beer

//! G0/G1 character-set designation and the DEC special graphics (line-drawing)

//! translation.

/// A designated character set (`ESC ( c` / `ESC ) c`).

#[derive(Clone, Copy, PartialEq, Eq, Debug)]

pub enum Charset {

    Ascii,

    DecSpecial,

}

/// Map a designation byte to a [`Charset`]. `0` selects DEC special graphics;

/// everything else falls back to ASCII.

pub fn charset(byte: u8) -> Charset {

    match byte {

        b'0' => Charset::DecSpecial,

        _ => Charset::Ascii,

    }

}

/// Translate a byte under the DEC special graphics set (VT100 line drawing).

pub fn dec_special(c: char) -> char {

    match c {

        '`' => '◆',

        'a' => '▒',

        'f' => '°',

        'g' => '±',

        'j' => '┘',

        'k' => '┐',

        'l' => '┌',

        'm' => '└',

        'n' => '┼',

        'o' => '⎺',

        'p' => '⎻',

        'q' => '─',

        'r' => '⎼',

        's' => '⎽',

        't' => '├',

        'u' => '┤',

        'v' => '┴',

        'w' => '┬',

        'x' => '│',

        'y' => '≤',

        'z' => '≥',

        '~' => '·',

        _ => c,

    }

}

#[cfg(test)]

mod tests {

    use super::*;

    #[test]

    fn line_drawing_translates() {

        assert_eq!(charset(b'0'), Charset::DecSpecial);

        assert_eq!(charset(b'B'), Charset::Ascii);

        assert_eq!(dec_special('q'), '─');

        assert_eq!(dec_special('x'), '│');

        assert_eq!(dec_special('A'), 'A'); // unmapped passes through

    }

}