// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
 
/***************************************************************************\
*
*
* A collection of TriggerBase-derived classes. See use in Style.cs and other
* places.
*
*
\***************************************************************************/
using System.Collections.ObjectModel; // Collection<T>
using MS.Internal;
 
namespace System.Windows
{
    /// <summary>
    ///     A set of TriggerBase's
    /// </summary>
    [Localizability(LocalizationCategory.None, Readability=Readability.Unreadable)]
    public sealed class TriggerCollection : Collection<TriggerBase>
    {
        #region Constructors
 
        internal TriggerCollection() : this(null)
        {
        }
        
        internal TriggerCollection(FrameworkElement owner) : base()
        {
            _sealed = false;
            _owner = owner;
        }
 
        #endregion Constructors
        
        #region ProtectedMethods
 
        /// <summary>
        ///     ClearItems override
        /// </summary>
        protected override void ClearItems()
        {
            CheckSealed();
            OnClear();
            base.ClearItems();
        }
 
        /// <summary>
        ///     InsertItem override
        /// </summary>
        protected override void InsertItem(int index, TriggerBase item)
        {
            CheckSealed();
            TriggerBaseValidation(item);
            OnAdd(item);
            base.InsertItem(index, item);
        }
 
        /// <summary>
        ///     RemoveItem override
        /// </summary>
        protected override void RemoveItem(int index)
        {
            CheckSealed();
            TriggerBase triggerBase = this[index];
            OnRemove(triggerBase);
            base.RemoveItem(index);
        }
 
        /// <summary>
        ///     SetItem override
        /// </summary>
        protected override void SetItem(int index, TriggerBase item)
        {
            CheckSealed();
            TriggerBaseValidation(item);
            OnAdd(item);
            base.SetItem(index, item);
        }
 
        #endregion ProtectedMethods
 
        #region PublicMethods
        
        /// <summary>
        ///     Returns the sealed state of this object.  If true, any attempt
        ///     at modifying the state of this object will trigger an exception.
        /// </summary>
        public bool IsSealed
        {
            get
            {
                return _sealed;
            }
        }
        
        #endregion PublicMethods
        
        #region InternalMethods
        
        internal void Seal()
        {
            Debug.Assert (Owner == null);
 
            _sealed = true;
 
            // Seal all the setters
            for (int i=0; i<Count; i++)
            {
                this[i].Seal();
            }
        }
        
        // This may be null (i.e. when used in a style or template)
        internal FrameworkElement Owner
        {
            get { return _owner; }
        }
 
 
        
        #endregion InternalMethods
 
        #region PrivateMethods
 
        private void CheckSealed()
        {
            if (_sealed)
            {
                throw new InvalidOperationException(SR.Format(SR.CannotChangeAfterSealed, "TriggerCollection"));
            }
        }
 
        private void TriggerBaseValidation(TriggerBase triggerBase)
        {
            ArgumentNullException.ThrowIfNull(triggerBase);
        }
 
        // Called by GenericCollection.tb when a trigger is added to the collection.
        // We use this opportunity to hook it into the tree.
        private void OnAdd( TriggerBase triggerBase )
        {
            // If we don't have an Owner (the Style/Template case), or the
            // element isn't initialized yet, we don't need to do anything
            if (Owner != null && Owner.IsInitialized)
            {
                EventTrigger.ProcessOneTrigger(Owner, triggerBase);
            }
 
            InheritanceContextHelper.ProvideContextForObject(Owner, triggerBase);
 
        }
 
        // Called by GenericCollection.tb when a trigger is removed from the collection.
        // We use this opportunity to pull its hooks out of the tree.
        private void OnRemove( TriggerBase triggerBase )
        {
            // If we don't have an Owner (the Style/Template case), 
			// we don't need to do anything
			if (Owner != null)
			{
				// If the owner is initialized, we need to disconnect the trigger.
				if (Owner.IsInitialized)
				{
					EventTrigger.DisconnectOneTrigger(Owner, triggerBase);
				}
 
				// We always need to update the inheritance context
 
				InheritanceContextHelper.RemoveContextFromObject(Owner, triggerBase);
			}
 
        }
 
        // Called by GenericCollection.tb when the collection is cleared.
        // We use this opportunity to pull all the hooks out of the tree.
        private void OnClear()
        {
			// If we don't have an Owner (the Style/Template case), 
			// we don't need to do anything
			if (Owner != null)
			{
				// If the owner is initialized, we need to disconnect all the trigger.
				if (Owner.IsInitialized)
				{
					EventTrigger.DisconnectAllTriggers(Owner);
				}
 
				// We always need to update the inheritance context
				for (int i = Count - 1; i >= 0; i--)
				{
					InheritanceContextHelper.RemoveContextFromObject(Owner, this[i]);
				}
			}
        }
 
        #endregion PrivateMethods
 
        #region Data
        
        private bool _sealed;
        private FrameworkElement _owner;
 
        #endregion Data
 
    }
}