private RegexExpression VisitRegexExpressionNode(IInternalTreeNode node)
{
RegexExpression expression = null;
IRegexTerm term = null;
foreach (var internalNode in node.Children.OfType <IInternalTreeNode>())
{
if (internalNode.Is(RegexGrammar.Expression))
{
expression = VisitRegexExpressionNode(internalNode);
}
else if (internalNode.Is(RegexGrammar.Term))
{
term = VisitRegexTermNode(internalNode);
}
}
if (expression != null && term != null)
{
return(new RegexExpressionAlteration(term, expression));
}
if (term != null)
{
return(new RegexExpressionTerm(term));
}
throw new InvalidOperationException("Unable to create null expression.");
}
private static Nfa Term(IRegexTerm termX)
{
switch (termX)
{
case RegexTermFactor termFactor:
return(Factor(termFactor.Factor));
case RegexTermFactorTerm regexTermFactor:
var factorNfa = Factor(regexTermFactor.Factor);
var termNfa = Term(regexTermFactor.Term);
return(Concatenation(factorNfa, termNfa));
}
throw new InvalidOperationException("Unrecognized Regex Term");
}
private IRegexTerm VisitRegexTermNode(IInternalTreeNode node)
{
IRegexFactor factorAtom = null;
IRegexTerm term = null;
foreach (var internalNode in node.Children.OfType <IInternalTreeNode>())
{
if (internalNode.Is(RegexGrammar.Factor))
{
factorAtom = VisitRegexFactorNode(internalNode);
}
else if (internalNode.Is(RegexGrammar.Term))
{
term = VisitRegexTermNode(internalNode);
}
}
if (term == null)
{
return(new RegexTermFactor(factorAtom));
}
return(new RegexTermFactorTerm(factorAtom, term));
}
public RegexTermFactorTerm(IRegexFactor factor, IRegexTerm term)
{
Factor = factor;
Term = term;
}
public RegexExpressionTerm(IRegexTerm term)
{
Term = term;
}
public RegexExpressionAlteration(IRegexTerm term, RegexExpression expression)
{
Term = term;
Expression = expression;
}
