//! A small bitmap font for labels in headless pictures (the CPU rasterizer has no text
//! otherwise): capitals, digits and a few marks on a 5 × 7 grid, drawn for FieldCraft. Lower case
//! is drawn in capitals; anything else is a question mark.

/// Glyph width and height in font pixels, and the advance between glyphs.
pub const W: usize = 5;
pub const H: usize = 7;
pub const ADVANCE: usize = 6;

/// The rows of a character, top first, the leftmost pixel in bit 4.
pub fn rows(c: char) -> [u8; H] {
    match c.to_ascii_uppercase() {
        'A' => [0x0e, 0x11, 0x11, 0x1f, 0x11, 0x11, 0x11],
        'B' => [0x1e, 0x11, 0x11, 0x1e, 0x11, 0x11, 0x1e],
        'C' => [0x0e, 0x11, 0x10, 0x10, 0x10, 0x11, 0x0e],
        'D' => [0x1e, 0x11, 0x11, 0x11, 0x11, 0x11, 0x1e],
        'E' => [0x1f, 0x10, 0x10, 0x1e, 0x10, 0x10, 0x1f],
        'F' => [0x1f, 0x10, 0x10, 0x1e, 0x10, 0x10, 0x10],
        'G' => [0x0e, 0x11, 0x10, 0x17, 0x11, 0x11, 0x0f],
        'H' => [0x11, 0x11, 0x11, 0x1f, 0x11, 0x11, 0x11],
        'I' => [0x0e, 0x04, 0x04, 0x04, 0x04, 0x04, 0x0e],
        'J' => [0x07, 0x02, 0x02, 0x02, 0x02, 0x12, 0x0c],
        'K' => [0x11, 0x12, 0x14, 0x18, 0x14, 0x12, 0x11],
        'L' => [0x10, 0x10, 0x10, 0x10, 0x10, 0x10, 0x1f],
        'M' => [0x11, 0x1b, 0x15, 0x15, 0x11, 0x11, 0x11],
        'N' => [0x11, 0x11, 0x19, 0x15, 0x13, 0x11, 0x11],
        'O' => [0x0e, 0x11, 0x11, 0x11, 0x11, 0x11, 0x0e],
        'P' => [0x1e, 0x11, 0x11, 0x1e, 0x10, 0x10, 0x10],
        'Q' => [0x0e, 0x11, 0x11, 0x11, 0x15, 0x12, 0x0d],
        'R' => [0x1e, 0x11, 0x11, 0x1e, 0x14, 0x12, 0x11],
        'S' => [0x0f, 0x10, 0x10, 0x0e, 0x01, 0x01, 0x1e],
        'T' => [0x1f, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04],
        'U' => [0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x0e],
        'V' => [0x11, 0x11, 0x11, 0x11, 0x11, 0x0a, 0x04],
        'W' => [0x11, 0x11, 0x11, 0x15, 0x15, 0x15, 0x0a],
        'X' => [0x11, 0x11, 0x0a, 0x04, 0x0a, 0x11, 0x11],
        'Y' => [0x11, 0x11, 0x0a, 0x04, 0x04, 0x04, 0x04],
        'Z' => [0x1f, 0x01, 0x02, 0x04, 0x08, 0x10, 0x1f],
        '0' => [0x0e, 0x11, 0x13, 0x15, 0x19, 0x11, 0x0e],
        '1' => [0x04, 0x0c, 0x04, 0x04, 0x04, 0x04, 0x0e],
        '2' => [0x0e, 0x11, 0x01, 0x02, 0x04, 0x08, 0x1f],
        '3' => [0x1f, 0x02, 0x04, 0x02, 0x01, 0x11, 0x0e],
        '4' => [0x02, 0x06, 0x0a, 0x12, 0x1f, 0x02, 0x02],
        '5' => [0x1f, 0x10, 0x1e, 0x01, 0x01, 0x11, 0x0e],
        '6' => [0x06, 0x08, 0x10, 0x1e, 0x11, 0x11, 0x0e],
        '7' => [0x1f, 0x01, 0x02, 0x04, 0x08, 0x08, 0x08],
        '8' => [0x0e, 0x11, 0x11, 0x0e, 0x11, 0x11, 0x0e],
        '9' => [0x0e, 0x11, 0x11, 0x0f, 0x01, 0x02, 0x0c],
        ' ' => [0; H],
        '-' => [0x00, 0x00, 0x00, 0x1f, 0x00, 0x00, 0x00],
        '_' => [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x1f],
        '.' => [0x00, 0x00, 0x00, 0x00, 0x00, 0x0c, 0x0c],
        ',' => [0x00, 0x00, 0x00, 0x00, 0x0c, 0x04, 0x08],
        ':' => [0x00, 0x0c, 0x0c, 0x00, 0x0c, 0x0c, 0x00],
        '(' => [0x02, 0x04, 0x08, 0x08, 0x08, 0x04, 0x02],
        ')' => [0x08, 0x04, 0x02, 0x02, 0x02, 0x04, 0x08],
        '/' => [0x01, 0x01, 0x02, 0x04, 0x08, 0x10, 0x10],
        '+' => [0x00, 0x04, 0x04, 0x1f, 0x04, 0x04, 0x00],
        '#' => [0x0a, 0x0a, 0x1f, 0x0a, 0x1f, 0x0a, 0x0a],
        _ => [0x0e, 0x11, 0x01, 0x02, 0x04, 0x00, 0x04],
    }
}

/// Whether font pixel (`x`, `y`) of `c` is set.
pub fn on(c: char, x: usize, y: usize) -> bool {
    x < W && rows(c).get(y).is_some_and(|r| r & (0x10 >> x) != 0)
}

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

    #[test]
    fn characters_are_distinct_and_lower_case_draws_capitals() {
        let set: Vec<char> = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-_.,:()/+#".chars().collect();
        for (i, a) in set.iter().enumerate() {
            assert!(rows(*a).iter().all(|r| *r < 0x20), "{a}");
            for b in set.iter().skip(i + 1) {
                assert_ne!(rows(*a), rows(*b), "{a} and {b}");
            }
        }
        assert_eq!(rows('r'), rows('R'));
        assert_eq!(rows('é'), rows('?'));
        assert!(on('L', 0, 6) && !on('L', 4, 0) && !on('L', 9, 0) && !on('L', 0, 9));
    }
}