/// <summary>
/// Returns an observable that contains only the values from the left notification channel
/// up to the specified <paramref name="count"/>.
/// </summary>
/// <typeparam name="TLeft">Type of the left notification channel.</typeparam>
/// <typeparam name="TRight">Type of the right notification channel.</typeparam>
/// <param name="source">The observable from which values are taken.</param>
/// <param name="count">The number of values to take.</param>
/// <returns>An observable of values containing the maximum specified number from the left
/// notification channel and all values from the right notification channel.</returns>
public static IObservable <Either <TLeft, TRight> > TakeLeft <TLeft, TRight>(
this IObservable <Either <TLeft, TRight> > source,
int count)
{
Contract.Requires(source != null);
Contract.Requires(count >= 0);
Contract.Ensures(Contract.Result <IObservable <Either <TLeft, TRight> > >() != null);
return(EitherObservable.Create <TLeft, TRight>(
observer =>
{
int remaining = count;
return source.SubscribeEither(
left =>
{
if (remaining > 0)
{
remaining--;
observer.OnNextLeft(left);
if (remaining == 0)
{
observer.OnCompleted();
}
}
},
observer.OnNextRight,
observer.OnError,
observer.OnCompleted);
}));
}
/// <summary>
/// Projects the values from both notification channels into a new sequence.
/// </summary>
/// <typeparam name="TLeft">Type of the left notification channel.</typeparam>
/// <typeparam name="TRight">Type of the right notification channel.</typeparam>
/// <typeparam name="TLeftResult">Result type of the left notification channel.</typeparam>
/// <typeparam name="TRightResult">Result type of the right notification channel.</typeparam>
/// <param name="source">The observable from which values are projected.</param>
/// <param name="leftSelector">Projects values from the left notification channel.</param>
/// <param name="rightSelector">Projects value from the right notification channel.</param>
/// <returns>An observable of results from the projection of values in both notification channels.</returns>
public static IObservable <Either <TLeftResult, TRightResult> > Select <TLeft, TRight, TLeftResult, TRightResult>(
this IObservable <Either <TLeft, TRight> > source,
Func <TLeft, TLeftResult> leftSelector,
Func <TRight, TRightResult> rightSelector)
{
Contract.Requires(source != null);
Contract.Requires(leftSelector != null);
Contract.Requires(rightSelector != null);
Contract.Ensures(Contract.Result <IObservable <Either <TLeftResult, TRightResult> > >() != null);
return(EitherObservable.Create <TLeftResult, TRightResult>(
observer =>
{
return source.SubscribeEither(
left => observer.OnNextLeft(leftSelector(left)),
right => observer.OnNextRight(rightSelector(right)),
observer.OnError,
observer.OnCompleted);
}));
}
/// <summary>
/// Creates an observable with two pairwise notification channels containing values from the specified
/// observable sequence in the left channel and values projected by the specified function in the right
/// channel.
/// </summary>
/// <typeparam name="TLeft">Type of the left notification channel.</typeparam>
/// <typeparam name="TRight">Type of the right notification channel.</typeparam>
/// <param name="leftSource">The observable sequence that provides notifications for the left channel.</param>
/// <param name="rightSelector">Selects a value for the right channel from each value in the specified observable sequence.</param>
/// <returns>The specified observable sequence paired with the values produced by the specified selector function.</returns>
public static IObservable <Either <TLeft, TRight> > Pair <TLeft, TRight>(
this IObservable <TLeft> leftSource,
Func <TLeft, TRight> rightSelector)
{
Contract.Requires(leftSource != null);
Contract.Requires(rightSelector != null);
Contract.Ensures(Contract.Result <IObservable <Either <TLeft, TRight> > >() != null);
return(EitherObservable.Create <TLeft, TRight>(
observer =>
{
return leftSource.SubscribeSafe(
left =>
{
observer.OnNextLeft(left);
observer.OnNextRight(rightSelector(left));
},
observer.OnError,
observer.OnCompleted);
}));
}
/// <summary>
/// Creates an observable with two pairwise notification channels from the specified observable sequence
/// by choosing which channels will receive each value based on the specified function.
/// </summary>
/// <typeparam name="TSource">The object that provides notification information.</typeparam>
/// <param name="source">The observable from which values will be paired based on the specified selector function.</param>
/// <param name="directionSelector">Selects the channels that will receive notifications for every value in the <paramref name="source"/>.</param>
/// <returns>An observable sequence with two pairwise notification channels projected from the specified
/// observable sequence based on the specified selector function.</returns>
public static IObservable <Either <TSource, TSource> > Pair <TSource>(
this IObservable <TSource> source,
Func <TSource, PairDirection> directionSelector)
{
return(EitherObservable.Create <TSource, TSource>(
observer =>
{
return source.SubscribeSafe(
value =>
{
switch (directionSelector(value))
{
case PairDirection.Left:
observer.OnNextLeft(value);
break;
case PairDirection.Right:
observer.OnNextRight(value);
break;
case PairDirection.Both:
observer.OnNextLeft(value);
observer.OnNextRight(value);
break;
case PairDirection.Neither:
break;
default:
throw new InvalidOperationException(Errors.InvalidPairDirectionValue);
}
},
observer.OnError,
observer.OnCompleted);
}));
}
public static IObservable <Either <IObservable <TSource>, TSource> > Introspect <TSource>(
this IObservable <TSource> source,
IScheduler scheduler)
{
Contract.Requires(source != null);
Contract.Requires(scheduler != null);
Contract.Ensures(Contract.Result <IObservable <Either <IObservable <TSource>, TSource> > >() != null);
return(EitherObservable.Create <IObservable <TSource>, TSource>(
observer =>
{
var subject = new Subject <Tuple <TSource, ISubject <TSource> > >();
var observations = Subject.Synchronize(subject, scheduler);
int pendingOnNext = 0;
bool sourceCompleted = false;
object gate = new object();
var observationsSubscription = observations.SubscribeSafe(
next =>
{
var value = next.Item1;
var introspection = next.Item2;
try
{
lock (gate)
{
observer.OnNextRight(value);
}
}
catch (Exception ex)
{
introspection.OnError(ex);
return;
}
introspection.OnCompleted();
lock (gate)
{
if (--pendingOnNext == 0 && sourceCompleted)
{
observer.OnCompleted();
}
}
},
ex =>
{
lock (gate)
{
observer.OnError(ex);
}
},
() =>
{
lock (gate)
{
observer.OnCompleted();
}
});
var sourceSubscription = source.SubscribeSafe(
value =>
{
var introspection = new ReplaySubject <TSource>(1);
lock (gate)
{
observer.OnNextLeft(introspection.AsObservable());
pendingOnNext++;
}
introspection.OnNext(value);
observations.OnNext(Tuple.Create(value, (ISubject <TSource>)introspection));
},
observations.OnError,
() =>
{
bool completeNow = false;
lock (gate)
{
sourceCompleted = true;
completeNow = pendingOnNext == 0;
}
if (completeNow)
{
observations.OnCompleted();
}
});
return new CompositeDisposable(sourceSubscription, observationsSubscription, subject);
}));
}
public static IObservable <Either <TSource, TException> > OnErrorResumeNext <TSource, TException>(
this IEnumerator <IObservable <TSource> > sources,
Func <TException, IEnumerator <IObservable <TSource> > > handler,
Func <TException, TimeSpan> backOffSelector)
where TException : Exception
{
Contract.Requires(sources != null);
Contract.Requires(handler != null);
Contract.Requires(backOffSelector != null);
Contract.Ensures(Contract.Result <IObservable <Either <TSource, TException> > >() != null);
return(EitherObservable.Create <TSource, TException>(
observer =>
{
bool movedNext;
IObservable <TSource> current = null;
Func <bool> moveNext = () =>
{
try
{
movedNext = sources.MoveNext();
if (movedNext)
{
current = sources.Current;
Contract.Assume(current != null);
return true;
}
}
catch (Exception ex)
{
observer.OnError(ex);
}
return false;
};
if (!moveNext())
{
observer.OnCompleted();
return sources;
}
var subscription = new SerialDisposable();
var sourcesDisposable = new SerialDisposable();
sourcesDisposable.Disposable = sources;
var disposable = Scheduler.CurrentThread.Schedule(
TimeSpan.Zero,
self =>
{
subscription.SetDisposableIndirectly(() =>
current.SubscribeSafe(
observer.OnNextLeft,
ex =>
{
var typedError = ex as TException;
if (typedError == null)
{
observer.OnError(ex);
}
else
{
observer.OnNextRight(typedError);
IEnumerator <IObservable <TSource> > next;
try
{
next = handler(typedError);
}
catch (Exception ex2)
{
observer.OnError(ex2);
return;
}
Contract.Assume(next != null);
if (sources != next)
{
sources = next;
sourcesDisposable.Disposable = sources;
}
if (moveNext())
{
TimeSpan delay;
try
{
delay = backOffSelector(typedError);
}
catch (Exception ex2)
{
observer.OnError(ex2);
return;
}
if (delay < TimeSpan.Zero)
/* Feature that allows callers to indicate when an exception is fatal based on its type */
{
observer.OnError(ex);
}
else
{
self(delay);
}
}
else
{
observer.OnCompleted();
}
}
},
() =>
{
if (moveNext())
{
self(TimeSpan.Zero);
}
else
{
observer.OnCompleted();
}
}));
});
return new CompositeDisposable(subscription, disposable, sourcesDisposable);
}));
}
/// <summary>
/// Repeats the source observable sequence when it throws the specified type of exception
/// consecutively using the specified back-off algorithm until it produces a value, successfully terminates
/// or the specified count has been reached and pairs it with an error channel.
/// </summary>
/// <typeparam name="TSource">The object that provides notification information.</typeparam>
/// <typeparam name="TException">The type of exception to catch.</typeparam>
/// <param name="source">The observable to be repeated.</param>
/// <param name="consecutiveRetryCount">The maximum number of times to retry the sequence consecutively
/// when it's faulted.</param>
/// <param name="backOffSelector">Selects the amount of time to delay before repeating when the sequence has faulted.</param>s
/// <remarks>
/// <see cref="RetryConsecutive{TSource,TException}(IObservable{TSource},int,Func{TException,int,TimeSpan})"/> is appropriate when permanent recovery is required for sequences
/// that experience ephemeral consecutive errors at unpredictable intervals, such as those originating
/// from network streams. For example, it can produce a sequence that automatically reconnects upon
/// consecutive network failures up to the specified <paramref name="consecutiveRetryCount"/> number of
/// times; furthermore, if the sequence is able to successfully generate a value after an error, then
/// the retry count is reset for subsequent consecutive failures.
/// </remarks>
/// <returns>The specified observable sequence with an error channel.</returns>
/// <seealso href="http://en.wikipedia.org/wiki/Exponential_backoff">
/// Exponential backoff
/// </seealso>
public static IObservable <Either <TSource, TException> > RetryConsecutive <TSource, TException>(
this IObservable <TSource> source,
int consecutiveRetryCount,
Func <TException, int, TimeSpan> backOffSelector)
where TException : Exception
{
Contract.Requires(source != null);
Contract.Requires(consecutiveRetryCount >= 0);
Contract.Requires(backOffSelector != null);
Contract.Ensures(Contract.Result <IObservable <Either <TSource, TException> > >() != null);
return(EitherObservable.Create <TSource, TException>(
observer =>
{
int attemptCount = 1;
bool decremented = false;
bool resetRequired = false;
var sources = Enumerable.Repeat(source, consecutiveRetryCount).GetEnumerator();
return sources
.Catch <TSource, TException>(
ex =>
{
if (resetRequired)
{
if (!decremented)
/* This behavior matches the Rx behavior of the retryCount parameter in the Retry method.
* The first iteration always counts as the first "retry", even though technically it's
* not a "retry" because it's first. (If consecutiveRetryCount is set to zero, then the
* sequence will end because the enumerator's MoveNext method called below will return false.)
*/
{
Contract.Assume(consecutiveRetryCount > 0);
consecutiveRetryCount--;
decremented = true;
}
attemptCount = 1;
resetRequired = false;
sources = Enumerable.Repeat(source, consecutiveRetryCount).GetEnumerator();
}
return sources;
},
ex => backOffSelector(ex, attemptCount++))
.SubscribeEither(
value =>
{
resetRequired = true;
observer.OnNextLeft(value);
},
observer.OnNextRight,
observer.OnError,
observer.OnCompleted);
}));
}
/// <summary>
/// Creates an observable with two pairwise notification channels by combining the latest values of the specified
/// observable sequences and choosing which channels will receive values based on the specified function.
/// </summary>
/// <typeparam name="TLeft">Type of the left notification channel.</typeparam>
/// <typeparam name="TRight">Type of the right notification channel.</typeparam>
/// <param name="leftSource">The observable sequence that provides notifications for the left channel.</param>
/// <param name="rightSource">The observable sequence that provides notifications for the right channel.</param>
/// <param name="directionSelector">Selects the channels that will receive notifications for every pair.</param>
/// <returns>A new observable sequence containing the latest values in the specified observable sequences.</returns>
public static IObservable <Either <TLeft, TRight> > Pair <TLeft, TRight>(
this IObservable <TLeft> leftSource,
IObservable <TRight> rightSource,
Func <TLeft, TRight, PairDirection> directionSelector)
{
Contract.Requires(leftSource != null);
Contract.Requires(rightSource != null);
Contract.Requires(directionSelector != null);
Contract.Ensures(Contract.Result <IObservable <Either <TLeft, TRight> > >() != null);
return(EitherObservable.Create <TLeft, TRight>(
observer =>
leftSource.Always().StartWith(Maybe.Empty <TLeft>())
.CombineLatest(
rightSource.Always().StartWith(Maybe.Empty <TRight>()),
(left, right) => new
{
left,
right
})
.SubscribeSafe(
pair =>
{
if (!pair.left.HasValue)
{
if (pair.right.HasValue)
{
observer.OnNextRight(pair.right.Value);
}
}
else if (!pair.right.HasValue)
{
observer.OnNextLeft(pair.left.Value);
}
else
{
var left = pair.left.Value;
var right = pair.right.Value;
switch (directionSelector(left, right))
{
case PairDirection.Left:
observer.OnNextLeft(left);
break;
case PairDirection.Right:
observer.OnNextRight(right);
break;
case PairDirection.Both:
observer.OnNextLeft(left);
observer.OnNextRight(right);
break;
case PairDirection.Neither:
break;
default:
throw new InvalidOperationException(Errors.InvalidPairDirectionValue);
}
}
},
observer.OnError,
observer.OnCompleted)));
}