index.js

const pump = require('pump')
const RpcEngine = require('json-rpc-engine')
const createErrorMiddleware = require('./createErrorMiddleware')
const createIdRemapMiddleware = require('json-rpc-engine/src/idRemapMiddleware')
const createJsonRpcStream = require('json-rpc-middleware-stream')
const LocalStorageStore = require('obs-store')
const asStream = require('obs-store/lib/asStream')
const ObjectMultiplex = require('obj-multiplex')
const util = require('util')
const SafeEventEmitter = require('safe-event-emitter')

module.exports = MetamaskInpageProvider

util.inherits(MetamaskInpageProvider, SafeEventEmitter)

function MetamaskInpageProvider (connectionStream) {
  const self = this
  self.selectedAddress = undefined
  self.networkVersion = undefined

  // super constructor
  SafeEventEmitter.call(self)

  // setup connectionStream multiplexing
  const mux = self.mux = new ObjectMultiplex()
  pump(
    connectionStream,
    mux,
    connectionStream,
    logStreamDisconnectWarning.bind(this, 'MetaMask')
  )

  // subscribe to metamask public config (one-way)
  self.publicConfigStore = new LocalStorageStore({ storageKey: 'MetaMask-Config' })

  // Emit events for some state changes
  self.publicConfigStore.subscribe(function (state) {

    // Emit accountsChanged event on account change
    if ('selectedAddress' in state && state.selectedAddress !== self.selectedAddress) {
      self.selectedAddress = state.selectedAddress
      self.emit('accountsChanged', [self.selectedAddress])
    }

    // Emit networkChanged event on network change
    if ('networkVersion' in state && state.networkVersion !== self.networkVersion) {
      self.networkVersion = state.networkVersion
      self.emit('networkChanged', state.networkVersion)
    }
  })

  pump(
    mux.createStream('publicConfig'),
    asStream(self.publicConfigStore),
    logStreamDisconnectWarning.bind(this, 'MetaMask PublicConfigStore')
  )

  // ignore phishing warning message (handled elsewhere)
  mux.ignoreStream('phishing')

  // connect to async provider
  const jsonRpcConnection = createJsonRpcStream()
  pump(
    jsonRpcConnection.stream,
    mux.createStream('provider'),
    jsonRpcConnection.stream,
    logStreamDisconnectWarning.bind(this, 'MetaMask RpcProvider')
  )

  // handle sendAsync requests via dapp-side rpc engine
  const rpcEngine = new RpcEngine()
  rpcEngine.push(createIdRemapMiddleware())
  rpcEngine.push(createErrorMiddleware())
  rpcEngine.push(jsonRpcConnection.middleware)
  self.rpcEngine = rpcEngine

  // forward json rpc notifications
  jsonRpcConnection.events.on('notification', function(payload) {
    self.emit('data', null, payload)
  })

  // Work around for https://github.com/metamask/metamask-extension/issues/5459
  // drizzle accidently breaking the `this` reference
  self.send = self.send.bind(self)
  self.sendAsync = self.sendAsync.bind(self)
}

// Web3 1.0 provider uses `send` with a callback for async queries
MetamaskInpageProvider.prototype.send = function (payload, callback) {
  const self = this

  if (callback) {
    self.sendAsync(payload, callback)
  } else {
    return self._sendSync(payload)
  }
}

// handle sendAsync requests via asyncProvider
// also remap ids inbound and outbound
MetamaskInpageProvider.prototype.sendAsync = function (payload, cb) {
  const self = this

  if (payload.method === 'eth_signTypedData') {
    console.warn('MetaMask: This experimental version of eth_signTypedData will be deprecated in the next release in favor of the standard as defined in EIP-712. See https://git.io/fNzPl for more information on the new standard.')
  }

  self.rpcEngine.handle(payload, cb)
}

MetamaskInpageProvider.prototype._sendSync = function (payload) {
  const self = this

  let selectedAddress
  let result = null
  switch (payload.method) {

    case 'eth_accounts':
      // read from localStorage
      selectedAddress = self.publicConfigStore.getState().selectedAddress
      result = selectedAddress ? [selectedAddress] : []
      break

    case 'eth_coinbase':
      // read from localStorage
      selectedAddress = self.publicConfigStore.getState().selectedAddress
      result = selectedAddress || null
      break

    case 'eth_uninstallFilter':
      self.sendAsync(payload, noop)
      result = true
      break

    case 'net_version':
      const networkVersion = self.publicConfigStore.getState().networkVersion
      result = networkVersion || null
      break

    // throw not-supported Error
    default:
      var link = 'https://github.com/MetaMask/faq/blob/master/DEVELOPERS.md#dizzy-all-async---think-of-metamask-as-a-light-client'
      var message = `The MetaMask Web3 object does not support synchronous methods like ${payload.method} without a callback parameter. See ${link} for details.`
      throw new Error(message)

  }

  // return the result
  return {
    id: payload.id,
    jsonrpc: payload.jsonrpc,
    result: result,
  }
}

MetamaskInpageProvider.prototype.isConnected = function () {
  return true
}

MetamaskInpageProvider.prototype.isMetaMask = true

// util

function logStreamDisconnectWarning (remoteLabel, err) {
  let warningMsg = `MetamaskInpageProvider - lost connection to ${remoteLabel}`
  if (err) warningMsg += '\n' + err.stack
  console.warn(warningMsg)
  const listeners = this.listenerCount('error')
  if (listeners > 0) {
    this.emit('error', warningMsg)
  }
}

function noop () {}