public object[] Parse(IEnumerable <IToken> tokens)
{
var root = this.Root;
if (root == null)
{
throw new NullReferenceException($"Property '{nameof(Root)}' not set.");
}
if (tokens == null)
{
throw new ArgumentNullException(nameof(tokens));
}
var stream = new TokenStream(tokens);
IParsingContext context = new ParsingContext(stream);
var initialNodes = ParsingHelper.GetNonIdleNodes(new[] { root });
context.SetNodes(initialNodes);
while (true)
{
var nodes = context.GetNodes();
if (stream.IsEndOfStream())
{
if (nodes.Contains(EndNode.Instance))
{
// met end of stream, but that is acceptable
return(context.ResultAccumulator.ToArray());
}
else
{
throw new UnexpectedEndOfClauseException(context.ResultAccumulator.ToArray());
}
}
var token = stream.CurrentToken;
if (token is IEmptyToken)
{
stream.AdvanceStreamPosition();
continue;
}
INode winner = null;
FallbackNode fallbackNode = null;
var gotEnd = false;
foreach (var node in nodes)
{
if (node is EndNode)
{
gotEnd = true;
continue;
}
var acceptsToken = node.AcceptsToken(token, context.ResultAccumulator);
if (acceptsToken)
{
if (node is FallbackNode anotherFallbackNode)
{
if (fallbackNode != null)
{
throw new NodeConcurrencyException(
token,
new INode[] { fallbackNode, anotherFallbackNode },
context.ResultAccumulator.ToArray());
}
fallbackNode = anotherFallbackNode;
}
else
{
if (winner != null)
{
throw new NodeConcurrencyException(
token,
new[] { winner, node },
context.ResultAccumulator.ToArray());
}
winner = node;
}
}
}
if (winner == null)
{
if (gotEnd)
{
if (this.WantsOnlyOneResult)
{
// error. stream has more tokens, but we won't want'em.
throw new UnexpectedTokenException(token, context.ResultAccumulator.ToArray());
}
// fine, got to end, start over.
context.SetNodes(initialNodes);
}
else if (fallbackNode != null)
{
fallbackNode.Act(token, context.ResultAccumulator); // will throw, and that's what we want.
}
else
{
throw new UnexpectedTokenException(token, context.ResultAccumulator.ToArray());
}
}
else
{
var oldVersion = context.ResultAccumulator.Version;
winner.Act(token, context.ResultAccumulator);
if (oldVersion + 1 != context.ResultAccumulator.Version)
{
throw new InternalParsingLogicException("Internal error. Non sequential result accumulator versions.");
}
// skip
context.TokenStream.AdvanceStreamPosition();
var successors = winner.ResolveLinks();
var nonIdleSuccessors = ParsingHelper.GetNonIdleNodes(successors);
// next nodes
context.SetNodes(nonIdleSuccessors);
}
}
}
