alix 0.8.0

A learning tool built for understanding, not just remembering.
Documentation 
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pub fn terminal_blocks(text: &str) -> Option<String> {
    let qr = qrcodegen::QrCode::encode_text(text, qrcodegen::QrCodeEcc::Low).ok()?;
    let quiet = 2i32;
    let mut out = String::new();
    for row in (-quiet..qr.size() + quiet).step_by(2) {
        out.push_str("  ");
        for col in -quiet..qr.size() + quiet {
            // Out-of-range modules read as light, which draws the quiet zone.
            out.push(
                match (qr.get_module(col, row), qr.get_module(col, row + 1)) {
                    (true, true) => '█',
                    (true, false) => '▀',
                    (false, true) => '▄',
                    (false, false) => ' ',
                },
            );
        }
        out.push('\n');
    }
    Some(out)
}

pub fn svg(text: &str) -> Option<String> {
    let qr = qrcodegen::QrCode::encode_text(text, qrcodegen::QrCodeEcc::Low).ok()?;
    let border = 4i32;
    let size = qr.size() + 2 * border;
    let mut path = String::new();
    for y in 0..qr.size() {
        for x in 0..qr.size() {
            if qr.get_module(x, y) {
                path.push_str(&format!("M{},{}h1v1h-1z", x + border, y + border));
            }
        }
    }
    Some(format!(
        "<svg xmlns=\"http://www.w3.org/2000/svg\" viewBox=\"0 0 {size} {size}\">\
         <rect width=\"100%\" height=\"100%\" fill=\"#fff\"/>\
         <path d=\"{path}\" fill=\"#000\"/></svg>"
    ))
}

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

    #[test]
    fn a_short_text_renders_terminal_blocks() {
        let q = terminal_blocks("HELLO").unwrap();
        assert!(q.contains('█'), "{q}");
        let lines: Vec<&str> = q.lines().collect();
        assert_eq!(13, lines.len(), "quiet zone + paired module rows");
        assert!(
            lines.iter().all(|line| line.chars().count() == 27),
            "every row carries the two-module quiet zone: {lines:?}"
        );
        assert_eq!(
            [
                "",
                "    █▀▀▀▀▀█  ▀▄ ▀ █▀▀▀▀▀█",
                "    █ ███ █  ▄▄ █ █ ███ █",
                "    █ ▀▀▀ █ ▀█▄█▀ █ ▀▀▀ █",
                "    ▀▀▀▀▀▀▀ █▄▀ █ ▀▀▀▀▀▀▀",
                "     ▄█▀▄▄▀▀█▄▀███▀▄▀▄▄▄▄",
                "    ▄▄█▀█▄▀  ▄▀▀█ ▄▀▀ █▄",
                "    ▀  ▀▀▀▀▀███ ▀▀ ▄▀ █▄",
                "    █▀▀▀▀▀█ ▀▄ ▄█▄  ▀▄ ▀█",
                "    █ ███ █ ▄▀  ███ ▄▀ ▄▀",
                "    █ ▀▀▀ █ ▀▄█ ▀█  █▄▀",
                "    ▀▀▀▀▀▀▀      ▀ ▀   ▀",
                "",
            ],
            lines
                .iter()
                .map(|line| line.trim_end())
                .collect::<Vec<_>>()
                .as_slice()
        );
    }

    #[test]
    fn a_short_text_renders_a_self_contained_svg() {
        let s = svg("http://192.168.1.10:7777/?token=abc").unwrap();
        assert!(s.starts_with("<svg "), "{s}");
        assert!(s.contains("<path "), "{s}");
        assert!(s.contains("viewBox"), "{s}");
        assert!(s.contains("viewBox=\"0 0 37 37\""), "{s}");
    }

    #[test]
    fn an_overlong_text_returns_none_instead_of_panicking() {
        assert!(svg(&"x".repeat(5000)).is_none());
    }
}