private static CombinatorType ReadCombinatorType(TokensQueue queue)
{
var hasWhite = false;
while (!queue.Empty) {
queue.SkipComments();
var preview = queue.Peek();
switch (preview.Type) {
case TokenType.Whitespace:
queue.Read();
hasWhite = true;
break;
case TokenType.Plus:
queue.Read();
return CombinatorType.Sibling;
case TokenType.Greater:
queue.Read();
return CombinatorType.Child;
case TokenType.Comma:
queue.Read();
return CombinatorType.Group;
case TokenType.OpenCurlyBracket:
case TokenType.CloseParenthesis:
return CombinatorType.Stop;
default:
return hasWhite ? CombinatorType.Descendant : CombinatorType.Combine;
}
}
return CombinatorType.Stop;
}
private static Expression ParseWithPriority(TokensQueue tokens, int priority)
{
var left = ParseOperand(tokens);
Token? whiteToken = null;
while (!tokens.Empty) {
tokens.SkipComments();
var preview = tokens.Peek();
switch (preview.Type) {
case TokenType.Semicolon:
case TokenType.CloseParenthesis:
case TokenType.ExclamationPoint:
return left;
}
var tokenPriority = GetPriority(preview.Type);
if (tokenPriority < priority) {
return left;
}
switch (preview.Type) {
case TokenType.Plus:
case TokenType.Minus:
case TokenType.Multiply:
case TokenType.Divide:
case TokenType.Percentage:
case TokenType.LeftShift:
case TokenType.RightShift:
case TokenType.Comma:
var token = tokens.Read();
left = ProcessBinaryExpression(token, left, tokens);
whiteToken = null;
break;
case TokenType.Whitespace:
whiteToken = tokens.Read();
break;
default:
if (whiteToken.HasValue) {
left = ProcessBinaryExpression(whiteToken.Value, left, tokens);
whiteToken = null;
break;
}
throw new TokenException("unexpected token " + preview.StringValue, preview);
}
}
return left;
}
private static SelectorExpression ParseWithPriority(TokensQueue tokens, int priority, SelectorExpression parent = null)
{
var left = ParseOperand(tokens, parent);
while (!tokens.Empty) {
tokens.SkipComments();
var preview = tokens.Peek();
switch (preview.Type) {
case TokenType.CloseParenthesis:
case TokenType.OpenCurlyBracket:
return left;
}
var combinatorType = PeekCombinatorType(tokens);
var tokenPriority = GetPriority(combinatorType);
if (tokenPriority < priority) {
return left;
}
combinatorType = ReadCombinatorType(tokens);
if (combinatorType == CombinatorType.Stop) return left;
left = ProcessBinaryExpression(combinatorType, left, tokens);
}
return left;
}