private bool Lookahead(string expected, bool takeIfMatch, bool caseSensitive)
{
Func <char, char> filter = c => c;
if (!caseSensitive)
{
filter = Char.ToLowerInvariant;
}
if (expected.Length == 0 || filter(CurrentCharacter) != filter(expected[0]))
{
return(false);
}
// Capture the current buffer content in case we have to backtrack
string oldBuffer = null;
if (takeIfMatch)
{
Buffer.ToString();
}
using (LookaheadToken lookahead = Source.BeginLookahead())
{
for (int i = 0; i < expected.Length; i++)
{
if (filter(CurrentCharacter) != filter(expected[i]))
{
if (takeIfMatch)
{
// Clear the buffer and put the old buffer text back
Buffer.Clear();
Buffer.Append(oldBuffer);
}
// Return without accepting lookahead (thus rejecting it)
return(false);
}
if (takeIfMatch)
{
TakeCurrent();
}
else
{
MoveNext();
}
}
if (takeIfMatch)
{
lookahead.Accept();
}
}
return(true);
}
public void After_Accepting_Lookahead_Tokenizer_Returns_Next_Token()
{
var tokenizer = new HtmlTokenizer(new SeekableTextReader(new StringReader("<foo>")));
using (LookaheadToken lookahead = tokenizer.Source.BeginLookahead())
{
Assert.Equal(new HtmlSymbol(0, 0, 0, "<", HtmlSymbolType.OpenAngle), tokenizer.NextSymbol());
Assert.Equal(new HtmlSymbol(1, 0, 1, "foo", HtmlSymbolType.Text), tokenizer.NextSymbol());
lookahead.Accept();
}
Assert.Equal(new HtmlSymbol(4, 0, 4, ">", HtmlSymbolType.CloseAngle), tokenizer.NextSymbol());
}