import FocusEvent from '../../event/events/FocusEvent.js';
import * as PropertySymbol from '../../PropertySymbol.js';
import type HTMLElement from '../html-element/HTMLElement.js';
import type SVGElement from '../svg-element/SVGElement.js';

/**
 * HTMLElement utility.
 */
export default class HTMLElementUtility {
	/**
	 * Triggers a blur event.
	 *
	 * @param element Element.
	 */
	public static blur(element: HTMLElement | SVGElement): void {
		const target = element[PropertySymbol.proxy] || element;
		const document = target[PropertySymbol.ownerDocument];

		if (
			document[PropertySymbol.activeElement] !== target ||
			!target[PropertySymbol.isConnected] ||
			(<any>target).disabled
		) {
			return;
		}

		const relatedTarget = document[PropertySymbol.nextActiveElement] ?? null;

		document[PropertySymbol.activeElement] = null;

		document[PropertySymbol.clearCache]();

		target.dispatchEvent(
			new FocusEvent('blur', {
				relatedTarget,
				bubbles: false,
				composed: true,
				cancelable: true
			})
		);
		target.dispatchEvent(
			new FocusEvent('focusout', {
				relatedTarget,
				bubbles: true,
				composed: true,
				cancelable: true
			})
		);
	}

	/**
	 * Triggers a focus event.
	 *
	 * @param element Element.
	 */
	public static focus(element: HTMLElement | SVGElement): void {
		const target = element[PropertySymbol.proxy] || element;
		const document = target[PropertySymbol.ownerDocument];

		if (
			document[PropertySymbol.activeElement] === target ||
			!target[PropertySymbol.isConnected] ||
			(<any>target).disabled ||
			this.isInert(<HTMLElement | SVGElement>target)
		) {
			return;
		}

		// Set the next active element so `blur` can use it for `relatedTarget`.
		document[PropertySymbol.nextActiveElement] = <HTMLElement>target;

		const relatedTarget = document[PropertySymbol.activeElement];

		if (document[PropertySymbol.activeElement] !== null) {
			document[PropertySymbol.activeElement].blur();
		}

		// Clean up after blur, so it does not affect next blur call.
		document[PropertySymbol.nextActiveElement] = null;

		document[PropertySymbol.activeElement] = <HTMLElement>target;

		document[PropertySymbol.clearCache]();

		target.dispatchEvent(
			new FocusEvent('focus', {
				relatedTarget,
				bubbles: false,
				composed: true
			})
		);
		target.dispatchEvent(
			new FocusEvent('focusin', {
				relatedTarget,
				bubbles: true,
				composed: true
			})
		);
	}

	/**
	 * Returns whether an element or any of its ancestors has the inert attribute.
	 *
	 * @param element Element to check.
	 * @returns True if the element is in an inert tree.
	 */
	private static isInert(element: HTMLElement | SVGElement): boolean {
		let current: HTMLElement | SVGElement | null = <HTMLElement | SVGElement>(
			(element[PropertySymbol.proxy] || element)
		);
		while (current && typeof current.getAttribute === 'function') {
			if (current.getAttribute('inert') !== null) {
				return true;
			}
			current = <HTMLElement | SVGElement | null>current[PropertySymbol.parentNode];
		}
		return false;
	}
}