//! Emit a Google Authenticator export QR for manual testing:
//! `cargo run -p da-http-api --example make-google-export -- out.png 8`
fn put_varint(v: u64, out: &mut Vec<u8>) {
    let mut v = v;
    loop {
        let mut b = (v & 0x7f) as u8;
        v >>= 7;
        if v != 0 {
            b |= 0x80;
        }
        out.push(b);
        if v == 0 {
            break;
        }
    }
}
fn put_bytes(field: u32, bytes: &[u8], out: &mut Vec<u8>) {
    put_varint((u64::from(field) << 3) | 2, out);
    put_varint(bytes.len() as u64, out);
    out.extend_from_slice(bytes);
}
fn put_uint(field: u32, v: u64, out: &mut Vec<u8>) {
    put_varint(u64::from(field) << 3, out);
    put_varint(v, out);
}

fn main() {
    let mut a = std::env::args().skip(1);
    let out = a
        .next()
        .expect("usage: make-google-export <out.png> [count]");
    let n: usize = a.next().unwrap_or_else(|| "6".into()).parse().unwrap();

    let names = [
        "Cloudflare",
        "Plex",
        "Ubisoft",
        "GitHub",
        "Steam",
        "Proton",
        "Fastmail",
        "Namecheap",
        "Vercel",
        "Backblaze",
    ];
    let mut payload = Vec::new();
    for i in 0..n {
        let mut e = Vec::new();
        put_bytes(1, &[0x41 + i as u8; 20], &mut e);
        put_bytes(2, b"miles@milesward.dev", &mut e);
        put_bytes(3, names[i % names.len()].as_bytes(), &mut e);
        put_uint(4, 1, &mut e);
        // Give one entry 8 digits so the UI's variant chips get exercised.
        put_uint(5, if i == 2 { 2 } else { 1 }, &mut e);
        // And make one HOTP so the "skipped" path shows up.
        put_uint(6, if i == 4 { 1 } else { 2 }, &mut e);
        put_bytes(1, &e, &mut payload);
    }
    put_uint(2, 1, &mut payload);
    put_uint(3, 2, &mut payload); // batch_size
    put_uint(4, 0, &mut payload); // batch_index
    put_uint(5, 77, &mut payload);

    use base64::Engine;
    let b64 = base64::engine::general_purpose::STANDARD.encode(&payload);
    let escaped = b64
        .replace('+', "%2B")
        .replace('/', "%2F")
        .replace('=', "%3D");
    let uri = format!("otpauth-migration://offline?data={escaped}");

    let code = qrcode::QrCode::new(uri.as_bytes()).unwrap();
    let img = code
        .render::<image::Luma<u8>>()
        .module_dimensions(6, 6)
        .quiet_zone(true)
        .build();
    image::DynamicImage::ImageLuma8(img).save(&out).unwrap();
    println!(
        "wrote {out} ({n} entries, {} bytes of payload)",
        payload.len()
    );
}