range.ts

import { createIterableIterator } from "./createIterableIterator.js";

/**
 * Range iterable generator (from `from` to `to`).
 *
 * @category Asynchronous Generators
 * @example
 * ```typescript
 * [...range(1)(0)(5)]; // [0, 1, 2, 3, 4, 5]
 * [...range(1)(5)(0)]; // [5, 4, 3, 2, 1, 0]
 * ```
 * @param step Step size.
 * @returns Curried function with `step` set in context.
 */
export const range =
	<Step extends bigint | number>(step: Step) =>
	(from: Step extends bigint ? bigint : number) =>
	(to: Step extends bigint ? bigint : number) =>
		// eslint-disable-next-line @typescript-eslint/require-await
		createIterableIterator(async function* () {
			// eslint-disable-next-line functional/no-let
			let current = from as number;

			yield current;

			// eslint-disable-next-line functional/no-conditional-statements
			if (from < to) {
				// eslint-disable-next-line functional/no-loop-statements
				while (current + (step as number) <= to) {
					yield (current += step as number) as Step extends bigint ?
						bigint
					:	number;
				}
				// eslint-disable-next-line functional/no-conditional-statements
			} else {
				// eslint-disable-next-line functional/no-loop-statements
				while (current - (step as number) >= to) {
					yield (current -= step as number) as Step extends bigint ?
						bigint
					:	number;
				}
			}
		});