Look back when importing postmix like-type change addresses

lib/bitcoin/hd-accounts-service.js

@@ -4,7 +4,7 @@
  */
 'use strict'
 
-const _ = require('lodash')
+const util = require('../util')
 const errors = require('../errors')
 const Logger = require('../logger')
 const db = require('../db/mysql-db-wrapper')
@@ -141,10 +141,10 @@ class HDAccountsService {
 
     Logger.info(`HdAccountsService : Created HD Account: ${xpub}${segwit}`)
 
-    const externalPrm = hdaHelper.deriveAddresses(xpub, 0, _.range(gap.external), scheme)
-    const internalPrm = hdaHelper.deriveAddresses(xpub, 1, _.range(gap.internal), scheme)
+    const externalPrm = hdaHelper.deriveAddresses(xpub, 0, util.range(0, gap.external), scheme)
+    const internalPrm = hdaHelper.deriveAddresses(xpub, 1, util.range(0, gap.internal), scheme)
 
-    const addresses = _.flatten(await Promise.all([externalPrm, internalPrm]))
+    const addresses = (await Promise.all([externalPrm, internalPrm])).flat()
 
     return db.addAddressesToHDAccount(xpub, addresses)
   }
@@ -269,7 +269,7 @@ class HDAccountsService {
     const postmixNode = hdaHelper.getNode(postmixAcct)
     const [externalUnused, internalUnused] = await db.getHDAccountNextUnusedIndices(postmixAcct)
 
-    const deriveRange = Array.from({ length: gap.internal }, (_, i) => i + internalUnused)
+    const deriveRange = util.range(Math.max(0, internalUnused - 50), internalUnused + gap.internal)
 
     const likeTypeChangeAddresses = await Promise.all(deriveRange.map((index) => {
       return [