using System.Text;

/// <summary>
/// A <code>Token</code> represents a terminal symbol.
/// Tokens are provided by the scanner for the parser.
/// They hold additional information about the symbol.
/// </summary>
public class Token
{

    // token codes
    public const int
        //error token
        NONE      =  0,
        //terminal classes
        IDENT     =  1, NUMBER    =  2, CHARCONST =  3,
        //+               -               *               /               %
        ADD       =  4, SUB       =  5, MUL       =  6, DIV       =  7, MOD       =  8,
        //relational operators (must be consecutive numbers, see Parser.Relop)
        //==              >=              >               <=              <               !=
        EQ        =  9, GE        = 10, GT        = 11, LE        = 12, LT        = 13, NE        = 14,
        //&&              ||
        AND       = 15, OR        = 16,
        //=               ++              --
        ASSIGN    = 17, INC       = 18, DEC       = 19,
        //;               ,               .
        SEMCOL    = 20, COMMA     = 21, DOT       = 22,
        //(               )               [               ]               {               }
        LPAR      = 23, RPAR      = 24, LBRACK    = 25, RBRACK    = 26, LBRACE    = 27, RBRACE    = 28,
        //KEYWORDS
        WRITE     = 29, CLASS     = 30, CONST     = 31, ELSE      = 32, IF        = 33, NEW       = 34,
        READ      = 35, RETURN    = 36, VOID      = 37, WHILE     = 38,
        //end of file
        EOF       = 39;

    // List of printable names for all kinds of tokens (e.g. for error messages).
    // The token codes must index correctly into this array!
    public static readonly string[] names = {
        "?",
        "identifier", "number", "character constant",
        "+", "-", "*", "/", "%",
        "==", ">=", ">", "<=", "<", "!=",
        "&&", "||",
        "=", "++", "--",
        ";", ",", ".",
        "(", ")", "[", "]", "{", "}",
        "write", "class", "const", "else", "if", "new",
        "read", "return", "void", "while",
        "end of file"
    };


    public int kind;    // token code (NONE, IDENT, ...)
    public int line;    // token line number (for error messages)
    public int col;     // token column number (for error messages)
    public int val;     // numerical value (for numbers and character constants)

    // We keep the string representation of numbers for error messages in case the
    // number literal in the source code is too big to fit into an int.
    public string str;  // string representation of token (for numbers and identifiers)


    public Token (int kind, int line, int col, int val, string str)
    {
        this.kind = kind;
        this.line = line; this.col = col;
        this.val = val; this.str = str;
    }


    // Returns a string representation of this Token object.
    // Always includes all attributes of the token in the string.
    // When string or val are irrelevant, they are put in parenthesis.
    public override string ToString ()
    {
        StringBuilder sb = new StringBuilder();
        sb.AppendFormat("line {0}, col {1}: {2}", line, col, names[kind]);
        switch (kind) {
            case IDENT:     sb.AppendFormat(" = {0}", str); break;
            case NUMBER:    sb.AppendFormat(" = {0} (\"{1}\")", val, str); break;
            case CHARCONST: sb.AppendFormat(" = '{0}'", (char) val); break;
        }
        return sb.ToString();
    }
}