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FillBackward.cs
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FillBackward.cs
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namespace SuperLinq.Async;
public static partial class AsyncSuperEnumerable
{
/// <summary>
/// Returns a sequence with each null reference or value in the source
/// replaced with the following non-null reference or value in
/// that sequence.
/// </summary>
/// <param name="source">The source sequence.</param>
/// <typeparam name="T">Type of the elements in the source sequence.</typeparam>
/// <returns>
/// An <see cref="IAsyncEnumerable{T}"/> with null references or values
/// replaced.
/// </returns>
/// <remarks>
/// This method uses deferred execution semantics and streams its
/// results. If references or values are null at the end of the
/// sequence then they remain null.
/// </remarks>
public static IAsyncEnumerable<T> FillBackward<T>(this IAsyncEnumerable<T> source)
{
return source.FillBackward(e => new ValueTask<bool>(e is null));
}
/// <summary>
/// Returns a sequence with each missing element in the source replaced
/// with the following non-missing element in that sequence. An
/// additional parameter specifies a function used to determine if an
/// element is considered missing or not.
/// </summary>
/// <param name="source">The source sequence.</param>
/// <param name="predicate">The function used to determine if
/// an element in the sequence is considered missing.</param>
/// <typeparam name="T">Type of the elements in the source sequence.</typeparam>
/// <returns>
/// An <see cref="IAsyncEnumerable{T}"/> with missing values replaced.
/// </returns>
/// <remarks>
/// This method uses deferred execution semantics and streams its
/// results. If elements are missing at the end of the sequence then
/// they remain missing.
/// </remarks>
public static IAsyncEnumerable<T> FillBackward<T>(this IAsyncEnumerable<T> source, Func<T, bool> predicate)
{
ArgumentNullException.ThrowIfNull(source);
ArgumentNullException.ThrowIfNull(predicate);
return FillBackwardImpl(source, i => new ValueTask<bool>(predicate(i)), fillSelector: null);
}
/// <summary>
/// Returns a sequence with each missing element in the source replaced
/// with the following non-missing element in that sequence. An
/// additional parameter specifies a function used to determine if an
/// element is considered missing or not.
/// </summary>
/// <param name="source">The source sequence.</param>
/// <param name="predicate">The function used to determine if
/// an element in the sequence is considered missing.</param>
/// <typeparam name="T">Type of the elements in the source sequence.</typeparam>
/// <returns>
/// An <see cref="IAsyncEnumerable{T}"/> with missing values replaced.
/// </returns>
/// <remarks>
/// This method uses deferred execution semantics and streams its
/// results. If elements are missing at the end of the sequence then
/// they remain missing.
/// </remarks>
public static IAsyncEnumerable<T> FillBackward<T>(this IAsyncEnumerable<T> source, Func<T, ValueTask<bool>> predicate)
{
ArgumentNullException.ThrowIfNull(source);
ArgumentNullException.ThrowIfNull(predicate);
return FillBackwardImpl(source, predicate, fillSelector: null);
}
/// <summary>
/// Returns a sequence with each missing element in the source replaced
/// with the following non-missing element in that sequence. Additional
/// parameters specify two functions, one used to determine if an
/// element is considered missing or not and another to provide the
/// replacement for the missing element.
/// </summary>
/// <param name="source">The source sequence.</param>
/// <param name="predicate">The function used to determine if
/// an element in the sequence is considered missing.</param>
/// <param name="fillSelector">The function used to produce the element
/// that will replace the missing one. Its first argument receives the
/// current element considered missing while the second argument
/// receives the next non-missing element.</param>
/// <typeparam name="T">Type of the elements in the source sequence.</typeparam>
/// <returns>
/// An <see cref="IAsyncEnumerable{T}"/> with missing elements filled.
/// </returns>
/// <remarks>
/// This method uses deferred execution semantics and streams its
/// results. If elements are missing at the end of the sequence then
/// they remain missing.
/// </remarks>
public static IAsyncEnumerable<T> FillBackward<T>(
this IAsyncEnumerable<T> source,
Func<T, bool> predicate,
Func<T, T, T> fillSelector
)
{
ArgumentNullException.ThrowIfNull(source);
ArgumentNullException.ThrowIfNull(predicate);
ArgumentNullException.ThrowIfNull(fillSelector);
return FillBackwardImpl(source, i => new ValueTask<bool>(predicate(i)), (a, b) => new ValueTask<T>(fillSelector(a, b)));
}
/// <summary>
/// Returns a sequence with each missing element in the source replaced
/// with the following non-missing element in that sequence. Additional
/// parameters specify two functions, one used to determine if an
/// element is considered missing or not and another to provide the
/// replacement for the missing element.
/// </summary>
/// <param name="source">The source sequence.</param>
/// <param name="predicate">The function used to determine if
/// an element in the sequence is considered missing.</param>
/// <param name="fillSelector">The function used to produce the element
/// that will replace the missing one. Its first argument receives the
/// current element considered missing while the second argument
/// receives the next non-missing element.</param>
/// <typeparam name="T">Type of the elements in the source sequence.</typeparam>
/// <returns>
/// An <see cref="IAsyncEnumerable{T}"/> with missing elements filled.
/// </returns>
/// <remarks>
/// This method uses deferred execution semantics and streams its
/// results. If elements are missing at the end of the sequence then
/// they remain missing.
/// </remarks>
public static IAsyncEnumerable<T> FillBackward<T>(
this IAsyncEnumerable<T> source,
Func<T, ValueTask<bool>> predicate,
Func<T, T, T> fillSelector
)
{
ArgumentNullException.ThrowIfNull(source);
ArgumentNullException.ThrowIfNull(predicate);
ArgumentNullException.ThrowIfNull(fillSelector);
return FillBackwardImpl(source, predicate, (a, b) => new ValueTask<T>(fillSelector(a, b)));
}
/// <summary>
/// Returns a sequence with each missing element in the source replaced
/// with the following non-missing element in that sequence. Additional
/// parameters specify two functions, one used to determine if an
/// element is considered missing or not and another to provide the
/// replacement for the missing element.
/// </summary>
/// <param name="source">The source sequence.</param>
/// <param name="predicate">The function used to determine if
/// an element in the sequence is considered missing.</param>
/// <param name="fillSelector">The function used to produce the element
/// that will replace the missing one. Its first argument receives the
/// current element considered missing while the second argument
/// receives the next non-missing element.</param>
/// <typeparam name="T">Type of the elements in the source sequence.</typeparam>
/// <returns>
/// An <see cref="IAsyncEnumerable{T}"/> with missing elements filled.
/// </returns>
/// <remarks>
/// This method uses deferred execution semantics and streams its
/// results. If elements are missing at the end of the sequence then
/// they remain missing.
/// </remarks>
public static IAsyncEnumerable<T> FillBackward<T>(
this IAsyncEnumerable<T> source,
Func<T, bool> predicate,
Func<T, T, ValueTask<T>> fillSelector
)
{
ArgumentNullException.ThrowIfNull(source);
ArgumentNullException.ThrowIfNull(predicate);
ArgumentNullException.ThrowIfNull(fillSelector);
return FillBackwardImpl(source, i => new ValueTask<bool>(predicate(i)), fillSelector);
}
/// <summary>
/// Returns a sequence with each missing element in the source replaced
/// with the following non-missing element in that sequence. Additional
/// parameters specify two functions, one used to determine if an
/// element is considered missing or not and another to provide the
/// replacement for the missing element.
/// </summary>
/// <param name="source">The source sequence.</param>
/// <param name="predicate">The function used to determine if
/// an element in the sequence is considered missing.</param>
/// <param name="fillSelector">The function used to produce the element
/// that will replace the missing one. Its first argument receives the
/// current element considered missing while the second argument
/// receives the next non-missing element.</param>
/// <typeparam name="T">Type of the elements in the source sequence.</typeparam>
/// <returns>
/// An <see cref="IAsyncEnumerable{T}"/> with missing elements filled.
/// </returns>
/// <remarks>
/// This method uses deferred execution semantics and streams its
/// results. If elements are missing at the end of the sequence then
/// they remain missing.
/// </remarks>
public static IAsyncEnumerable<T> FillBackward<T>(
this IAsyncEnumerable<T> source,
Func<T, ValueTask<bool>> predicate,
Func<T, T, ValueTask<T>> fillSelector
)
{
ArgumentNullException.ThrowIfNull(source);
ArgumentNullException.ThrowIfNull(predicate);
ArgumentNullException.ThrowIfNull(fillSelector);
return FillBackwardImpl(source, predicate, fillSelector);
}
private static async IAsyncEnumerable<T> FillBackwardImpl<T>(
IAsyncEnumerable<T> source,
Func<T, ValueTask<bool>> predicate,
Func<T, T, ValueTask<T>>? fillSelector,
[EnumeratorCancellation] CancellationToken cancellationToken = default
)
{
List<T>? blanks = null;
await foreach (var item in source.WithCancellation(cancellationToken).ConfigureAwait(false))
{
var isBlank = await predicate(item).ConfigureAwait(false);
if (isBlank)
{
(blanks ??= []).Add(item);
}
else
{
if (blanks is not null)
{
foreach (var blank in blanks)
{
yield return fillSelector is not null
? await fillSelector(blank, item).ConfigureAwait(false)
: item;
}
blanks.Clear();
}
yield return item;
}
}
if (blanks?.Count > 0)
{
foreach (var blank in blanks)
yield return blank;
}
}
}