Last active
October 7, 2020 17:56
-
-
Save RolandPheasant/6ba8a5e390f347847b299955f4315226 to your computer and use it in GitHub Desktop.
Unique changes
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
public static class ChangeSetEx | |
{ | |
public static IObservable<IChangeSet<TObject, TKey>> EnsureUniqueChanges<TObject, TKey>(this IObservable<IChangeSet<TObject, TKey>> source) | |
{ | |
return source.Select(EnsureUniqueChanges); | |
} | |
public static IChangeSet<TObject, TKey> EnsureUniqueChanges<TObject, TKey>(this IChangeSet<TObject, TKey> input) | |
{ | |
var changes = input | |
.GroupBy(kvp => kvp.Key) | |
.Select(g => g.Aggregate(Optional<Change<TObject, TKey>>.None, Reduce)) | |
.Where(x => x.HasValue) | |
.Select(x => x.Value); | |
return new ChangeSet<TObject, TKey>(changes); | |
} | |
internal static Optional<Change<TObject, TKey>> Reduce<TObject, TKey>(Optional<Change<TObject, TKey>> previous, Change<TObject, TKey> next) | |
{ | |
if (!previous.HasValue) | |
{ | |
return next; | |
} | |
var previousValue = previous.Value; | |
switch (previousValue.Reason) | |
{ | |
case ChangeReason.Add when next.Reason == ChangeReason.Remove: | |
return Optional<Change<TObject, TKey>>.None; | |
case ChangeReason.Remove when next.Reason == ChangeReason.Add: | |
return new Change<TObject, TKey>(ChangeReason.Update, next.Key, next.Current, previousValue.Current, next.CurrentIndex, previousValue.CurrentIndex); | |
case ChangeReason.Add when next.Reason == ChangeReason.Update: | |
return new Change<TObject, TKey>(ChangeReason.Add, next.Key, next.Current, next.CurrentIndex); | |
case ChangeReason.Update when next.Reason == ChangeReason.Update: | |
return new Change<TObject, TKey>(ChangeReason.Update, previousValue.Key, next.Current, previousValue.Previous, next.CurrentIndex, previousValue.PreviousIndex); | |
default: | |
return next; | |
} | |
} | |
} |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment