import EventEmitter from 'events'
import ObservableStore from 'obs-store'
import ethUtil from 'ethereumjs-util'
import { ethErrors } from 'eth-json-rpc-errors'
import log from 'loglevel'
import createId from './random-id'
import { MESSAGE_TYPE } from './enums'

const hexRe = /^[0-9A-Fa-f]+$/ug

/**
 * Represents, and contains data about, an 'eth_decrypt' type decryption request. These are created when a
 * decryption for an eth_decrypt call is requested.
 *
 * @typedef {Object} DecryptMessage
 * @property {number} id An id to track and identify the message object
 * @property {Object} msgParams The parameters to pass to the decryptMessage method once the decryption request is
 * approved.
 * @property {Object} msgParams.metamaskId Added to msgParams for tracking and identification within MetaMask.
 * @property {string} msgParams.data A hex string conversion of the raw buffer data of the decryption request
 * @property {number} time The epoch time at which the this message was created
 * @property {string} status Indicates whether the decryption request is 'unapproved', 'approved', 'decrypted' or 'rejected'
 * @property {string} type The json-prc decryption method for which a decryption request has been made. A 'Message' will
 * always have a 'eth_decrypt' type.
 *
 */

export default class DecryptMessageManager extends EventEmitter {

  /**
   * Controller in charge of managing - storing, adding, removing, updating - DecryptMessage.
   *
   * @typedef {Object} DecryptMessageManager
   * @property {Object} memStore The observable store where DecryptMessage are saved.
   * @property {Object} memStore.unapprovedDecryptMsgs A collection of all DecryptMessages in the 'unapproved' state
   * @property {number} memStore.unapprovedDecryptMsgCount The count of all DecryptMessages in this.memStore.unapprovedDecryptMsgs
   * @property {array} messages Holds all messages that have been created by this DecryptMessageManager
   *
   */
  constructor () {
    super()
    this.memStore = new ObservableStore({
      unapprovedDecryptMsgs: {},
      unapprovedDecryptMsgCount: 0,
    })
    this.messages = []
  }

  /**
   * A getter for the number of 'unapproved' DecryptMessages in this.messages
   *
   * @returns {number} The number of 'unapproved' DecryptMessages in this.messages
   *
   */
  get unapprovedDecryptMsgCount () {
    return Object.keys(this.getUnapprovedMsgs()).length
  }

  /**
   * A getter for the 'unapproved' DecryptMessages in this.messages
   *
   * @returns {Object} An index of DecryptMessage ids to DecryptMessages, for all 'unapproved' DecryptMessages in
   * this.messages
   *
   */
  getUnapprovedMsgs () {
    return this.messages.filter((msg) => msg.status === 'unapproved')
      .reduce((result, msg) => {
        result[msg.id] = msg
        return result
      }, {})
  }

  /**
   * Creates a new DecryptMessage with an 'unapproved' status using the passed msgParams. this.addMsg is called to add
   * the new DecryptMessage to this.messages, and to save the unapproved DecryptMessages from that list to
   * this.memStore.
   *
   * @param {Object} msgParams The params for the eth_decrypt call to be made after the message is approved.
   * @param {Object} req (optional) The original request object possibly containing the origin
   * @returns {Promise<Buffer>} The raw decrypted message contents
   *
   */
  addUnapprovedMessageAsync (msgParams, req) {
    return new Promise((resolve, reject) => {
      if (!msgParams.from) {
        reject(new Error('MetaMask Decryption: from field is required.'))
        return
      }
      const msgId = this.addUnapprovedMessage(msgParams, req)
      this.once(`${msgId}:finished`, (data) => {
        switch (data.status) {
          case 'decrypted':
            resolve(data.rawData)
            return
          case 'rejected':
            reject(ethErrors.provider.userRejectedRequest('MetaMask Decryption: User denied message decryption.'))
            return
          case 'errored':
            reject(new Error('This message cannot be decrypted'))
            return
          default:
            reject(new Error(`MetaMask Decryption: Unknown problem: ${JSON.stringify(msgParams)}`))
        }
      })
    })
  }

  /**
   * Creates a new DecryptMessage with an 'unapproved' status using the passed msgParams. this.addMsg is called to add
   * the new DecryptMessage to this.messages, and to save the unapproved DecryptMessages from that list to
   * this.memStore.
   *
   * @param {Object} msgParams The params for the eth_decryptMsg call to be made after the message is approved.
   * @param {Object} req (optional) The original request object possibly containing the origin
   * @returns {number} The id of the newly created DecryptMessage.
   *
   */
  addUnapprovedMessage (msgParams, req) {
    log.debug(`DecryptMessageManager addUnapprovedMessage: ${JSON.stringify(msgParams)}`)
    // add origin from request
    if (req) {
      msgParams.origin = req.origin
    }
    msgParams.data = this.normalizeMsgData(msgParams.data)
    // create txData obj with parameters and meta data
    const time = (new Date()).getTime()
    const msgId = createId()
    const msgData = {
      id: msgId,
      msgParams,
      time,
      status: 'unapproved',
      type: MESSAGE_TYPE.ETH_DECRYPT,
    }
    this.addMsg(msgData)

    // signal update
    this.emit('update')
    return msgId
  }

  /**
   * Adds a passed DecryptMessage to this.messages, and calls this._saveMsgList() to save the unapproved DecryptMessages from that
   * list to this.memStore.
   *
   * @param {Message} msg The DecryptMessage to add to this.messages
   *
   */
  addMsg (msg) {
    this.messages.push(msg)
    this._saveMsgList()
  }

  /**
   * Returns a specified DecryptMessage.
   *
   * @param {number} msgId The id of the DecryptMessage to get
   * @returns {DecryptMessage|undefined} The DecryptMessage with the id that matches the passed msgId, or undefined
   * if no DecryptMessage has that id.
   *
   */
  getMsg (msgId) {
    return this.messages.find((msg) => msg.id === msgId)
  }

  /**
   * Approves a DecryptMessage. Sets the message status via a call to this.setMsgStatusApproved, and returns a promise
   * with the message params modified for proper decryption.
   *
   * @param {Object} msgParams The msgParams to be used when eth_decryptMsg is called, plus data added by MetaMask.
   * @param {Object} msgParams.metamaskId Added to msgParams for tracking and identification within MetaMask.
   * @returns {Promise<object>} Promises the msgParams object with metamaskId removed.
   *
   */
  approveMessage (msgParams) {
    this.setMsgStatusApproved(msgParams.metamaskId)
    return this.prepMsgForDecryption(msgParams)
  }

  /**
   * Sets a DecryptMessage status to 'approved' via a call to this._setMsgStatus.
   *
   * @param {number} msgId The id of the DecryptMessage to approve.
   *
   */
  setMsgStatusApproved (msgId) {
    this._setMsgStatus(msgId, 'approved')
  }

  /**
   * Sets a DecryptMessage status to 'decrypted' via a call to this._setMsgStatus and updates that DecryptMessage in
   * this.messages by adding the raw decryption data of the decryption request to the DecryptMessage
   *
   * @param {number} msgId The id of the DecryptMessage to decrypt.
   * @param {buffer} rawData The raw data of the message request
   *
   */
  setMsgStatusDecrypted (msgId, rawData) {
    const msg = this.getMsg(msgId)
    msg.rawData = rawData
    this._updateMsg(msg)
    this._setMsgStatus(msgId, 'decrypted')
  }

  /**
   * Removes the metamaskId property from passed msgParams and returns a promise which resolves the updated msgParams
   *
   * @param {Object} msgParams The msgParams to modify
   * @returns {Promise<object>} Promises the msgParams with the metamaskId property removed
   *
   */
  prepMsgForDecryption (msgParams) {
    delete msgParams.metamaskId
    return Promise.resolve(msgParams)
  }

  /**
   * Sets a DecryptMessage status to 'rejected' via a call to this._setMsgStatus.
   *
   * @param {number} msgId The id of the DecryptMessage to reject.
   *
   */
  rejectMsg (msgId) {
    this._setMsgStatus(msgId, 'rejected')
  }

  /**
   * Sets a TypedMessage status to 'errored' via a call to this._setMsgStatus.
   *
   * @param {number} msgId The id of the TypedMessage to error
   *
   */
  errorMessage (msgId, error) {
    const msg = this.getMsg(msgId)
    msg.error = error
    this._updateMsg(msg)
    this._setMsgStatus(msgId, 'errored')
  }

  /**
   * Updates the status of a DecryptMessage in this.messages via a call to this._updateMsg
   *
   * @private
   * @param {number} msgId The id of the DecryptMessage to update.
   * @param {string} status The new status of the DecryptMessage.
   * @throws A 'DecryptMessageManager - DecryptMessage not found for id: "${msgId}".' if there is no DecryptMessage
   * in this.messages with an id equal to the passed msgId
   * @fires An event with a name equal to `${msgId}:${status}`. The DecryptMessage is also fired.
   * @fires If status is 'rejected' or 'decrypted', an event with a name equal to `${msgId}:finished` is fired along
   * with the DecryptMessage
   *
   */
  _setMsgStatus (msgId, status) {
    const msg = this.getMsg(msgId)
    if (!msg) {
      throw new Error(`DecryptMessageManager - Message not found for id: "${msgId}".`)
    }
    msg.status = status
    this._updateMsg(msg)
    this.emit(`${msgId}:${status}`, msg)
    if (status === 'rejected' || status === 'decrypted' || status === 'errored') {
      this.emit(`${msgId}:finished`, msg)
    }
  }

  /**
   * Sets a DecryptMessage in this.messages to the passed DecryptMessage if the ids are equal. Then saves the
   * unapprovedDecryptMsgs index to storage via this._saveMsgList
   *
   * @private
   * @param {msg} DecryptMessage A DecryptMessage that will replace an existing DecryptMessage (with the same
   * id) in this.messages
   *
   */
  _updateMsg (msg) {
    const index = this.messages.findIndex((message) => message.id === msg.id)
    if (index !== -1) {
      this.messages[index] = msg
    }
    this._saveMsgList()
  }

  /**
   * Saves the unapproved DecryptMessages, and their count, to this.memStore
   *
   * @private
   * @fires 'updateBadge'
   *
   */
  _saveMsgList () {
    const unapprovedDecryptMsgs = this.getUnapprovedMsgs()
    const unapprovedDecryptMsgCount = Object.keys(unapprovedDecryptMsgs).length
    this.memStore.updateState({ unapprovedDecryptMsgs, unapprovedDecryptMsgCount })
    this.emit('updateBadge')
  }

  /**
   * A helper function that converts raw buffer data to a hex, or just returns the data if it is already formatted as a hex.
   *
   * @param {any} data The buffer data to convert to a hex
   * @returns {string} A hex string conversion of the buffer data
   *
   */
  normalizeMsgData (data) {
    try {
      const stripped = ethUtil.stripHexPrefix(data)
      if (stripped.match(hexRe)) {
        return ethUtil.addHexPrefix(stripped)
      }
    } catch (e) {
      log.debug(`Message was not hex encoded, interpreting as utf8.`)
    }

    return ethUtil.bufferToHex(Buffer.from(data, 'utf8'))
  }

}