use std::any::Any;
use std::fmt;

/// struct that contains a single token
pub struct Token<'a> {
    // the type
    pub token_type: TokenType,

    // the actual part of the code that resulted in this token
    pub lexeme: &'a str,

    // numeric (ie 1,2, 1.0 etc) and alphanumeric (any quoted text) values
    pub literal: Box<dyn Any>,

    // the line that contains the code for this token instance
    pub line: usize,
}

impl Token<'_> {
    pub fn get_literal_as_string(&self) -> Option<&str> {
        self.literal.downcast_ref::<String>().map(|s| s.as_str())
    }

    pub fn get_literal_as_float(&self) -> Option<f64> {
        self.literal.downcast_ref::<f64>().map(|f| *f)
    }
}

impl fmt::Debug for Token<'_> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let lit = match self.literal.downcast_ref::<String>() {
            Some(as_string) => {
                as_string.to_string()
            }
            None => {
                format!("{:?}", self.literal)
            }
        };

        write!(f, "Token [ type: {:?}, lexeme: {}, literal: {}, line: {} ]", self.token_type, self.lexeme, lit, self.line)
    }
}

#[derive(Eq, PartialEq, Debug, Clone, Copy)]
pub enum TokenType {
    // Single-character tokens.
    LEFTPAREN,
    RIGHTPAREN,
    LEFTBRACE,
    RIGHTBRACE,
    COMMA,
    DOT,
    MINUS,
    PLUS,
    SEMICOLON,
    STAR,
    SLASH,

    // One or two character tokens.
    BANG,
    BANGEQUAL,
    EQUAL,
    EQUALEQUAL,
    GREATER,
    GREATEREQUAL,
    LESS,
    LESSEQUAL,

    // Literals.
    STRING,
    NUMBER,
    IDENTIFIER,

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

    EOF,         // end of file
}