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/*
Copyright 2012 Twitter, Inc.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package com.twitter.scalding

import cascading.tap.Tap
import java.util.Properties
import cascading.tuple._
import cascading.scheme.Scheme
import cascading.flow.FlowProcess

import scala.collection.mutable.Buffer
import scala.collection.JavaConverters._

class MemoryTap[In, Out](val scheme: Scheme[Properties, In, Out, _, _], val tupleBuffer: Buffer[Tuple])
  extends Tap[Properties, In, Out](scheme) {

  private var modifiedTime: Long = 1L
  def updateModifiedTime(): Unit = {
    modifiedTime = System.currentTimeMillis
  }

  override def createResource(conf: Properties) = {
    updateModifiedTime()
    true
  }
  override def deleteResource(conf: Properties) = {
    tupleBuffer.clear()
    true
  }
  override def resourceExists(conf: Properties) = tupleBuffer.size > 0
  override def getModifiedTime(conf: Properties) = if (resourceExists(conf)) modifiedTime else 0L
  override lazy val getIdentifier: String = scala.math.random.toString

  override def openForRead(flowProcess: FlowProcess[_ <: Properties], input: In) = {
    new TupleEntryChainIterator(scheme.getSourceFields, tupleBuffer.toIterator.asJava)
  }

  override def openForWrite(flowProcess: FlowProcess[_ <: Properties], output: Out): TupleEntryCollector = {
    tupleBuffer.clear()
    new MemoryTupleEntryCollector(tupleBuffer, this)
  }

  override def equals(other: Any) = this.eq(other.asInstanceOf[AnyRef])

  override def hashCode() = System.identityHashCode(this)

}

class MemoryTupleEntryCollector(val tupleBuffer: Buffer[Tuple], mt: MemoryTap[_, _]) extends TupleEntryCollector {

  override def collect(tupleEntry: TupleEntry): Unit = {
    mt.updateModifiedTime()
    tupleBuffer += tupleEntry.getTupleCopy
  }
}