// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
namespace System.Windows
{
    /// <summary>
    ///     Creates and recycles instance of EventRoute
    /// </summary>
    internal static class EventRouteFactory
    {
        #region Operations
 
        /// <summary>
        ///     Fetch a recycled object if available 
        ///     else create a new instance
        /// </summary>
        internal static EventRoute FetchObject(RoutedEvent routedEvent)
        {
            EventRoute eventRoute = Pop();
 
            if (eventRoute == null)
            {
                eventRoute = new EventRoute(routedEvent);
            }
            else
            {
                eventRoute.RoutedEvent = routedEvent;
            }
 
            return eventRoute;            
        }
 
        /// <summary>
        ///     Recycle the given instance of EventRoute
        /// </summary>
        internal static void RecycleObject(EventRoute eventRoute)
        {
            // Cleanup all refernces held
            eventRoute.Clear();
 
            // Push instance on to the stack
            Push(eventRoute);
        }
        
        #endregion Operations
        
        #region HelperMethods
 
        /// <summary>
        ///     Push the given instance of EventRoute on to the stack
        /// </summary>
        private static void Push(EventRoute eventRoute)
        {
            lock (_synchronized)
            {
                // In a normal scenario it is extremely rare to 
                // require more than 2 EventRoutes at the same time
                if (_eventRouteStack == null)
                {
                    _eventRouteStack = new EventRoute[2];
                    _stackTop = 0;
                }
 
                if (_stackTop < 2)
                {
                    _eventRouteStack[_stackTop++] = eventRoute;
                }
            }
        }
 
        /// <summary>
        ///     Pop off the last instance of EventRoute in the stack
        /// </summary>
        private static EventRoute Pop()
        {
            lock (_synchronized)
            {
                if (_stackTop > 0)
                {
                    EventRoute eventRoute = _eventRouteStack[--_stackTop];
                    _eventRouteStack[_stackTop] = null;
                    return eventRoute;
                }
            }
 
            return null;
        }
 
        #endregion HelperMethods
 
        #region Data
 
        private static EventRoute[] _eventRouteStack;
        private static int _stackTop;
        private static readonly object _synchronized = new object();
 
        #endregion Data
    }
}