/// <summary>
/// Create sequence of read operations to load data up to a specified offset.
/// </summary>
/// <typeparam name="TResultItem"></typeparam>
/// <param name="pagedBackingStoreCollection"></param>
/// <param name="offset"></param>
/// <returns></returns>
public static IDisposable CreateReadsUpTo <TResultItem>(this IPagedBackingStoreCollection <TResultItem> pagedBackingStoreCollection, int offset)
{
return(pagedBackingStoreCollection.CreateOffsetsUpTo(offset).
Select(o => pagedBackingStoreCollection.ChangeSetProvider.CreateReadRequest(o)).ToObservable().
SelectMany(pr => pagedBackingStoreCollection.ChangeSetProvider.ReadPageObservable(pr)).
Subscribe());
}
public StrategyBasedReadOnlyCollection(IPagedBackingStoreCollection <TItem> pagedBackingStoreCollection,
ICollectionItemTouchedStrategy touchedStrategy) : base(pagedBackingStoreCollection)
{
Guard.NotNull(pagedBackingStoreCollection);
Guard.NotNull(touchedStrategy);
_touchedStrategy = touchedStrategy;
}
/// <summary>
///
/// </summary>
/// <param name="pagedBackingStoreCollection"></param>
/// <param name="bundleTicks">The number of ticks to wait before kicking of reads of data</param>
/// <param name="uiScheduler">The scheduler upon which the reads are kicked off</param>
/// <param name="readScheduler">The scheduler the reads are performed upon</param>
public CollectionItemTouchedStrategy(IPagedBackingStoreCollection <TItem> pagedBackingStoreCollection,
int bundleTicks = 0,
IScheduler uiScheduler = null,
IScheduler readScheduler = null)
{
_pagedBackingStoreCollection = pagedBackingStoreCollection;
_bundleTicks = bundleTicks;
_uiScheduler = uiScheduler ?? RxApp.MainThreadScheduler;
_readScheduler = readScheduler ?? RxApp.TaskpoolScheduler;
}
/// <summary>
/// Create a collection with a specified <see cref="IPagedBackingStoreCollection{TItem}"/> and <see cref="ICollectionItemTouchedStrategy"/>
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="backingStoreCollection"></param>
/// <param name="collectionTouchedStrategy">If not specified, <see cref="CollectionItemTouchedStrategy{TItem}"/> is used.</param>
/// <returns></returns>
public static ReadOnlyCollectionFromBackingStore <T> Create <T>(IPagedBackingStoreCollection <T> backingStoreCollection, ICollectionItemTouchedStrategy collectionTouchedStrategy = null) where T : class
{
// the strategy to request page loads in the backing store
var touched = collectionTouchedStrategy ?? new CollectionItemTouchedStrategy <T>(backingStoreCollection);
// the actual list we will bind to...
var collection = new StrategyBasedReadOnlyCollection <T>(backingStoreCollection, touched);
return(collection);
}
/// <summary>
/// Return
/// </summary>
/// <typeparam name="TResultItem"></typeparam>
/// <param name="pagedBackingStoreCollection"></param>
/// <param name="readOffset"></param>
/// <returns></returns>
public static IEnumerable <int> CreateOffsets <TResultItem>(
this IPagedBackingStoreCollection <TResultItem> pagedBackingStoreCollection, int readOffset)
{
var maxPageSize = pagedBackingStoreCollection.ChangeSetProvider.MaxPageSize;
var offsetsToRead = new HashSet <int>();
// work out the aligned base that this falls into)
// we potentially align upwards to force the read of the page following, ensuring a contiguous run.
var alignedOffset = (maxPageSize == int.MaxValue)
? readOffset
: ((int)Math.Round(((float)readOffset) / maxPageSize)) * maxPageSize;
// if don't have a total, or we are below the total amount then enqueue the read...
if (!pagedBackingStoreCollection.Total.HasValue || alignedOffset < pagedBackingStoreCollection.Total)
{
offsetsToRead.Add(alignedOffset);
}
return(offsetsToRead);
}
/// <summary>
/// Create a paged collection which wrappers a backing store.
/// </summary>
/// <param name="pagedBackingStoreCollection"></param>
public ReadOnlyCollectionFromBackingStore(IPagedBackingStoreCollection <TItem> pagedBackingStoreCollection)
{
Guard.NotNull(pagedBackingStoreCollection);
// Setup the subscription to pass along changes to those that are interested...
var subscription = pagedBackingStoreCollection.
ChangeSetProvider.
Changes.
Subscribe(changes =>
{
// need to raise the appropriate collection changed things...
// as changes an observable can provide...
foreach (var change in changes)
{
switch (change.Reason)
{
case ListChangeReason.Add:
CollectionChanged?.Invoke(this, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, change.Item.Current, change.Item.CurrentIndex));
break;
case ListChangeReason.AddRange:
CollectionChanged?.Invoke(this, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, change.Range));
break;
case ListChangeReason.Remove:
if (change.Range != null)
{
CollectionChanged?.Invoke(this,
new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove,
change.Range, change.Range.Index));
}
else
{
CollectionChanged?.Invoke(this,
new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove,
change.Item.Current, change.Item.CurrentIndex));
}
break;
case ListChangeReason.Replace:
{
var @event = new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Replace, change.Item.Current, change.Item.Previous.Value, change.Item.CurrentIndex);
CollectionChanged?.Invoke(this, @event);
break;
}
case ListChangeReason.Clear:
CollectionChanged?.Invoke(this, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
break;
case ListChangeReason.Moved:
CollectionChanged?.Invoke(this, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Move, change.Item.Current, change.Item.CurrentIndex, change.Item.PreviousIndex));
break;
}
}
});
_changeSetDisposable.Disposable = subscription;
_backingStoreCollection = pagedBackingStoreCollection;
}
/// <summary>
/// Create a collection backed from a <see cref="SourceCache{TObject,TKey}"/>
/// </summary>
/// <typeparam name="T">The type stored in the collection</typeparam>
/// <typeparam name="TKey">The key type</typeparam>
/// <param name="readPageObservable">The observable which provides the pages of content</param>
/// <param name="keySelector">The key selector</param>
/// <param name="maxPageSize">The maximum size of page to be read, the default being 10</param>
/// <param name="onException">The observable to be used when errors on paging are seen. Null will result in the default behavior, which is fail.</param>
/// <param name="collectionTouchedStrategy">The strategy to be used when items in a collection are touched. If null <see cref="CollectionItemTouchedStrategy{TItem}"/> is used.</param>
/// <param name="backingStoreCollection">The store to be used to back the collection. If null <see cref="SimpleBackingStoreCollection{TItem}" /> is used</param>
/// <returns></returns>
public static ReadOnlyCollectionFromBackingStore <T> FromSourceCachePager <T, TKey>(Func <PageReadRequest, IObservable <PageReadResult <T> > > readPageObservable,
Func <T, TKey> keySelector,
int maxPageSize = 10,
Func <PageReadRequest, Exception, IObservable <bool> > onException = null,
ICollectionItemTouchedStrategy collectionTouchedStrategy = null,
IPagedBackingStoreCollection <T> backingStoreCollection = null) where T : class
{
var provider = SourceCacheBacked <T, TKey> .FromObservable(readPageObservable, keySelector, maxPageSize, onException);
return(Create(provider, collectionTouchedStrategy));
}
/// <summary>
/// Create a collection with a null touch strategy.
/// </summary>
/// <param name="pagedBackingStoreCollection"></param>
public StrategyBasedReadOnlyCollection(IPagedBackingStoreCollection <TItem> pagedBackingStoreCollection)
: this(pagedBackingStoreCollection, NullCollectionItemTouchedStrategy.Instance)
{
}
/// <summary>
/// Create an enumeration of offsets required to read up to a specified offset.
/// </summary>
/// <typeparam name="TResultItem"></typeparam>
/// <param name="pagedBackingStoreCollection"></param>
/// <param name="offset"></param>
/// <returns></returns>
public static IEnumerable <int> CreateOffsetsUpTo <TResultItem>(
this IPagedBackingStoreCollection <TResultItem> pagedBackingStoreCollection, int offset)
{
return(pagedBackingStoreCollection.ChangeSetProvider.CreateOffsetsUpTo(pagedBackingStoreCollection.Total, offset));
}