thi-ng/umbrella

import type { Reducer, Transducer } from "@thi.ng/transducers";
import { compR } from "@thi.ng/transducers/compr";
import { iterator1 } from "@thi.ng/transducers/iterator";
import { Deque } from "./deque.js";

export function movingMaximum(period: number): Transducer<number, number>;
export function movingMaximum(
    period: number,
    src: Iterable<number>
): IterableIterator<number>;
export function movingMaximum(period: number, src?: Iterable<number>): any {
    return src
        ? iterator1(movingMaximum(period), src)
        : (rfn: Reducer<number, any>) => {
                const samples: number[] = [];
                const deque = new Deque(samples, (a, b) => a <= b);
                return compR(rfn, (acc: any, x: number) => {
                    const num = samples.push(x);
                    deque.add(x);
                    if (num > period) {
                        samples.shift();
                        deque.shift();
                    }
                    return num >= period ? rfn[2](acc, deque.head()) : acc;
                });
          };
}