'use strict';

const crypto = require('crypto');

const MIN_CODE = 10000000;
const MAX_CODE = 100000000;

/** Generate a random 8-digit numeric string (10000000–99999999). */
const generateCode = () => String(crypto.randomInt(MIN_CODE, MAX_CODE));

/**
 * Allocate a unique code for a Mongoose model field.
 * Retries on collision up to maxAttempts times.
 */
const generateUniqueCode = async (Model, field = 'uniqueCode', maxAttempts = 24) => {
  if (!Model) throw new Error('Model is required to generate a unique code');

  for (let attempt = 0; attempt < maxAttempts; attempt += 1) {
    const code = generateCode();
    const exists = await Model.exists({ [field]: code });
    if (!exists) return code;
  }

  throw new Error(`Could not generate a unique ${field} after ${maxAttempts} attempts`);
};

module.exports = {
  generateCode,
  generateUniqueCode
};