private static void CheckNumber(RawToken token)
{
if (Value.IsNumber(token.Content))
{
return;
}
token.Error = true;
token.ErrorMessage = Messages.UnrecognizedNumber;
token.ErrorParams = new object[] { token.Content };
}
public Token(PageLine line, int index, RawToken token)
{
Page = line.Page;
Line = line;
Index = index;
ColumnStart = token.ColumnStart;
ColumnEnd = token.ColumnEnd;
Type = token.Type;
Hints = TokenHints.None;
Content = token.Content;
}
public static void TryParse(string line, out IList <RawToken> tokens)
{
// A big function with a goto statement - I had to try it at least once, for old time's sake
int index = 0;
List <RawToken> tokenList = new List <RawToken>();
bool hasCurrent = index < line.Length;
char currentChar = line[index];
void Step()
{
index++;
hasCurrent = index < line.Length;
if (hasCurrent)
{
currentChar = line[index];
}
}
RawToken currentToken;
// Walk the string one char at a time
while (hasCurrent)
{
if (char.IsWhiteSpace(currentChar))
{
Step();
continue;
}
// While there are still chars left, follow a three step process
currentToken = new RawToken
{
ColumnStart = index,
Content = ""
};
char stringBoundary = '"';
// Step 1: identify the current char as being the start of a certain type of token
// (Or break early if the char is unexpected)
// Some token types look indentical to begin with - these share the same token "prototype"
// For example, a keyword, type and variable name all share the prototype "Word"
TokenPrototype?prototype = null;
if (Symbols.IsKeyCharacter(currentChar))
{
prototype = TokenPrototype.KeySymbol;
}
else if (Symbols.IsWordStart(currentChar))
{
prototype = TokenPrototype.Word;
}
else if (Symbols.IsNumberStart(currentChar))
{
prototype = TokenPrototype.Number;
}
else if (Symbols.IsStringStart(currentChar))
{
prototype = TokenPrototype.String;
}
else if (Symbols.IsOperatorStart(currentChar))
{
prototype = TokenPrototype.Operator;
}
else if (Symbols.IsCommentStart(currentChar))
{
prototype = TokenPrototype.Comment;
}
if (prototype.HasValue)
{
// Special case for strings: the first char will be a "string start"
// char (" or ') not part of the string
if (prototype == TokenPrototype.String)
{
// We do need which of " or ' it is for later
stringBoundary = currentChar;
}
else
{
currentToken.Content = currentChar.ToString();
}
}
else
{
// It might be nice to make an unrecognized character token instead
// That would allow us to continue instead of break out of the line
currentToken.Error = true;
currentToken.ErrorMessage = Messages.UnrecognizedSymbols;
currentToken.Type = TokenType.Unknown;
currentToken.Content = "";
while (hasCurrent && Symbols.IsUnkownStart(currentChar))
{
currentToken.Content += currentChar;
Step();
}
currentToken.ColumnEnd = index;
tokenList.Add(currentToken);
continue;
}
// Step 2: keep stepping forward while the chars match the interior of
// the current token prototype
// (Append the current char to the token content at each step)
Step();
while (hasCurrent)
{
switch (prototype)
{
case TokenPrototype.Word when !Symbols.IsWordCharacter(currentChar):
case TokenPrototype.Number when !Symbols.IsNumberCharacter(currentChar):
case TokenPrototype.Operator when !Symbols.IsOperatorCharacter(currentChar):
// Special case for key symbols: they have no interior
case TokenPrototype.KeySymbol:
// Special case for strings: two ends possible, it must match the start
case TokenPrototype.String when stringBoundary == currentChar:
goto CompleteToken;
default: break;
}
currentToken.Content += currentChar;
Step();
}
CompleteToken :;
// Special case for strings: the last char will be the "string end"
// char (" or '), not part of the string
if (prototype == TokenPrototype.String)
{
Step();
}
// Step 3: Identity the full type of the token from the completed content,
// and add the completed token to the list.
// (Break early if the token cannot be identified)
currentToken.ColumnEnd = index;
TokenType completedType;
string content = currentToken.Content;
switch (prototype)
{
// Some words have immediately recognizable meaning
case TokenPrototype.Word when Operator.IsOperator(text: content) : completedType = TokenType.Operator; break;
case TokenPrototype.Word when Keywords.IsKeyword(content): completedType = TokenType.KeyWord; break;
case TokenPrototype.Word when SprakType.IsType(content): completedType = TokenType.Type; break;
case TokenPrototype.Word when Value.IsBoolean(content): completedType = TokenType.Boolean; break;
// The rest can only be checked for validity at a higher level
case TokenPrototype.Word: completedType = TokenType.Name; break;
// Numbers can be recognized as valid/invalid straight away.
case TokenPrototype.Number:
completedType = TokenType.Number;
CheckNumber(currentToken);
break;
// These will always be valid tokens
// Technically, operator tokens might not represent a real
// operator, but fully checking that requires more context and
// is left until later.
case TokenPrototype.Operator: completedType = TokenType.Operator; break;
case TokenPrototype.KeySymbol: completedType = TokenType.KeySymbol; break;
case TokenPrototype.String: completedType = TokenType.String; break;
case TokenPrototype.Comment: completedType = TokenType.Comment; break;
// Ideally, this can't happen, unless I've made a mistake somewhere above
default:
string prototypeName = Enum.GetName(typeof(TokenPrototype), prototype);
string message = $"Token type not recognised: [{prototypeName}:{content}]";
throw new NotImplementedException(message);
}
currentToken.Type = completedType;
tokenList.Add(currentToken);
} // end main while
tokens = tokenList;
}
private static bool TryParse(IList <RawToken> tokens, out Value result)
{
result = null;
if (tokens.Count == 0)
{
return(false);
}
else if (tokens.Count == 1)
{
RawToken token = tokens[0];
string content = token.Content;
switch (token.Type)
{
case TokenType.Boolean
when SprakBoolean.TryParse(content, out SprakBoolean raw):
result = raw;
return(true);
case TokenType.Number
when SprakNumber.TryParse(content, out SprakNumber raw):
result = raw;
return(true);
case TokenType.String:
result = new SprakString(content);
return(true);
}
}
else
{
if (tokens[0].Type != TokenType.KeySymbol || tokens[0].Content[0] != Symbols.OpenSquareBracket)
{
return(false);
}
if (tokens[0].Type != TokenType.KeySymbol || tokens[0].Content[0] != Symbols.CloseSquareBracket)
{
return(false);
}
List <Value> items = new List <Value>();
List <RawToken> current = new List <RawToken>();
for (int i = 1; i < tokens.Count - 1; i++)
{
if (tokens[i].Type == TokenType.KeySymbol && tokens[i].Content[0] == Symbols.Comma)
{
if (!TryParse(tokens, out Value item))
{
return(false);
}
items.Add(item);
current.Clear();
}
else
{
current.Add(tokens[i]);
}
}
}
return(false);
}