import { generateVerhoeffCheckDigit } from './verhoeff';

import { formatAadhaar } from './formatter';

export interface GenerateAadhaarOptions {

/**

* Separator between 4-digit groups (e.g. ' ' or '-').

* If not provided, returns raw 12-digit string without separators.

*/

separator?: string;

}

/**

* Generates a synthetically valid 12-digit Aadhaar number compliant with UIDAI format rules

* and Verhoeff checksum algorithm. Ideal for test suites, staging environments, and mock KYC flows.

*

* Notice: This generates mathematically valid numbers for testing only and does NOT represent

* an issued identity.

*

* @param options - Generation options (optional separator)

* @returns 12-digit valid Aadhaar string

*/

export function generateAadhaar(options?: GenerateAadhaarOptions): string {

// First digit must be between 2 and 9 (UIDAI reserve rule: 0 and 1 never used)

const firstDigit = Math.floor(Math.random() * 8) + 2;

let remaining10Digits = '';

// Generate next 10 digits

for (let i = 0; i < 10; i++) {

remaining10Digits += Math.floor(Math.random() * 10).toString();

}

const base11 = `${firstDigit}${remaining10Digits}`;

// Guard against impossible edge case of all 11 identical digits

if (/^(\d)\1{10}$/.test(base11)) {

return generateAadhaar(options);

}

const checkDigit = generateVerhoeffCheckDigit(base11);

const full12 = `${base11}${checkDigit}`;

// Guard against all 12 identical digits

if (/^(\d)\1{11}$/.test(full12)) {

return generateAadhaar(options);

}

if (options?.separator !== undefined) {

return formatAadhaar(full12, options.separator);

}

return full12;

}