Check digits

use check_digits.qweruse check_digit, check_digit_valid from check_digits      // Quillo 0.6: only these

// A bookshop's catalog import: ISBNs and barcodes checked, and new internal codes given check digits.////   quillo run check_digits.qwe      then open http://localhost:8080/isbn?code=0-306-40615-2use "check_digits.qwer"route GET /isbn ? { code: str } = isbn_check(code)route GET /barcodes = ["4006381333931", "036000291452", "96385074", "4006381333932", "978-0-306-40615-7"] | map((c) => { code: c, check: barcode_check(c) })route GET /make ? { code: str = "100023" } = {    luhn: `${code}${check_digit(code, "luhn")?}`,    ean: check_digit("400638133393", "ean")?,    verhoeff: `${code}${check_digit(code, "verhoeff")?}`,    // An ISO 11649 creditor reference: the check digits of the reference with "RF" after it.    reference: `RF${check_digit("539007547034RF", "mod97")?}539007547034`,    verhoeff_236: check_digit("236", "verhoeff")?,    imei: imei_valid("490154203237518"),}

//! Check digits made and checked for the codes on books, products, phones and bank references: ISBN-10 and ISBN-13, EAN-13, EAN-8 and UPC-A, IMEI, Luhn, ISO 7064 mod 97-10 and Verhoeff.//! version: 1.0.0//!//! [dependencies]use serde_json::{json, Value};fn clean(code: &str) -> String {    code.chars().filter(|c| !c.is_whitespace() && *c != '-').collect::<String>().to_uppercase()}fn digits(s: &str) -> Option<Vec<u32>> {    if s.is_empty() || s.len() > 100 { return None }    s.chars().map(|c| c.to_digit(10)).collect()}fn luhn_digit(ds: &[u32]) -> u32 {    let s: u32 = ds.iter().rev().enumerate().map(|(i, &n)| if i % 2 == 0 { let x = n * 2; if x > 9 { x - 9 } else { x } } else { n }).sum();    (10 - s % 10) % 10}/// GS1 (EAN, UPC, ISBN-13): weights 3 and 1 from the right.fn gs1_digit(ds: &[u32]) -> u32 {    let s: u32 = ds.iter().rev().enumerate().map(|(i, &n)| if i % 2 == 0 { n * 3 } else { n }).sum();    (10 - s % 10) % 10}fn isbn10_digit(ds: &[u32]) -> char {    let s: u32 = ds.iter().enumerate().map(|(i, &n)| n * (10 - i as u32)).sum();    match (11 - s % 11) % 11 { 10 => 'X', c => char::from_digit(c, 10).unwrap_or('0') }}fn mod97(s: &str) -> Option<u64> {    let mut r = 0u64;    for c in s.chars() {        let v = if c.is_ascii_digit() { c.to_digit(10)? as u64 } else if c.is_ascii_uppercase() { c as u64 - 'A' as u64 + 10 } else { return None };        r = if v >= 10 { (r * 100 + v) % 97 } else { (r * 10 + v) % 97 };    }    Some(r)}const VD: [[u8; 10]; 10] = [[0,1,2,3,4,5,6,7,8,9],[1,2,3,4,0,6,7,8,9,5],[2,3,4,0,1,7,8,9,5,6],[3,4,0,1,2,8,9,5,6,7],[4,0,1,2,3,9,5,6,7,8],[5,9,8,7,6,0,4,3,2,1],[6,5,9,8,7,1,0,4,3,2],[7,6,5,9,8,2,1,0,4,3],[8,7,6,5,9,3,2,1,0,4],[9,8,7,6,5,4,3,2,1,0]];const VP: [[u8; 10]; 8] = [[0,1,2,3,4,5,6,7,8,9],[1,5,7,6,2,8,3,0,9,4],[5,8,0,3,7,9,6,1,4,2],[8,9,1,6,0,4,3,5,2,7],[9,4,5,3,1,2,6,8,7,0],[4,2,8,6,5,7,3,9,0,1],[2,7,9,3,8,0,6,4,1,5],[7,0,4,6,9,1,3,2,5,8]];const VINV: [u8; 10] = [0, 4, 3, 2, 1, 5, 6, 7, 8, 9];fn verhoeff(ds: &[u32], with_check: bool) -> u8 {    let mut c = 0u8;    for (i, &n) in ds.iter().rev().enumerate() {        let pos = if with_check { i } else { i + 1 };        c = VD[c as usize][VP[pos % 8][n as usize] as usize];    }    c}/// The check digit to append to `code` (digits only, spaces and dashes ignored) by `scheme`: "luhn" (card numbers, IMEI), "ean" (EAN-13, EAN-8, UPC-A, GTIN, ISBN-13), "isbn10" (may be "X"), "mod97" (ISO 7064 97-10: two digits, as IBANs and Belgian references use; letters count as 10 to 35) or "verhoeff".pub fn check_digit(code: &str, scheme: &str) -> Result<String, String> {    let c = clean(code);    if scheme == "mod97" {        let r = mod97(&format!("{}00", c)).ok_or("digits and letters only")?;        return Ok(format!("{:02}", 98 - r));    }    let ds = digits(&c).ok_or("digits only")?;    Ok(match scheme {        "luhn" => luhn_digit(&ds).to_string(),        "ean" => gs1_digit(&ds).to_string(),        "isbn10" => {            if ds.len() != 9 { return Err("an ISBN-10 has 9 digits before its check digit".into()) }            isbn10_digit(&ds).to_string()        }        "verhoeff" => VINV[verhoeff(&ds, false) as usize].to_string(),        o => return Err(format!("scheme is luhn, ean, isbn10, mod97 or verhoeff, not {:?}", o)),    })}/// Whether `code`, its check digit included at the end, is right by `scheme` (as for `check_digit`).pub fn check_digit_valid(code: &str, scheme: &str) -> bool {    let c = clean(code);    match scheme {        "mod97" => c.len() > 2 && mod97(&c) == Some(1),        "isbn10" => c.len() == 10 && digits(&c[..9]).map_or(false, |ds| isbn10_digit(&ds) == c.chars().last().unwrap_or(' ')),        "verhoeff" => digits(&c).map_or(false, |ds| ds.len() > 1 && verhoeff(&ds, true) == 0),        _ => c.len() > 1 && check_digit(&c[..c.len() - 1], scheme).map_or(false, |d| c.ends_with(&d)),    }}/// An ISBN read and checked, 10 or 13 digits, dashes and spaces ignored: `{ valid, isbn13, isbn10 }`, both forms written out when it has them (only 978 ISBNs have a 10-digit form).pub fn isbn_check(isbn: &str) -> Value {    let c = clean(isbn);    let (valid, isbn13) = match c.len() {        10 if check_digit_valid(&c, "isbn10") => {            let body = format!("978{}", &c[..9]);            (true, Some(format!("{}{}", body, gs1_digit(&digits(&body).unwrap_or_default()))))        }        13 if (c.starts_with("978") || c.starts_with("979")) && check_digit_valid(&c, "ean") => (true, Some(c.clone())),        _ => (false, None),    };    let isbn10 = isbn13.as_ref().filter(|s| s.starts_with("978")).and_then(|s| digits(&s[3..12]).map(|ds| format!("{}{}", &s[3..12], isbn10_digit(&ds))));    json!({ "valid": valid, "isbn13": isbn13, "isbn10": isbn10 })}/// A product barcode read and checked: `{ valid, kind }`, `kind` being "EAN-13", "EAN-8", "UPC-A", "GTIN-14", "ISBN" (EAN-13 starting 978 or 979) or null.pub fn barcode_check(code: &str) -> Value {    let c = clean(code);    let ok = digits(&c).is_some() && check_digit_valid(&c, "ean");    let kind = match c.len() {        8 => Some("EAN-8"),        12 => Some("UPC-A"),        13 if c.starts_with("978") || c.starts_with("979") => Some("ISBN"),        13 => Some("EAN-13"),        14 => Some("GTIN-14"),        _ => None,    };    json!({ "valid": ok && kind.is_some(), "kind": kind })}/// Whether `imei` is a valid 15-digit phone IMEI (by its Luhn check digit).pub fn imei_valid(imei: &str) -> bool {    let c = clean(imei);    c.len() == 15 && check_digit_valid(&c, "luhn")}