import { getGlobal } from '../lib/teact/teactn';

import { ANIMATION_LEVEL_MIN } from '../config';
import { animate } from './animation';
import { fastRaf } from './schedulers';

const DEFAULT_DURATION = 300;

export default function fastSmoothScrollHorizontal(container: HTMLElement, left: number, duration = DEFAULT_DURATION) {
  if (getGlobal().settings.byKey.animationLevel === ANIMATION_LEVEL_MIN) {
    duration = 0;
  }

  scrollWithJs(container, left, duration);
}

function scrollWithJs(container: HTMLElement, left: number, duration: number) {
  const isRtl = container.getAttribute('dir') === 'rtl';
  const { scrollLeft, offsetWidth: containerWidth, scrollWidth } = container;
  let path = left - scrollLeft;

  if (path < 0) {
    const remainingPath = -scrollLeft * (isRtl ? -1 : 1);
    path = Math.max(path, remainingPath);
  } else if (path > 0) {
    const remainingPath = scrollWidth - (scrollLeft + containerWidth);
    path = Math.min(path, remainingPath);
  }

  if (path === 0) {
    return;
  }

  const target = scrollLeft + path;

  if (duration === 0) {
    container.scrollLeft = target;
    return;
  }

  const startAt = Date.now();

  fastRaf(() => {
    animate(() => {
      const t = Math.min((Date.now() - startAt) / duration, 1);

      const currentPath = path * (1 - transition(t));
      container.scrollLeft = Math.round(target - currentPath);

      return t < 1;
    });
  });
}

function transition(t: number) {
  return 1 - ((1 - t) ** 3.5);
}