split-sms/lib/unicodesplitter.js

An SMS message splitter with support for both GSM and Unicode.

function isHighSurrogate(code) {
  return code >= 0xD800 && code <= 0xDBFF;
}

module.exports.split = function (message, options) {
  options = options || { summary: false };

  if (message === '') {
    return {
      parts: [{
        content: options.summary ? undefined : '',
        length: 0,
        bytes: 0
      }],
      totalLength: 0,
      totalBytes: 0
    };
  }

  var messages = [];
  var length = 0;
  var bytes = 0;
  var totalBytes = 0;
  var totalLength = 0;
  var partStart = 0;

  function bank(partEnd) {
    var msg = {
      content: options.summary ? undefined : (partEnd ? message.substring(partStart, partEnd + 1) : message.substring(partStart)),
      length: length,
      bytes: bytes
    };
    messages.push(msg);

    partStart = partEnd + 1;

    totalLength += length;
    length = 0;
    totalBytes += bytes;
    bytes = 0;
  }

  for (var i = 0, count = message.length; i < count; i++) {

    var code = message.charCodeAt(i);
    var highSurrogate = isHighSurrogate(code);

    if (highSurrogate) {
      if (bytes === 132) bank(i - 1);
      bytes += 2;
      i++;
    }

    bytes += 2;
    length++;

    if (bytes === 134) bank(i);
  }

  if (bytes > 0) bank();

  if (messages[1] && totalBytes <= 140) {
    return {
      parts: [{
        content: options.summary ? undefined : message,
        length: totalLength,
        bytes: totalBytes
      }],
      totalLength: totalLength,
      totalBytes: totalBytes
    };
  }

  return {
    parts: messages,
    totalLength: totalLength,
    totalBytes: totalBytes
  };
};