const EventEmitter = require('events').EventEmitter
const Wallet = require('ethereumjs-wallet')
const ethUtil = require('ethereumjs-util')
const type = 'Simple Key Pair'
const sigUtil = require('../lib/sig-util')

class SimpleKeyring extends EventEmitter {

  /* PUBLIC METHODS */

  constructor (opts) {
    super()
    this.type = type
    this.opts = opts || {}
    this.wallets = []
  }

  serialize () {
    return Promise.resolve(this.wallets.map(w => w.getPrivateKey().toString('hex')))
  }

  deserialize (privateKeys = []) {
    return new Promise((resolve, reject) => {
      try {
        this.wallets = privateKeys.map((privateKey) => {
          const stripped = ethUtil.stripHexPrefix(privateKey)
          const buffer = new Buffer(stripped, 'hex')
          const wallet = Wallet.fromPrivateKey(buffer)
          return wallet
        })
      } catch (e) {
        reject(e)
      }
      resolve()
    })
  }

  addAccounts (n = 1) {
    var newWallets = []
    for (var i = 0; i < n; i++) {
      newWallets.push(Wallet.generate())
    }
    this.wallets = this.wallets.concat(newWallets)
    const hexWallets = newWallets.map(w => ethUtil.bufferToHex(w.getAddress()))
    return Promise.resolve(hexWallets)
  }

  getAccounts () {
    return Promise.resolve(this.wallets.map(w => ethUtil.bufferToHex(w.getAddress())))
  }

  // tx is an instance of the ethereumjs-transaction class.
  signTransaction (address, tx) {
    const wallet = this._getWalletForAccount(address)
    var privKey = wallet.getPrivateKey()
    tx.sign(privKey)
    return Promise.resolve(tx)
  }

  // For eth_sign, we need to sign transactions:
  signMessage (withAccount, msgHex) {
    const wallet = this._getWalletForAccount(withAccount)
    const privKey = wallet.getPrivateKey()
    const msgBuffer = ethUtil.toBuffer(msgHex)
    const msgHash = ethUtil.hashPersonalMessage(msgBuffer)
    const msgSig = ethUtil.ecsign(msgHash, privKey)
    const rawMsgSig = ethUtil.bufferToHex(sigUtil.concatSig(msgSig.v, msgSig.r, msgSig.s))
    return Promise.resolve(rawMsgSig)
  }

  exportAccount (address) {
    const wallet = this._getWalletForAccount(address)
    return Promise.resolve(wallet.getPrivateKey().toString('hex'))
  }


  /* PRIVATE METHODS */

  _getWalletForAccount (account) {
    let wallet = this.wallets.find(w => ethUtil.bufferToHex(w.getAddress()) === account)
    if (!wallet) throw new Error('Simple Keyring - Unable to find matching address.')
    return wallet
  }

}

SimpleKeyring.type = type
module.exports = SimpleKeyring