/**
 * Element that can be marked as pending.
 *
 * @abstract
 * @class
 *
 * @constructor
 * @param {Object} [config] Configuration options
 * @cfg {jQuery} [$pending] Element to mark as pending, defaults to this.$element
 */
OO.ui.PendingElement = function OoUiPendingElement( config ) {
	// Configuration initialization
	config = config || {};

	// Properties
	this.pending = 0;
	this.$pending = null;

	// Initialisation
	this.setPendingElement( config.$pending || this.$element );
};

/* Setup */

OO.initClass( OO.ui.PendingElement );

/* Methods */

/**
 * Set the pending element (and clean up any existing one).
 *
 * @param {jQuery} $pending The element to set to pending.
 */
OO.ui.PendingElement.prototype.setPendingElement = function ( $pending ) {
	if ( this.$pending ) {
		this.$pending.removeClass( 'oo-ui-pendingElement-pending' );
	}

	this.$pending = $pending;
	if ( this.pending > 0 ) {
		this.$pending.addClass( 'oo-ui-pendingElement-pending' );
	}
};

/**
 * Check if input is pending.
 *
 * @return {boolean}
 */
OO.ui.PendingElement.prototype.isPending = function () {
	return !!this.pending;
};

/**
 * Increase the pending stack.
 *
 * @chainable
 */
OO.ui.PendingElement.prototype.pushPending = function () {
	if ( this.pending === 0 ) {
		this.$pending.addClass( 'oo-ui-pendingElement-pending' );
		this.updateThemeClasses();
	}
	this.pending++;

	return this;
};

/**
 * Reduce the pending stack.
 *
 * Clamped at zero.
 *
 * @chainable
 */
OO.ui.PendingElement.prototype.popPending = function () {
	if ( this.pending === 1 ) {
		this.$pending.removeClass( 'oo-ui-pendingElement-pending' );
		this.updateThemeClasses();
	}
	this.pending = Math.max( 0, this.pending - 1 );

	return this;
};