using System;
using System.Text;
using System.Text.RegularExpressions;
namespace JavaToCSharp
{
public static class TypeNameParser
{
private enum TokenType
{
EndOfString = 0,
Identifier,
Extends,
Super,
LeftBracket,
RightBracket,
Comma,
QuestionMark
}
private static readonly Regex _tokenizePattern = new(@"\w+|<|>|,|\?", RegexOptions.Compiled);
private static (string, TokenType)[] _tokens;
private static (string text, TokenType type) _token;
private static int _currentIndex;
private static readonly StringBuilder _sb = new();
private static Func _translate;
internal static string ParseTypeName(string typename, Func translateIdentifier)
{
// Example: List>
//
// EBNF:
// TypeName = identifier [ "<" TypeArgument { "," TypeArgument } ">" ].
// TypeArgument = [ "?" [ "extends" | "super" ] ] TypeName.
_translate = translateIdentifier;
_tokens = Tokenize(typename);
_currentIndex = -1;
NextToken();
_sb.Clear();
if (TypeName() && _token.type is TokenType.EndOfString)
{
// Otherwise we have extra tokens.
return _sb.ToString();
}
return typename;
}
private static (string, TokenType)[] Tokenize(string typeName)
{
var matches = _tokenizePattern.Matches(typeName);
var tokens = new (string, TokenType)[matches.Count];
for (int i = 0; i < matches.Count; i++)
{
var match = matches[i];
string s = match.Value;
tokens[i] = s switch
{
"<" => (s, TokenType.LeftBracket),
">" => (s, TokenType.RightBracket),
"," => (s, TokenType.Comma),
"?" => (s, TokenType.QuestionMark),
"extends" => (s, TokenType.Extends),
"super" => (s, TokenType.Super),
_ => (s, TokenType.Identifier)
};
}
return tokens;
}
private static void NextToken()
{
_currentIndex++;
_token = _currentIndex < _tokens.Length ? _tokens[_currentIndex] : default;
}
private static bool TypeName()
{
// TypeName = identifier [ "<" TypeArgument { "," TypeArgument } ">" ].
if (_token.type is TokenType.Identifier)
{
_sb.Append(_translate(_token.text));
NextToken();
if (_token.type is TokenType.LeftBracket)
{
_sb.Append("<");
NextToken();
if (TypeArgument())
{
while (_token.type is TokenType.Comma)
{
_sb.Append(", ");
NextToken();
if (!TypeArgument()) return false;
}
if (_token.type is TokenType.RightBracket)
{
_sb.Append(">");
NextToken();
return true;
}
}
}
else
{
return true;
}
}
return false;
}
private static bool TypeArgument()
{
// TypeArgument = [ "?" [ "extends" | "super" ] ] TypeName.
if (_token.type is TokenType.QuestionMark)
{
// C# does not have this. Ignore. We could fix it by replacing IList by IList for example.
NextToken();
if (_token.type is TokenType.Extends or TokenType.Super)
{
NextToken();
}
}
return TypeName();
}
}
}