Pix

use pix.qweruse pix_crc, pix_key_type from pix      // Quillo 0.6: only these

serde_json = { version = "1", features = ["preserve_order"] }qrcode = { version = "0.14", default-features = false, features = ["svg"] }

// A shop's Pix checkout: a static code ("copia e cola") for an order, read back as a banking app// reads it, each kind of key told apart, and what a changed code or a wrong key gives.////   quillo run pix.qwe      then open http://localhost:8080/code, /code.svg, /read, /manual, /keys and /refuseduse "pix.qwer"let ORDER = { key: "ada@example.com.br", name: "Padaria São João", city: "São Paulo", amount: "42.5", description: "Pedido 1001", txid: "PEDIDO1001", postcode: "01310-100" }route GET /code = respond(200, pix_build(ORDER)?, { "content-type": "text/plain" })route GET /code.svg = respond(200, pix_svg(pix_build(ORDER)?, 300)?, { "content-type": "image/svg+xml" })route GET /read = pix_parse(pix_build(ORDER)?)?// The example of the Banco Central's BR Code manual, a random key and no amount.route GET /manual = pix_parse("00020126580014br.gov.bcb.pix0136123e4567-e12b-12d1-a456-4266554400005204000053039865802BR5913Fulano de Tal6008BRASILIA62070503***63041D3D")?route GET /keys = {    cpf: pix_key_type("11144477735")?,    cnpj: pix_key_type("11222333000181")?,    phone: pix_key_type("+5511987654321")?,    email: pix_key_type("ada@example.com.br")?,    random: pix_key_type("123e4567-e12b-12d1-a456-426655440000")?,    cleaned: [pix_key_clean("111.444.777-35")?, pix_key_clean("11.222.333/0001-81")?, pix_key_clean("(11) 98765-4321")?],}route GET /refused {    let good = pix_build(ORDER)?    {        changed: pix_parse(replace(good, "42.50", "12.50")).error,        bad_cpf: pix_key_type("11144477736").error,        all_same: pix_key_type("11111111111").error,        bad_cnpj: pix_key_type("11222333000182").error,        phone: pix_key_type("+15551234567").error,        decimals: pix_build(merge(ORDER, { amount: "1.999" })).error,        txid: pix_build(merge(ORDER, { txid: "not allowed!" })).error,        no_city: pix_build(merge(ORDER, { city: "" })).error,    }}

//! Brazil's Pix: static BR Codes (copia e cola) built and read, EMV fields and CRC16-CCITT checked, keys told apart (CPF, CNPJ, phone, e-mail, random), and an SVG of the code.//! version: 1.0.0//!//! [dependencies]//! serde_json = { version = "1", features = ["preserve_order"] }//! qrcode = { version = "0.14", default-features = false, features = ["svg"] }use qrcode::render::svg;use qrcode::{EcLevel, QrCode};use serde_json::{json, Value};const GUI: &str = "br.gov.bcb.pix";fn crc16(data: &[u8]) -> u16 {    let mut c: u16 = 0xFFFF;    for b in data {        c ^= (*b as u16) << 8;        for _ in 0..8 {            c = if c & 0x8000 != 0 { (c << 1) ^ 0x1021 } else { c << 1 };        }    }    c}/// The CRC16-CCITT (polynomial 1021, start FFFF) of a text, as four upper-case hex digits, as tag 63 holds it.pub fn pix_crc(text: &str) -> String {    format!("{:04X}", crc16(text.as_bytes()))}fn cpf_ok(d: &[u32]) -> bool {    if d.len() != 11 || d.iter().all(|x| *x == d[0]) {        return false;    }    let digit = |n: usize| { let s: u32 = (0..n).map(|i| d[i] * (n as u32 + 1 - i as u32)).sum(); let r = s * 10 % 11; if r == 10 { 0 } else { r } };    digit(9) == d[9] && digit(10) == d[10]}fn cnpj_ok(c: &[u32]) -> bool {    if c.len() != 14 || c.iter().all(|x| *x == c[0]) {        return false;    }    let digit = |n: usize| {        let w: &[u32] = if n == 12 { &[5, 4, 3, 2, 9, 8, 7, 6, 5, 4, 3, 2] } else { &[6, 5, 4, 3, 2, 9, 8, 7, 6, 5, 4, 3, 2] };        let s: u32 = (0..n).map(|i| c[i] * w[i]).sum();        let r = s % 11;        if r < 2 { 0 } else { 11 - r }    };    digit(12) == c[12] && digit(13) == c[13]}/// The type of a Pix key: "cpf", "cnpj", "phone", "email" or "random"; an error says why it is none of them. Formatting in a CPF or CNPJ is forgiven by `pix_key_clean`, not here: a key in a code is written bare.pub fn pix_key_type(key: &str) -> Result<String, String> {    let k = key.trim();    if k.is_empty() {        return Err("the Pix key is empty".into());    }    let digits: Vec<u32> = k.chars().filter_map(|c| c.to_digit(10)).collect();    if k.starts_with('+') {        let body = &k[1..];        if !body.starts_with("55") || !body.bytes().all(|b| b.is_ascii_digit()) || !(12..=13).contains(&body.len()) {            return Err(format!("`{}` is not a Brazilian phone key: +55, the area code and the number", k));        }        return Ok("phone".into());    }    if k.contains('@') {        let (user, host) = k.rsplit_once('@').unwrap();        if user.is_empty() || !host.contains('.') || k.len() > 77 || k.contains(char::is_whitespace) || host.starts_with('.') || host.ends_with('.') {            return Err(format!("`{}` is not an e-mail key", k));        }        return Ok("email".into());    }    let b = k.as_bytes();    if k.len() == 36 && [8, 13, 18, 23].iter().all(|i| b[*i] == b'-') && k.bytes().enumerate().all(|(i, c)| [8, 13, 18, 23].contains(&i) || c.is_ascii_hexdigit()) {        return Ok("random".into());    }    if k.bytes().all(|c| c.is_ascii_digit()) {        return match k.len() {            11 if cpf_ok(&digits) => Ok("cpf".into()),            11 => Err(format!("`{}` is not a valid CPF: its check digits are wrong", k)),            14 if cnpj_ok(&digits) => Ok("cnpj".into()),            14 => Err(format!("`{}` is not a valid CNPJ: its check digits are wrong", k)),            n => Err(format!("`{}` has {} digits: a CPF has 11, a CNPJ 14, and a phone starts with +55", k, n)),        };    }    Err(format!("`{}` is no kind of Pix key", k))}/// A key as it goes in a code: a CPF or CNPJ without its dots and dashes, a phone with +55 added when it has 10 digits or its area code in brackets (11 bare digits are a CPF), an e-mail and a random key in lower case.pub fn pix_key_clean(key: &str) -> Result<String, String> {    let k = key.trim();    let out = if k.contains('@') || (k.len() == 36 && k.matches('-').count() == 4) {        k.to_lowercase()    } else {        let plus = k.starts_with('+');        let d: String = k.chars().filter(char::is_ascii_digit).collect();        if k.chars().any(|c| c.is_alphabetic()) {            k.to_string()        } else if plus {            format!("+{}", d)        } else if k.contains('(') || (d.len() == 10) {            format!("+55{}", d)        } else {            d        }    };    pix_key_type(&out)?;    Ok(out)}fn tlv(tag: &str, value: &str) -> Result<String, String> {    let n = value.chars().count();    if n > 99 {        return Err(format!("field {} is {} characters; at most 99", tag, n));    }    Ok(format!("{}{:02}{}", tag, n, value))}/// Takes the accents off Portuguese letters: names and cities in a code are plain ASCII.fn plain(x: &str) -> String {    x.chars().filter_map(|c| {        let r = match c {            'á' | 'à' | 'â' | 'ã' | 'ä' => 'a', 'Á' | 'À' | 'Â' | 'Ã' | 'Ä' => 'A',            'é' | 'ê' | 'è' | 'ë' => 'e', 'É' | 'Ê' | 'È' | 'Ë' => 'E',            'í' | 'î' | 'ì' | 'ï' => 'i', 'Í' | 'Î' | 'Ì' | 'Ï' => 'I',            'ó' | 'ô' | 'õ' | 'ò' | 'ö' => 'o', 'Ó' | 'Ô' | 'Õ' | 'Ò' | 'Ö' => 'O',            'ú' | 'û' | 'ù' | 'ü' => 'u', 'Ú' | 'Û' | 'Ù' | 'Ü' => 'U',            'ç' => 'c', 'Ç' => 'C', 'ñ' => 'n', 'Ñ' => 'N',            o if (' '..='~').contains(&o) => o,            _ => return None,        };        Some(r)    }).collect()}fn s(v: &Value, k: &str) -> String {    match v.get(k) {        Some(Value::String(x)) => x.trim().to_string(),        Some(Value::Number(n)) => n.to_string(),        _ => String::new(),    }}/// The text of a static BR Code from `{ key, name, city, amount, description, txid, postcode }`. `key`, `name` (cut to 25 letters) and `city` (to 15) are needed; accents are taken off. `amount` is reais with up to two decimals, or left out for the payer to type. `txid` is up to 25 letters and digits, `***` when there is none.pub fn pix_build(payment: serde_json::Value) -> Result<String, String> {    let key = pix_key_clean(&s(&payment, "key"))?;    let (name, city) = (plain(&s(&payment, "name")), plain(&s(&payment, "city")));    if name.is_empty() {        return Err("the receiver's name is required".into());    }    if city.is_empty() {        return Err("the receiver's city is required".into());    }    let mut account = tlv("00", GUI)? + &tlv("01", &key)?;    let description = plain(&s(&payment, "description"));    if !description.is_empty() {        account += &tlv("02", &description)?;    }    if account.len() > 99 {        return Err(format!("the key and description together take {} of the account field's 99 characters; shorten the description", account.len()));    }    let mut out = tlv("00", "01")? + &tlv("26", &account)? + &tlv("52", "0000")? + &tlv("53", "986")?;    let amount = s(&payment, "amount");    if !amount.is_empty() {        let (w, f) = amount.split_once('.').unwrap_or((&amount, ""));        if w.is_empty() || !w.bytes().all(|b| b.is_ascii_digit()) || !f.bytes().all(|b| b.is_ascii_digit()) || f.len() > 2 {            return Err(format!("amount `{}` should be reais with at most two decimals, with a point", amount));        }        if w.trim_start_matches('0').len() + 3 > 13 {            return Err(format!("amount {} is too long", amount));        }        let cents: u64 = format!("{}{:0<2}", w, f).parse().map_err(|_| "amount too large")?;        if cents == 0 {            return Err("an amount of zero: leave it out for the payer to type one".into());        }        out += &tlv("54", &format!("{}.{:02}", cents / 100, cents % 100))?;    }    out += &tlv("58", "BR")?;    out += &tlv("59", &name.chars().take(25).collect::<String>())?;    out += &tlv("60", &city.chars().take(15).collect::<String>())?;    let post: String = s(&payment, "postcode").chars().filter(char::is_ascii_digit).collect();    if !post.is_empty() {        if post.len() != 8 {            return Err(format!("postcode `{}` should be the 8 digits of a CEP", post));        }        out += &tlv("61", &post)?;    }    let txid = { let t = s(&payment, "txid"); if t.is_empty() { "***".to_string() } else { t } };    if txid != "***" && (txid.len() > 25 || !txid.bytes().all(|b| b.is_ascii_alphanumeric())) {        return Err(format!("txid `{}` should be up to 25 letters and digits", txid));    }    out += &tlv("62", &tlv("05", &txid)?)?;    out += "6304";    let crc = pix_crc(&out);    Ok(out + &crc)}fn fields(text: &str, at: &str) -> Result<Vec<(String, String)>, String> {    let c: Vec<char> = text.chars().collect();    let mut i = 0;    let mut out = vec![];    while i < c.len() {        if i + 4 > c.len() {            return Err(format!("{}: {} characters left over at position {}", at, c.len() - i, i));        }        let tag: String = c[i..i + 2].iter().collect();        let len: String = c[i + 2..i + 4].iter().collect();        if !tag.chars().all(|x| x.is_ascii_digit()) || !len.chars().all(|x| x.is_ascii_digit()) {            return Err(format!("{}: `{}{}` at position {} is not a field's tag and length", at, tag, len, i));        }        let n: usize = len.parse().unwrap();        if i + 4 + n > c.len() {            return Err(format!("{}: field {} says {} characters, and fewer are left", at, tag, n));        }        out.push((tag, c[i + 4..i + 4 + n].iter().collect()));        i += 4 + n;    }    Ok(out)}/// Reads a BR Code into `{ key, key_type, url, name, city, amount, cents, description, txid, postcode, currency, country, static, crc }`. A wrong CRC, a missing field or a merchant field of no Pix is an error. A dynamic code has a `url` to fetch instead of a key.pub fn pix_parse(code: &str) -> Result<Value, String> {    let code = code.trim();    if code.len() < 8 {        return Err("too short to be a BR Code".into());    }    let (body, have) = code.split_at(code.len() - 4);    if !body.ends_with("6304") {        return Err("a BR Code ends with its CRC, field 63, and this does not".into());    }    let want = pix_crc(body);    if !have.eq_ignore_ascii_case(&want) {        return Err(format!("the CRC is {} and should be {}", have, want));    }    let f = fields(code, "BR Code")?;    let get = |t: &str| f.iter().find(|x| x.0 == t).map(|x| x.1.as_str());    if f.first().map(|x| x.0.as_str()) != Some("00") || get("00") != Some("01") {        return Err("field 00 should come first and be 01".into());    }    let account = f.iter().filter(|x| ("26".."52").contains(&x.0.as_str())).find_map(|x| {        let sub = fields(&x.1, &format!("field {}", x.0)).ok()?;        sub.iter().find(|y| y.0 == "00" && y.1.eq_ignore_ascii_case(GUI)).map(|_| sub.clone())    }).ok_or("no Pix merchant field: nothing with br.gov.bcb.pix")?;    let sub = |t: &str| account.iter().find(|x| x.0 == t).map(|x| x.1.clone());    let (key, url) = (sub("01"), sub("25"));    if key.is_none() && url.is_none() {        return Err("the Pix field has neither a key (01) nor a URL (25)".into());    }    let key_type = match &key {        Some(k) => Some(pix_key_type(k).map_err(|e| format!("field 26: {}", e))?),        None => None,    };    for (tag, name) in [("52", "the merchant category"), ("53", "the currency"), ("58", "the country"), ("59", "the name"), ("60", "the city")] {        if get(tag).is_none() {            return Err(format!("field {}, {}, is missing", tag, name));        }    }    if get("53") != Some("986") {        return Err(format!("currency `{}` should be 986, the real", get("53").unwrap_or("")));    }    if get("58") != Some("BR") {        return Err(format!("country `{}` should be BR", get("58").unwrap_or("")));    }    let extra = match get("62") {        Some(x) => fields(x, "field 62")?,        None => vec![],    };    let cents = get("54").and_then(|a| {        let (w, f) = a.split_once('.').unwrap_or((a, ""));        Some(w.parse::<i64>().ok()? * 100 + format!("{:0<2}", f).parse::<i64>().ok()?)    });    Ok(json!({        "key": key, "key_type": key_type, "url": url, "name": get("59"), "city": get("60"), "amount": get("54"), "cents": cents,        "description": sub("02"), "txid": extra.iter().find(|x| x.0 == "05").map(|x| x.1.clone()), "postcode": get("61"),        "currency": "BRL", "country": "BR", "static": get("01") != Some("12"), "crc": have.to_uppercase(),    }))}/// An SVG of the code. `size` is the smallest width in pixels.pub fn pix_svg(code: &str, size: i64) -> Result<String, String> {    let c = QrCode::with_error_correction_level(code.as_bytes(), EcLevel::M).map_err(|e| e.to_string())?;    let px = size.clamp(64, 4096) as u32;    Ok(c.render::<svg::Color>().min_dimensions(px, px).build())}