# Pairs tokens with location data.

import options

type
    TokenType* {.pure.} = enum
        # Base
        LEFT_PAREN, RIGHT_PAREN, LEFT_BRACE, RIGHT_BRACE,
        COMMA, DOT, MINUS, PLUS, SEMICOLON, SLASH, STAR,

        # One or two character tokens.
        BANG, BANG_EQUAL,
        EQUAL, EQUAL_EQUAL,
        GREATER, GREATER_EQUAL,
        LESS, LESS_EQUAL,

        # Literals.
        IDENTIFIER, STRING, NUMBER,

        # Keywords.
        AND, CLASS, ELSE, FALSE, FUN, FOR, IF, NIL, OR,
        PRINT, RETURN, SUPER, THIS, TRUE, VAR, WHILE,

        EOF
    
    Literal* = ref object of RootObj
        s: Option[string]
        f: Option[float]
    
    Token* = ref object of RootObj
        token_type: TokenType
        lexeme: string
        literal: Option[Literal]
        line: int

proc new_string_literal*(s: string): Literal =
    Literal(s: some(s), f: none(float))

proc new_float_literal*(f: float): Literal =
    Literal(s: none(string), f: some(f))

proc `$`*(self: Literal): string =
    if self.s.isSome():
        self.s.get()
    else:
        $self.f.get()

proc new_literal_token*(
        token_type: TokenType,
        lexeme: string,
        literal: Literal,
        line: int
    ): Token =
    Token(token_type: token_type, lexeme: lexeme, literal: some(literal), line: line)

proc new_none_token*(
        token_type: TokenType,
        lexeme: string,
        line: int
    ): Token =
    Token(token_type: token_type, lexeme: lexeme, literal: none(Literal), line: line)

proc `$`*(token: Token): string =
    let lit =
        if token.literal.isNone():
            ""
        else:
            $token.literal.get()
    $token.token_type & " " & token.lexeme & " " & lit