metamask-extension/app/scripts/controllers/ens/index.js

import punycode from 'punycode/punycode'
import ethUtil from 'ethereumjs-util'
import { ObservableStore } from '@metamask/obs-store'
import log from 'loglevel'
import Ens from './ens'

const ZERO_ADDRESS = '0x0000000000000000000000000000000000000000'
const ZERO_X_ERROR_ADDRESS = '0x'

export default class EnsController {
  constructor({ ens, provider, networkStore } = {}) {
    const initState = {
      ensResolutionsByAddress: {},
    }

    this._ens = ens
    if (!this._ens) {
      const network = networkStore.getState()
      if (Ens.getNetworkEnsSupport(network)) {
        this._ens = new Ens({
          network,
          provider,
        })
      }
    }

    this.store = new ObservableStore(initState)
    networkStore.subscribe((network) => {
      this.store.putState(initState)
      if (Ens.getNetworkEnsSupport(network)) {
        this._ens = new Ens({
          network,
          provider,
        })
      } else {
        delete this._ens
      }
    })
  }

  reverseResolveAddress(address) {
    return this._reverseResolveAddress(ethUtil.toChecksumAddress(address))
  }

  async _reverseResolveAddress(address) {
    if (!this._ens) {
      return undefined
    }

    const state = this.store.getState()
    if (state.ensResolutionsByAddress[address]) {
      return state.ensResolutionsByAddress[address]
    }

    let domain
    try {
      domain = await this._ens.reverse(address)
    } catch (error) {
      log.debug(error)
      return undefined
    }

    let registeredAddress
    try {
      registeredAddress = await this._ens.lookup(domain)
    } catch (error) {
      log.debug(error)
      return undefined
    }

    if (
      registeredAddress === ZERO_ADDRESS ||
      registeredAddress === ZERO_X_ERROR_ADDRESS
    ) {
      return undefined
    }

    if (ethUtil.toChecksumAddress(registeredAddress) !== address) {
      return undefined
    }

    this._updateResolutionsByAddress(address, punycode.toASCII(domain))
    return domain
  }

  _updateResolutionsByAddress(address, domain) {
    const oldState = this.store.getState()
    this.store.putState({
      ensResolutionsByAddress: {
        ...oldState.ensResolutionsByAddress,
        [address]: domain,
      },
    })
  }
}