/// <summary>
/// Expand pattern into an (almost) equivalent one, but with single Either.
/// Example: ((-a | -b) (-c | -d)) => (-a -c | -a -d | -b -c | -b -d)
/// Quirks: [-a] => (-a), (-a...) => (-a -a)
/// </summary>
/// <param name="pattern"></param>
/// <returns></returns>
public static Either Transform(Pattern pattern)
{
var result = new List<IList<Pattern>>();
var groups = new List<IList<Pattern>> {new List<Pattern> {pattern}};
while (groups.Count > 0)
{
var children = groups[0];
groups.RemoveAt(0);
var parents = new[]
{
typeof (Required), typeof (Optional), typeof (OptionsShortcut), typeof (Either), typeof (OneOrMore)
};
if (parents.Any(t => children.Any(c => c.GetType() == t)))
{
var child = children.First(c => parents.Contains(c.GetType()));
children.Remove(child);
if (child is Either)
{
foreach (var c in (child as Either).Children)
{
var l = new List<Pattern> {c};
l.AddRange(children);
groups.Add(l);
}
}
else if (child is OneOrMore)
{
var l = new List<Pattern>();
l.AddRange((child as OneOrMore).Children);
l.AddRange((child as OneOrMore).Children); // add twice
l.AddRange(children);
groups.Add(l);
}
else
{
var l = new List<Pattern>();
if (child.HasChildren)
l.AddRange(child.Children);
l.AddRange(children);
groups.Add(l);
}
}
else
{
result.Add(children);
}
}
return new Either(result.Select(r => new Required(r.ToArray()) as Pattern).ToArray());
}
public SingleMatchResult(int index, Pattern match)
{
Position = index;
Match = match;
}
