thi-ng/umbrella

import type { Fn } from "@thi.ng/api";
import { identity } from "@thi.ng/compose/identity";
import type { Reducer } from "./api.js";
import { groupByMap } from "./group-by-map.js";
import { normCount } from "./norm-count.js";
import { $$reduce } from "./reduce.js";

/**
 * Similar to {@link frequencies}, but with each bin value normalized to given
 * `norm`.
 *
 * @remarks
 * Also see {@link normFrequenciesAuto}.
 *
 * @example
 * ```ts
 * import { normFrequencies } from "@thi.ng/transducers";
 *
 * const items = [1, 2, 3, 1, 1, 4, 2, 5, 1, 2];
 *
 * normFrequencies(10, items)
 * // Map(5) { 1 => 0.4, 2 => 0.3, 3 => 0.1, 4 => 0.1, 5 => 0.1 }
 * ```
 *
 * @param norm -
 */
export function normFrequencies<A>(norm: number): Reducer<A, Map<A, number>>;
export function normFrequencies<A>(
    norm: number,
    src: Iterable<A>
): Map<A, number>;
export function normFrequencies<A, B>(
    norm: number,
    key: Fn<A, B>
): Reducer<A, Map<B, number>>;
export function normFrequencies<A, B>(
    norm: number,
    key: Fn<A, B>,
    src: Iterable<A>
): Map<B, number>;
export function normFrequencies(...args: any[]): any {
    return (
        $$reduce(normFrequencies, args) ||
        groupByMap({
            key: args[1] || identity,
            group: normCount(args[0]),
        })
    );
}