//! Linux key codes (what virtio-input reports) to keys, US layout.

use port_input_device::Key;

pub const LEFT_SHIFT: u16 = 42;
pub const RIGHT_SHIFT: u16 = 54;
pub const LEFT_CTRL: u16 = 29;
pub const RIGHT_CTRL: u16 = 97;

/// A letter typed with Ctrl held is its control character, as on a
/// terminal: Ctrl+C is 3. Anything else is itself.
pub fn with_ctrl(key: Key) -> Key {
    match key {
        Key::Char(c) if c.is_ascii_alphabetic() => Key::Char(c.to_ascii_lowercase() & 0x1f),
        k => k,
    }
}

/// Rows of the main block: the first key's code, then each key unshifted
/// and shifted.
const ROWS: [(u16, &[u8], &[u8]); 4] = [
    (2, b"1234567890-=", b"!@#$%^&*()_+"),
    (16, b"qwertyuiop[]", b"QWERTYUIOP{}"),
    (30, b"asdfghjkl;'`", b"ASDFGHJKL:\"~"),
    (44, b"zxcvbnm,./", b"ZXCVBNM<>?"),
];

pub fn key(code: u16, shift: bool) -> Option<Key> {
    let named = match code {
        1 => Some(Key::Escape),
        14 => Some(Key::Backspace),
        15 => Some(Key::Tab),
        28 => Some(Key::Enter),
        57 => Some(Key::Space),
        103 => Some(Key::Up),
        108 => Some(Key::Down),
        105 => Some(Key::Left),
        106 => Some(Key::Right),
        43 => Some(Key::Char(if shift { b'|' } else { b'\\' })),
        _ => None,
    };
    named.or_else(|| {
        ROWS.iter().find_map(|(first, plain, shifted)| {
            let i = usize::from(code.checked_sub(*first)?);
            let row = if shift { shifted } else { plain };
            row.get(i).map(|c| Key::Char(*c))
        })
    })
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn ctrl_letters_are_control_characters() {
        assert_eq!(with_ctrl(Key::Char(b'c')), Key::Char(3));
        assert_eq!(with_ctrl(Key::Char(b'C')), Key::Char(3));
        assert_eq!(with_ctrl(Key::Char(b'1')), Key::Char(b'1'));
        assert_eq!(with_ctrl(Key::Enter), Key::Enter);
    }

    #[test]
    fn letters_digits_and_shift() {
        assert_eq!(key(35, false), Some(Key::Char(b'h')));
        assert_eq!(key(35, true), Some(Key::Char(b'H')));
        assert_eq!(key(11, false), Some(Key::Char(b'0')));
        assert_eq!(key(12, true), Some(Key::Char(b'_')));
        assert_eq!(key(53, false), Some(Key::Char(b'/')));
        assert_eq!(key(41, true), Some(Key::Char(b'~')));
        assert_eq!(key(28, false), Some(Key::Enter));
        assert_eq!(key(103, false), Some(Key::Up));
        assert_eq!(key(29, false), None, "left ctrl is not a character");
    }
}