private ConstraintParserState ParseFirstChar(ConstraintParserState state, char ch)
{
if (ch == '\0')
{
if (eqRelationDefined)
{
AppendTerm();
return(ConstraintParserState.done);
}
else
{
errorMessage = "End of expression is reached, but operator is not defined";
return(ConstraintParserState.syntaxError);
}
}
else if (char.IsDigit(ch))
{
word.Append(ch);
return(ConstraintParserState.leadNumber);
}
else if (char.IsLetter(ch))
{
word.Append(ch);
return(ConstraintParserState.word);
}
else if (IsMultiplicationOperator(ch))
{
SetMultipler(true);
segmentOp = ch;
return(ConstraintParserState.word);
}
else if (IsAditionOperator(ch))
{
AppendTerm();
segmentSign = ch;
return(ConstraintParserState.firstChar);
}
else if (IsEqualityOperator(ch))
{
if (!eqRelationDefined)
{
AppendTerm();
SetEquationSign(ch);
return(ConstraintParserState.equality);
}
else
{
errorMessage = "Operator already defined";
return(ConstraintParserState.syntaxError);
}
}
else
{
errorMessage = "Unexpected symbol";
return(ConstraintParserState.syntaxError);
}
}
private ConstraintParserState ParseEquality(ConstraintParserState state, char ch)
{
if (ch == '=')
{
return(ConstraintParserState.firstChar);
}
else
{
errorMessage = "Symbol '=' expected";
return(ConstraintParserState.syntaxError);
}
}
public ConstraintParser()
{
state = ConstraintParserState.word;
stateTable = new Dictionary <ConstraintParserState, Func <ConstraintParserState, char, ConstraintParserState> >
{
{ ConstraintParserState.firstChar, ParseFirstChar },
{ ConstraintParserState.leadNumber, ParseLeadNumber },
{ ConstraintParserState.word, ParseWord },
{ ConstraintParserState.anchor, ParseAnchor },
{ ConstraintParserState.number, ParseNumber },
{ ConstraintParserState.equality, ParseEquality },
{ ConstraintParserState.done, ParseDone },
};
}
public ConstraintDescription Parse(string constraint)
{
state = ConstraintParserState.firstChar;
word.Clear();
prototype = new ConstraintDescription();
prototype.Terms = new List <ConstraintSegment>();
errorMessage = null;
hasLeadNumber = false;
eqRelationDefined = false;
int charNumber = 0;
foreach (var ch in constraint.Append('\0'))
{
if (char.IsWhiteSpace(ch))
{
charNumber++;
continue;
}
state = stateTable[state](state, ch);
if (state == ConstraintParserState.syntaxError)
{
throw new SyntaxErrorException($"{errorMessage} at char {charNumber}");
}
charNumber++;
}
if (!prototype.Terms.Any(x => x.OwnerId != null))
{
throw new SemanticErrorException($"parsed expression does not contains anchors");
}
if (state != ConstraintParserState.done)
{
throw new InternalErrorException($"parser ended work in invalid state: {state}");
}
return(prototype);
}
private ConstraintParserState ParseWord(ConstraintParserState state, char ch)
{
if (ch == '\0')
{
errorMessage = "Unexpected end of expression";
return(ConstraintParserState.syntaxError);
}
else if (char.IsLetterOrDigit(ch))
{
word.Append(ch);
return(ConstraintParserState.word);
}
else if (ch == '.')
{
SetTarget();
return(ConstraintParserState.anchor);
}
else
{
errorMessage = "Anchor name expected";
return(ConstraintParserState.syntaxError);
}
}
private ConstraintParserState ParseDone(ConstraintParserState state, char ch)
{
errorMessage = "symbol after expression end";
return(ConstraintParserState.syntaxError); // we are ended parsing, there shouldn't be any characters after that
}