// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
//
// Description: CommitManager provides global services for committing dirty bindings.
//
 
using System.Windows;
using System.Windows.Data;
using System.Windows.Media;
 
namespace MS.Internal.Data
{
    internal class CommitManager
    {
        #region Internal Methods
 
        internal bool IsEmpty
        {
            get { return _bindings.Count == 0 && _bindingGroups.Count == 0; }
        }
 
        internal void AddBindingGroup(BindingGroup bindingGroup)
        {
            _bindingGroups.Add(bindingGroup);
        }
 
        internal void RemoveBindingGroup(BindingGroup bindingGroup)
        {
            _bindingGroups.Remove(bindingGroup);
        }
 
        internal void AddBinding(BindingExpressionBase binding)
        {
            _bindings.Add(binding);
        }
 
        internal void RemoveBinding(BindingExpressionBase binding)
        {
            _bindings.Remove(binding);
        }
 
        internal List<BindingGroup> GetBindingGroupsInScope(DependencyObject element)
        {
            // iterate over a copy of the full list - callouts can
            // change the original list
            List<BindingGroup> fullList = _bindingGroups.ToList();
            List<BindingGroup> list = EmptyBindingGroupList;
 
            foreach (BindingGroup bindingGroup in fullList)
            {
                DependencyObject owner = bindingGroup.Owner;
                if (owner != null && IsInScope(element, owner))
                {
                    if (list == EmptyBindingGroupList)
                    {
                        list = new List<BindingGroup>();
                    }
 
                    list.Add(bindingGroup);
                }
            }
 
            return list;
        }
 
        internal List<BindingExpressionBase> GetBindingsInScope(DependencyObject element)
        {
            // iterate over a copy of the full list - calling TargetElement can
            // change the original list
            List<BindingExpressionBase> fullList = _bindings.ToList();
            List<BindingExpressionBase> list = EmptyBindingList;
 
            foreach (BindingExpressionBase binding in fullList)
            {
                DependencyObject owner = binding.TargetElement;
                if (owner != null &&
                    binding.IsEligibleForCommit &&
                    IsInScope(element, owner))
                {
                    if (list == EmptyBindingList)
                    {
                        list = new List<BindingExpressionBase>();
                    }
 
                    list.Add(binding);
                }
            }
 
            return list;
        }
 
        // remove stale entries
        internal bool Purge()
        {
            bool foundDirt = false;
 
            int count = _bindings.Count;
            if (count > 0)
            {
                List<BindingExpressionBase> list = _bindings.ToList();
                foreach (BindingExpressionBase binding in list)
                {
                    // fetching TargetElement may detach the binding, removing it from _bindings
                    DependencyObject owner = binding.TargetElement;
                }
            }
            foundDirt = foundDirt || (_bindings.Count < count);
 
            count = _bindingGroups.Count;
            if (count > 0)
            {
                List<BindingGroup> list = _bindingGroups.ToList();
                foreach (BindingGroup bindingGroup in list)
                {
                    // fetching Owner may detach the binding group, removing it from _bindingGroups
                    DependencyObject owner = bindingGroup.Owner;
                }
            }
            foundDirt = foundDirt || (_bindingGroups.Count < count);
 
            return foundDirt;
        }
 
        #endregion Internal Methods
 
        #region Private Methods
 
        // return true if element is a descendant of ancestor
        private bool IsInScope(DependencyObject ancestor, DependencyObject element)
        {
            bool result = (ancestor == null) || VisualTreeHelper.IsAncestorOf(ancestor, element);
            return result;
        }
 
        #endregion Private Methods
 
        #region Private Data
 
        private Set<BindingGroup> _bindingGroups = new Set<BindingGroup>();
        private Set<BindingExpressionBase> _bindings = new Set<BindingExpressionBase>();
        
        private static readonly List<BindingGroup> EmptyBindingGroupList = new List<BindingGroup>();
        private static readonly List<BindingExpressionBase> EmptyBindingList = new List<BindingExpressionBase>();
 
        #endregion Private Data
 
        #region Private types
 
        private class Set<T> : Dictionary<T, object>, IEnumerable<T>
        {
            public Set()
                : base()
            {
            }
 
            public Set(IDictionary<T, object> other)
                : base(other)
            {
            }
 
            public Set(IEqualityComparer<T> comparer)
                : base(comparer)
            {
            }
 
            public void Add(T item)
            {
                if (!ContainsKey(item))
                {
                    Add(item, null);
                }
            }
 
            IEnumerator<T> IEnumerable<T>.GetEnumerator()
            {
                return Keys.GetEnumerator();
            }
 
            public List<T> ToList()
            {
                return new List<T>(Keys);
            }
        }
 
        #endregion Private types
    }
}