private PatternNode?ReadNode(SeekableStringReader reader, char?stopChar = null)
{
PatternNode?node = null;
int c, len, start;
Reset();
void Reset()
{
len = 0;
start = reader.NextPosition;
}
PatternNode?AppendMatch(string pattern)
{
if (len > 0)
{
node += new MatchNode(pattern.Substring(start, len));
}
return(node);
}
while ((c = reader.Read()) > -1)
{
if (c == stopChar)
{
return(AppendMatch(pattern));
}
PatternNode?next;
switch (c)
{
case Constants.Slash:
next = SegmentStartNode.Instance;
break;
case Constants.Wildcard:
next = WildcardNode.Instance;
break;
case Constants.VariableStart:
next = ReadVariableNode(reader);
break;
case Constants.OptionalStart:
next = ReadOptionalNode(reader);
break;
case Constants.OptionalEnd:
errorsSink.AddError($"There is an unexpected '{(char)c}'.", reader.NextPosition - 1);
return(null);
case Constants.EscapeSequenceStart:
if (!ShouldEscape(reader))
{
len++;
continue;
}
AppendMatch(pattern);
reader.NextPosition += Constants.EscapeSequence.Length;
start = reader.NextPosition - 1;
len = 1;
continue;
default:
len++;
continue;
}
// failed to parse!
if (next is null)
{
return(null);
}
if (len > 0)
{
node += new MatchNode(pattern.Substring(start, len));
}
node += next;
Reset();
}
// expected an end char but didn't find it
if (stopChar.HasValue)
{
errorsSink.AddError($"There is a missing '{stopChar}'.");
return(null);
}
node += len == 0
? MatchNode.Empty
: new MatchNode(pattern.Substring(reader.NextPosition - len, len));
return(node);
}
internal PatternNode?Parse()
{
using (var reader = new SeekableStringReader(pattern))
return(ReadNode(reader));
}
