/*
 * Copyright 2015-2016 IBM Corporation
 *
 * 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 services

import java.util.Calendar

import scala.concurrent.Await
import scala.concurrent.duration.DurationInt
import scala.language.postfixOps

import org.apache.kafka.clients.consumer.CommitFailedException
import org.junit.runner.RunWith
import org.scalatest.BeforeAndAfterAll
import org.scalatest.FlatSpec
import org.scalatest.Matchers
import org.scalatest.junit.JUnitRunner

import akka.event.Logging.ErrorLevel
import whisk.common.TransactionId
import whisk.connector.kafka.KafkaConsumerConnector
import whisk.connector.kafka.KafkaProducerConnector
import whisk.core.WhiskConfig
import whisk.core.connector.Message
import whisk.utils.ExecutionContextFactory
import common.WskActorSystem
import scala.concurrent.duration.FiniteDuration
import whisk.utils.retry
import java.io.PrintStream
import java.io.ByteArrayOutputStream
import org.apache.commons.lang3.StringUtils
import scala.concurrent.duration.FiniteDuration

@RunWith(classOf[JUnitRunner])
class KafkaConnectorTests extends FlatSpec with Matchers with WskActorSystem with BeforeAndAfterAll {
    implicit val transid = TransactionId.testing
    implicit val ec = ExecutionContextFactory.makeCachedThreadPoolExecutionContext()

    val config = new WhiskConfig(WhiskConfig.kafkaHost)
    assert(config.isValid)

    val groupid = "kafkatest"
    val topic = "Dinosaurs"
    val sessionTimeout = 10 seconds
    val producer = new KafkaProducerConnector(config.kafkaHost, ec)
    val consumer = new TestKafkaConsumerConnector(config.kafkaHost, groupid, topic, sessionTimeout = sessionTimeout)

    producer.setVerbosity(ErrorLevel)
    consumer.setVerbosity(ErrorLevel)

    override def afterAll() {
        producer.close()
        consumer.close()
        super.afterAll()
    }

    behavior of "Kafka connector"

    it should "send and receive a kafka message which sets up the topic" in {
        for (i <- 0 until 5) {
            val message = new Message { override val serialize = Calendar.getInstance().getTime().toString }
            val start = java.lang.System.currentTimeMillis
            val sent = Await.result(producer.send(topic, message), 10 seconds)
            val received = consumer.peek(10 seconds).map { case (_, _, _, msg) => new String(msg, "utf-8") }
            val end = java.lang.System.currentTimeMillis
            val elapsed = end - start
            println(s"($i) Received ${received.size}. Took $elapsed msec: $received\n")
            received.size should be >= 1
            received.last should be(message.serialize)
            consumer.commit()
        }
    }

    it should "send and receive a kafka message even after session timeout" in {
        for (i <- 0 until 4) {
            val message = new Message { override val serialize = Calendar.getInstance().getTime().toString }
            val start = java.lang.System.currentTimeMillis
            val sent = Await.result(producer.send(topic, message), 1 seconds)
            val received = consumer.peek(1 seconds).map { case (_, _, _, msg) => new String(msg, "utf-8") }
            val end = java.lang.System.currentTimeMillis
            val elapsed = end - start
            println(s"($i) Received ${received.size}. Took $elapsed msec: $received\n")

            // only the last iteration will have an updated cursor
            // iteration 0: get whatever is on the topic (at least 1 but may be more if a previous test failed)
            // iteration 1: get iteration 0 records + 1 more (since we intentionally failed the commit on previous iteration)
            // iteration 2: get iteration 1 records + 1 more (since we intentionally failed the commit on previous iteration)
            // iteration 3: get exactly 1 records since iteration 2 should have forwarded the cursor
            if (i < 3) {
                received.size should be >= i + 1
            } else {
                received.size should be(1)
            }
            received.last should be(message.serialize)

            if (i < 2) {
                Thread.sleep((sessionTimeout + 1.second).toMillis)
                a[CommitFailedException] should be thrownBy {
                    consumer.commit() // sleep should cause commit to fail
                }
            } else consumer.commit()
        }
    }

    it should "catch a failing commit" in {
        val stream = new ByteArrayOutputStream
        val printstream = new PrintStream(stream)
        consumer.outputStream = printstream
        val messageReceived = "message received"
        try {
            consumer.onMessage((topic, partition, offset, bytes) => {
                printstream.println(messageReceived)
            })
            val message = new Message { override val serialize = Calendar.getInstance().getTime().toString }

            // Send message while commit throws no exception -> Should be processed
            consumer.commitFails = false
            Await.result(producer.send(topic, message), 10 seconds)
            retry(stream.toString should include(messageReceived), 20, Some(500 millisecond))

            // Send message while commit throws exception -> Message will not be processed
            consumer.commitFails = true
            retry(stream.toString should include("failed to commit to kafka: commit failed"), 50, Some(100 millisecond))
            Await.result(producer.send(topic, message), 10 seconds)
            retry(stream.toString should include("failed to commit to kafka: commit failed"), 50, Some(100 millisecond))

            // Send message again -> No commit exception -> Should work again
            consumer.commitFails = false
            Await.result(producer.send(topic, message), 10 seconds)
            retry(StringUtils.countMatches(stream.toString, messageReceived) should be(2), 50, Some(100 milliseconds))

            // Wait a few seconds and ensure that the message is not processed three times
            Thread.sleep(5000)
            StringUtils.countMatches(stream.toString, messageReceived) should be(2)
        } finally {
            printstream.close()
            stream.close()
        }
    }

}

class TestKafkaConsumerConnector(
    kafkahost: String,
    groupid: String,
    topic: String,
    sessionTimeout: FiniteDuration) extends KafkaConsumerConnector(kafkahost, groupid, topic, sessionTimeout = sessionTimeout) {

    override def commit() = {
        if (commitFails) {
            throw new CommitFailedException("commit failed")
        } else {
            super.commit()
        }
    }

    var commitFails = false
}