metamask源码学习-background.js

这个就是浏览器后台所进行操作的地方了，它就是页面也区块链进行交互的中间部分。

metamask-background描述了为web扩展单例的文件app/scripts/background.js。该上下文实例化了一个MetaMask控制器的实例，该实例表示用户的帐户、到区块链的连接以及与新Dapps的交互。

Since background.js is essentially the Extension setup file, we can see it doing all the things specific to the extension platform:

因为background.js本质上是扩展设置文件，我们可以看到它做所有特定于扩展平台的事情

• Defining how to open the UI for new messages, transactions, and even requests to unlock (reveal to the site) their account.定义如何为新消息、事务、甚至为解锁(向站点显示)其帐户的请求打开UI
• Provide the instance's initial state, leaving MetaMask persistence to the platform.提供实例的初始状态，将MetaMask持久化保留到平台
• Providing a platform object. This is becoming our catch-all adapter for platforms to define a few other platform-variant features we require, like opening a web link. (Soon we will be moving encryption out here too, since our browser-encryption isn't portable enough!)提供平台对象。这将成为平台的通用适配器，用于定义我们需要的其他一些平台变体特性，比如打开web链接。(不久我们也将把加密技术移到这里，因为我们的浏览器加密还不够便携!)

/**
 * @file The entry point for the web extension singleton process.
 */

const urlUtil = require('url')
const endOfStream = require('end-of-stream')
const pump = require('pump')
const debounce = require('debounce-stream')
const log = require('loglevel')
const extension = require('extensionizer')
const LocalStorageStore = require('obs-store/lib/localStorage')
const LocalStore = require('./lib/local-store')
const storeTransform = require('obs-store/lib/transform')
const asStream = require('obs-store/lib/asStream')
const ExtensionPlatform = require('./platforms/extension')
const Migrator = require('./lib/migrator/') //初始化就是设置migrations有默认设置的就用默认的，否则就用最新版本的，不然就用0版本
const migrations = require('./migrations/') //Data (user data, config files etc.) is migrated from one version to another.从版本2一直到28，0为初始版本
const PortStream = require('./lib/port-stream.js')
const createStreamSink = require('./lib/createStreamSink')
const NotificationManager = require('./lib/notification-manager.js')
const MetamaskController = require('./metamask-controller')
const firstTimeState = require('./first-time-state')
const setupRaven = require('./lib/setupRaven')
const reportFailedTxToSentry = require('./lib/reportFailedTxToSentry')
const setupMetamaskMeshMetrics = require('./lib/setupMetamaskMeshMetrics')
const EdgeEncryptor = require('./edge-encryptor')
const getFirstPreferredLangCode = require('./lib/get-first-preferred-lang-code')
const getObjStructure = require('./lib/getObjStructure')
const ipfsContent = require('./lib/ipfsContent.js')

const {
  ENVIRONMENT_TYPE_POPUP,
  ENVIRONMENT_TYPE_NOTIFICATION,
  ENVIRONMENT_TYPE_FULLSCREEN,
} = require('./lib/enums')

const STORAGE_KEY = 'metamask-config'
const METAMASK_DEBUG = process.env.METAMASK_DEBUG

log.setDefaultLevel(process.env.METAMASK_DEBUG ? 'debug' : 'warn')

const platform = new ExtensionPlatform()
const notificationManager = new NotificationManager()
global.METAMASK_NOTIFIER = notificationManager

// setup sentry error reporting
const release = platform.getVersion()
const raven = setupRaven({ release })

// browser check if it is Edge - https://*.com/questions/9847580/how-to-detect-safari-chrome-ie-firefox-and-opera-browser
// Internet Explorer 6-11，即How to detect Safari, Chrome, IE, Firefox and Opera browser?
const isIE = !!document.documentMode //查看所使用的浏览器类型
// Edge 20+
const isEdge = !isIE && !!window.StyleMedia

let ipfsHandle
let popupIsOpen = false //弹出窗口是否打开
let notificationIsOpen = false //通知是否打开
const openMetamaskTabsIDs = {}

// state persistence
const diskStore = new LocalStorageStore({ storageKey: STORAGE_KEY }) //硬盘的存储
const localStore = new LocalStore() //本地的存储
let versionedData

// initialization flow
initialize().catch(log.error)

// setup metamask mesh testing container
setupMetamaskMeshMetrics()

/**
 * An object representing a transaction, in whatever state it is in.
 * @typedef TransactionMeta 交易中信息的意义
 *
 * @property {number} id - An internally unique tx identifier.
 * @property {number} time - Time the tx was first suggested, in unix epoch time (ms).
 * @property {string} status - The current transaction status (unapproved, signed, submitted, dropped, failed, rejected), as defined in `tx-state-manager.js`.
 * @property {string} metamaskNetworkId - The transaction's network ID, used for EIP-155 compliance.
 * @property {boolean} loadingDefaults - TODO: Document
 * @property {Object} txParams - The tx params as passed to the network provider.
 * @property {Object[]} history - A history of mutations to this TransactionMeta object.
 * @property {boolean} gasPriceSpecified - True if the suggesting dapp specified a gas price, prevents auto-estimation.
 * @property {boolean} gasLimitSpecified - True if the suggesting dapp specified a gas limit, prevents auto-estimation.
 * @property {string} estimatedGas - A hex string represented the estimated gas limit required to complete the transaction.
 * @property {string} origin - A string representing the interface that suggested the transaction.
 * @property {Object} nonceDetails - A metadata object containing information used to derive the suggested nonce, useful for debugging nonce issues.
 * @property {string} rawTx - A hex string of the final signed transaction, ready to submit to the network.
 * @property {string} hash - A hex string of the transaction hash, used to identify the transaction on the network.
 * @property {number} submittedTime - The time the transaction was submitted to the network, in Unix epoch time (ms).
 */

/**
 * The data emitted from the MetaMaskController.store EventEmitter, also used to initialize the MetaMaskController. Available in UI on React state as state.metamask.
 * @typedef MetaMaskState 存储信息
 * @property {boolean} isInitialized - Whether the first vault has been created. metamask是否初始化
 * @property {boolean} isUnlocked - Whether the vault is currently decrypted and accounts are available for selection. metamask是否没上锁
 * @property {boolean} isAccountMenuOpen - Represents whether the main account selection UI is currently displayed.
 * @property {boolean} isMascara - True if the current context is the extensionless MetaMascara project.
 * @property {boolean} isPopup - Returns true if the current view is an externally-triggered notification.
 * @property {string} rpcTarget - DEPRECATED - The URL of the current RPC provider.
 * @property {Object} identities - An object matching lower-case hex addresses to Identity objects with "address" and "name" (nickname) keys.
 * @property {Object} unapprovedTxs - An object mapping transaction hashes to unapproved transactions.
 * @property {boolean} noActiveNotices - False if there are notices the user should confirm before using the application.
 * @property {Array} frequentRpcList - A list of frequently used RPCs, including custom user-provided ones.
 * @property {Array} addressBook - A list of previously sent to addresses.
 * @property {address} selectedTokenAddress - Used to indicate if a token is globally selected. Should be deprecated in favor of UI-centric token selection.
 * @property {Object} tokenExchangeRates - Info about current token prices.
 * @property {Array} tokens - Tokens held by the current user, including their balances.
 * @property {Object} send - TODO: Document
 * @property {Object} coinOptions - TODO: Document
 * @property {boolean} useBlockie - Indicates preferred user identicon format. True for blockie, false for Jazzicon.
 * @property {Object} featureFlags - An object for optional feature flags.
 * @property {string} networkEndpointType - TODO: Document
 * @property {boolean} isRevealingSeedWords - True if seed words are currently being recovered, and should be shown to user.
 * @property {boolean} welcomeScreen - True if welcome screen should be shown.
 * @property {string} currentLocale - A locale string matching the user's preferred display language.这个语言的选择
 * @property {Object} provider - The current selected network provider.
 * @property {string} provider.rpcTarget - The address for the RPC API, if using an RPC API.
 * @property {string} provider.type - An identifier for the type of network selected, allows MetaMask to use custom provider strategies for known networks.
 * @property {string} network - A stringified number of the current network ID.
 * @property {Object} accounts - An object mapping lower-case hex addresses to objects with "balance" and "address" keys, both storing hex string values.
 * @property {hex} currentBlockGasLimit - The most recently seen block gas limit, in a lower case hex prefixed string.
 * @property {TransactionMeta[]} selectedAddressTxList - An array of transactions associated with the currently selected account.
 * @property {Object} unapprovedMsgs - An object of messages associated with the currently selected account, mapping a unique ID to the options.
 * @property {number} unapprovedMsgCount - The number of messages in unapprovedMsgs.
 * @property {Object} unapprovedPersonalMsgs - An object of messages associated with the currently selected account, mapping a unique ID to the options.
 * @property {number} unapprovedPersonalMsgCount - The number of messages in unapprovedPersonalMsgs.
 * @property {Object} unapprovedTypedMsgs - An object of messages associated with the currently selected account, mapping a unique ID to the options.
 * @property {number} unapprovedTypedMsgCount - The number of messages in unapprovedTypedMsgs.
 * @property {string[]} keyringTypes - An array of unique keyring identifying strings, representing available strategies for creating accounts.
 * @property {Keyring[]} keyrings - An array of keyring descriptions, summarizing the accounts that are available for use, and what keyrings they belong to.
 * @property {Object} computedBalances - Maps accounts to their balances, accounting for balance changes from pending transactions.
 * @property {string} currentAccountTab - A view identifying string for displaying the current displayed view, allows user to have a preferred tab in the old UI (between tokens and history).
 * @property {string} selectedAddress - A lower case hex string of the currently selected address.
 * @property {string} currentCurrency - A string identifying the user's preferred display currency, for use in showing conversion rates.
 * @property {number} conversionRate - A number representing the current exchange rate from the user's preferred currency to Ether.
 * @property {number} conversionDate - A unix epoch date (ms) for the time the current conversion rate was last retrieved.
 * @property {Object} infuraNetworkStatus - An object of infura network status checks.
 * @property {Block[]} recentBlocks - An array of recent blocks, used to calculate an effective but cheap gas price.
 * @property {Array} shapeShiftTxList - An array of objects describing shapeshift exchange attempts.
 * @property {Array} lostAccounts - TODO: Remove this feature. A leftover from the version-3 migration where our seed-phrase library changed to fix a bug where some accounts were mis-generated, but we recovered the old accounts as "lost" instead of losing them.
 * @property {boolean} forgottenPassword - Returns true if the user has initiated the password recovery screen, is recovering from seed phrase.
 */

/**
 * @typedef VersionedData
 * @property {MetaMaskState} data - The data emitted from MetaMask controller, or used to initialize it.
 * @property {Number} version - The latest migration version that has been run.
 */

/**
 * Initializes the MetaMask controller, and sets up all platform configuration.
 * @returns {Promise} Setup complete.
 */
async function initialize () {
  const initState = await loadStateFromPersistence() //得到state信息
  const initLangCode = await getFirstPreferredLangCode() //设置使用的语言
  await setupController(initState, initLangCode)//metamask控制器的创建
  log.debug('MetaMask initialization complete.')
  ipfsHandle = ipfsContent(initState.NetworkController.provider)
}

//
// State and Persistence
//

/**
 * Loads any stored data, prioritizing the latest storage strategy.加载所有存储数据，优先考虑最新的存储策略
 * Migrates that data schema in case it was last loaded on an older version.迁移该数据模式，以防最后一次加载到旧版本
 * @returns {Promise<MetaMaskState>} Last data emitted from previous instance of MetaMask.返回上次MetaMask实例发出的数据
 */
async function loadStateFromPersistence () {
  // migrations
  const migrator = new Migrator({ migrations })

  // read from disk
  // first from preferred, async API: 先从本地读取，没有则从硬盘读取，最后则是初始化生成
  versionedData = (await localStore.get()) ||
                  diskStore.getState() ||
                  migrator.generateInitialState(firstTimeState)

  // check if somehow state is empty 就是如果不知道为何state为空
  // this should never happen but new error reporting suggests that it has
  // for a small number of users
  // https://github.com/metamask/metamask-extension/issues/3919
  if (versionedData && !versionedData.data) {
    // try to recover from diskStore incase only localStore is bad
    const diskStoreState = diskStore.getState() //首先是试着从硬盘中的数据进行恢复，以免只是本地数据出现了问题
    if (diskStoreState && diskStoreState.data) {
      // we were able to recover (though it might be old)
      versionedData = diskStoreState
      const vaultStructure = getObjStructure(versionedData)
      raven.captureMessage('MetaMask - Empty vault found - recovered from diskStore', {
        // "extra" key is required by Sentry
        extra: { vaultStructure },
      })
    } else {//发现连硬盘中的数据也损坏了，那就没有办法恢复了
      // unable to recover, clear state
      versionedData = migrator.generateInitialState(firstTimeState)
      raven.captureMessage('MetaMask - Empty vault found - unable to recover')
    }
  }

  // report migration errors to sentry
  migrator.on('error', (err) => {
    // get vault structure without secrets
    const vaultStructure = getObjStructure(versionedData)
    raven.captureException(err, {
      // "extra" key is required by Sentry
      extra: { vaultStructure },
    })
  })

  // migrate data
  versionedData = await migrator.migrateData(versionedData)
  if (!versionedData) {
    throw new Error('MetaMask - migrator returned undefined')
  }

  // write to disk
  if (localStore.isSupported) {
    localStore.set(versionedData)
  } else {
    // throw in setTimeout so as to not block boot
    setTimeout(() => {
      throw new Error('MetaMask - Localstore not supported')
    })
  }

  // return just the data
  return versionedData.data
}

/**
 * Initializes the MetaMask Controller with any initial state and default language. 使用初始状态和默认语言来初始化metamask控制器
 * Configures platform-specific error reporting strategy. 配置特定于平台的错误报告策略
 * Streams emitted state updates to platform-specific storage strategy.流 向 特定于平台的存储策略发出状态更新
 * Creates platform listeners for new Dapps/Contexts, and sets up their data connections to the controller.为新的Dapps/上下文创建平台侦听器，并设置它们与控制器的数据连接
 *
 * @param {Object} initState - The initial state to start the controller with, matches the state that is emitted from the controller.
 * @param {String} initLangCode - The region code for the language preferred by the current user.
 * @returns {Promise} After setup is complete. 当设置完成后返回
 */
function setupController (initState, initLangCode) {
  //
  // MetaMask Controller
  //

  const controller = new MetamaskController({//metamask控制器的创建
    // User confirmation callbacks:
    showUnconfirmedMessage: triggerUi,
    unlockAccountMessage: triggerUi,
    showUnapprovedTx: triggerUi,
    // initial state
    initState,
    // initial locale code
    initLangCode,
    // platform specific api
    platform,
    encryptor: isEdge ? new EdgeEncryptor() : undefined,//EdgeEncryptor是一个特定于边缘的Microsoft加密类，它公开了eth-keykeyring-controller所期望的接口
  })
  global.metamaskController = controller

  controller.networkController.on('networkDidChange', () => { //如果网络变化则跟着变化
    ipfsHandle && ipfsHandle.remove()
    ipfsHandle = ipfsContent(controller.networkController.providerStore.getState())
  })

  // report failed transactions to Sentry 报告错误的交易
  controller.txController.on(`tx:status-update`, (txId, status) => {
    if (status !== 'failed') return
    const txMeta = controller.txController.txStateManager.getTx(txId)
    try {
      reportFailedTxToSentry({ raven, txMeta })
    } catch (e) {
      console.error(e)
    }
  })

  // setup state persistence
  pump(
    asStream(controller.store),
    debounce(),
    storeTransform(versionifyData),
    createStreamSink(persistData),
    (error) => {
      log.error('MetaMask - Persistence pipeline failed', error)
    }
  )

  /**
   * Assigns the given state to the versioned object (with metadata), and returns that.将给定状态分配给版本对象
   * @param {Object} state - The state object as emitted by the MetaMaskController.
   * @returns {VersionedData} The state object wrapped in an object that includes a metadata key.
   */
  function versionifyData (state) {
    versionedData.data = state
    return versionedData
  }

  async function persistData (state) {
    if (!state) {
      throw new Error('MetaMask - updated state is missing', state)
    }
    if (!state.data) {
      throw new Error('MetaMask - updated state does not have data', state)
    }
    if (localStore.isSupported) {
      try {
        await localStore.set(state)
      } catch (err) {
        // log error so we dont break the pipeline
        log.error('error setting state in local store:', err)
      }
    }
  }

  //
  // connect to other contexts
  //
  extension.runtime.onConnect.addListener(connectRemote)
  extension.runtime.onConnectExternal.addListener(connectExternal)

  const metamaskInternalProcessHash = {
    [ENVIRONMENT_TYPE_POPUP]: true,
    [ENVIRONMENT_TYPE_NOTIFICATION]: true,
    [ENVIRONMENT_TYPE_FULLSCREEN]: true,
  }

  const isClientOpenStatus = () => {
    return popupIsOpen || Boolean(Object.keys(openMetamaskTabsIDs).length) || notificationIsOpen
  }

  /**
   * A runtime.Port object, as provided by the browser:
   * @see https://developer.mozilla.org/en-US/Add-ons/WebExtensions/API/runtime/Port
   * @typedef Port
   * @type Object
   */

  /**
   * Connects a Port to the MetaMask controller via a multiplexed duplex stream.通过多路复用双流将端口连接到MetaMask控制器
   * This method identifies trusted (MetaMask) interfaces, and connects them differently from untrusted (web pages).此方法识别受信任(MetaMask)接口，并以不同于不受信任(web页面)的方式连接它们
   * @param {Port} remotePort - The port provided by a new context.
   */
  function connectRemote (remotePort) {
    const processName = remotePort.name
    const isMetaMaskInternalProcess = metamaskInternalProcessHash[processName]

    if (isMetaMaskInternalProcess) {//如果是内部进程，受信赖的，就相当于本地的浏览器跟metamask连接了，然后这时候浏览器的页面与metamask进行交互了
      const portStream = new PortStream(remotePort)
      // communication with popup
      controller.isClientOpen = true
      controller.setupTrustedCommunication(portStream, 'MetaMask')//用于通过远程端口连接用户界面

      if (processName === ENVIRONMENT_TYPE_POPUP) {//如果连接用户界面是一个弹出窗口，后面查查看这些常量是什么意思？？？？？
        popupIsOpen = true

        endOfStream(portStream, () => {
          popupIsOpen = false
          controller.isClientOpen = isClientOpenStatus()
        })
      }

      if (processName === ENVIRONMENT_TYPE_NOTIFICATION) { //如果是一个通知窗口
        notificationIsOpen = true

        endOfStream(portStream, () => {
          notificationIsOpen = false
          controller.isClientOpen = isClientOpenStatus()
        })
      }

      if (processName === ENVIRONMENT_TYPE_FULLSCREEN) {//如果是一个全屏
        const tabId = remotePort.sender.tab.id
        openMetamaskTabsIDs[tabId] = true

        endOfStream(portStream, () => {
          delete openMetamaskTabsIDs[tabId]
          controller.isClientOpen = isClientOpenStatus()
        })
      }
    } else {
      connectExternal(remotePort)//否则就使用不受信赖的联系方式
    }
  }

  // communication with page or other extension
  function connectExternal (remotePort) {
    const originDomain = urlUtil.parse(remotePort.sender.url).hostname
    const portStream = new PortStream(remotePort)
    controller.setupUntrustedCommunication(portStream, originDomain)//此方法用于将新web站点的web3 API连接到MetaMask的区块链连接。另外，originDomain可以用来阻止检测到的钓鱼网站
  }

  //
  // User Interface setup
  //

  updateBadge()
  controller.txController.on('update:badge', updateBadge)
  controller.messageManager.on('updateBadge', updateBadge)
  controller.personalMessageManager.on('updateBadge', updateBadge)

  /**
   * Updates the Web Extension's "badge" number, on the little fox in the toolbar.
   * The number reflects the current number of pending transactions or message signatures needing user approval.
   */
  function updateBadge () {
    var label = ''
    var unapprovedTxCount = controller.txController.getUnapprovedTxCount()
    var unapprovedMsgCount = controller.messageManager.unapprovedMsgCount
    var unapprovedPersonalMsgs = controller.personalMessageManager.unapprovedPersonalMsgCount
    var unapprovedTypedMsgs = controller.typedMessageManager.unapprovedTypedMessagesCount
    var count = unapprovedTxCount + unapprovedMsgCount + unapprovedPersonalMsgs + unapprovedTypedMsgs
    if (count) {
      label = String(count)
    }
    extension.browserAction.setBadgeText({ text: label })
    extension.browserAction.setBadgeBackgroundColor({ color: '#506F8B' })
  }

  return Promise.resolve()
}

//
// Etc...
//

/**
 * Opens the browser popup for user confirmation 就是打开浏览器的一个弹出窗口来用于metamask上进行的操作的确认
 */
function triggerUi () {
  extension.tabs.query({ active: true }, tabs => {
    const currentlyActiveMetamaskTab = Boolean(tabs.find(tab => openMetamaskTabsIDs[tab.id]))
    if (!popupIsOpen && !currentlyActiveMetamaskTab && !notificationIsOpen) {
      notificationManager.showPopup()
    }
  })
}

// On first install, open a window to MetaMask website to how-it-works.
extension.runtime.onInstalled.addListener(function (details) {
  if ((details.reason === 'install') && (!METAMASK_DEBUG)) {
    extension.tabs.create({url: 'https://metamask.io/#how-it-works'})
  }
})

⚠️这上面的很多详细信息要结合metamask-controller.js一起理解才行

MetaMask has two kinds of duplex stream APIs that it exposes:    MetaMask有两种公开的双向流api

• metamask.setupTrustedCommunication(connectionStream, originDomain) - This stream is used to connect the user interface over a remote port, and may not be necessary for contexts where the interface and the metamask-controller share a process.此流用于通过远程端口连接用户界面，对于接口和metamask控制器共享进程的上下文可能不需要此流

都在metamask-extension/app/scripts/metamask-controller.js中

  /**
   * Used to create a multiplexed stream for connecting to a trusted context,
   * like our own user interfaces, which have the provider APIs, but also
   * receive the exported API from this controller, which includes trusted
   * functions, like the ability to approve transactions or sign messages.
   *
   * @param {*} connectionStream - The duplex stream to connect to.
   * @param {string} originDomain - The domain requesting the connection,
   * used in logging and error reporting.
   */
  setupTrustedCommunication (connectionStream, originDomain) {
    // setup multiplexing
    const mux = setupMultiplex(connectionStream)
    // connect features
    this.setupControllerConnection(mux.createStream('controller'))
    this.setupProviderConnection(mux.createStream('provider'), originDomain)
  }

• metamask.setupUntrustedCommunication(connectionStream, originDomain) - This method is used to connect a new web site's web3 API to MetaMask's blockchain connection. Additionally, the originDomain is used to block detected phishing sites.此方法用于将新web站点的web3 API连接到MetaMask的区块链连接。另外，originDomain可以用来阻止检测到的钓鱼网站

//=============================================================================
// SETUP
//=============================================================================

  /**
   * Used to create a multiplexed stream for connecting to an untrusted context
   * like a Dapp or other extension.
   * @param {*} connectionStream - The Duplex stream to connect to.
   * @param {string} originDomain - The domain requesting the stream, which
   * may trigger a blacklist reload.
   */
  setupUntrustedCommunication (connectionStream, originDomain) {
    // Check if new connection is blacklisted查黑名单看其是否为钓鱼网站，不是才连接
    if (this.blacklistController.checkForPhishing(originDomain)) {
      log.debug('MetaMask - sending phishing warning for', originDomain)
      this.sendPhishingWarning(connectionStream, originDomain)
      return
    }

    // setup multiplexing
    const mux = setupMultiplex(connectionStream)
    // connect features
    this.setupProviderConnection(mux.createStream('provider'), originDomain)
    this.setupPublicConfig(mux.createStream('publicConfig'))
  }