/**
 * TODO: Revisit when we move to MW 1.43 and the interface is more stable
 */

/**
 * Creates default portlet.
 * Based on Vector
 *
 * @param {Element} portlet
 * @return {Element}
 */
function addDefaultPortlet( portlet ) {
	const ul = portlet.querySelector( 'ul' );
	if ( !ul ) {
		return portlet;
	}
	ul.classList.add( 'citizen-menu__content-list' );
	const label = portlet.querySelector( 'label' );
	if ( label ) {
		const labelDiv = document.createElement( 'div' );
		labelDiv.classList.add( 'citizen-menu__heading' );
		labelDiv.innerHTML = label.textContent || '';
		portlet.insertBefore( labelDiv, label );
		label.remove();
	}
	let wrapper = portlet.querySelector( 'div:last-child' );
	if ( wrapper ) {
		ul.remove();
		wrapper.appendChild( ul );
		wrapper.classList.add( 'citizen-menu__content' );
	} else {
		wrapper = document.createElement( 'div' );
		wrapper.classList.add( 'citizen-menu__content' );
		ul.remove();
		wrapper.appendChild( ul );
		portlet.appendChild( wrapper );
	}
	portlet.classList.add( 'citizen-menu' );
	return portlet;
}

/**
 * Polyfill for mw.util.addPortlet for < MW 1.41
 * Creates a detached portlet Element in the skin with no elements.
 *
 * @param {string} id of the new portlet.
 * @param {string} [label] of the new portlet.
 * @param {string} [before] selector of the element preceding the new portlet. If not passed
 *  the caller is responsible for appending the element to the DOM before using addPortletLink.
 * @return {HTMLElement|null} will be null if it was not possible to create an portlet with
 *  the required information e.g. the selector given in before parameter could not be resolved
 *  to an existing element in the page.
 */
function addPortlet( id, label, before ) {
	if ( mw.util.addPortlet ) {
		return addDefaultPortlet( mw.util.addPortlet( id, label, before ) );
	}

	const portlet = document.createElement( 'div' );
	portlet.classList.add( 'mw-portlet', 'mw-portlet-' + id, 'emptyPortlet',
		// Additional class is added to allow skins to track portlets added via this mechanism.
		'mw-portlet-js'
	);
	portlet.id = id;
	if ( label ) {
		const labelNode = document.createElement( 'label' );
		labelNode.textContent = label;
		portlet.appendChild( labelNode );
	}
	const listWrapper = document.createElement( 'div' );
	const list = document.createElement( 'ul' );
	listWrapper.appendChild( list );
	portlet.appendChild( listWrapper );
	if ( before ) {
		let referenceNode;
		try {
			referenceNode = document.querySelector( before );
		} catch ( e ) {
			// CSS selector not supported by browser.
		}
		if ( referenceNode ) {
			const parentNode = referenceNode.parentNode;
			parentNode.insertBefore( portlet, referenceNode );
		} else {
			return null;
		}
	}
	mw.hook( 'util.addPortlet' ).fire( portlet, before );
	return addDefaultPortlet( portlet );
}

/** @module addPortlet */
module.exports = addPortlet;