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using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.Specialized;
namespace Xamarin.Forms.Pages
{
internal class DataSourceList : IList<IDataItem>, IReadOnlyList<IDataItem>, INotifyCollectionChanged
{
readonly List<int> _maskedIndexes = new List<int>(); // Indices
readonly HashSet<string> _maskedKeys = new HashSet<string>();
IList<IDataItem> _mainList;
public IList<IDataItem> MainList
{
get { return _mainList; }
set
{
var observable = _mainList as INotifyCollectionChanged;
if (observable != null)
observable.CollectionChanged -= OnMainCollectionChanged;
_mainList = value;
observable = _mainList as INotifyCollectionChanged;
if (observable != null)
observable.CollectionChanged += OnMainCollectionChanged;
_maskedIndexes.Clear();
for (var i = 0; i < _mainList.Count; i++)
{
IDataItem data = _mainList[i];
if (_maskedKeys.Contains(data.Name))
_maskedIndexes.Add(i);
}
OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
}
}
public IEnumerable<string> MaskedKeys => _maskedKeys;
public void Add(IDataItem item)
{
throw new NotSupportedException();
}
public void Clear()
{
throw new NotSupportedException();
}
public bool Contains(IDataItem item)
{
return MainList != null && !_maskedKeys.Contains(item.Name) && MainList.Contains(item);
}
public void CopyTo(IDataItem[] array, int arrayIndex)
{
throw new NotSupportedException();
}
public int Count
{
get
{
if (MainList == null)
return 0;
var result = 0;
result += MainList.Count;
result -= _maskedIndexes.Count;
return result;
}
}
public bool IsReadOnly => true;
public bool Remove(IDataItem item)
{
throw new NotSupportedException();
}
IEnumerator IEnumerable.GetEnumerator()
{
return GetEnumerator();
}
public IEnumerator<IDataItem> GetEnumerator()
{
var index = 0;
if (MainList == null)
yield break;
foreach (IDataItem item in MainList)
{
if (!_maskedIndexes.Contains(index))
yield return item;
index++;
}
}
public int IndexOf(IDataItem item)
{
if (_maskedKeys.Contains(item.Name))
return -1;
if (MainList != null)
{
int result = MainList.IndexOf(item);
if (result >= 0)
return PublicIndexFromMainIndex(result);
}
return -1;
}
public void Insert(int index, IDataItem item)
{
throw new NotSupportedException();
}
public IDataItem this[int index]
{
get
{
foreach (int i in _maskedIndexes)
{
if (i <= index)
index++;
}
if (_mainList == null)
throw new IndexOutOfRangeException();
return _mainList[index];
}
set { throw new NotSupportedException(); }
}
public void RemoveAt(int index)
{
throw new NotSupportedException();
}
public event NotifyCollectionChangedEventHandler CollectionChanged;
public void MaskKey(string key)
{
if (_maskedKeys.Contains(key) || _mainList == null)
return;
_maskedKeys.Add(key);
var index = 0;
foreach (IDataItem item in _mainList)
{
if (item.Name == key)
{
// We need to keep our indexes list sorted, so we insert everything pre-sorted
var added = false;
for (var i = 0; i < _maskedIndexes.Count; i++)
{
if (_maskedIndexes[i] > index)
{
_maskedIndexes.Insert(i, index);
added = true;
break;
}
}
if (!added)
_maskedIndexes.Add(index);
OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove, item, PublicIndexFromMainIndex(index)));
break;
}
index++;
}
}
public void UnmaskKey(string key)
{
_maskedKeys.Remove(key);
if (_mainList == null)
return;
var index = 0;
foreach (IDataItem item in _mainList)
{
if (item.Name == key)
{
bool removed = _maskedIndexes.Remove(index);
if (removed)
{
OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, item, PublicIndexFromMainIndex(index)));
}
break;
}
index++;
}
}
protected void OnCollectionChanged(NotifyCollectionChangedEventArgs args)
{
CollectionChanged?.Invoke(this, args);
}
void OnMainCollectionChanged(object sender, NotifyCollectionChangedEventArgs args)
{
// much complexity to be had here
switch (args.Action)
{
case NotifyCollectionChangedAction.Add:
OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, args.NewItems, PublicIndexFromMainIndex(args.NewStartingIndex)));
break;
case NotifyCollectionChangedAction.Move:
OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Move, args.OldItems, PublicIndexFromMainIndex(args.NewStartingIndex),
PublicIndexFromMainIndex(args.OldStartingIndex)));
break;
case NotifyCollectionChangedAction.Remove:
OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove, args.OldItems, PublicIndexFromMainIndex(args.OldStartingIndex)));
break;
case NotifyCollectionChangedAction.Replace:
OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Replace, args.NewItems, args.OldItems, PublicIndexFromMainIndex(args.OldStartingIndex)));
break;
case NotifyCollectionChangedAction.Reset:
OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
break;
default:
throw new ArgumentOutOfRangeException();
}
}
int PublicIndexFromMainIndex(int index)
{
var count = 0;
for (var x = 0; x < _maskedIndexes.Count; x++)
{
int i = _maskedIndexes[x];
if (i < index)
count++;
}
return index - count;
}
}
}
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