// 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.Controls
{
    /// <summary>
    ///     Holds all of the information that we need to attach to row items so that we can restore rows when they're devirtualized.
    /// </summary>
    internal class DataGridItemAttachedStorage
    {
        public void SetValue(object item, DependencyProperty property, object value)
        {
            var map = EnsureItem(item);
            map[property] = value;
        }
        
        public bool TryGetValue(object item, DependencyProperty property, out object value)
        {
            value = null;
            Dictionary<DependencyProperty, object> map;
            
            EnsureItemStorageMap();
            if (_itemStorageMap.TryGetValue(item, out map))
            {
                return map.TryGetValue(property, out value);
            }
 
            return false;
        }
 
        public void ClearValue(object item, DependencyProperty property)
        {
            Dictionary<DependencyProperty, object> map;
 
            EnsureItemStorageMap();
            if (_itemStorageMap.TryGetValue(item, out map))
            {
                map.Remove(property);
            }
        }
 
        public void ClearItem(object item)
        {
            EnsureItemStorageMap();
            _itemStorageMap.Remove(item);
        }
 
        public void Clear()
        {
            _itemStorageMap = null;
        }
 
        private void EnsureItemStorageMap()
        {
            if (_itemStorageMap == null)
            {
                _itemStorageMap = new Dictionary<object, Dictionary<DependencyProperty, object>>();
            }
        }
 
        private Dictionary<DependencyProperty, object> EnsureItem(object item)
        {
            Dictionary<DependencyProperty, object> map;
            
            EnsureItemStorageMap();
            if (!_itemStorageMap.TryGetValue(item, out map))
            {
                map = new Dictionary<DependencyProperty, object>();
                _itemStorageMap[item] = map;
            }
 
            return map;
        }
 
        /// <summary>
        ///     A map between row items and the associated data.
        /// </summary>
        private Dictionary<object, Dictionary<DependencyProperty, object>> _itemStorageMap;        
    }
}