private static FixedSingleResultOpt <TSource> WhereSingleImmediate <TSource>(this IEnumerable <TSource> source, Func <TSource, bool> predicate)
{
const bool usingPredicate = true;
if (source is IOpt <TSource> sourceOpt)
{
return(SingleResultOpt.GetFixedFromOpt(sourceOpt.ToFixed().WhereRaw(predicate), usingPredicate));
}
else
{
bool hasValue = false;
TSource value = default;
foreach (var element in source)
{
if (predicate(element))
{
if (hasValue)
{
return(SingleResultOpt.GetFixedMoreThanOne <TSource>(usingPredicate));
}
else
{
value = element;
hasValue = true;
}
}
}
return(SingleResultOpt.GetFixedFromValue(hasValue, value, usingPredicate));
}
}
private static FixedSingleResultOpt <TSource> WhereSingleImmediate <TSource>(this IEnumerable <TSource> source)
{
const bool usingPredicate = false;
if (source is IOpt <TSource> sourceOpt)
{
return(SingleResultOpt.GetFixedFromOpt(sourceOpt.ToFixed(), usingPredicate));
}
else if (source is IList <TSource> sourceList)
{
if (sourceList.Count > 1)
{
return(SingleResultOpt.GetFixedMoreThanOne <TSource>(usingPredicate));
}
else if (sourceList.Count == 0)
{
return(SingleResultOpt.GetFixedZero <TSource>(usingPredicate));
}
else
{
return(SingleResultOpt.GetFixedOne(usingPredicate, sourceList[0]));
}
}
else
{
using (var sourceEnumerator = source.GetEnumerator())
{
return(EnumeratorSingleToFixedOpt(sourceEnumerator, usingPredicate));
}
}
}