EMV QR codes

use emv_qr.qweruse emv_qr_crc, emv_qr_tlv from emv_qr      // Quillo 0.6: only these

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

// EMV merchant-presented QR codes: a Thai PromptPay code, a Singapore PayNow code and a Malaysian// DuitNow code, a code of your own scheme, and any code read back, a broken one refused.////   quillo run emv_qr.qwe      then open http://localhost:8080/promptpay, /paynow, /duitnow, /custom, /read, /code.svg and /refuseduse "emv_qr.qwer"route GET /promptpay = {    mobile: emv_qr_promptpay({ mobile: "081-234-5678" })?,    amount: emv_qr_promptpay({ national_id: "1234567890123", amount: "420" })?,    read: emv_qr_parse(emv_qr_promptpay({ mobile: "0812345678" })?)?.schemes,}route GET /paynow {    let code = emv_qr_paynow({ uen: "201403121W", name: "Kopi Corner", amount: "12.5", reference: "INV-77", editable: false, expiry: "20261231" })?    let r = emv_qr_parse(code)?    { code: code, scheme: r.schemes[0].scheme, proxy: r.schemes[0].fields, amount: r.amount, reference: r.additional.bill_number }}route GET /duitnow = {    // PayNet's first example: the code it prints, made here.    made: emv_qr_duitnow({ acquirer_id: "501664", qr_id: "123456789", name: "QRCSDNBHD", city: "BANGI", category: "9999", amount: "10" })?,    read: emv_qr_parse("00020201021126410014A000000615000101065016640209123456789520499995303458540510.005802MY5909QRCSDNBHD6005BANGI6304343F")?.schemes,}// Any other scheme: the tags given directly, a template as a nested map.route GET /custom {    let code = emv_qr_build({        "01": "11",        "27": { "00": "com.example.pay", "01": "MERCHANT42" },        "52": "5812", "53": "840", "58": "US", "59": "Blue Bottle", "60": "Oakland",        "62": { "03": "STORE7", "07": "TILL2" },        "64": { "00": "ZH", "01": "蓝瓶" },    })?    let r = emv_qr_parse(code)?    { code: code, additional: r.additional, language: r.language, tree: emv_qr_tlv(code)?[2] }}route GET /code.svg = respond(200, emv_qr_svg(emv_qr_promptpay({ mobile: "0812345678" })?, 300)?, { "content-type": "image/svg+xml" })route GET /refused {    let good = emv_qr_promptpay({ mobile: "0812345678", amount: "10" })?    {        changed: emv_qr_parse(replace(good, "10.00", "90.00")).error,        short: emv_qr_parse("000201010211").error,        runs_off: emv_qr_tlv("00020129990016A0000006").error,        no_id: emv_qr_promptpay({}).error,        long: emv_qr_build({ "59": repeat("x", 120) }).error,    }}

//! EMVCo merchant-presented QR codes in general: TLV read and written with nested templates and named fields, the CRC checked, and codes made for PromptPay, PayNow and DuitNow, or any scheme's own merchant template.//! 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, Map, Value};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 CRC of a payload as four upper-case hex digits (CRC16-CCITT-FALSE), taken over everything up to and including `6304`.pub fn emv_qr_crc(text: &str) -> String {    format!("{:04X}", crc16(text.as_bytes()))}fn tag_name(tag: &str) -> &'static str {    let n: u32 = tag.parse().unwrap_or(100);    match n {        26..=51 => return "merchant_account",        65..=79 => return "emvco_template",        80..=99 => return "unreserved_template",        _ => {}    }    match tag {        "00" => "payload_format",        "01" => "initiation_method",        "02" | "03" => "visa",        "04" | "05" => "mastercard",        "06" | "07" | "08" => "emvco",        "09" | "10" => "discover",        "11" | "12" => "amex",        "13" | "14" => "jcb",        "15" | "16" => "unionpay",        "17" | "18" | "19" | "20" | "21" | "22" | "23" | "24" | "25" => "emvco",        "52" => "merchant_category",        "53" => "currency",        "54" => "amount",        "55" => "tip_indicator",        "56" => "convenience_fee_fixed",        "57" => "convenience_fee_percent",        "58" => "country",        "59" => "merchant_name",        "60" => "merchant_city",        "61" => "postal_code",        "62" => "additional_data",        "63" => "crc",        "64" => "language_template",        _ => "",    }}fn additional_name(tag: &str) -> &'static str {    match tag {        "01" => "bill_number",        "02" => "mobile_number",        "03" => "store_label",        "04" => "loyalty_number",        "05" => "reference_label",        "06" => "customer_label",        "07" => "terminal_label",        "08" => "purpose",        "09" => "consumer_data_request",        "10" => "merchant_tax_id",        "11" => "merchant_channel",        _ => "",    }}fn language_name(tag: &str) -> &'static str {    match tag {        "00" => "language",        "01" => "merchant_name",        "02" => "merchant_city",        _ => "",    }}fn nested(tag: &str) -> bool {    matches!(tag.parse::<u32>(), Ok(26..=51 | 62 | 64 | 65..=99))}fn split(text: &str, at: &str) -> Result<Vec<(String, String)>, String> {    let c: Vec<char> = text.chars().collect();    let (mut i, mut out) = (0, 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, len): (String, String) = (c[i..i + 2].iter().collect(), 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 tag and a length", at, tag, len, i));        }        let n: usize = len.parse().unwrap();        if n == 0 {            return Err(format!("{}: field {} is empty, which the format does not allow", at, tag));        }        if i + 4 + n > c.len() {            return Err(format!("{}: field {} says {} characters, and {} are left", at, tag, n, c.len() - i - 4));        }        out.push((tag, c[i + 4..i + 4 + n].iter().collect()));        i += 4 + n;    }    Ok(out)}fn node(tag: &str, value: &str, name: &str, depth: usize) -> Value {    let mut m = Map::new();    m.insert("tag".into(), json!(tag));    if !name.is_empty() {        m.insert("name".into(), json!(name));    }    m.insert("value".into(), json!(value));    if depth == 0 && nested(tag) {        if let Ok(sub) = split(value, tag) {            let kids: Vec<Value> = sub.iter().map(|(t, v)| {                let n = match tag { "62" => additional_name(t), "64" => language_name(t), _ if t == "00" => "globally_unique_id", _ => "" };                node(t, v, n, 1)            }).collect();            m.insert("fields".into(), Value::Array(kids));        }    }    Value::Object(m)}/// Any EMV QR text as a tree without judging it: `[{ tag, name, value, fields }]`, `fields` for templates (26 to 51, 62, 64, 65 to 99).pub fn emv_qr_tlv(text: &str) -> Result<Vec<Value>, String> {    let f = split(text.trim(), "payload")?;    Ok(f.iter().map(|(t, v)| node(t, v, tag_name(t), 0)).collect())}fn scheme_of(gui: &str) -> &'static str {    match gui.to_uppercase().as_str() {        "A000000677010111" | "A000000677010112" | "A000000677010113" => "promptpay",        "SG.PAYNOW" => "paynow",        "A0000006150001" => "duitnow",        "BR.GOV.BCB.PIX" => "pix",        "A000000727" => "vietqr",        "ID.CO.QRIS.WWW" => "qris",        "SG.COM.NETS" => "nets",        "COM.P2PQRPAY" => "qrph",        _ => "",    }}/// Reads a merchant-presented code: `{ valid_crc, missing, format, static, category, currency, amount, country, merchant_name, merchant_city, postal_code, schemes, additional, language, fields }`. `schemes` lists the merchant accounts, each with its `gui` and, where known, `scheme`. `missing` lists mandatory fields left out, which is common: PromptPay codes have no name or category. A bad CRC, a length that runs off the end, a first field not 00 or no merchant account at all is an error.pub fn emv_qr_parse(text: &str) -> Result<Value, String> {    let code = text.trim();    let f = split(code, "payload")?;    if f.first().map(|x| x.0.as_str()) != Some("00") {        return Err("the first field must be the payload format, 00".into());    }    let Some(last) = f.last().filter(|x| x.0 == "63") else {        return Err("the last field must be the CRC, 63".into());    };    if last.1.chars().count() != 4 {        return Err(format!("the CRC `{}` should be four characters", last.1));    }    let body = &code[..code.len() - 4];    let want = emv_qr_crc(body);    if !last.1.eq_ignore_ascii_case(&want) {        return Err(format!("the CRC is {} and should be {}", last.1, want));    }    let get = |t: &str| f.iter().find(|x| x.0 == t).map(|x| x.1.clone());    for (i, x) in f.iter().enumerate() {        if f[..i].iter().any(|y| y.0 == x.0) {            return Err(format!("field {} appears twice", x.0));        }    }    let missing: Vec<&str> = [("52", "merchant_category"), ("53", "currency"), ("58", "country"), ("59", "merchant_name"), ("60", "merchant_city")].iter().filter(|x| get(x.0).is_none()).map(|x| x.1).collect();    let mut schemes = vec![];    for (t, v) in &f {        if ("02".."52").contains(&t.as_str()) {            if ("26".."52").contains(&t.as_str()) {                let sub = split(v, t)?;                let gui = sub.iter().find(|x| x.0 == "00").map(|x| x.1.clone()).ok_or(format!("field {}: a merchant template needs a unique id, sub-field 00", t))?;                let fields: Map<String, Value> = sub.iter().filter(|x| x.0 != "00").map(|(a, b)| (a.clone(), json!(b))).collect();                schemes.push(json!({ "tag": t, "gui": gui, "scheme": scheme_of(&gui), "fields": fields }));            } else {                schemes.push(json!({ "tag": t, "scheme": tag_name(t), "account": v }));            }        }    }    if schemes.is_empty() {        return Err("no merchant account: nothing between fields 02 and 51".into());    }    let sub_map = |tag: &str, name: fn(&str) -> &'static str| -> Result<Value, String> {        let Some(v) = get(tag) else { return Ok(Value::Null) };        let mut m = Map::new();        for (t, x) in split(&v, tag)? {            let n = name(&t);            m.insert(if n.is_empty() { t } else { n.to_string() }, json!(x));        }        Ok(Value::Object(m))    };    Ok(json!({        "valid_crc": true, "missing": missing, "format": get("00"), "static": get("01").as_deref() != Some("12"), "category": get("52"), "currency": get("53"), "amount": get("54"),        "country": get("58"), "merchant_name": get("59"), "merchant_city": get("60"), "postal_code": get("61"), "schemes": schemes,        "additional": sub_map("62", additional_name)?, "language": sub_map("64", language_name)?, "fields": emv_qr_tlv(code)?,    }))}fn tlv(tag: &str, value: &str) -> Result<String, String> {    let n = value.chars().count();    if tag.len() != 2 || !tag.bytes().all(|b| b.is_ascii_digit()) {        return Err(format!("tag `{}` should be two digits", tag));    }    if n == 0 || n > 99 {        return Err(format!("field {} is {} characters; it takes 1 to 99", tag, n));    }    Ok(format!("{}{:02}{}", tag, n, value))}fn scalar(v: &Value) -> Option<String> {    match v {        Value::String(s) if !s.is_empty() => Some(s.clone()),        Value::Number(n) => Some(n.to_string()),        _ => None,    }}fn encode(fields: &Value) -> Result<Vec<(String, String)>, String> {    let mut out = vec![];    let list: Vec<(String, Value)> = match fields {        Value::Object(m) => m.iter().map(|(k, v)| (k.clone(), v.clone())).collect(),        Value::Array(a) => a.iter().map(|x| (x["tag"].as_str().unwrap_or("").to_string(), if x.get("fields").is_some() { x["fields"].clone() } else { x["value"].clone() })).collect(),        _ => return Err("fields should be a map of tags, or a list of `{ tag, value }`".into()),    };    for (tag, v) in list {        match v {            Value::Null => {}            Value::Object(_) | Value::Array(_) => {                let inner: String = encode(&v)?.iter().map(|(t, x)| tlv(t, x)).collect::<Result<_, _>>()?;                out.push((tag, inner));            }            o => {                let x = scalar(&o).ok_or(format!("field {} is empty: leave it out", tag))?;                out.push((tag, x));            }        }    }    Ok(out)}/// A payload from a map of tags: `{ "01": "11", "29": { "00": "A000000677010111", "01": "0066812345678" }, "52": "0000", ... }`, nested maps being templates. Fields go in tag order, 00 first (written as 01 unless given) and the CRC added last. A field over 99 characters is refused.pub fn emv_qr_build(fields: serde_json::Value) -> Result<String, String> {    let mut list = encode(&fields)?;    if list.iter().any(|x| x.0 == "63") {        return Err("field 63 is the CRC, which this adds".into());    }    if !list.iter().any(|x| x.0 == "00") {        list.push(("00".into(), "01".into()));    }    list.sort_by(|a, b| a.0.cmp(&b.0));    let mut out = String::new();    for (t, v) in &list {        out += &tlv(t, v)?;    }    out += "6304";    let crc = emv_qr_crc(&out);    Ok(out + &crc)}fn amount_text(v: Option<&Value>, places: usize) -> Result<Option<String>, String> {    let Some(a) = v.and_then(scalar) else { return Ok(None) };    let (w, f) = a.split_once('.').unwrap_or((&a, ""));    if w.is_empty() || !w.bytes().all(|b| b.is_ascii_digit()) || !f.bytes().all(|b| b.is_ascii_digit()) {        return Err(format!("amount `{}` is not a number", a));    }    if f.len() > places {        return Err(format!("amount {} has more than {} decimals", a, places));    }    if w.bytes().all(|b| b == b'0') && f.bytes().all(|b| b == b'0') {        return Err("an amount of zero: leave it out".into());    }    let text = format!("{}.{:0<w$}", w, f, w = places);    if text.len() > 13 {        return Err(format!("amount {} is over 13 characters", a));    }    Ok(Some(text))}fn only_digits(x: &str) -> String {    x.chars().filter(char::is_ascii_digit).collect()}/// A Thai PromptPay code from `{ mobile }`, `{ national_id }` (13 digits) or `{ ewallet }` (15), with `amount` if fixed. A mobile like 0812345678 becomes 0066812345678. With an amount the code is single-use (12), as the banks' apps treat it, unless `static` is given.pub fn emv_qr_promptpay(payment: serde_json::Value) -> Result<String, String> {    let g = |k: &str| payment.get(k).and_then(scalar).map(|x| only_digits(&x)).filter(|x| !x.is_empty());    let (tag, id) = if let Some(m) = g("mobile") {        let m = m.strip_prefix("66").map(str::to_string).unwrap_or_else(|| m.strip_prefix('0').unwrap_or(&m).to_string());        if m.len() != 9 {            return Err("a Thai mobile number has 9 digits after the 0".into());        }        ("01", format!("0066{}", m))    } else if let Some(n) = g("national_id") {        if n.len() != 13 {            return Err(format!("a national or tax id has 13 digits, this has {}", n.len()));        }        ("02", n)    } else if let Some(n) = g("ewallet") {        if n.len() != 15 {            return Err(format!("an e-wallet id has 15 digits, this has {}", n.len()));        }        ("03", n)    } else {        return Err("give mobile, national_id or ewallet".into());    };    let amount = amount_text(payment.get("amount"), 2)?;    let fixed = amount.is_some() && !payment.get("static").and_then(Value::as_bool).unwrap_or(false);    let mut m = Map::new();    m.insert("00".into(), json!("01"));    m.insert("01".into(), json!(if fixed { "12" } else { "11" }));    let mut account = Map::new();    account.insert("00".into(), json!("A000000677010111"));    account.insert(tag.into(), json!(id));    m.insert("29".into(), Value::Object(account));    m.insert("53".into(), json!("764"));    if let Some(a) = amount { m.insert("54".into(), json!(a)); }    m.insert("58".into(), json!("TH"));    let text: String = encode(&Value::Object(m))?.iter().map(|(t, v)| tlv(t, v)).collect::<Result<_, _>>()?;    let out = text + "6304";    let crc = emv_qr_crc(&out);    Ok(out + &crc)}/// A Singapore PayNow code from `{ mobile }` (+65 and 8 digits) or `{ uen }`, with `name`, `amount`, `reference`, `editable` (may the payer change the amount, default no without an amount given, yes with none) and `expiry` (YYYYMMDD).pub fn emv_qr_paynow(payment: serde_json::Value) -> Result<String, String> {    let g = |k: &str| payment.get(k).and_then(scalar).map(|x| x.trim().to_string()).filter(|x| !x.is_empty());    let (kind, proxy) = if let Some(m) = g("mobile") {        let d = only_digits(&m);        let d = if d.len() == 8 { format!("65{}", d) } else { d };        if d.len() != 10 || !d.starts_with("65") {            return Err(format!("`{}` is not a Singapore mobile number", m));        }        ("0", format!("+{}", d))    } else if let Some(u) = g("uen") {        let u = u.to_uppercase();        if !(9..=10).contains(&u.len()) || !u.bytes().all(|b| b.is_ascii_alphanumeric()) {            return Err(format!("`{}` is not a UEN: 9 or 10 letters and digits", u));        }        ("2", u)    } else {        return Err("give mobile or uen".into());    };    let name = g("name").ok_or("the merchant's name is required")?;    let amount = amount_text(payment.get("amount"), 2)?;    let editable = payment.get("editable").and_then(Value::as_bool).unwrap_or(amount.is_none());    let expiry = g("expiry");    if let Some(e) = &expiry {        if e.len() != 8 || !e.bytes().all(|b| b.is_ascii_digit()) {            return Err(format!("expiry `{}` should be YYYYMMDD", e));        }    }    let mut account = Map::new();    account.insert("00".into(), json!("SG.PAYNOW"));    account.insert("01".into(), json!(kind));    account.insert("02".into(), json!(proxy));    account.insert("03".into(), json!(if editable { "1" } else { "0" }));    if let Some(e) = expiry { account.insert("04".into(), json!(e)); }    let mut m = Map::new();    m.insert("01".into(), json!(if amount.is_some() { "12" } else { "11" }));    m.insert("26".into(), Value::Object(account));    m.insert("52".into(), json!("0000"));    m.insert("53".into(), json!("702"));    if let Some(a) = amount { m.insert("54".into(), json!(a)); }    m.insert("58".into(), json!("SG"));    m.insert("59".into(), json!(name.chars().take(25).collect::<String>()));    m.insert("60".into(), json!("Singapore"));    if let Some(r) = g("reference") {        let mut extra = Map::new();        extra.insert("01".into(), json!(r));        m.insert("62".into(), Value::Object(extra));    }    emv_qr_build(Value::Object(m))}/// A Malaysian DuitNow code, as PayNet's QR specification lays it out, from `{ acquirer_id, qr_id, name, city, category, amount, postcode, descriptor, mobile, dynamic }`: the acquirer's id and the QR id come from your acquirer. Payload format 02, currency 458, country MY; static (11) unless `dynamic` is true, an amount or not.pub fn emv_qr_duitnow(payment: serde_json::Value) -> Result<String, String> {    let g = |k: &str| payment.get(k).and_then(scalar).map(|x| x.trim().to_string()).filter(|x| !x.is_empty());    let acquirer = g("acquirer_id").ok_or("acquirer_id is required: your acquirer gives it")?;    let id = g("qr_id").ok_or("qr_id is required: your acquirer gives it")?;    if acquirer.len() > 6 {        return Err(format!("acquirer_id `{}` is at most 6 characters", acquirer));    }    if id.len() > 28 || !id.bytes().all(|b| b.is_ascii_alphanumeric()) {        return Err(format!("qr_id `{}` is at most 28 letters and digits", id));    }    let name = g("name").ok_or("the merchant's name is required")?;    let city = g("city").ok_or("the merchant's city is required")?;    let amount = amount_text(payment.get("amount"), 2)?;    let mut account = Map::new();    account.insert("00".into(), json!("A0000006150001"));    account.insert("01".into(), json!(acquirer));    account.insert("02".into(), json!(id));    if let Some(d) = g("descriptor") { account.insert("03".into(), json!(d)); }    if let Some(d) = g("mobile") { account.insert("04".into(), json!(d)); }    let mut m = Map::new();    m.insert("00".into(), json!("02"));    m.insert("01".into(), json!(if payment.get("dynamic").and_then(Value::as_bool).unwrap_or(false) { "12" } else { "11" }));    m.insert("26".into(), Value::Object(account));    m.insert("52".into(), json!(g("category").unwrap_or_else(|| "0000".into())));    m.insert("53".into(), json!("458"));    if let Some(a) = amount { m.insert("54".into(), json!(a)); }    m.insert("58".into(), json!("MY"));    m.insert("59".into(), json!(name.chars().take(25).collect::<String>()));    m.insert("60".into(), json!(city.chars().take(15).collect::<String>()));    if let Some(p) = g("postcode") { m.insert("61".into(), json!(p)); }    emv_qr_build(Value::Object(m))}/// An SVG of a code. `size` is the smallest width in pixels.pub fn emv_qr_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())}