/**

* requestAnimationFrame polyfill

*/

import { isServer } from '..';

let prev = Date.now();

/* istanbul ignore next */

function fallback(fn: FrameRequestCallback): number {

const curr = Date.now();

const ms = Math.max(0, 16 - (curr - prev));

const id = setTimeout(fn, ms);

prev = curr + ms;

return id;

}

/* istanbul ignore next */

const root = <Window>(isServer ? global : window);

/* istanbul ignore next */

const iRaf = root.requestAnimationFrame || fallback;

/* istanbul ignore next */

const iCancel = root.cancelAnimationFrame || root.clearTimeout;

export function raf(fn: FrameRequestCallback): number {

return iRaf.call(root, fn);

}

// double raf for animation

export function doubleRaf(fn: FrameRequestCallback): void {

raf(() => {

raf(fn);

});

}

export function cancelRaf(id: number) {

iCancel.call(root, id);

}