internal static SelectorMatch Evaluate(
ILogical logical, IChildIndexProvider childIndexProvider,
int step, int offset, bool reversed)
{
var index = childIndexProvider.GetChildIndex(logical);
if (index < 0)
{
return(SelectorMatch.NeverThisInstance);
}
if (reversed)
{
if (childIndexProvider.TryGetTotalCount(out var totalCountValue))
{
index = totalCountValue - index;
}
else
{
return(SelectorMatch.NeverThisInstance);
}
}
else
{
// nth child index is 1-based
index += 1;
}
var n = Math.Sign(step);
var diff = index - offset;
var match = diff == 0 || (Math.Sign(diff) == n && diff % step == 0);
return(match ? SelectorMatch.AlwaysThisInstance : SelectorMatch.NeverThisInstance);
}
public NthChildActivator(
ILogical control,
IChildIndexProvider provider,
int step, int offset, bool reversed)
{
_control = control;
_provider = provider;
_step = step;
_offset = offset;
_reversed = reversed;
}
