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// Copyright 2018-2025 the Deno authors. MIT license.
// This module is browser compatible.
/** Options for {@linkcode slidingWindows}. */
export interface SlidingWindowsOptions {
/**
* If step is set, each window will start that many elements after the last
* window's start.
*
* @default {1}
*/
step?: number;
/**
* If partial is set, windows will be generated for the last elements of the
* collection, resulting in some undefined values if size is greater than 1.
*
* @default {false}
*/
partial?: boolean;
}
/**
* Generates sliding views of the given array of the given size and returns a
* new array containing all of them.
*
* If step is set, each window will start that many elements after the last
* window's start. (Default: 1)
*
* If partial is set, windows will be generated for the last elements of the
* collection, resulting in some undefined values if size is greater than 1.
*
* @typeParam T The type of the array elements.
*
* @param array The array to generate sliding windows from.
* @param size The size of the sliding windows.
* @param options The options for generating sliding windows.
*
* @returns A new array containing all sliding windows of the given size.
*
* @example Usage
* ```ts
* import { slidingWindows } from "@std/collections/sliding-windows";
* import { assertEquals } from "@std/assert";
* const numbers = [1, 2, 3, 4, 5];
*
* const windows = slidingWindows(numbers, 3);
* assertEquals(windows, [
* [1, 2, 3],
* [2, 3, 4],
* [3, 4, 5],
* ]);
*
* const windowsWithStep = slidingWindows(numbers, 3, { step: 2 });
* assertEquals(windowsWithStep, [
* [1, 2, 3],
* [3, 4, 5],
* ]);
*
* const windowsWithPartial = slidingWindows(numbers, 3, { partial: true });
* assertEquals(windowsWithPartial, [
* [1, 2, 3],
* [2, 3, 4],
* [3, 4, 5],
* [4, 5],
* [5],
* ]);
* ```
*/
export function slidingWindows<T>(
array: readonly T[],
size: number,
options: SlidingWindowsOptions = {},
): T[][] {
const { step = 1, partial = false } = options;
if (
!Number.isInteger(size) || !Number.isInteger(step) || size <= 0 || step <= 0
) {
throw new RangeError("Both size and step must be positive integer");
}
return Array.from(
{ length: Math.floor((array.length - (partial ? 1 : size)) / step + 1) },
(_, i) => array.slice(i * step, i * step + size),
);
}
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