fuel-core/utils/toArray.js

Essential javascript architecture for the Fuel side chain

module.exports = function (stream, limit = null, transform = null, done) {
  if (!stream) {
    // no arguments, meaning stream = this
    stream = this
  } else if (typeof stream === 'function') {
    // stream = this, callback passed
    done = stream
    stream = this
  }

  // Handle empty transform
  if (transform === null) {
    transform = v => v;
  }

  var deferred
  if (!stream.readable) deferred = Promise.resolve([])
  else deferred = new Promise(function (resolve, reject) {
    // stream is already ended
    if (!stream.readable) return resolve([])
    var arr = []

    stream.on('data', onData)
    stream.on('end', onEnd)
    stream.on('error', onEnd)
    stream.on('close', onClose)

    function onData(doc) {
      if (limit !== null && arr.length >= limit) {
        stream.destroy();
        return;
      }

      const _doc = transform(doc);
      if (_doc !== null) {
        arr.push(_doc);
      }
    }

    function onEnd(err) {
      if (err) reject(err)
      else resolve(arr)
      cleanup()
    }

    function onClose() {
      resolve(arr)
      cleanup()
    }

    function cleanup() {
      arr = null
      stream.removeListener('data', onData)
      stream.removeListener('end', onEnd)
      stream.removeListener('error', onEnd)
      stream.removeListener('close', onClose)
    }
  })

  if (typeof done === 'function') {
    deferred.then(function (arr) {
      process.nextTick(function() {
        done(null, arr)
      })
    }, done)
  }

  return deferred
}