sms-validator/index.js

SMS validation utility for Africa's Talking SMS service. Supports GSM-7/Unicode detection, E.164 validation, segment count, and optional sanitization.

// index.js
const { parsePhoneNumberFromString } = require("libphonenumber-js");

// GSM-7 charset
const GSM_CHARSET =
  "@£$¥èéùìòÇ\nØø\rÅåΔ_ΦΓΛΩΠΨΣΘΞ\x1BÆæßÉ !\"#¤%&'()*+,-./0123456789:;<=>?" +
  "¡ABCDEFGHIJKLMNOPQRSTUVWXYZÄÖÑܧ¿abcdefghijklmnopqrstuvwxyzäöñüà";

// Max length per encoding type for AT SMS
const MAX_SEGMENTS = {
  GSM7: 3 * 153,
  UCS2: 3 * 67,
};

function isValidPhoneNumber(phone) {
  const parsed = parsePhoneNumberFromString(phone);
  return parsed?.isValid() || false;
}

function isGSM7(text) {
  for (let char of text) {
    if (!GSM_CHARSET.includes(char)) return false;
  }
  return true;
}

function detectEncoding(text) {
  return isGSM7(text) ? "GSM-7" : "UCS-2";
}

function getSmsSegments(text) {
  const encoding = detectEncoding(text);
  const singleLimit = encoding === "GSM-7" ? 160 : 70;
  const multiLimit = encoding === "GSM-7" ? 153 : 67;

  if (text.length <= singleLimit) return 1;
  return Math.ceil(text.length / multiLimit);
}

function sanitizeMessage(message) {
  return message.replace(/[^\x00-\x7F]/g, "").trim();
}

function getMessageBreakdown(message, costPerSegment = 0) {
  const encoding = detectEncoding(message);
  const segments = getSmsSegments(message);
  return {
    encoding,
    segments,
    cost: segments * costPerSegment,
    length: message.length,
  };
}

function validateSms(phone, message, options = {}) {
  const { sanitize = false, maxSegments = 3 } = options;
  const cleanMessage = sanitize ? sanitizeMessage(message) : message;
  const encoding = detectEncoding(cleanMessage);
  const segments = getSmsSegments(cleanMessage);
  const isLengthValid = segments <= maxSegments;

  return {
    isPhoneValid: isValidPhoneNumber(phone),
    encoding,
    segments,
    messageLength: cleanMessage.length,
    isLengthValid,
    sanitized: sanitize ? cleanMessage : null,
  };
}

module.exports = {
  validateSms,
  isValidPhoneNumber,
  detectEncoding,
  getSmsSegments,
  getMessageBreakdown,
  sanitizeMessage,
};