import { getOffset } from './offset.js';


const locks = new Set();


/**
 * Prevents body scrolling.
 * Keeps track of which elements requested a lock so multiple levels of locking are possible
 * without premature unlocking.
 */
export const lockBodyScrolling = (lockingEl: HTMLElement) => {
	locks.add(lockingEl);
	document.body.classList.add('scroll-lock');
};


/**
 * Unlocks body scrolling.
 * Scrolling will only be unlocked once all elements that requested a lock call this method.
 */
export const unlockBodyScrolling = (lockingEl: HTMLElement) => {
	locks.delete(lockingEl);

	if (locks.size === 0)
		document.body.classList.remove('scroll-lock');
};


/**
 * Scrolls an element into view of its container.
 * If the element is already in view, nothing will happen.
 */
export const scrollIntoView = (
	element: HTMLElement,
	container: HTMLElement,
	direction: 'horizontal' | 'vertical' | 'both' = 'vertical',
	behavior: 'smooth' | 'auto' = 'smooth',
) => {
	const containerStyles = getComputedStyle(container);
	const [ padInStart, padInEnd, padBlStart, padBlEnd ] = [
		parseInt(containerStyles.paddingInlineStart),
		parseInt(containerStyles.paddingInlineEnd),
		parseInt(containerStyles.paddingBlockStart),
		parseInt(containerStyles.paddingBlockEnd),
	];

	const offset = getOffset(element, container);
	const offsetTop = offset.top + container.scrollTop;
	const offsetLeft = offset.left + container.scrollLeft;
	const minX = container.scrollLeft;
	const maxX = container.scrollLeft + container.offsetWidth;
	const minY = container.scrollTop;
	const maxY = container.scrollTop + container.offsetHeight;

	if (direction === 'horizontal' || direction === 'both') {
		if (offsetLeft < minX)
			container.scrollTo({ left: offsetLeft - padInStart, behavior });
		else if (offsetLeft + element.clientWidth > maxX)
			container.scrollTo({ left: offsetLeft + padInEnd - container.offsetWidth + element.clientWidth, behavior });
	}

	if (direction === 'vertical' || direction === 'both') {
		if (offsetTop < minY)
			container.scrollTo({ top: offsetTop - padBlStart, behavior });
		else if (offsetTop + element.clientHeight > maxY)
			container.scrollTo({ top: offsetTop + padBlEnd - container.offsetHeight + element.clientHeight, behavior });
	}
};