absenat/general/message.js

dedicated messaging service core

/**
 * @author mr-exception
 * @description generates the main message
 * @param {string} id 
 * @param {array[string]} chunks 
 * @param {string} dst_public_key 
 */
const generateMessages = (id, chunks, dst_public_key) => {
  // declare count of chunks have to be sent
  const c = chunks.length;
  // devlare the array of sending chunks before encrypting
  const result = [];
  for (let i = 0; i < chunks.length; i++) {
    const chunk = {
      i, c, id,
      data: chunks[i],
    };
    if (i === c - 1)
      chunk.pk = dst_public_key;
    result.push(chunk);
  }
  return result;
}
/**
 * @author mr-exception
 * @description converts a message into chunks
 * @param {string} id
 * @param {string} content
 * @param {string} dst_public_key
 */
const chunkStringMessage = (id, content, dst_public_key) => {
  const chunks = [];
  // creating rsa node from public key
  const dstPublicKey = createPublicKey(dst_public_key);

  for (let i = 0; i < content.length; i += 128) {
    chunks.push(dstPublicKey.encrypt(content.substring(i, i + 128)));
  }
  return generateMessages(id, chunks, dst_public_key);
}
/**
 * @author mr-exception
 * @description stringifies message
 * @param {string} id
 * @param {string} content
 * @param {string} dst_public_key
 */
global.chunkMessage = (id, content, dst_public_key) => {
  const message = JSON.stringify(content);
  return chunkStringMessage(id, message, dst_public_key);
}
/**
 * @author mr-exception
 * @description saves a chunked message into a single file and submits it in database
 * @param {string} id
 * @param {string} src_public_key
 * @param {string} dst_public_key
 * @param {array[Burffer]} chunks
 */
global.saveMessage = (id, src_public_key, dst_public_key, chunks) => {
  // saving message conent in a file
  if (!fs.existsSync('./storage')) {
    fs.mkdirSync('./storage');
    if (!fs.existsSync('./storage/bridge')) {
      fs.mkdirSync('./storage/bridge');
    }
  }
  const file = fs.createWriteStream(`./storage/bridge/${id}.data`);
  for (const i in chunks) {
    const data = Buffer.from(chunks[i]);
    file.write(data);
  }
  file.end();
  // saving message informations in database
  db.saveBridgeMessage(id, src_public_key, dst_public_key, `./storage/bridge/${id}.data`);
  return true;
}