr` was a closed dialect with its own `sum` and the rule
 * was that this repo may hold only one. A `{...}` gap is JavaScript now, so
 * `sum(rows, "amount_cents")` here and
 * `rows.reduce((t, r) => t + r.amount_cents, 0)` in a screen are the same
 * language reaching the same arithmetic — there is no second implementation to
 * avoid, only a second copy of the REDUCE, and that still lives in core.
 *
 * One posture, as everywhere in this package: the number (or the points), or
 * `undefined` — loading and a mismatch both. An island renders a placeholder,
 * never a throw.
 */
import { type Json, type NumericReduction } from "../../core/index.js";
/** Total of a numeric column. */
export declare const sum: (rows: Json | undefined, field: string) => number | undefined;
/** Mean of a numeric column; no values means no answer. */
export declare const average: (rows: Json | undefined, field: string) => number | undefined;
export declare const min: (rows: Json | undefined, field: string) => number | undefined;
export declare const max: (rows: Json | undefined, field: string) => number | undefined;
/** How many rows the list holds. */
export declare const count: (rows: Json | undefined) => number | undefined;
/** `left - right`, with either side absent meaning no answer. */
export declare const difference: (left: Json | undefined, right: Json | undefined) => number | undefined;
/** Whole days from now (UTC day boundaries) to an ISO date string. `now` is
 *  injectable so a render is testable — the ONE clock read in this module, and
 *  the reason it is a parameter rather than an ambient call. */
export declare const daysUntil: (date: Json | undefined, options?: {
    now?: number;
}) => number | undefined;
/** The buckets {@link groupBy} can cut a date field into. */
export type GroupByBucket = "day" | "month" | "year";
/** The reductions {@link groupBy} can aggregate a bucket with. */
export type GroupByAggregate = NumericReduction | "count";
/** One bucket of a {@link groupBy}, ready for a Kit chart's `{ key, value }`. */
export interface GroupedPoint {
    key: string;
    value: number;
}
/**
 * Bucket rows by a date field and aggregate each bucket, oldest bucket first.
 * `valueField` is unused by (and unnecessary for) `count`.
 */
export declare const groupBy: (rows: Json | undefined, keyField: string, bucket: GroupByBucket, aggregate: GroupByAggregate, valueField?: string) => GroupedPoint[] | undefined;