How to use the @tradle/constants.PREV_HASH function in @tradle/constants

var test = require('tape')
var extend = require('xtend')
var leveldown = require('memdown')
var Q = require('q')
var collect = require('stream-collector')
var constants = require('@tradle/constants')
var Log = require('logbase').Log
var Entry = require('logbase').Entry
var fakeKeeper = require('@tradle/test-helpers').fakeKeeper
var createIdentityDB = require('../lib/identityDB')
var ted = require('./fixtures/ted-pub')
var EventType = require('../lib/eventType')
var utils = require('../lib/utils')
var TYPE = constants.TYPE
var ROOT_HASH = constants.ROOT_HASH
var PREV_HASH = constants.PREV_HASH
var CUR_HASH = constants.CUR_HASH
var IDENTITY_TYPE = constants.TYPES.IDENTITY
var dbCounter = 0
var nextDBName = function () {
  return 'db' + (dbCounter++)
}

test('ignore identities that collide on keys', function (t) {
  t.plan(ted.pubkeys.length)

  var log = new Log(nextDBName(), {
    db: leveldown
  })

  ted = extend(ted) // defensive copy
  var badPerson = extend(ted, { name: 'evil ted' })

var ted = Identity.fromJSON(tedPub)
var rufusPub = require('./fixtures/rufus-pub')
var rufusPriv = require('./fixtures/rufus-priv')
var rufus = Identity.fromJSON(rufusPub)
var constants = require('@tradle/constants')
// var testDrivers = require('./helpers/testDriver')
var BASE_PORT = 33333
var billPort = BASE_PORT++
var tedPort = BASE_PORT++
var rufusPort = BASE_PORT++
var bootstrapDHT
var BOOTSTRAP_DHT_PORT = BASE_PORT++
var TYPE = constants.TYPE
var ROOT_HASH = constants.ROOT_HASH
var CUR_HASH = constants.CUR_HASH
var PREV_HASH = constants.PREV_HASH
var NONCE = constants.NONCE
var SIG = constants.SIG
var STORAGE_DIR = path.resolve('./storage')
// var tedHash = tedPub[ROOT_HASH] = 'c67905793f6cc0f0ab8d20aecfec441932ffb13d'
// var billHash = billPub[ROOT_HASH] ='fb07729c0cef307ab7c28cb76088cc60dbc98cdd'
// var tedHash = 'c67905793f6cc0f0ab8d20aecfec441932ffb13d'
// var billHash = 'fb07729c0cef307ab7c28cb76088cc60dbc98cdd'
var help = require('@tradle/test-helpers')
// var fakeKeeper = help.fakeKeeper
var fakeWallet = help.fakeWallet
var FakeKeeper = help.fakeKeeper
// var bill = Identity.fromJSON(billPriv)
// var ted = Identity.fromJSON(tedPriv)
var NETWORK_NAME = 'testnet'
// var blockchain = new Fakechain({ networkName: NETWORK_NAME })
var Driver = require('../')

var Errors = require('./lib/errors')
var utils = require('./lib/utils')
var getViaCache = require('./lib/getViaCache')
var RETRY_UNCHAIN_ERRORS = [
  ChainLoader.Errors.ParticipantsNotFound,
  ChainLoader.Errors.FileNotFound
].map(function (ErrType) {
  return ErrType.type
})

var DEV = process.env.NODE_ENV !== 'production'
var TYPE = constants.TYPE
var TYPES = constants.TYPES
var SIGNEE = constants.SIGNEE
var ROOT_HASH = constants.ROOT_HASH
var PREV_HASH = constants.PREV_HASH
var CUR_HASH = constants.CUR_HASH
var NONCE = constants.NONCE
var CONFIRMATIONS_BEFORE_CONFIRMED = 10
Driver.BLOCKCHAIN_KEY_PURPOSE = 'messaging'
Driver.MIN_BALANCE = 10000
Driver.CHAIN_WRITE_THROTTLE = 60000
Driver.CHAIN_READ_THROTTLE = 300000
Driver.SEND_THROTTLE = 10000
Driver.CATCH_UP_INTERVAL = 2000
Driver.UNCHAIN_THROTTLE = 20000
// Driver.Zlorp = Zlorp
Driver.Kiki = kiki
Driver.Identity = Identity
Driver.Wallet = Wallet
Driver.EventType = EventType
Driver.PROTOCOL_VERSION = '1.0.0'

var extend = require('xtend')
var typeforce = require('typeforce')
var find = require('array-find')
var map = require('map-stream')
var constants = require('@tradle/constants')
var tutils = require('@tradle/utils')
var bitcoin = require('@tradle/bitcoinjs-lib')
var hrtime = require('monotonic-timestamp')
var Errors = require('./errors')
var Builder = require('@tradle/chained-obj').Builder
var Entry = require('logbase').Entry
var debug = require('debug')('tim-utils')
var NONCE = constants.NONCE
var CUR_HASH = constants.CUR_HASH
var ROOT_HASH = constants.ROOT_HASH
var PREV_HASH = constants.PREV_HASH
var TxData = require('@tradle/tx-data').TxData
var Entry = require('logbase').Entry
var MAX_ERRORS = 10

var PRIVATE_MSG_SCHEMA = {
  txType: 'Number',
  encryptedPermission: 'Buffer',
  encryptedData: 'Buffer',
  // txData: '?Buffer',
  v: '?String'
}

var PUBLIC_MSG_SCHEMA = {
  txType: 'Number',
  data: 'Buffer',
  // txData: '?Buffer',

var constants = require('@tradle/constants');
var EventType = require('./eventType');
var Dir = require('./dir');
var createIdentityDB = require('./identityDB');
var createMsgDB = require('./msgDB');
var createTxDB = require('./txDB');
var Errors = require('./errors');
var utils = require('./utils');
var RETRY_UNCHAIN_ERRORS = [ChainLoader.Errors.ParticipantsNotFound, ChainLoader.Errors.FileNotFound].map(function (ErrType) {
  return ErrType.type;
});

var TYPE = constants.TYPE;
var SIGNEE = constants.SIGNEE;
var ROOT_HASH = constants.ROOT_HASH;
var PREV_HASH = constants.PREV_HASH;
var CUR_HASH = constants.CUR_HASH;
var PREFIX = constants.OP_RETURN_PREFIX;
var NONCE = constants.NONCE;
var CONFIRMATIONS_BEFORE_CONFIRMED = 10;
var KEY_PURPOSE = 'messaging';
Driver.MIN_BALANCE = 10000;
Driver.CHAIN_WRITE_THROTTLE = 60000;
Driver.CHAIN_READ_THROTTLE = 60000;
Driver.SEND_THROTTLE = 10000;
Driver.CATCH_UP_INTERVAL = 2000;
Driver.Zlorp = Zlorp;
Driver.Kiki = kiki;
Driver.Identity = Identity;
Driver.Wallet = Wallet;
Driver.Messengers = Messengers;
Driver.EventType = EventType;

var createIdentityDB = require('./identityDB')
var createMsgDB = require('./msgDB')
var createTxDB = require('./txDB')
var Errors = require('./errors')
var utils = require('./utils')
var RETRY_UNCHAIN_ERRORS = [
  ChainLoader.Errors.ParticipantsNotFound,
  ChainLoader.Errors.FileNotFound
].map(function (ErrType) {
  return ErrType.type
})

var TYPE = constants.TYPE
var SIGNEE = constants.SIGNEE
var ROOT_HASH = constants.ROOT_HASH
var PREV_HASH = constants.PREV_HASH
var CUR_HASH = constants.CUR_HASH
var PREFIX = constants.OP_RETURN_PREFIX
var NONCE = constants.NONCE
var CONFIRMATIONS_BEFORE_CONFIRMED = 10
var KEY_PURPOSE = 'messaging'
Driver.MIN_BALANCE = 10000
Driver.CHAIN_WRITE_THROTTLE = 60000
Driver.CHAIN_READ_THROTTLE = 60000
Driver.SEND_THROTTLE = 10000
Driver.CATCH_UP_INTERVAL = 2000
Driver.Zlorp = Zlorp
Driver.Kiki = kiki
Driver.Identity = Identity
Driver.Wallet = Wallet
Driver.Messengers = Messengers
Driver.EventType = EventType