metamask中的import account的代码实现

metamask-extension/app/scripts/account-import-strategies/index.js

这部分就是用户如果往metamask中import一个已有的账户调用的接口，就是是直接输入私钥privateKey还是使用json file

即如下图：

const Wallet = require('ethereumjs-wallet')
const importers = require('ethereumjs-wallet/thirdparty')
const ethUtil = require('ethereumjs-util')

const accountImporter = {

  importAccount (strategy, args) {
    try {
      const importer = this.strategies[strategy]//确认使用的是那种import的方法
      const privateKeyHex = importer.apply(null, args) //args就是输入的值，如privateKey或者input, password
      return Promise.resolve(privateKeyHex)
    } catch (e) {
      return Promise.reject(e)
    }
  },

  strategies: {
    'Private Key': (privateKey) => {//输入私钥
      if (!privateKey) {
        throw new Error('Cannot import an empty key.')
      }

      const prefixed = ethUtil.addHexPrefix(privateKey)//加入0x前缀
      const buffer = ethUtil.toBuffer(prefixed)

      if (!ethUtil.isValidPrivate(buffer)) {
        throw new Error('Cannot import invalid private key.')
      }

      const stripped = ethUtil.stripHexPrefix(prefixed)//去掉前缀
      return stripped//输出私钥
    },
    'JSON File': (input, password) => {
      let wallet
      try {
        wallet = importers.fromEtherWallet(input, password)
      } catch (e) {
        console.log('Attempt to import as EtherWallet format failed, trying V3...')
      }

      if (!wallet) {
        wallet = Wallet.fromV3(input, password, true)
      }

      return walletToPrivateKey(wallet)
    },
  },

}

function walletToPrivateKey (wallet) {
  const privateKeyBuffer = wallet.getPrivateKey()
  return ethUtil.bufferToHex(privateKeyBuffer)
}

module.exports = accountImporter

ethereumjs-wallet

• fromV1(input, password) - import a wallet (Version 1 of the Ethereum wallet format)
• fromV3(input, password, [nonStrict]) - import a wallet (Version 3 of the Ethereum wallet format). Set nonStrict true to accept files with mixed-caps.

var thirdparty = require('ethereumjs-wallet/thirdparty')

• fromEtherWallet(input, password) - import a wallet generated by EtherWallet