protocol_extractor.js

const fs = require('fs')
const async = require('async')

if (process.argv.length !== 3) {
  console.log('Usage : node protocol_extractor.js <decompiledFilesDir>')
  process.exit(1)
}

const decompiledFilesDir = process.argv[2]

getProtocol()
// getFields("jd");
// getFields("hp");

function getProtocol () {
  async.waterfall([
    readPacketsIds,
    dataToCleanLines,
    linesToProtocol
  ], write)
}

function write (err, protocol) {
  if (err) {
    console.log('problem ' + err)
    return
  }
  // console.log(JSON.stringify(protocol,null,2));
  fs.writeFile('protocol.json', JSON.stringify(reorder(['handshaking', 'status', 'login', 'play'], protocol), null, 2))
}

function readPacketsIds (cb) {
  readClass('el', cb)
}

function dataToCleanLines (data, cb) {
  let c = true
  const lines = data.split('\n')
  cb(null, lines
    .map(function (s) { return s.trim() })
    .filter(function (s) { return s.indexOf('import') === -1 && s.indexOf('public') === -1 && s !== '}' && s !== '{' && s !== '},' && s !== '' })
    .filter(function (s) { if (s === '};') c = false; return c }))
}

function linesToProtocol (cleanLines, cb) {
  let currentState
  let currentToClientId
  let currentToServerId
  cb(null, cleanLines.reduce(function (protocol, line) {
    let results
    if (results = line.match(/[a-z]\((-?[0-9])\) {/)) { // eslint-disable-line no-cond-assign
      currentState = states[results[1]]
      currentToClientId = 0
      currentToServerId = 0
      protocol[currentState] = {}
    } else if (results = line.match(/this\.a\(fg\.([ab]), ([a-z.]+)\.class\);/)) { // eslint-disable-line no-cond-assign
      const direction = results[1] === 'b' ? 'toClient' : 'toServer'
      const theClass = results[2]
      const id = idToHexString(direction === 'toClient' ? currentToClientId : currentToServerId)
      if (protocol[currentState][direction] === undefined) { protocol[currentState][direction] = {} }
      protocol[currentState][direction][theClass] = { id, fields: getFields(theClass) }
      if (direction === 'toClient') currentToClientId++
      else currentToServerId++
    }
    return protocol
  }, {}))
}

function reorder (order, obj) {
  return order.reduce(function (rslt, prop) {
    rslt[prop] = obj[prop]
    return rslt
  }, {})
}

function idToHexString (id) {
  let hexString = id.toString(16)
  if (hexString.length === 1) { hexString = '0' + hexString }
  return '0x' + hexString
}

const states = {
  0: 'play',
  1: 'status',
  2: 'login',
  '-1': 'handshaking'
}

function readClass (className, cb) {
  fs.readFile(decompiledFilesDir + '/' + className + '.java', 'utf8', cb)
}

function readClassSync (className) {
  return fs.readFileSync(decompiledFilesDir + '/' + className + '.java', 'utf8')
}

function getFields (className) {
  if (className.indexOf('.') !== -1) return ['error']
  const data = readClassSync(className)
  // console.log(fields);
  return processPacketDefinition(data)
}

// get the whole reading method instead and map the method call to types
function processPacketDefinition (data) {
  return data
    .split('\n')
    .map(function (s) { return s.trim() })
    .filter(function (s) { return s.indexOf('.read') !== -1 })
    .map(function (s) {
      const results = s.match(/read(.+?)\(/)
      return results[1]
    })
    .filter(function (type) { return type !== undefined })
    .map(function (type) { return transformType(type) })
}

function transformType (type) {
  type = type.toLowerCase()
  return type.replace('unsigned', 'u')
}