Akka-CQRS（7）- CQRS Reader Actor 示范

我们在这篇通过一个具体CQRS-Reader-Actor的例子来示范akka-persistence的query端编程和应用。在前面的博客里我们设计了一个CQRS模式POS机程序的操作动作录入过程，并示范了如何实现CQRS的写端编程。现在我们可以根据这个例子来示范如何通过CQRS的读端reader-actor读取由writer-actor所写入的操作事件并将二进制格式的事件恢复成数据库表的行数据。

首先看看reader是如何从cassandra数据库里按顺序读出写入事件的：cassandra-plugin提供了currentEventsByPersistenceId函数，使用方法如下：

  // obtain read journal by plugin id
  val readJournal =
    PersistenceQuery(system).readJournalFor[CassandraReadJournal](CassandraReadJournal.Identifier)

  // issue query to journal
  val source: Source[EventEnvelope, NotUsed] =
    readJournal.currentEventsByPersistenceId("2022", 0, Long.MaxValue)

这个函数返回一个akka-stream的Source[EventEnvelope,_]类型，一个静态Source。还有另外一个eventsByPersistenceId函数可以返回实时动态的akka-stream Source。我们可以runFold一个静态的Source对流元素进行汇总形成一个集合：

  // materialize stream, consuming events
  val futureActions: Future[List[Any]]  = source.runFold(List[Any]()) { (lstAny, evl) => evl.event :: lstAny }

我们可以通过模式匹配pattern-matching把List元素分辨出来：

  implicit val system = ActorSystem("reader")
  implicit val ec = system.dispatcher
  implicit val mat = ActorMaterializer()

  futureActions.onComplete {
      case Success(acts) => acts.reverse.foreach {act => act match {
        case LogOned(txn) => println(s"LogOn: $txn" )
        case SalesLogged(txn) => println(s"LogSales: $txn")
        case _ => println("unkown action !!!!!")
      }}
      case Failure(exception) => println(exception.getMessage)
  }

试着运行一下得到下面的输出：

LogOn: TxnItem(20190509,16:12:23,1001,0,1,6,8,1,0,0,0,,1001,,,,,,,)
LogSales: TxnItem(20190509,16:12:34,1001,0,2,0,0,0,1300,0,0,,005,hainan pineapple,02,Grocery,01,,01,Sunkist)
LogSales: TxnItem(20190509,16:12:35,1001,0,3,0,0,0,300,0,0,,004,demon banana,02,Grocery,01,,01,Sunkist)
LogSales: TxnItem(20190509,16:12:36,1001,0,4,0,0,0,1050,0,0,,002,red grape,02,Grocery,01,,01,Sunkist)
unkown action !!!!!
unkown action !!!!!

如此已经可以将写操作中存入的事件恢复成为Action类结构了。

好了，现在我们稍微认真点做个详细的reader示范。回到我们的POS例子：如果我们调用以下写端指令：

        posref ! POSMessage(1022, LogOn("1001", "123"))
        scala.io.StdIn.readLine()

        posref ! POSMessage(1022, LogSales("0", "0", apple.code, 1,820))
        scala.io.StdIn.readLine()

        posref ! POSMessage(1022, LogSales("0", "0", pineapple.code, 2, 1300))
        scala.io.StdIn.readLine()

        posref ! POSMessage(1022, Subtotal(0))
        scala.io.StdIn.readLine()

        posref ! POSMessage(1022, Discount(DISCTYPE.duplicated,false,"001",5))
        scala.io.StdIn.readLine()

        posref ! POSMessage(1022, LogSales("0", "0", banana.code, 1, 300))
        scala.io.StdIn.readLine()

        posref ! POSMessage(1022, LogSales("0", "0", grape.code, 3, 1050))
        scala.io.StdIn.readLine()

        posref ! POSMessage(1022, Subtotal(1))
        scala.io.StdIn.readLine()

        posref ! POSMessage(1022, Discount(DISCTYPE.duplicated,true,"001",10))
        scala.io.StdIn.readLine()

        posref ! POSMessage(1022, LogSales("0", "0", orage.code, 10, 350))
        scala.io.StdIn.readLine()

        posref ! POSMessage(1022, Discount(DISCTYPE.duplicated,false,"001",10))
        scala.io.StdIn.readLine()

        posref ! POSMessage(1022, Subtotal(0))
        scala.io.StdIn.readLine()

        posref ! POSMessage(1022, Suspend)
        scala.io.StdIn.readLine()

前面的博文里一再强调：CQRS的写端应简单直接地将指令存写入数据库，避免任何复杂的控制程序，尽量在读端读出指令、模拟处理过程中的状态转变处理，还原指令预期应产生的结果，在这个示范里就是正式的交易数据了。实际上我们在写端已经做了些状态转变处理过程：就在updataState函数里：

 def updateState(evt: Action, lastSeqNr: BigInt = 0)(implicit nodeAddress: NodeAddress, persistenceId: PID, state: VchStates, items: VchItems, curItem: TxnItem): (VchStates, VchItems) = {
    val (vs, vi) = updateStateImpl(evt, lastSeqNr)
    log.step(s"${nodeAddress.address}-${persistenceId.id} run updateState($evt, $lastSeqNr) with results state[$vs], txns[$vi].")
    (vs, vi)
  }

  def updateStateImpl(evt: Action, lastSeqNr: BigInt = 0)(implicit state: VchStates, items: VchItems, curItem: TxnItem): (VchStates, VchItems) = evt match {
    case LogOned(csr) => (state.copy(seq = state.seq + 1, opr = csr, jseq = lastSeqNr), items)
    case LogOffed => (state.copy(seq = state.seq + 1, opr = ""), items)
    case RefundOned => (state.copy(seq = state.seq + 1, refd = true), items)
    case RefundOffed => (state.copy(seq = state.seq + 1, refd = false), items)
    case VoidOned => (state.copy(seq = state.seq + 1, void = true), items)
    case VoidOffed => (state.copy(seq = state.seq + 1, void = false), items)
    case SuperOned(suser) => (state.copy(seq = state.seq + 1, su = suser), items)
    case SuperOffed => (state.copy(seq = state.seq + 1, su = ""), items)
    case MemberOned(num) => (state.copy(seq = state.seq + 1, mbr = num), items)
    case MemberOffed => (state.copy(seq = state.seq + 1, mbr = ""), items)

    case SalesLogged(_,_,_,_,_) => (state.copy(
      seq = state.seq + 1)
      , items.addItem(curItem))

    case Subtotaled(_) => (state.copy(
      seq = state.seq + 1)
      , items.addItem(curItem))

    case Discounted(_,_,_,_) => (state.copy(
      seq = state.seq + 1)
      , items.addItem(curItem))

    case PaymentMade(_,_,_) =>
      val due = if (items.totalSales > 0) items.totalSales - items.totalPaid else items.totalSales + items.totalPaid
      val bal = if (items.totalSales > 0) due - curItem.amount else due + curItem.amount
      (state.copy(
        seq = state.seq + 1,
        due = (if ((curItem.amount.abs + items.totalPaid.abs) >= items.totalSales.abs) false else true)
      )
        ,items.addItem(curItem.copy(
        salestype = SALESTYPE.ttl,
        price = due,
        amount = curItem.amount,
        dscamt = bal
      )))

    case VoucherNumed(_, tnum) =>
      val vi = items.copy(txnitems = items.txnitems.map { it => it.copy(num = tnum) })
      (state.copy(seq = state.seq + 1, num = tnum), vi)

    case EndVoucher(vnum) => (state.nextVoucher.copy(jseq = lastSeqNr + 1), VchItems())

    case _ => (state, items)
  }

在写端的这个模拟处理结果是为了实时向客户端反馈它发出指令后产生的结果，如：

  case cmd @ LogSales(acct,sdpt,scode,sqty,sprice) if cmdFilter(cmd,sender()) => {
      log.step(s"${nodeAddress.address}-${persistenceId} running LogSales($acct,$sdpt,$scode,$sqty,$sprice) with state[$vchState],txns[$vchItems] ...")
      var pqty = sqty
      if (vchState.void || vchState.refd) pqty = -sqty
      log.step(s"${nodeAddress.address}-${persistenceId} run LogSales($acct,$sdpt,$scode,$sqty,$sprice).")
      persistEvent(SalesLogged(acct,sdpt,scode,sqty,sprice)) { evt =>
        curTxnItem = buildTxnItem(evt).copy(
          qty =pqty,
          amount = pqty * sprice
        )
        val sts = updateState(evt)
        vchState = sts._1
        vchItems = sts._2
        if (vchState.void) {
          val (lstTxns, found) = vchItems.txnitems.foldLeft((List[TxnItem](), false)) { case (b, ti) =>
            if (b._2)
              (ti :: b._1, true)
            else if (ti.txntype == TXNTYPE.sales && ti.salestype == SALESTYPE.itm && ti.acct == acct &&
              ti.dpt == sdpt && ti.code == scode && ti.qty == sqty && ti.price == sprice)
              (ti.copy(txntype = TXNTYPE.voided) :: b._1, true)
            else (ti :: b._1, false)

          }
          vchItems = vchItems.copy(txnitems = lstTxns.reverse)
          sender() ! POSResponse(STATUS.OK, s"终端-$persistenceId： 成功冲销商品销售。", vchState, List(vchItems.topTxnItem))
        } else {
          sender() ! POSResponse(STATUS.OK, s"终端-$persistenceId： 商品销售操作成功。", vchState, List(vchItems.topTxnItem))
        }

      }
    }

上面这个POSResponse类实时把当前交易状态返回给客户端。而这个vchItems.topTxnItem正是一条正式的交易记录，也就是我们需要在读端还原的数据。所以，这个updateState在读端还是需要调用的。先看看整体reader示范的程序结构：

object ReaderDemo extends App {

  implicit val system = ActorSystem("reader")
  implicit val ec = system.dispatcher
  implicit val mat = ActorMaterializer()

  val cluster = Cluster(system)
  implicit val nodeAddress: NodeAddress = NodeAddress(cluster.selfAddress.toString)

  States.setShowSteps(true)

  Reader.readActions(0, Long.MaxValue,"1022")

  scala.io.StdIn.readLine()

  mat.shutdown()
  system.terminate()
}

object Reader extends LogSupport {

  def readActions(startSeq: Long, endSeq: Long, persistenceId: String)(implicit sys: ActorSystem, ec: ExecutionContextExecutor, mat: ActorMaterializer, nodeAddress: NodeAddress) = {
    implicit var vchState = VchStates()
    implicit var vchItems = VchItems()
    implicit var curTxnItem = TxnItem()
    implicit val pid = PID(persistenceId)
    // obtain read journal by plugin id
    val readJournal =
      PersistenceQuery(sys).readJournalFor[CassandraReadJournal](CassandraReadJournal.Identifier)

    // issue query to journal
    val source: Source[EventEnvelope, NotUsed] =
      readJournal.currentEventsByPersistenceId(persistenceId, startSeq, endSeq)

    // materialize stream, consuming events
    val futureActions: Future[List[Any]] = source.runFold(List[Any]()) { (lstAny, evl) => evl.event :: lstAny }

    futureActions.onComplete {
      case Success(txns) =>
        buildVoucher(txns)
//vchItems.txnitems里就是恢复的正式交易记录。可以在这里把它们写入到业务数据库
        println(vchItems.txnitems.reverse)
      case Failure(excpt) =>
    }

    def buildVoucher(actions: List[Any])= {

      actions.reverse.foreach { txn =>
        txn match {
          case EndVoucher(_) =>
            vchItems.txnitems.foreach(println)
          case ti@_ =>
            curTxnItem = buildTxnItem(ti.asInstanceOf[Action])
            val sts = updateState(ti.asInstanceOf[Action],0)
            vchState = sts._1
            vchItems = sts._2
        }
      }
    }
  }

}

顺便提一下：这个updateState函数的其中一个主要功能是对集合vchItems.txnitems内的txnitem元素进行更改处理，但我们使用的是函数式编程模式的不可变集合（immutable collections），每次都需要对集合进行遍历，如fold：

    def subTotal: (Int, Int, Int, Int) = txnitems.foldRight((0, 0, 0, 0)) { case (txn, b) =>
      if (txn.salestype == SALESTYPE.itm && txn.txntype == TXNTYPE.sales)
        b.copy(_1 = b._1 + 1, _2 = b._2 + txn.qty, _3 = b._3 + txn.amount, _4 = b._4 + txn.dscamt)
      else b
    }

突然想到如果在一个很大的集合中只需要更新前面几条数据怎么办？难道还是需要traverse所有元素吗？在我们的例子里还真有这么样的需求：

    def groupTotal(level:Int): (Int, Int, Int, Int) = {
      val gts = txnitems.foldLeftWhile((0, 0, 0, 0, 0)) { case (b,txn) =>
        if (txn.salestype == SALESTYPE.itm && txn.txntype == TXNTYPE.sales)
          ((b._1._1 +1,b._1._2 + txn.qty, b._1._3 + txn.amount, b._1._4 + txn.dscamt, b._1._5),false)
        else {
          if (txn.salestype == SALESTYPE.sub) {
            if (((b._1._5) + 1) >= level)
              ((b._1._1, b._1._2, b._1._3, b._1._4, b._1._5 + 1), true)
            else
              ((b._1._1, b._1._2, b._1._3, b._1._4, b._1._5 + 1), false)
          } else b
        }
      }
      (gts._1,gts._2,gts._3,gts._4)
    }

这是一个分层小记函数：在遍历指令集时遇到另一条小记指令就终止小记运算，调用了foldLeftWhile函数来实现这样的场景。foldLeftWhile是一个定制的函数：

  implicit class FoldLeftWhile[A](trav: Seq[A]) {
    def foldLeftWhile[B](z: B)(op: ((B,Boolean), A) => (B, Boolean)): B = {
      def go(acc: (B, Boolean), l: Seq[A]): (B, Boolean) = l match {
        case h +: t =>
          val nacc = op(acc, h)
          if (!nacc._2)
            go(nacc, t)
          else
            nacc
        case _ => acc
      }
      go((z, false), trav)._1
    }
  }

下面附上本次示范中的源代码

build.sbt

name := "akka-cluster-reader"

version := "0.1"

scalaVersion := "2.12.8"

libraryDependencies := Seq(
  "com.typesafe.akka" %% "akka-cluster-sharding" % "2.5.19",
  "com.typesafe.akka" %% "akka-persistence" % "2.5.19",
  "com.typesafe.akka" %% "akka-persistence-query" % "2.5.19",
  "com.typesafe.akka" %% "akka-persistence-cassandra" % "0.93",
  "com.typesafe.akka" %% "akka-persistence-cassandra-launcher" % "0.93" % Test,
  "ch.qos.logback"  %  "logback-classic"   % "1.2.3"
)

resources/application.conf

akka.actor.warn-about-java-serializer-usage = off
akka.log-dead-letters-during-shutdown = off
akka.log-dead-letters = off
akka.remote.use-passive-connections=off

akka {
  loglevel = INFO
  actor {
    provider = "cluster"
  }

  remote {
    log-remote-lifecycle-events = on
    netty.tcp {
      hostname = "192.168.11.189"
      port = 2551
    }
  }

  cluster {
    seed-nodes = [
      "akka.tcp://reader@192.168.11.189:2551"]

    log-info = off
    sharding {
      role = "shard"
      passivate-idle-entity-after = 10 m
    }
  }

  persistence {
    journal.plugin = "cassandra-journal"
    snapshot-store.plugin = "cassandra-snapshot-store"
  }

}

cassandra-journal {
  contact-points = ["192.168.11.189"]
}

cassandra-snapshot-store {
  contact-points = ["192.168.11.189"]
}

message/Messages.scala

package datatech.cloud.pos

import java.time.LocalDate
import java.time.LocalDateTime
import java.time.format.DateTimeFormatter
import java.util.Locale
import akka.cluster.sharding._

object Messages {

  val  dateTimeFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss", Locale.CHINA)

  sealed trait Command {}

  case class LogOn(opr: String, passwd: String) extends Command
  case object LogOff extends Command
  case class SuperOn(su: String, passwd: String) extends Command
  case object SuperOff extends Command
  case class MemberOn(cardnum: String, passwd: String) extends Command
  case object MemberOff extends Command   //remove member status for the voucher
  case object RefundOn extends Command
  case object RefundOff extends Command
  case object VoidOn extends Command
  case object VoidOff extends Command
  case object VoidAll extends Command
  case object Suspend extends Command

  case class VoucherNum(vnum: Int) extends Command

  case class LogSales(acct: String, dpt: String, code: String, qty: Int, price: Int) extends Command
  case class Subtotal(level: Int) extends Command
  case class Discount(disctype: Int, grouped: Boolean, code: String, percent: Int) extends Command

  case class Payment(acct: String, num: String, amount: Int) extends Command          //settlement   结算支付

  // read only command, no update event
  case class Plu(itemCode: String) extends Command  //read only
  case object GetTxnItems extends Command

  /* discount type */
  object DISCTYPE  {
    val duplicated: Int = 0
    val best: Int = 1
    val least: Int = 2
    val keep: Int = 3
  }

  /* result message returned to client on the wire */
  object TXNTYPE {
    val sales: Int = 0
    val refund: Int = 1
    val void: Int = 2
    val voided: Int = 3
    val voidall: Int = 4
    val subtotal: Int = 5
    val logon: Int = 6
    val supon: Int = 7       // super user on/off
    val suspend: Int = 8

  }

  object SALESTYPE {
    val itm: Int = 2
    val sub: Int = 10
    val ttl: Int = 11
    val dsc: Int = 12
    val crd: Int = 13
  }

  case class TxnItem(
                      txndate: String = LocalDate.now.format(DateTimeFormatter.ofPattern("yyyyMMdd"))
                      ,txntime: String = LocalDateTime.now.format(dateTimeFormatter).substring(11)
                      ,opr: String = ""//工号
                      ,num: Int = 0 //销售单号
                      ,seq: Int = 1 //交易序号
                      ,txntype: Int = TXNTYPE.sales//交易类型
                      ,salestype: Int = SALESTYPE.itm //销售类型
                      ,qty: Int =  1 //交易数量
                      ,price: Int = 0 //单价（分）
                      ,amount: Int = 0 //码洋（分）
                      ,disc: Int = 0   //折扣率 (%)
                      ,dscamt: Int = 0 //折扣额：负值  net实洋 = amount + dscamt
                      ,member: String = "" //会员卡号
                      ,code: String = "" //编号（商品、卡号...）
                      ,acct: String = "" //账号
                      ,dpt: String = "" //部类
                    )
  object TxnItem {
    def apply(vs: VchStates): TxnItem = TxnItem().copy(
      opr = vs.opr,
      num = vs.num,
      seq = vs.seq,
      member = vs.mbr
    )
  }

  case class VchStatus( //操作状态锁留给前端维护
                        qty: Int = 1,
                        refund: Boolean = false,
                        void: Boolean = false)

  case class VchStates(
                        opr: String = "",      //收款员
                        jseq: BigInt = 0,      //begin journal sequence for read-side replay
                        num: Int = 0,          //当前单号
                        seq: Int = 0,          //当前序号
                        void: Boolean = false, //取消模式
                        refd: Boolean = false, //退款模式
                        due: Boolean = true,   //当前余额
                        su: String = "",
                        mbr: String = ""
                      ) {

    def nextVoucher : VchStates = VchStates().copy(
      opr = this.opr,
      jseq = this.jseq + 1,
      num = this.num + 1
    )
  }

  object STATUS {
    val OK: Int = 0
    val FAIL: Int = -1
  }

  case class POSResponse (sts: Int, msg: String, voucher: VchStates, txnItems: List[TxnItem])

  /* message on the wire (exchanged message) */
  val shardName = "POSShard"

  case class POSMessage(id: Long, cmd: Command) {
    def shopId = id.toString.head.toString
    def posId = id.toString
  }

  val getPOSId: ShardRegion.ExtractEntityId =  {
    case posCommand: POSMessage => (posCommand.posId,posCommand.cmd)
  }
  val getShopId: ShardRegion.ExtractShardId = {
    case posCommand: POSMessage => posCommand.shopId
  }

  case object PassivatePOS    //passivate message
  case object FilteredOut
  case class DebugMode(debug: Boolean)
  case class NodeAddress(address: String)
  case class PID(id: String)

}

States.scala

package datatech.cloud.pos
import java.time.LocalDate
import java.time.LocalDateTime
import java.time.format.DateTimeFormatter

import Messages._
import sdp.logging._

object Actions {

  implicit class FoldLeftWhile[A](trav: Seq[A]) {
    def foldLeftWhile[B](z: B)(op: ((B,Boolean), A) => (B, Boolean)): B = {
      def go(acc: (B, Boolean), l: Seq[A]): (B, Boolean) = l match {
        case h +: t =>
          val nacc = op(acc, h)
          if (!nacc._2)
            go(nacc, t)
          else
            nacc
        case _ => acc
      }
      go((z, false), trav)._1
    }
  }

  case class ReadActions(startSeq: Int, endSeq: Int, persistenceId: String)

  sealed trait Action {}
  case class LogOned(opr: String) extends Action
  case object LogOffed extends Action
  case class SuperOned(su: String) extends Action
  case object SuperOffed extends Action
  case class MemberOned(cardnum: String) extends Action
  case object MemberOffed extends Action   //remove member status for the voucher
  case object RefundOned extends Action
  case object RefundOffed extends Action
  case object VoidOned extends Action
  case object VoidOffed extends Action

  case class SalesLogged(acct: String, dpt: String, code: String, qty: Int, price: Int) extends Action
  case class Subtotaled(level: Int) extends Action
  case class Discounted(disctype: Int, grouped: Boolean, code: String, percent: Int) extends Action

  case class NewVoucher(vnum: Int) extends Action //新单, reminder for read-side to set new vnum
  case class EndVoucher(vnum: Int) extends Action //单据终结标示
  case object VoidVoucher extends Action

  case object SuspVoucher extends Action

  case class VoucherNumed(fnum: Int, tnum: Int) extends Action

  case class PaymentMade(acct: String, num: String, amount: Int) extends Action          //settlement   结算支付

}

object States extends LogSupport {
  import Actions._

  def setShowSteps(b: Boolean) = log.stepOn = b

  def buildTxnItem(evt: Action)(implicit vs: VchStates, vi: VchItems): TxnItem = evt match {
    case LogOned(op) => TxnItem(vs).copy(
      txntype = TXNTYPE.logon,
      salestype = SALESTYPE.crd,
      opr = op,
      code = op
    )
    case LogOffed => TxnItem(vs).copy(
      txntype = TXNTYPE.logon,
      salestype = SALESTYPE.crd
    )
    case SuperOned(su) => TxnItem(vs).copy(
      txntype = TXNTYPE.supon,
      salestype = SALESTYPE.crd,
      code = su
    )
    case SuperOffed => TxnItem(vs).copy(
      txntype = TXNTYPE.supon,
      salestype = SALESTYPE.crd
    )
    case MemberOned(cardnum) => TxnItem(vs).copy(
      txntype = TXNTYPE.sales,
      salestype = SALESTYPE.crd,
      member = cardnum
    )
    case MemberOffed => TxnItem(vs).copy(
      txntype = TXNTYPE.sales,
      salestype = SALESTYPE.crd
    )
    case RefundOned => TxnItem(vs).copy(
      txntype = TXNTYPE.refund
    )
    case RefundOffed => TxnItem(vs).copy(
      txntype = TXNTYPE.refund
    )
    case VoidOned => TxnItem(vs).copy(
      txntype = TXNTYPE.void
    )
    case VoidOffed => TxnItem(vs).copy(
      txntype = TXNTYPE.void
    )
    case VoidVoucher => TxnItem(vs).copy(
      txntype = TXNTYPE.voidall,
      code = vs.num.toString,
      acct = vs.num.toString
    )
    case SuspVoucher => TxnItem(vs).copy(
      txntype = TXNTYPE.suspend,
      code = vs.num.toString,
      acct = vs.num.toString
    )
    case Subtotaled(level) =>
      TxnItem(vs).copy(
        txntype = TXNTYPE.sales,
        salestype = SALESTYPE.sub
      )
    case Discounted(dt,gp,code,pct) => TxnItem(vs).copy(
      txntype = TXNTYPE.sales,
      salestype = SALESTYPE.dsc,
      acct = code,
      disc = pct
    )
    case PaymentMade(act,num,amt) => TxnItem(vs).copy(
      txntype = TXNTYPE.sales,
      salestype = SALESTYPE.ttl,
      acct = act,
      code = num,
      amount = amt
    )

    case SalesLogged(sacct,sdpt,scode,sqty,sprice)  => TxnItem(vs).copy(
      txntype = TXNTYPE.sales,
      salestype = SALESTYPE.itm,
      acct = sacct,
      dpt = sdpt,
      code = scode,
      qty = sqty,
      price = sprice,
      amount = sprice * sqty,
      dscamt = 0
    )
    case _ => TxnItem(vs)
  }

  case class VchItems(txnitems: List[TxnItem] = Nil) {

    def noSales: Boolean = (txnitems.find(txn => txn.salestype == SALESTYPE.itm)).isEmpty

    def subTotal: (Int, Int, Int, Int) = txnitems.foldRight((0, 0, 0, 0)) { case (txn, b) =>
      if (txn.salestype == SALESTYPE.itm && txn.txntype == TXNTYPE.sales)
        b.copy(_1 = b._1 + 1, _2 = b._2 + txn.qty, _3 = b._3 + txn.amount, _4 = b._4 + txn.dscamt)
      else b
    }

    def groupTotal(level:Int): (Int, Int, Int, Int) = {
      val gts = txnitems.foldLeftWhile((0, 0, 0, 0, 0)) { case (b,txn) =>
        if (txn.salestype == SALESTYPE.itm && txn.txntype == TXNTYPE.sales)
          ((b._1._1 +1,b._1._2 + txn.qty, b._1._3 + txn.amount, b._1._4 + txn.dscamt, b._1._5),false)
        else {
          if (txn.salestype == SALESTYPE.sub) {
            if (((b._1._5) + 1) >= level)
              ((b._1._1, b._1._2, b._1._3, b._1._4, b._1._5 + 1), true)
            else
              ((b._1._1, b._1._2, b._1._3, b._1._4, b._1._5 + 1), false)
          } else b
        }
      }
      (gts._1,gts._2,gts._3,gts._4)
    }

    def updateDisc(dt: Int, grouped: Boolean, disc: Int): (List[TxnItem],(Int,Int,Int,Int)) = {
      //(salestype,（cnt,qty,amt,dsc),hassub,list）
      val accu = txnitems.foldLeft((-1, (0,0,0,0), false, List[TxnItem]())) { case (b, txn) =>
        var discAmt = 0
        if ((b._1) < 0) {
          if (txn.salestype == SALESTYPE.itm && txn.txntype == TXNTYPE.sales) {
            if (txn.dscamt == 0)
              ((txn.salestype, (
                (b._2._1) + 1,
                (b._2._2) + txn.qty,
                (b._2._3) + txn.amount,
                (b._2._4) - (txn.amount * disc / 100)
                ), false, txn.copy(
                dscamt = - (txn.amount * disc / 100)) :: (b._4)))
            else {
              dt match {
                case DISCTYPE.duplicated =>
                  if (txn.dscamt != 0) {
                    ((txn.salestype, (
                      (b._2._1) + 1,
                      (b._2._2) + txn.qty,
                      (b._2._3) + txn.amount,
                      (b._2._4) - (txn.amount + txn.dscamt) * disc / 100
                      ), false, txn.copy(
                      dscamt = -(txn.amount + txn.dscamt) * disc / 100) :: (b._4)
                    ))
                  } else {
                    ((txn.salestype, (
                      (b._2._1) + 1,
                      (b._2._2) + txn.qty,
                      (b._2._3) + txn.amount,
                      (b._2._4) - txn.amount * disc / 100
                      ), false, txn.copy(
                      dscamt = -txn.amount * disc / 100) :: (b._4)
                    ))
                  }
                case DISCTYPE.keep => ((txn.salestype, (
                  (b._2._1) + 1,
                  (b._2._2) + txn.qty,
                  (b._2._3) + txn.amount,
                  (b._2._4) + txn.dscamt), false, txn :: (b._4)))
                case DISCTYPE.best =>
                  discAmt = -(txn.amount * disc / 100)
                  if (discAmt < txn.dscamt)
                    ((txn.salestype, (
                      (b._2._1) + 1,
                      (b._2._2) + txn.qty,
                      (b._2._3) + txn.amount,
                      (b._2._4) + discAmt), false, txn.copy(
                      dscamt = discAmt
                    ) :: (b._4)))
                  else
                    ((txn.salestype, (
                      (b._2._1) + 1,
                      (b._2._2) + txn.qty,
                      (b._2._3) + txn.amount,
                      (b._2._4) + txn.dscamt), false, txn :: (b._4)))
              }
            }

          } else ((b._1,b._2,b._3,txn :: (b._4)))
        } else {
          if ((b._3))
            (((b._1), (b._2), true, txn :: (b._4)))
          else {
            if (txn.salestype == SALESTYPE.sub) {
              if (grouped)
                (((b._1), (b._2), true, txn :: (b._4)))
              else
                (((b._1), (b._2), false, txn :: (b._4)))
            } else {
              if (txn.salestype == SALESTYPE.itm && txn.txntype == TXNTYPE.sales) {
                dt match {
                  case DISCTYPE.duplicated =>
                    if (txn.dscamt != 0) {
                      ((txn.salestype, (
                        (b._2._1) + 1,
                        (b._2._2) + txn.qty,
                        (b._2._3) + txn.amount,
                        (b._2._4) - (txn.amount + txn.dscamt) * disc / 100), false, txn.copy(
                        dscamt = -(txn.amount + txn.dscamt) * disc / 100) :: (b._4)
                      ))
                    } else {
                      ((txn.salestype, (
                        (b._2._1) + 1,
                        (b._2._2) + txn.qty,
                        (b._2._3) + txn.amount,
                        (b._2._4) - txn.amount * disc / 100), false, txn.copy(
                        dscamt = -(txn.amount * disc / 100)) :: (b._4)
                      ))
                    }
                  case DISCTYPE.keep => ((txn.salestype, (
                    (b._2._1) + 1,
                    (b._2._2) + txn.qty,
                    (b._2._3) + txn.amount,
                    (b._2._4) + txn.dscamt), false, txn :: (b._4)))
                  case DISCTYPE.best =>
                    discAmt = -(txn.amount * disc / 100)
                    if (discAmt < txn.dscamt)
                      ((txn.salestype, (
                        (b._2._1) + 1,
                        (b._2._2) + txn.qty,
                        (b._2._3) + txn.amount,
                        (b._2._4) + discAmt), false, txn.copy(
                        dscamt = discAmt
                      ) :: (b._4)))
                    else
                      ((txn.salestype, (
                        (b._2._1) + 1,
                        (b._2._2) + txn.qty,
                        (b._2._3) + txn.amount,
                        (b._2._4) + txn.dscamt), false, txn :: (b._4)))
                }
              }
              else ((b._1, b._2, b._3, txn :: (b._4)))
            }
          }
        }

      }
      (accu._4.reverse,accu._2)
    }

    def totalSales: Int = txnitems.foldRight(0) { case (txn, b) =>
      if (txn.salestype == SALESTYPE.itm)
        (txn.amount + txn.dscamt) + b
      else b

      /*
            val amt: Int = txn.salestype match {
              case (SALESTYPE.plu | SALESTYPE.cat | SALESTYPE.brd | SALESTYPE.ra) => txn.amount + txn.dscamt
              case _ => 0
            }
            amt + b */
    }

    def totalPaid: Int = txnitems.foldRight(0) { case (txn, b) =>
      if (txn.txntype == TXNTYPE.sales && txn.salestype == SALESTYPE.ttl)
        txn.amount + b
      else b
    }

    def addItem(item: TxnItem): VchItems = VchItems((item :: txnitems)) //.reverse)

  }

  def LastSecOfDate(ldate: LocalDate): LocalDateTime = {
    val dtStr = ldate.format(DateTimeFormatter.ofPattern("yyyy-MM-dd")) + " 23:59:59"
    LocalDateTime.parse(dtStr, DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"))
  }

  def dateStr(dt: LocalDate): String = dt.format(DateTimeFormatter.ofPattern("yyyy-MM-dd"))

  def updateState(evt: Action, lastSeqNr: BigInt = 0)(implicit nodeAddress: NodeAddress, persistenceId: PID, state: VchStates, items: VchItems, curItem: TxnItem): (VchStates, VchItems) = {
    val (vs, vi) = updateStateImpl(evt, lastSeqNr)
    log.step(s"${nodeAddress.address}-${persistenceId.id} run updateState($evt, $lastSeqNr) with results state[$vs], txns[$vi].")
    (vs, vi)
  }

  def updateStateImpl(evt: Action, lastSeqNr: BigInt = 0)(implicit state: VchStates, items: VchItems, curItem: TxnItem): (VchStates, VchItems) = evt match {
    case LogOned(csr) => (state.copy(seq = state.seq + 1, opr = csr, jseq = lastSeqNr), items)
    case LogOffed => (state.copy(seq = state.seq + 1, opr = ""), items)
    case RefundOned => (state.copy(seq = state.seq + 1, refd = true), items)
    case RefundOffed => (state.copy(seq = state.seq + 1, refd = false), items)
    case VoidOned => (state.copy(seq = state.seq + 1, void = true), items)
    case VoidOffed => (state.copy(seq = state.seq + 1, void = false), items)
    case SuperOned(suser) => (state.copy(seq = state.seq + 1, su = suser), items)
    case SuperOffed => (state.copy(seq = state.seq + 1, su = ""), items)
    case MemberOned(num) => (state.copy(seq = state.seq + 1, mbr = num), items)
    case MemberOffed => (state.copy(seq = state.seq + 1, mbr = ""), items)

    case SalesLogged(_,_,_,_,_) => (state.copy(
      seq = state.seq + 1)
      , items.addItem(curItem))

    case Subtotaled(level) =>
      var subs = (0,0,0,0)
      if (level == 0)
        subs = items.subTotal
      else
        subs = items.groupTotal(level)
      val (cnt, tqty, tamt, tdsc) = subs

      val subttlItem =
        TxnItem(state).copy(
          txntype = TXNTYPE.sales,
          salestype = SALESTYPE.sub,
          qty = tqty,
          amount = tamt,
          dscamt = tdsc,
          price = cnt
        )
      (state.copy(
      seq = state.seq + 1)
      , items.addItem(subttlItem))

    case Discounted(dt,gp,code,pct) =>
      val (lstItems, accum) = items.updateDisc(dt,gp,pct)
      val discItem = TxnItem(state).copy(
        txntype = TXNTYPE.sales,
        salestype = SALESTYPE.dsc,
        acct = code,
        disc = pct,
        price = accum._1,
        qty = accum._2,
        amount = accum._3,
        dscamt = accum._4
      )
      (state.copy(
      seq = state.seq + 1)
      , items.copy(txnitems = lstItems).addItem(discItem))

    case PaymentMade(_,_,_) =>
      val due = if (items.totalSales > 0) items.totalSales - items.totalPaid else items.totalSales + items.totalPaid
      val bal = if (items.totalSales > 0) due - curItem.amount else due + curItem.amount
      (state.copy(
        seq = state.seq + 1,
        due = (if ((curItem.amount.abs + items.totalPaid.abs) >= items.totalSales.abs) false else true)
      )
        ,items.addItem(curItem.copy(
        salestype = SALESTYPE.ttl,
        price = due,
        amount = curItem.amount,
        dscamt = bal
      )))

    case VoucherNumed(_, tnum) =>
      val vi = items.copy(txnitems = items.txnitems.map { it => it.copy(num = tnum) })
      (state.copy(seq = state.seq + 1, num = tnum), vi)

    case EndVoucher(vnum) => (state.nextVoucher.copy(jseq = lastSeqNr + 1), VchItems())

    case _ => (state, items)
  }

}

Reader.scala

package datatech.cloud.pos
import akka.actor._
import akka.stream.scaladsl._

import scala.util._
import akka._
import akka.persistence.query._
import akka.persistence.cassandra.query.scaladsl.CassandraReadJournal

import scala.concurrent._
import akka.stream._
import sdp.logging._
import Actions._
import States._
import Messages._
import akka.cluster._

class Reader extends Actor with LogSupport {
import Reader._
  val cluster = Cluster(context.system)
  implicit val nodeAddress: NodeAddress = NodeAddress(cluster.selfAddress.toString)
  override def receive: Receive = {
    case ReadActions(si, ei, pid) => readActions(si,ei, pid)(context.system, context.dispatcher, ActorMaterializer(),nodeAddress)
  }
}

object Reader extends LogSupport {

  def readActions(startSeq: Long, endSeq: Long, persistenceId: String)(implicit sys: ActorSystem, ec: ExecutionContextExecutor, mat: ActorMaterializer, nodeAddress: NodeAddress) = {
    implicit var vchState = VchStates()
    implicit var vchItems = VchItems()
    implicit var curTxnItem = TxnItem()
    implicit val pid = PID(persistenceId)
    // obtain read journal by plugin id
    val readJournal =
      PersistenceQuery(sys).readJournalFor[CassandraReadJournal](CassandraReadJournal.Identifier)

    // issue query to journal
    val source: Source[EventEnvelope, NotUsed] =
      readJournal.currentEventsByPersistenceId(persistenceId, startSeq, endSeq)

    // materialize stream, consuming events
    val futureActions: Future[List[Any]] = source.runFold(List[Any]()) { (lstAny, evl) => evl.event :: lstAny }

    futureActions.onComplete {
      case Success(txns) => buildVoucher(txns)
      case Failure(excpt) =>
    }

    def buildVoucher(actions: List[Any])= {

      actions.reverse.foreach { txn =>
        txn match {
          case EndVoucher(_) =>
            vchItems.txnitems.foreach(println)
          case ti@_ =>
            curTxnItem = buildTxnItem(ti.asInstanceOf[Action])
            val sts = updateState(ti.asInstanceOf[Action],0)
            vchState = sts._1
            vchItems = sts._2
        }
      }
    }
  }

}

ReaderDemo.scala

import akka.actor._
import akka.stream._
import akka.stream.scaladsl._
import akka.cluster._

import scala.concurrent._
import scala.util._
import akka._
import akka.persistence.query._
import akka.persistence.cassandra.query.scaladsl.CassandraReadJournal
import datatech.cloud.pos._
import Actions._
import Messages._
import Reader._
import sdp.logging.LogSupport

object ReaderDemo extends App {

  implicit val system = ActorSystem("reader")
  implicit val ec = system.dispatcher
  implicit val mat = ActorMaterializer()

  val cluster = Cluster(system)
  implicit val nodeAddress: NodeAddress = NodeAddress(cluster.selfAddress.toString)

  States.setShowSteps(true)

  Reader.readActions(0, Long.MaxValue,"1022")

  scala.io.StdIn.readLine()

  mat.shutdown()
  system.terminate()
}