Bill

bill — Iranian utility bill parsing & validation

import { Bill } from "@persian-tools/persian-tools";
// CommonJS
const { Bill } = require("@persian-tools/persian-tools");

Public exports

class Bill { ... }

type BillTypes =
  | "آب" | "برق" | "گاز" | "تلفن ثابت" | "تلفن همراه"
  | "عوارض شهرداری" | "سازمان مالیات"
  | "جرایم راهنمایی و رانندگی" | "unknown";

type Currency = "toman" | "rial";

const billTypes: { [k: number]: BillTypes };   // numeric code → BillTypes

interface BillParams {
  billId?: number;
  paymentId?: number;
  currency?: Currency;
  barcode?: string;
}

interface BillResult {
  amount: number;
  type: string;                  // NB: field is `type`, not `billType`
  barcode: string;
  isValid: boolean;
  isValidBillId: boolean;
  isValidBillPayment: boolean;
}

Construction

import { Bill } from "@persian-tools/persian-tools";

// From bill ID + payment ID
const b = new Bill({ billId: 1117753200, paymentId: 1234567890 });

// With currency (default "toman")
const b2 = new Bill({ billId: 1117753200, paymentId: 1234567890, currency: "rial" });

// From barcode (combined 26-digit string)
const b3 = new Bill({ barcode: "1117753200000123456789..." });

All params are optional, but most methods require either billId + paymentId or barcode to do real work.

Public methods

b.getAmount(): number               // amount in the chosen currency
b.getBillType(): BillTypes          // service category (water/electricity/...)
b.getBarcode(): string              // billId + "000" + paymentId
b.findByBarcode(barcode?: string): { billId: number; paymentId: number }
b.verificationBillId(): boolean     // check digit on the bill ID
b.verificationBillPayment(): boolean // check digit on the payment ID
b.verificationBill(): boolean       // both must pass
b.getResult(): BillResult           // single object with everything above

const r = b.getResult();
// {
//   amount: ...,
//   type: "برق",           // ← field is `type` (NOT `billType`)
//   barcode: "...",
//   isValid: true,
//   isValidBillId: true,
//   isValidBillPayment: true,
// }

Algorithm — the check digit

CalTheBit(num) (private) iterates digits right-to-left multiplying by cycling weights 2..7 (resets to 2 after 7), sums % 11. Mapped 0/1 → 0, otherwise 11 - sum.

• Bill ID validity: last digit must equal CalTheBit(billId.slice(0, -1)), AND the bill type (extracted from billId.slice(-2, -1)) must not be "unknown".
• Payment ID validity: last two digits are control bits; first checks CalTheBit(paymentIdWithoutLastTwo), second checks CalTheBit(billId + paymentIdWithoutLastTwo + firstControlBit).

Bill type encoding

The penultimate digit of the bill ID encodes the service:

Amount calculation

amount = parseInt(paymentId.slice(0, -5)) * (currency === "rial" ? 1000 : 100)

The last 5 digits of payment ID are control + scaling; the rest are the amount in 100s of toman / 1000s of rial. Pick currency to match your downstream domain — getting it wrong is a 10× error.

Common pitfalls

• Field name is type, not billType — older docs use billType. Accessing result.billType will be undefined.
• Constructor params are optional, but getResult() on an empty Bill returns { amount: NaN, type: "unknown", barcode: "nullnull", isValid: false, ... }. Guard upstream.
• Persian/Arabic digit barcodes aren't normalized. Pass English digits or normalize first with autoConvertDigitsToEN.
• Bill type "unknown" forces verificationBillId() to return false even if the math checks out. This is intentional — only known service categories are accepted.

Composition with phone-number bill type

The penultimate digit 4 and 5 correspond to landline and mobile bills respectively. If you want to display "تلفن همراه 0912xxxxxxx" with operator info, combine with phoneNumber skill's phoneNumberDetail.

References

• Tests: test/bill.spec.ts
• Related: phoneNumber skill (for telecom bill detail)