private IChangeSet <T> Reset(List <T> original, ChangeAwareList <T> target)
{
var sorted = original.OrderBy(t => t, _comparer).ToList();
target.Clear();
target.AddRange(sorted);
return(target.CaptureChanges());
}
private IChangeSet <T> ChangeComparer(ChangeAwareList <T> target, IComparer <T> comparer)
{
_comparer = comparer;
var sorted = target.OrderBy(t => t, _comparer).ToList();
target.Clear();
target.AddRange(sorted);
return(target.CaptureChanges());
}
private void Requery(Func <T, bool> predicate, List <ItemWithMatch> all, ChangeAwareList <ItemWithMatch> filtered)
{
if (_policy == ListFilterPolicy.ClearAndReplace)
{
var newMatches = all.Where(iwm => predicate(iwm.Item)).ToList();
//mark items as matched?
filtered.Clear();
filtered.AddRange(newMatches);
//reset state
all.Where(iwm => iwm.IsMatch).ForEach(iwm => iwm.IsMatch = false);
newMatches.ForEach(iwm => iwm.IsMatch = true);
return;
}
var mutatedMatches = new List <Action>(all.Count);
var newState = all.Select(item =>
{
var match = predicate(item.Item);
var wasMatch = item.IsMatch;
//Mutate match - defer until filtered list has been modified
//[to prevent potential IndexOf failures]
if (item.IsMatch != match)
{
mutatedMatches.Add(() => item.IsMatch = match);
}
return(new
{
Item = item,
IsMatch = match,
WasMatch = wasMatch
});
}).ToList();
//reflect items which are no longer matched
var noLongerMatched = newState.Where(state => !state.IsMatch && state.WasMatch).Select(state => state.Item);
filtered.RemoveMany(noLongerMatched);
//reflect new matches in the list
var newMatched = newState.Where(state => state.IsMatch && !state.WasMatch).Select(state => state.Item);
filtered.AddRange(newMatched);
//finally apply mutations
mutatedMatches.ForEach(m => m());
}
private IChangeSet <T> ChangeComparer(ChangeAwareList <T> target, IComparer <T> comparer)
{
_comparer = comparer;
if (_resetThreshold > 0 && target.Count <= _resetThreshold)
{
return(Reorder(target));
}
var sorted = target.OrderBy(t => t, _comparer).ToList();
target.Clear();
target.AddRange(sorted);
return(target.CaptureChanges());
}
private IChangeSet <ItemWithMatch> Requery(Func <T, bool> predicate, List <ItemWithMatch> all, ChangeAwareList <ItemWithMatch> filtered)
{
if (all.Count == 0)
{
return(ChangeSet <ItemWithMatch> .Empty);
}
if (_policy == ListFilterPolicy.ClearAndReplace)
{
var itemsWithMatch = all.Select(iwm => new ItemWithMatch(iwm.Item, predicate(iwm.Item), iwm.IsMatch)).ToList();
//mark items as matched?
filtered.Clear();
filtered.AddRange(itemsWithMatch.Where(iwm => iwm.IsMatch));
//reset state for all items
all.Clear();
all.AddRange(itemsWithMatch);
return(filtered.CaptureChanges());
}
var toAdd = new List <ItemWithMatch>(all.Count);
var toRemove = new List <ItemWithMatch>(all.Count);
for (int i = 0; i < all.Count; i++)
{
var original = all[i];
var newItem = new ItemWithMatch(original.Item, predicate(original.Item), original.IsMatch);
all[i] = newItem;
if (newItem.IsMatch && !newItem.WasMatch)
{
toAdd.Add(newItem);
}
else if (!newItem.IsMatch && newItem.WasMatch)
{
toRemove.Add(newItem);
}
}
filtered.RemoveMany(toRemove);
filtered.AddRange(toAdd);
return(filtered.CaptureChanges());
}
private static IChangeSet <TValue> Process(Dictionary <TValue, int> values, ChangeAwareList <TValue> result, IChangeSet <ItemWithMatch> changes)
{
void AddAction(TValue value) => values.Lookup(value)
.IfHasValue(count => values[value] = count + 1)
.Else(() =>
{
values[value] = 1;
result.Add(value);
});
void RemoveAction(TValue value)
{
var counter = values.Lookup(value);
if (!counter.HasValue)
{
return;
}
//decrement counter
var newCount = counter.Value - 1;
values[value] = newCount;
if (newCount != 0)
{
return;
}
//if there are none, then remove and notify
result.Remove(value);
values.Remove(value);
}
foreach (var change in changes)
{
switch (change.Reason)
{
case ListChangeReason.Add:
{
var value = change.Item.Current.Value;
AddAction(value);
break;
}
case ListChangeReason.AddRange:
{
change.Range.Select(item => item.Value).ForEach(AddAction);
break;
}
case ListChangeReason.Refresh:
{
var value = change.Item.Current.Value;
var previous = change.Item.Current.Previous;
if (value.Equals(previous))
{
continue;
}
RemoveAction(previous);
AddAction(value);
break;
}
case ListChangeReason.Replace:
{
var value = change.Item.Current.Value;
var previous = change.Item.Previous.Value.Value;
if (value.Equals(previous))
{
continue;
}
RemoveAction(previous);
AddAction(value);
break;
}
case ListChangeReason.Remove:
{
var previous = change.Item.Current.Value;
RemoveAction(previous);
break;
}
case ListChangeReason.RemoveRange:
{
change.Range.Select(item => item.Value).ForEach(RemoveAction);
break;
}
case ListChangeReason.Clear:
{
result.Clear();
values.Clear();
break;
}
}
}
return(result.CaptureChanges());
}
private IChangeSet <T> ProcessImpl(ChangeAwareList <T> target, IChangeSet <T> changes)
{
var refreshes = new List <T>(changes.Refreshes);
foreach (var change in changes)
{
switch (change.Reason)
{
case ListChangeReason.Add:
{
var current = change.Item.Current;
Insert(target, current);
break;
}
case ListChangeReason.AddRange:
{
var ordered = change.Range.OrderBy(t => t, _comparer).ToList();
if (target.Count == 0)
{
target.AddRange(ordered);
}
else
{
ordered.ForEach(item => Insert(target, item));
}
break;
}
case ListChangeReason.Remove:
{
var current = change.Item.Current;
Remove(target, current);
break;
}
case ListChangeReason.Refresh:
{
// add to refresh list so position can be calculated
refreshes.Add(change.Item.Current);
// add to current list so downstream operators can receive a refresh
// notification, so get the latest index and pass the index up the chain
var indexed = target.IndexOfOptional(change.Item.Current).ValueOrThrow(() => new SortException($"Cannot find index of {typeof(T).Name} -> {change.Item.Current}. Expected to be in the list"));
target.Refresh(indexed.Item, indexed.Index);
break;
}
case ListChangeReason.Replace:
{
var current = change.Item.Current;
// TODO: check whether an item should stay in the same position
// i.e. update and move
Remove(target, change.Item.Previous.Value);
Insert(target, current);
break;
}
case ListChangeReason.RemoveRange:
{
target.RemoveMany(change.Range);
break;
}
case ListChangeReason.Clear:
{
target.Clear();
break;
}
}
}
// Now deal with refreshes [can be expensive]
foreach (var item in refreshes)
{
var old = target.IndexOf(item);
if (old == -1)
{
continue;
}
int newPosition = GetInsertPositionLinear(target, item);
if (old < newPosition)
{
newPosition--;
}
if (old == newPosition)
{
continue;
}
target.Move(old, newPosition);
}
return(target.CaptureChanges());
}
private IChangeSet <T> ProcessImpl(ChangeAwareList <T> target, IChangeSet <T> changes)
{
if (_comparer == null)
{
target.Clone(changes);
return(target.CaptureChanges());
}
foreach (var change in changes)
{
switch (change.Reason)
{
case ListChangeReason.Add:
{
var current = change.Item.Current;
Insert(target, current);
break;
}
case ListChangeReason.AddRange:
{
var ordered = change.Range.OrderBy(t => t, _comparer).ToList();
if (target.Count == 0)
{
target.AddRange(ordered);
}
else
{
ordered.ForEach(item => Insert(target, item));
}
break;
}
case ListChangeReason.Replace:
{
var current = change.Item.Current;
//TODO: check whether an item should stay in the same position
//i.e. update and move
Remove(target, change.Item.Previous.Value);
Insert(target, current);
break;
}
case ListChangeReason.Remove:
{
var current = change.Item.Current;
Remove(target, current);
break;
}
case ListChangeReason.RemoveRange:
{
target.RemoveMany(change.Range);
break;
}
case ListChangeReason.Clear:
{
target.Clear();
break;
}
}
}
return(target.CaptureChanges());
}