metamask-extension/app/scripts/lib/network-store.js

import log from 'loglevel'

const FIXTURE_SERVER_HOST = 'localhost'
const FIXTURE_SERVER_PORT = 12345
const FIXTURE_SERVER_URL = `http://${FIXTURE_SERVER_HOST}:${FIXTURE_SERVER_PORT}/state.json`

/**
 * A read-only network-based storage wrapper
 */
export default class ReadOnlyNetworkStore {
  constructor() {
    this._initialized = false
    this._initializing = this._init()
    this._state = undefined
  }

  /**
   * Declares this store as compatible with the current browser
   */
  isSupported = true

  /**
   * Initializes by loading state from the network
   */
  async _init() {
    try {
      const response = await window.fetch(FIXTURE_SERVER_URL)
      if (response.ok) {
        this._state = await response.json()
      }
    } catch (error) {
      log.debug(`Error loading network state: '${error.message}'`)
    } finally {
      this._initialized = true
    }
  }

  /**
   * Returns state
   * @returns {Promise<object>}
   */
  async get() {
    if (!this._initialized) {
      await this._initializing
    }
    return this._state
  }

  /**
   * Set state
   * @param {Object} state - The state to set
   * @returns {Promise<void>}
   */
  async set(state) {
    if (!this._initialized) {
      await this._initializing
    }
    this._state = state
  }
}