Add barneshut assignment

.gitignore

@@ -0,0 +1,16 @@
+# General
+*.DS_Store
+*.swp
+*~
+
+# Dotty
+*.class
+*.tasty
+*.hasTasty
+
+# sbt
+target/
+
+# Dotty IDE
+/.dotty-ide-artifact
+/.dotty-ide.json

.gitlab-ci.yml

@@ -0,0 +1,36 @@
+# DO NOT EDIT THIS FILE
+
+stages:
+  - build
+  - grade
+
+compile:
+  stage: build
+  image: lampepfl/moocs:dotty-2020-02-12
+  except:
+    - tags
+  tags:
+    - cs206
+  script:
+    - sbt packageSubmission
+  artifacts:
+    expire_in: 1 day
+    paths:
+      - submission.jar
+
+grade:
+  stage: grade
+  except:
+    - tags
+  tags:
+    - cs206
+  image:
+    name: smarter3/moocs:concpar-pubsub-2020-03-15
+    entrypoint: [""]
+  allow_failure: true
+  before_script:
+    - mkdir -p /shared/submission/
+    - cp submission.jar /shared/submission/submission.jar
+  script:
+    - cd /grader
+    - /grader/grade | /grader/feedback-printer

.vscode/settings.json

@@ -0,0 +1,8 @@
+{
+  "dotty": {
+    "trace": {
+      "remoteTracingUrl": "wss://lamppc36.epfl.ch/dotty-remote-tracer/upload/lsp.log",
+      "server": { "format": "JSON", "verbosity": "verbose" }
+    }
+  }
+}

assignment.sbt

@@ -0,0 +1,4 @@
+// Student tasks (i.e. submit, packageSubmission)
+enablePlugins(StudentTasks)
+
+

build.sbt

@@ -0,0 +1,11 @@
+course := "concpar"
+assignment := "pubsub"
+
+scalaVersion := "0.23.0-bin-20200211-5b006fb-NIGHTLY"
+
+scalacOptions ++= Seq("-language:implicitConversions", "-deprecation")
+
+libraryDependencies += "com.novocode" % "junit-interface" % "0.11" % Test
+
+testOptions in Test += Tests.Argument(TestFrameworks.JUnit, "-a", "-v", "-s")
+testSuite := "pubsub.BoundedBufferSuite"

project/MOOCSettings.scala

@@ -0,0 +1,46 @@
+package ch.epfl.lamp
+
+import sbt._
+import sbt.Keys._
+
+/**
+ * Coursera uses two versions of each assignment. They both have the same assignment key and part id but have
+ * different item ids.
+ *
+ * @param key Assignment key
+ * @param partId Assignment partId
+ * @param itemId Item id of the non premium version
+ * @param premiumItemId Item id of the premium version (`None` if the assignment is optional)
+ */
+case class CourseraId(key: String, partId: String, itemId: String, premiumItemId: Option[String])
+
+/**
+  * Settings shared by all assignments, reused in various tasks.
+  */
+object MOOCSettings extends AutoPlugin {
+
+  object autoImport {
+    val course = SettingKey[String]("course")
+    val assignment = SettingKey[String]("assignment")
+    val options = SettingKey[Map[String, Map[String, String]]]("options")
+    val courseraId = settingKey[CourseraId]("Coursera-specific information identifying the assignment")
+    val testSuite = settingKey[String]("Fully qualified name of the test suite of this assignment")
+    // Convenient alias
+    type CourseraId = ch.epfl.lamp.CourseraId
+    val CourseraId = ch.epfl.lamp.CourseraId
+  }
+
+  import autoImport._
+
+  override val globalSettings: Seq[Def.Setting[_]] = Seq(
+    // supershell is verbose, buggy and useless.
+    useSuperShell := false
+  )
+
+  override val projectSettings: Seq[Def.Setting[_]] = Seq(
+    parallelExecution in Test := false,
+    // Report test result after each test instead of waiting for every test to finish
+    logBuffered in Test := false,
+    name := s"${course.value}-${assignment.value}"
+  )
+}

project/StudentTasks.scala

@@ -0,0 +1,318 @@
+package ch.epfl.lamp
+
+import sbt._
+import Keys._
+
+// import scalaj.http._
+import java.io.{File, FileInputStream, IOException}
+import org.apache.commons.codec.binary.Base64
+// import play.api.libs.json.{Json, JsObject, JsPath}
+import scala.util.{Failure, Success, Try}
+
+/**
+  * Provides tasks for submitting the assignment
+  */
+object StudentTasks extends AutoPlugin {
+
+  override def requires = super.requires && MOOCSettings
+
+  object autoImport {
+    val packageSourcesOnly = TaskKey[File]("packageSourcesOnly", "Package the sources of the project")
+    val packageBinWithoutResources = TaskKey[File]("packageBinWithoutResources", "Like packageBin, but without the resources")
+    val packageSubmissionZip = TaskKey[File]("packageSubmissionZip")
+    val packageSubmission = inputKey[Unit]("package solution as an archive file")
+    val runGradingTests = taskKey[Unit]("run black-box tests used for final grading")
+  }
+
+
+  import autoImport._
+  import MOOCSettings.autoImport._
+
+  override lazy val projectSettings = Seq(
+    packageSubmissionSetting,
+    // submitSetting,
+    runGradingTestsSettings,
+
+    fork := true,
+    connectInput in run := true,
+    outputStrategy := Some(StdoutOutput),
+  ) ++ packageSubmissionZipSettings
+
+  lazy val runGradingTestsSettings = runGradingTests := {
+    val testSuiteJar = "grading-tests.jar"
+    if (!new File(testSuiteJar).exists) {
+      throw new MessageOnlyException(s"Could not find tests JarFile: $testSuiteJar")
+    }
+
+    val classPath = s"${(Test / dependencyClasspath).value.map(_.data).mkString(File.pathSeparator)}${File.pathSeparator}$testSuiteJar"
+    val junitProcess =
+      Fork.java.fork(
+        ForkOptions(),
+        "-cp" :: classPath ::
+        "org.junit.runner.JUnitCore" ::
+        (Test / testSuite).value ::
+        Nil
+      )
+
+    // Wait for tests to complete.
+    junitProcess.exitValue()
+  }
+
+
+  /** **********************************************************
+    * SUBMITTING A SOLUTION TO COURSERA
+    */
+
+  val packageSubmissionZipSettings = Seq(
+    packageSubmissionZip := {
+      val submission = crossTarget.value / "submission.zip"
+      val sources = (packageSourcesOnly in Compile).value
+      val binaries = (packageBinWithoutResources in Compile).value
+      IO.zip(Seq(sources -> "sources.zip", binaries -> "binaries.jar"), submission)
+      submission
+    },
+    artifactClassifier in packageSourcesOnly := Some("sources"),
+    artifact in (Compile, packageBinWithoutResources) ~= (art => art.withName(art.name + "-without-resources"))
+  ) ++
+  inConfig(Compile)(
+    Defaults.packageTaskSettings(packageSourcesOnly, Defaults.sourceMappings) ++
+    Defaults.packageTaskSettings(packageBinWithoutResources, Def.task {
+      val relativePaths =
+        (unmanagedResources in Compile).value.flatMap(Path.relativeTo((unmanagedResourceDirectories in Compile).value)(_))
+      (mappings in (Compile, packageBin)).value.filterNot { case (_, path) => relativePaths.contains(path) }
+    })
+  )
+
+  val maxSubmitFileSize = {
+    val mb = 1024 * 1024
+    10 * mb
+  }
+
+  /** Check that the jar exists, isn't empty, isn't crazy big, and can be read
+    * If so, encode jar as base64 so we can send it to Coursera
+    */
+  def prepareJar(jar: File, s: TaskStreams): String = {
+    val errPrefix = "Error submitting assignment jar: "
+    val fileLength = jar.length()
+    if (!jar.exists()) {
+      s.log.error(errPrefix + "jar archive does not exist\n" + jar.getAbsolutePath)
+      failSubmit()
+    } else if (fileLength == 0L) {
+      s.log.error(errPrefix + "jar archive is empty\n" + jar.getAbsolutePath)
+      failSubmit()
+    } else if (fileLength > maxSubmitFileSize) {
+      s.log.error(errPrefix + "jar archive is too big. Allowed size: " +
+        maxSubmitFileSize + " bytes, found " + fileLength + " bytes.\n" +
+        jar.getAbsolutePath)
+      failSubmit()
+    } else {
+      val bytes = new Array[Byte](fileLength.toInt)
+      val sizeRead = try {
+        val is = new FileInputStream(jar)
+        val read = is.read(bytes)
+        is.close()
+        read
+      } catch {
+        case ex: IOException =>
+          s.log.error(errPrefix + "failed to read sources jar archive\n" + ex.toString)
+          failSubmit()
+      }
+      if (sizeRead != bytes.length) {
+        s.log.error(errPrefix + "failed to read the sources jar archive, size read: " + sizeRead)
+        failSubmit()
+      } else encodeBase64(bytes)
+    }
+  }
+
+  /** Task to package solution to a given file path */
+  lazy val packageSubmissionSetting = packageSubmission := {
+    val args: Seq[String] = Def.spaceDelimited("[path]").parsed
+    val s: TaskStreams = streams.value // for logging
+    val jar = (packageSubmissionZip in Compile).value
+
+    val base64Jar = prepareJar(jar, s)
+
+    val path = args.headOption.getOrElse((baseDirectory.value / "submission.jar").absolutePath)
+    scala.tools.nsc.io.File(path).writeAll(base64Jar)
+  }
+
+/*
+  /** Task to submit a solution to coursera */
+  val submit = inputKey[Unit]("submit solution to Coursera")
+  lazy val submitSetting = submit := {
+    // Fail if scalafix linting does not pass.
+    scalafixLinting.value
+
+    val args: Seq[String] = Def.spaceDelimited("<arg>").parsed
+    val s: TaskStreams = streams.value // for logging
+    val jar = (packageSubmissionZip in Compile).value
+
+    val assignmentDetails =
+      courseraId.?.value.getOrElse(throw new MessageOnlyException("This assignment can not be submitted to Coursera because the `courseraId` setting is undefined"))
+    val assignmentKey = assignmentDetails.key
+    val courseName =
+      course.value match {
+        case "capstone" => "scala-capstone"
+        case "bigdata"  => "scala-spark-big-data"
+        case other      => other
+      }
+
+    val partId = assignmentDetails.partId
+    val itemId = assignmentDetails.itemId
+    val premiumItemId = assignmentDetails.premiumItemId
+
+    val (email, secret) = args match {
+      case email :: secret :: Nil =>
+        (email, secret)
+      case _ =>
+        val inputErr =
+          s"""|Invalid input to `submit`. The required syntax for `submit` is:
+              |submit <email-address> <submit-token>
+              |
+              |The submit token is NOT YOUR LOGIN PASSWORD.
+              |It can be obtained from the assignment page:
+              |https://www.coursera.org/learn/$courseName/programming/$itemId
+              |${
+                premiumItemId.fold("") { id =>
+                  s"""or (for premium learners):
+                     |https://www.coursera.org/learn/$courseName/programming/$id
+                   """.stripMargin
+                }
+              }
+          """.stripMargin
+        s.log.error(inputErr)
+        failSubmit()
+    }
+
+    val base64Jar = prepareJar(jar, s)
+    val json =
+      s"""|{
+          |   "assignmentKey":"$assignmentKey",
+          |   "submitterEmail":"$email",
+          |   "secret":"$secret",
+          |   "parts":{
+          |      "$partId":{
+          |         "output":"$base64Jar"
+          |      }
+          |   }
+          |}""".stripMargin
+
+    def postSubmission[T](data: String): Try[HttpResponse[String]] = {
+      val http = Http("https://www.coursera.org/api/onDemandProgrammingScriptSubmissions.v1")
+      val hs = List(
+        ("Cache-Control", "no-cache"),
+        ("Content-Type", "application/json")
+      )
+      s.log.info("Connecting to Coursera...")
+      val response = Try(http.postData(data)
+                         .headers(hs)
+                         .option(HttpOptions.connTimeout(10000)) // scalaj default timeout is only 100ms, changing that to 10s
+                         .asString) // kick off HTTP POST
+      response
+    }
+
+    val connectMsg =
+      s"""|Attempting to submit "${assignment.value}" assignment in "$courseName" course
+          |Using:
+          |- email: $email
+          |- submit token: $secret""".stripMargin
+    s.log.info(connectMsg)
+
+    def reportCourseraResponse(response: HttpResponse[String]): Unit = {
+      val code = response.code
+      val respBody = response.body
+
+       /* Sample JSON response from Coursera
+      {
+        "message": "Invalid email or token.",
+        "details": {
+          "learnerMessage": "Invalid email or token."
+        }
+      }
+      */
+
+      // Success, Coursera responds with 2xx HTTP status code
+      if (response.is2xx) {
+        val successfulSubmitMsg =
+          s"""|Successfully connected to Coursera. (Status $code)
+              |
+                |Assignment submitted successfully!
+              |
+                |You can see how you scored by going to:
+              |https://www.coursera.org/learn/$courseName/programming/$itemId/
+              |${
+            premiumItemId.fold("") { id =>
+              s"""or (for premium learners):
+                 |https://www.coursera.org/learn/$courseName/programming/$id
+                       """.stripMargin
+            }
+          }
+              |and clicking on "My Submission".""".stripMargin
+        s.log.info(successfulSubmitMsg)
+      }
+
+      // Failure, Coursera responds with 4xx HTTP status code (client-side failure)
+      else if (response.is4xx) {
+        val result = Try(Json.parse(respBody)).toOption
+        val learnerMsg = result match {
+          case Some(resp: JsObject) =>
+            (JsPath \ "details" \ "learnerMessage").read[String].reads(resp).get
+          case Some(x) => // shouldn't happen
+            "Could not parse Coursera's response:\n" + x
+          case None =>
+            "Could not parse Coursera's response:\n" + respBody
+        }
+        val failedSubmitMsg =
+          s"""|Submission failed.
+              |There was something wrong while attempting to submit.
+              |Coursera says:
+              |$learnerMsg (Status $code)""".stripMargin
+        s.log.error(failedSubmitMsg)
+      }
+
+      // Failure, Coursera responds with 5xx HTTP status code (server-side failure)
+      else if (response.is5xx) {
+        val failedSubmitMsg =
+          s"""|Submission failed.
+              |Coursera seems to be unavailable at the moment (Status $code)
+              |Check https://status.coursera.org/ and try again in a few minutes.
+           """.stripMargin
+        s.log.error(failedSubmitMsg)
+      }
+
+      // Failure, Coursera repsonds with an unexpected status code
+      else {
+        val failedSubmitMsg =
+          s"""|Submission failed.
+              |Coursera replied with an unexpected code (Status $code)
+           """.stripMargin
+        s.log.error(failedSubmitMsg)
+      }
+    }
+
+    // kick it all off, actually make request
+    postSubmission(json) match {
+      case Success(resp) => reportCourseraResponse(resp)
+      case Failure(e) =>
+        val failedConnectMsg =
+          s"""|Connection to Coursera failed.
+              |There was something wrong while attempting to connect to Coursera.
+              |Check your internet connection.
+              |${e.toString}""".stripMargin
+        s.log.error(failedConnectMsg)
+    }
+
+   }
+*/
+
+  def failSubmit(): Nothing = {
+    sys.error("Submission failed")
+  }
+
+  /**
+    * *****************
+    * DEALING WITH JARS
+    */
+  def encodeBase64(bytes: Array[Byte]): String =
+    new String(Base64.encodeBase64(bytes))
+}

project/build.properties

@@ -0,0 +1 @@
+sbt.version=1.3.8

project/buildSettings.sbt

@@ -0,0 +1,5 @@
+// Used for Coursera submission (StudentPlugin)
+// libraryDependencies += "org.scalaj" %% "scalaj-http" % "2.4.2"
+// libraryDependencies += "com.typesafe.play" %% "play-json" % "2.7.4"
+// Used for Base64 (StudentPlugin)
+libraryDependencies += "commons-codec" % "commons-codec" % "1.10"

project/plugins.sbt

@@ -0,0 +1,2 @@
+addSbtPlugin("org.scala-js" % "sbt-scalajs" % "0.6.28")
+addSbtPlugin("ch.epfl.lamp" % "sbt-dotty" % "0.4.0")

src/main/scala/pubsub/Client.scala

@@ -0,0 +1,34 @@
+package pubsub
+
+import java.net.Socket
+import java.nio.charset.Charset
+
+case class Client(socket: Socket, id: Int)
+    (implicit charset: Charset = Charset.forName("UTF-8")) {
+  private var name_ = "client_" + id
+  val outStream = socket.getOutputStream()
+
+  def name = name_
+  def name_=(newName: String) = name_ = newName
+
+  def isConnected: Boolean = socket.isConnected()
+
+  def close(): Unit = socket.close()
+
+  def send(message: String): Unit = {
+    val payload = message.getBytes(charset)
+    outStream.write(payload)
+    outStream.flush()
+  }
+
+  def sendAck(ackType: String, message: String): Unit =
+    send(s"${ackType}_ack $message\n")
+
+  def sayHello(): Unit = sendAck("connection", name_)
+  def sayGoodbye(): Unit = send(s"Bye Bye dear $name_!\n")
+
+  def invalidPreviousCommand(): Unit = send("! previous command was invalid\n")
+
+  def sendMessage(sender: String, topic: String, message: String): Unit =
+    send(s"$sender@$topic $message\n")
+}

src/main/scala/pubsub/Server.scala

@@ -0,0 +1,51 @@
+package pubsub
+
+import java.net.ServerSocket
+import java.net.Socket
+import java.io.BufferedReader
+import java.io.InputStreamReader
+import java.net.URL
+import java.util.concurrent.Executors
+
+import scala.concurrent.JavaConversions._
+import scala.concurrent.{ExecutionContext, Future}
+import scala.concurrent.ExecutionContext.Implicits.global
+import pubsub.collection._
+import pubsub.command._
+import pubsub.network.TCPReader
+
+object Server extends App {
+  val port = 7676
+  val maxWorkers = 12
+  val bufferSize = 20
+  val socket = new ServerSocket(port)
+  try {
+    val whatismyip = new URL("http://checkip.amazonaws.com")
+    val in = new BufferedReader(new InputStreamReader(whatismyip.openStream()));
+    val serverIP = in.readLine()
+    println(s"Connect to $serverIP (or `localhost`), port $port with `telnet` to join this server")
+  } catch  {
+    case e: Exception =>
+      println("There is a problem with your internet connection, you can only access it via localhost")
+  }
+
+  val buffer = new BoundedBuffer[Command](20)
+  val commandHandlers = for{
+    i <- 0 until maxWorkers
+  } yield {
+    Future {
+      new CommandHandler(buffer).handle()
+    }
+  }
+  val threadPool = Executors.newFixedThreadPool(maxWorkers)
+
+  var clientId = 0
+  while(true) {
+    val client = socket.accept();
+    val cid = clientId
+    clientId += 1
+    Future{
+      new TCPReader(clientId, client, buffer).read()
+    }(ExecutionContext.fromExecutorService(threadPool))
+  }
+}

src/main/scala/pubsub/collection/AbstractBoundedBuffer.scala

@@ -0,0 +1,34 @@
+package pubsub.collection
+
+import instrumentation.Monitor
+
+trait InternalBuffer[T] {
+  def update(index: Int, elem: T): Unit
+  def apply(index: Int): T
+  def delete(index: Int): Unit
+  val size: Int
+}
+
+
+abstract class AbstractBoundedBuffer[T](bufferSize: Int) extends Monitor {
+  require(bufferSize > 0)
+
+  def put(element: T): Unit
+  def take(): T
+
+  val buffer: InternalBuffer[T] = new InternalBuffer[T] {
+    private val buffer: Array[Option[T]] = new Array(bufferSize)
+    def update(index: Int, elem: T): Unit = buffer(index) = Some(elem)
+    def apply(index: Int): T = buffer(index).get
+    def delete(index: Int): Unit = buffer(index) = None
+    val size = bufferSize
+  }
+
+  def head: Int = _head
+  def head_=(e: Int): Unit = _head = e
+  def count: Int = _count
+  def count_=(e: Int): Unit = _count = e
+
+  private var _head = 0;
+  private var _count = 0;
+}

src/main/scala/pubsub/collection/BoundedBuffer.scala

@@ -0,0 +1,26 @@
+package pubsub.collection
+
+class BoundedBuffer[T](size: Int) extends AbstractBoundedBuffer[T](size) {
+
+  // You have at your disposition the following two variables:
+  // - count : Int
+  // - head : Int
+  // In addition, you have access to an array-like internal buffer:
+  // - buffer
+  // You can access elements of this buffer using:
+  // - buffer(i)
+  // Similarly, you can set elements using:
+  // - buffer(i) = e
+  //
+  // You do not need to create those variables yourself!
+  // They are inherited from the AbstractBoundedBuffer class.
+
+  override def put(e: T): Unit = ???
+
+  override def take(): T = ???
+
+  // You may want to add methods to:
+  // - check whether the buffer is empty
+  // - check whether the buffer is full
+  // - get the index of tail
+}

src/main/scala/pubsub/collection/ConcurrentMultiMap.scala

@@ -0,0 +1,65 @@
+package pubsub.collection
+
+import scala.collection.mutable
+import java.util.concurrent.locks.ReentrantReadWriteLock
+
+class ConcurrentMultiMap[K,V] {
+
+  private val lockRW = new ReentrantReadWriteLock()
+  val map = mutable.HashMap[K, Set[V]]()
+
+  def lock(): Unit = lockRW.writeLock().lock()
+
+  def unlock(): Unit = lockRW.writeLock().unlock()
+
+  def add(key: K, value: V): Unit = {
+    try {
+      lockRW.writeLock().lock()
+      map.get(key) match {
+        case Some(set) =>
+          if (! set.contains(value)) {
+            map += ((key, set + value))
+          }
+        case None =>
+          map += ((key, Set(value)))
+      }
+    } finally {
+      lockRW.writeLock().unlock()
+    }
+  }
+
+  def get(key: K): Option[Set[V]] = {
+    try {
+      lockRW.readLock().lock()
+      val v = map.get(key)
+      v
+    } finally {
+      lockRW.readLock().unlock()
+    }
+  }
+
+  def remove(key: K, value: V): Unit = {
+    try {
+      lockRW.writeLock().lock()
+      map.get(key) match {
+        case Some(set) =>
+          if (set.contains(value)) {
+            map += ((key, set - value))
+          }
+        case None =>
+      }
+    } finally {
+      lockRW.writeLock().unlock()
+    }
+  }
+
+  def removeValueFromAll(value: V): Unit = {
+    try {
+      lockRW.writeLock().lock()
+      map.keys.foreach(remove(_, value))
+    } finally {
+      lockRW.writeLock().unlock()
+    }
+  }
+
+}

src/main/scala/pubsub/command/CommandHandler.scala

@@ -0,0 +1,43 @@
+package pubsub.command
+
+import pubsub.Client
+import pubsub.collection._
+
+class CommandHandler(buffer: BoundedBuffer[Command]) {
+  import CommandHandler._
+
+  def handle(): Unit = {
+    val command = buffer.take()
+
+    command match {
+      case Subscribe(topic, client) =>
+        multiMap.add(topic, client)
+        client.sendAck("subscribe", topic)
+
+      case Unsubscribe(topic, client) =>
+        multiMap.remove(topic, client)
+        client.sendAck("unsubscribe", topic)
+
+      case Publish(topic, message, sender) =>
+        for {
+          subscribers <- multiMap.get(topic)
+          client <- subscribers
+        } client.sendMessage(sender.name, topic, message)
+
+      case EndOfClient(client) =>
+        multiMap.removeValueFromAll(client)
+
+      case Rename(newName,client) =>
+        client.name = newName
+        client.sendAck("rename", newName)
+
+      case _ =>
+        // nothing should happen
+    }
+  }
+}
+
+
+object CommandHandler {
+  val multiMap = new ConcurrentMultiMap[String, Client]()
+}

src/main/scala/pubsub/command/CommandReader.scala

@@ -0,0 +1,45 @@
+package pubsub.command
+
+import java.io.BufferedReader
+import java.io.InputStreamReader
+import java.io.InputStream
+
+import pubsub.Client
+
+class CommandReader(inStream: InputStream, client: Client) {
+  val inputBuffer = new BufferedReader(new InputStreamReader(inStream))
+
+  def fetchCommand(): Command = {
+    val line = inputBuffer.readLine()
+
+    if (line == null || line.startsWith("leave")) {
+      EndOfClient(client)
+    }
+    else {
+      val quoteIndex = line.indexOf('\'')
+      val hasPayload = quoteIndex != -1
+      val parts =
+        if(!hasPayload) {
+          line.split(" ").toList
+        } else {
+          val (command, payload) = line.splitAt(quoteIndex)
+          command.split(" ").toList :+ payload
+        }
+
+      parts match {
+        case "subscribe" :: topic :: Nil   => Subscribe(topic, client)
+        case "unsubscribe" :: topic :: Nil => Unsubscribe(topic, client)
+        case "rename" :: newName :: Nil    => Rename(newName, client)
+
+        case "publish" :: topic :: msg :: Nil if hasPayload && msg != "\'" =>
+          var message = msg
+          while(!message.endsWith("\'")) {
+            message += "\n" + inputBuffer.readLine()
+          }
+          Publish(topic, message, client)
+
+        case _ => MalformedCommand(client)
+      }
+    }
+  }
+}

src/main/scala/pubsub/command/CommandType.scala

@@ -0,0 +1,33 @@
+package pubsub.command
+
+import pubsub.Client
+
+sealed trait Topic {
+   val topic: String
+}
+
+sealed abstract class Command(from: Client) {
+  def toString(): String
+}
+case class EndOfClient(from: Client) extends Command(from) {
+  override def toString(): String = s"${from.name}: End of client"
+}
+case class MalformedCommand(from: Client) extends Command(from) {
+  override def toString(): String = s"${from.name}: Invalid Command"
+}
+case class Subscribe(topic: String,
+    from: Client) extends Command(from) with Topic {
+  override def toString(): String = s"${from.name}: Subscribe @ $topic"
+}
+case class Unsubscribe(topic: String,
+    from: Client) extends Command(from) with Topic {
+  override def toString(): String = s"${from.name}: Unsubscribe @ $topic"
+}
+case class Publish(topic: String, message: String,
+    from: Client) extends Command(from) with Topic {
+  override def toString(): String = s"${from.name}: Publish @ $topic -> $message"
+}
+
+case class Rename(newName: String, from: Client) extends Command(from) {
+  override def toString(): String = s"${from.name}: Renamed to $newName"
+}

src/main/scala/pubsub/instrumentation/MockedMonitor.scala

@@ -0,0 +1,72 @@
+package instrumentation
+
+trait MockedMonitor extends Monitor {
+  def scheduler: Scheduler
+
+  // Can be overriden.
+  override def waitDefault() = {
+    scheduler.log("wait")
+    scheduler updateThreadState Wait(this, scheduler.threadLocks.tail)
+  }
+  override def synchronizedDefault[T](toExecute: =>T): T = {
+    scheduler.log("synchronized check")
+    val prevLocks = scheduler.threadLocks
+    scheduler updateThreadState Sync(this, prevLocks) // If this belongs to prevLocks, should just continue.
+    scheduler.log("synchronized -> enter")
+    try {
+      toExecute
+    } finally {
+      scheduler updateThreadState Running(prevLocks)
+      scheduler.log("synchronized -> out")
+    }
+  }
+  override def notifyDefault() = {
+    scheduler mapOtherStates {
+      state => state match {
+        case Wait(lockToAquire, locks) if lockToAquire == this => SyncUnique(this, state.locks)
+        case e => e
+      }
+    }
+    scheduler.log("notify")
+  }
+  override def notifyAllDefault() = {
+    scheduler mapOtherStates {
+      state => state match {
+        case Wait(lockToAquire, locks) if lockToAquire == this => Sync(this, state.locks)
+        case SyncUnique(lockToAquire, locks) if lockToAquire == this => Sync(this, state.locks)
+        case e => e
+      }
+    }
+    scheduler.log("notifyAll")
+  }
+}
+
+trait LockFreeMonitor extends Monitor {
+  override def waitDefault() = {
+    throw new Exception("Please use lock-free structures and do not use wait()")
+  }
+  override def synchronizedDefault[T](toExecute: =>T): T = {
+    throw new Exception("Please use lock-free structures and do not use synchronized()")
+  }
+  override def notifyDefault() = {
+    throw new Exception("Please use lock-free structures and do not use notify()")
+  }
+  override def notifyAllDefault() = {
+    throw new Exception("Please use lock-free structures and do not use notifyAll()")
+  }
+}
+
+
+abstract class ThreadState {
+  def locks: Seq[AnyRef]
+}
+trait CanContinueIfAcquiresLock extends ThreadState {
+  def lockToAquire: AnyRef
+}
+case object Start extends ThreadState { def locks: Seq[AnyRef] = Seq.empty }
+case object End extends ThreadState { def locks: Seq[AnyRef] = Seq.empty }
+case class Wait(lockToAquire: AnyRef, locks: Seq[AnyRef]) extends ThreadState
+case class SyncUnique(lockToAquire: AnyRef, locks: Seq[AnyRef]) extends ThreadState with CanContinueIfAcquiresLock
+case class Sync(lockToAquire: AnyRef, locks: Seq[AnyRef]) extends ThreadState with CanContinueIfAcquiresLock
+case class Running(locks: Seq[AnyRef]) extends ThreadState
+case class VariableReadWrite(locks: Seq[AnyRef]) extends ThreadState

src/main/scala/pubsub/instrumentation/Monitor.scala

@@ -0,0 +1,23 @@
+package instrumentation
+
+class Dummy
+
+trait Monitor {
+  implicit val dummy: Dummy = new Dummy
+
+  def wait()(implicit i: Dummy) = waitDefault()
+
+  def synchronized[T](e: => T)(implicit i: Dummy) = synchronizedDefault(e)
+
+  def notify()(implicit i: Dummy) = notifyDefault()
+
+  def notifyAll()(implicit i: Dummy) = notifyAllDefault()
+
+  private val lock = new AnyRef
+
+  // Can be overriden.
+  def waitDefault(): Unit = lock.wait()
+  def synchronizedDefault[T](toExecute: =>T): T = lock.synchronized(toExecute)
+  def notifyDefault(): Unit = lock.notify()
+  def notifyAllDefault(): Unit = lock.notifyAll()
+}

src/main/scala/pubsub/instrumentation/SchedulableInternalBuffer.scala

@@ -0,0 +1,63 @@
+package instrumentation
+
+import java.util.concurrent._;
+import scala.concurrent.duration._
+import scala.collection.mutable._
+import Stats._
+
+import java.util.concurrent.atomic.AtomicInteger
+
+import pubsub.collection._
+
+class SchedulableInternalBuffer[T](val size: Int, scheduler: Scheduler) extends InternalBuffer[T] {
+  private val buffer = new Array[Option[T]](size)
+  private val threadBuffer = new Array[Option[Int]](size) // Who last wrote in the array.
+
+  def update(index: Int, elem: T): Unit = {
+    scheduler.exec {
+      buffer(index) = Some(elem)
+      threadBuffer(index) = Some(scheduler.threadId)
+    }(s"Write buffer($index) = $elem")
+  }
+
+  def apply(index: Int): T = scheduler.exec {
+    buffer(index).fold {
+      threadBuffer(index).fold {
+        throw new Exception(s"buffer($index) was never set ! ")
+      } { tid =>
+        throw new Exception(s"buffer($index) was deleted by thread $tid ! ")
+      }
+    }(identity)
+  }(s"Read buffer($index)")
+
+  def delete(index: Int): Unit = {
+    scheduler.exec {
+      buffer(index) = None
+      threadBuffer(index) = Some(scheduler.threadId)
+    }(s"Delete buffer($index)")
+  }
+}
+
+trait MockedInternals[T] { self: SchedulableBoundedBuffer[T] =>
+  override val buffer = new SchedulableInternalBuffer[T](self.size, self.scheduler)
+
+  var h: Int = 0
+  var c: Int = 0
+
+  override def head_=(i: Int) = scheduler.exec {
+    h = i
+  }(s"Write head  = $i")
+  override def head: Int = scheduler.exec { h }(s"Read  head  -> $h")
+
+  override def count_=(i: Int) = scheduler.exec {
+    c = i
+  }(s"Write count = $i")
+
+  override def count: Int = scheduler.exec { c }(s"Read  count -> $c")
+}
+
+class SchedulableBoundedBuffer[T](val size: Int, val scheduler: Scheduler)
+    extends BoundedBuffer[T](size) with MockedMonitor with MockedInternals[T] {
+
+}
+

src/main/scala/pubsub/instrumentation/Scheduler.scala

@@ -0,0 +1,305 @@
+package instrumentation
+
+import java.util.concurrent._;
+import scala.concurrent.duration._
+import scala.collection.mutable._
+import Stats._
+
+import java.util.concurrent.atomic.AtomicInteger
+
+sealed abstract class Result
+case class RetVal(rets: List[Any]) extends Result
+case class Except(msg: String, stackTrace: Array[StackTraceElement]) extends Result
+case class Timeout(msg: String) extends Result
+
+/**
+ * A class that maintains schedule and a set of thread ids.
+ * The schedules are advanced after an operation of a SchedulableBuffer is performed.
+ * Note: the real schedule that is executed may deviate from the input schedule
+ * due to the adjustments that had to be made for locks
+ */
+class Scheduler(sched: List[Int]) {
+  val maxOps = 500 // a limit on the maximum number of operations the code is allowed to perform
+
+  private var schedule = sched
+  private var numThreads = 0
+  private val realToFakeThreadId = Map[Long, Int]()
+  private val opLog = ListBuffer[String]() // a mutable list (used for efficient concat)
+  private val threadStates = Map[Int, ThreadState]()
+
+  /**
+   * Runs a set of operations in parallel as per the schedule.
+   * Each operation may consist of many primitive operations like reads or writes
+   * to shared data structure each of which should be executed using the function `exec`.
+   * @timeout in milliseconds
+   * @return true - all threads completed on time,  false -some tests timed out.
+   */
+  def runInParallel(timeout: Long, ops: List[() => Any]): Result = {
+    numThreads = ops.length
+    val threadRes = Array.fill(numThreads) { None: Any }
+    var exception: Option[Except] = None
+    val syncObject = new Object()
+    var completed = new AtomicInteger(0)
+    // create threads
+    val threads = ops.zipWithIndex.map {
+      case (op, i) =>
+        new Thread(new Runnable() {
+          def run(): Unit = {
+            val fakeId = i + 1
+            setThreadId(fakeId)
+            try {
+              updateThreadState(Start)
+              val res = op()
+              updateThreadState(End)
+              threadRes(i) = res
+              // notify the master thread if all threads have completed
+              if (completed.incrementAndGet() == ops.length) {
+                syncObject.synchronized { syncObject.notifyAll() }
+              }
+            } catch {
+              case e: Throwable if exception != None => // do nothing here and silently fail
+              case e: Throwable =>
+                log(s"throw ${e.toString}")
+                exception = Some(Except(s"Thread $fakeId crashed on the following schedule: \n" + opLog.mkString("\n"),
+                    e.getStackTrace))
+                syncObject.synchronized { syncObject.notifyAll() }
+              //println(s"$fakeId: ${e.toString}")
+              //Runtime.getRuntime().halt(0) //exit the JVM and all running threads (no other way to kill other threads)
+            }
+          }
+        })
+    }
+    // start all threads
+    threads.foreach(_.start())
+    // wait for all threads to complete, or for an exception to be thrown, or for the time out to expire
+    var remTime = timeout
+    syncObject.synchronized {
+
+      timed { if(completed.get() != ops.length) syncObject.wait(timeout) } { time => remTime -= time }
+    }
+    if (exception.isDefined) {
+      exception.get
+    } else if (remTime <= 1) { // timeout ? using 1 instead of zero to allow for some errors
+      Timeout(opLog.mkString("\n"))
+    } else {
+      // every thing executed normally
+      RetVal(threadRes.toList)
+    }
+  }
+
+  // Updates the state of the current thread
+  def updateThreadState(state: ThreadState): Unit = {
+    val tid = threadId
+    synchronized {
+      threadStates(tid) = state
+    }
+    state match {
+      case Sync(lockToAquire, locks) =>
+        if (locks.indexOf(lockToAquire) < 0) waitForTurn else {
+          // Re-aqcuiring the same lock
+          updateThreadState(Running(lockToAquire +: locks))
+        }
+      case Start      => waitStart()
+      case End        => removeFromSchedule(tid)
+      case Running(_) =>
+      case _          => waitForTurn // Wait, SyncUnique, VariableReadWrite
+    }
+  }
+
+  def waitStart(): Unit = {
+    //while (threadStates.size < numThreads) {
+    //Thread.sleep(1)
+    //}
+    synchronized {
+      if (threadStates.size < numThreads) {
+        wait()
+      } else {
+        notifyAll()
+      }
+    }
+  }
+
+  def threadLocks = {
+    synchronized {
+      threadStates(threadId).locks
+    }
+  }
+
+  def threadState = {
+    synchronized {
+      threadStates(threadId)
+    }
+  }
+
+  def mapOtherStates(f: ThreadState => ThreadState) = {
+    val exception = threadId
+    synchronized {
+      for (k <- threadStates.keys if k != exception) {
+        threadStates(k) = f(threadStates(k))
+      }
+    }
+  }
+
+  def log(str: String) = {
+    if((realToFakeThreadId contains Thread.currentThread().getId())) {
+      val space = (" " * ((threadId - 1) * 2))
+      val s = space + threadId + ":" + "\n".r.replaceAllIn(str, "\n" + space + "  ")
+      opLog += s
+    }
+  }
+
+  /**
+   * Executes a read or write operation to a global data structure as per the given schedule
+   * @param msg a message corresponding to the operation that will be logged
+   */
+  def exec[T](primop: => T)(msg: => String, postMsg: => Option[T => String] = None): T = {
+    if(! (realToFakeThreadId contains Thread.currentThread().getId())) {
+      primop
+    } else {
+      updateThreadState(VariableReadWrite(threadLocks))
+      val m = msg
+      if(m != "") log(m)
+      if (opLog.size > maxOps)
+        throw new Exception(s"Total number of reads/writes performed by threads exceed $maxOps. A possible deadlock!")
+      val res = primop
+      postMsg match {
+        case Some(m) => log(m(res))
+        case None =>
+      }
+      res
+    }
+  }
+
+  private def setThreadId(fakeId: Int) = synchronized {
+    realToFakeThreadId(Thread.currentThread.getId) = fakeId
+  }
+
+  def threadId =
+    try {
+      realToFakeThreadId(Thread.currentThread().getId())
+    } catch {
+    case e: NoSuchElementException =>
+      throw new Exception("You are accessing shared variables in the constructor. This is not allowed. The variables are already initialized!")
+    }
+
+  private def isTurn(tid: Int) = synchronized {
+    (!schedule.isEmpty && schedule.head != tid)
+  }
+
+  def canProceed(): Boolean = {
+    val tid = threadId
+    canContinue match {
+      case Some((i, state)) if i == tid =>
+        //println(s"$tid: Runs ! Was in state $state")
+        canContinue = None
+        state match {
+          case Sync(lockToAquire, locks) => updateThreadState(Running(lockToAquire +: locks))
+          case SyncUnique(lockToAquire, locks) =>
+            mapOtherStates {
+              _ match {
+                case SyncUnique(lockToAquire2, locks2) if lockToAquire2 == lockToAquire => Wait(lockToAquire2, locks2)
+                case e => e
+              }
+            }
+            updateThreadState(Running(lockToAquire +: locks))
+          case VariableReadWrite(locks) => updateThreadState(Running(locks))
+        }
+        true
+      case Some((i, state)) =>
+        //println(s"$tid: not my turn but $i !")
+        false
+      case None =>
+        false
+    }
+  }
+
+  var threadPreference = 0 // In the case the schedule is over, which thread should have the preference to execute.
+
+  /** returns true if the thread can continue to execute, and false otherwise */
+  def decide(): Option[(Int, ThreadState)] = {
+    if (!threadStates.isEmpty) { // The last thread who enters the decision loop takes the decision.
+      //println(s"$threadId: I'm taking a decision")
+      if (threadStates.values.forall { case e: Wait => true case _ => false }) {
+        val waiting = threadStates.keys.map(_.toString).mkString(", ")
+        val s = if (threadStates.size > 1) "s" else ""
+        val are = if (threadStates.size > 1) "are" else "is"
+        throw new Exception(s"Deadlock: Thread$s $waiting $are waiting but all others have ended and cannot notify them.")
+      } else {
+        // Threads can be in Wait, Sync, SyncUnique, and VariableReadWrite mode.
+        // Let's determine which ones can continue.
+        val notFree = threadStates.collect { case (id, state) => state.locks }.flatten.toSet
+        val threadsNotBlocked = threadStates.toSeq.filter {
+          case (id, v: VariableReadWrite)         => true
+          case (id, v: CanContinueIfAcquiresLock) => !notFree(v.lockToAquire) || (v.locks contains v.lockToAquire)
+          case _                                  => false
+        }
+        if (threadsNotBlocked.isEmpty) {
+          val waiting = threadStates.keys.map(_.toString).mkString(", ")
+          val s = if (threadStates.size > 1) "s" else ""
+          val are = if (threadStates.size > 1) "are" else "is"
+          val whoHasLock = threadStates.toSeq.flatMap { case (id, state) => state.locks.map(lock => (lock, id)) }.toMap
+          val reason = threadStates.collect {
+            case (id, state: CanContinueIfAcquiresLock) if !notFree(state.lockToAquire) =>
+              s"Thread $id is waiting on lock ${state.lockToAquire} held by thread ${whoHasLock(state.lockToAquire)}"
+          }.mkString("\n")
+          throw new Exception(s"Deadlock: Thread$s $waiting are interlocked. Indeed:\n$reason")
+        } else if (threadsNotBlocked.size == 1) { // Do not consume the schedule if only one thread can execute.
+          Some(threadsNotBlocked(0))
+        } else {
+          val next = schedule.indexWhere(t => threadsNotBlocked.exists { case (id, state) => id == t })
+          if (next != -1) {
+            //println(s"$threadId: schedule is $schedule, next chosen is ${schedule(next)}")
+            val chosenOne = schedule(next) // TODO: Make schedule a mutable list.
+            schedule = schedule.take(next) ++ schedule.drop(next + 1)
+            Some((chosenOne, threadStates(chosenOne)))
+          } else {
+            threadPreference = (threadPreference + 1) % threadsNotBlocked.size
+            val chosenOne = threadsNotBlocked(threadPreference) // Maybe another strategy
+            Some(chosenOne)
+            //threadsNotBlocked.indexOf(threadId) >= 0
+            /*
+            val tnb = threadsNotBlocked.map(_._1).mkString(",")
+            val s = if (schedule.isEmpty) "empty" else schedule.mkString(",")
+            val only = if (schedule.isEmpty) "" else " only"
+            throw new Exception(s"The schedule is $s but$only threads ${tnb} can continue")*/
+          }
+        }
+      }
+    } else canContinue
+  }
+
+  /**
+   * This will be called before a schedulable operation begins.
+   * This should not use synchronized
+   */
+  var numThreadsWaiting = new AtomicInteger(0)
+  //var waitingForDecision = Map[Int, Option[Int]]() // Mapping from thread ids to a number indicating who is going to make the choice.
+  var canContinue: Option[(Int, ThreadState)] = None // The result of the decision thread Id of the thread authorized to continue.
+  private def waitForTurn = {
+    synchronized {
+      if (numThreadsWaiting.incrementAndGet() == threadStates.size) {
+        canContinue = decide()
+        notifyAll()
+      }
+      //waitingForDecision(threadId) = Some(numThreadsWaiting)
+      //println(s"$threadId Entering waiting with ticket number $numThreadsWaiting/${waitingForDecision.size}")
+      while (!canProceed()) wait()
+    }
+    numThreadsWaiting.decrementAndGet()
+  }
+
+  /**
+   * To be invoked when a thread is about to complete
+   */
+  private def removeFromSchedule(fakeid: Int) = synchronized {
+    //println(s"$fakeid: I'm taking a decision because I finished")
+    schedule = schedule.filterNot(_ == fakeid)
+    threadStates -= fakeid
+    if (numThreadsWaiting.get() == threadStates.size) {
+      canContinue = decide()
+      notifyAll()
+    }
+  }
+
+  def getOperationLog() = opLog
+}

src/main/scala/pubsub/instrumentation/Stats.scala

@@ -0,0 +1,23 @@
+/* Copyright 2009-2015 EPFL, Lausanne */
+package instrumentation
+
+import java.lang.management._
+
+/**
+ * A collection of methods that can be used to collect run-time statistics about Leon programs.
+ * This is mostly used to test the resources properties of Leon programs
+ */
+object Stats {
+  def timed[T](code: => T)(cont: Long => Unit): T = {
+    var t1 = System.currentTimeMillis()
+    val r = code
+    cont((System.currentTimeMillis() - t1))
+    r
+  }
+
+  def withTime[T](code: => T): (T, Long) = {
+    var t1 = System.currentTimeMillis()
+    val r = code
+    (r, (System.currentTimeMillis() - t1))
+  }
+}

src/main/scala/pubsub/instrumentation/TestHelper.scala

@@ -0,0 +1,124 @@
+package instrumentation
+
+import scala.util.Random
+import scala.collection.mutable.{Map => MutableMap}
+
+import Stats._
+
+object TestHelper {
+  val noOfSchedules = 10000 // set this to 100k during deployment
+  val readWritesPerThread = 20 // maximum number of read/writes possible in one thread
+  val contextSwitchBound = 10
+  val testTimeout = 240 // the total time out for a test in seconds
+  val schedTimeout = 15 // the total time out for execution of a schedule in secs
+
+  // Helpers
+  /*def testManySchedules(op1: => Any): Unit = testManySchedules(List(() => op1))
+  def testManySchedules(op1: => Any, op2: => Any): Unit = testManySchedules(List(() => op1, () => op2))
+  def testManySchedules(op1: => Any, op2: => Any, op3: => Any): Unit = testManySchedules(List(() => op1, () => op2, () => op3))
+  def testManySchedules(op1: => Any, op2: => Any, op3: => Any, op4: => Any): Unit = testManySchedules(List(() => op1, () => op2, () => op3, () => op4))*/
+
+  def testSequential[T](ops: Scheduler => Any)(assertions: T => (Boolean, String)) =
+    testManySchedules(1,
+      (sched: Scheduler) => {
+        (List(() => ops(sched)),
+         (res: List[Any]) => assertions(res.head.asInstanceOf[T]))
+      })
+
+  /**
+   * @numThreads number of threads
+   * @ops operations to be executed, one per thread
+   * @assertion as condition that will executed after all threads have completed (without exceptions)
+   * 					 the arguments are the results of the threads
+   */
+  def testManySchedules(numThreads: Int,
+      ops: Scheduler =>
+        (List[() => Any], // Threads
+         List[Any] => (Boolean, String)) // Assertion
+      ) = {
+    var timeout = testTimeout * 1000L
+    val threadIds = (1 to numThreads)
+    //(1 to scheduleLength).flatMap(_ => threadIds).toList.permutations.take(noOfSchedules).foreach {
+    val schedules = (new ScheduleGenerator(numThreads)).schedules()
+    var schedsExplored = 0
+    schedules.takeWhile(_ => schedsExplored <= noOfSchedules && timeout > 0).foreach {
+      //case _ if timeout <= 0 => // break
+      case schedule =>
+        schedsExplored += 1
+        val schedr = new Scheduler(schedule)
+        //println("Exploring Sched: "+schedule)
+        val (threadOps, assertion) = ops(schedr)
+        if (threadOps.size != numThreads)
+          throw new IllegalStateException(s"Number of threads: $numThreads, do not match operations of threads: $threadOps")
+        timed { schedr.runInParallel(schedTimeout * 1000, threadOps) } { t => timeout -= t } match {
+          case Timeout(msg) =>
+            throw new java.lang.AssertionError("assertion failed\n"+"The schedule took too long to complete. A possible deadlock! \n"+msg)
+          case Except(msg, stkTrace) =>
+            val traceStr = "Thread Stack trace: \n"+stkTrace.map(" at "+_.toString).mkString("\n")
+            throw new java.lang.AssertionError("assertion failed\n"+msg+"\n"+traceStr)
+          case RetVal(threadRes) =>
+            // check the assertion
+            val (success, custom_msg) = assertion(threadRes)
+            if(!success) {
+              val msg = "The following schedule resulted in wrong results: \n" + custom_msg + "\n" + schedr.getOperationLog().mkString("\n")
+              throw new java.lang.AssertionError("Assertion failed: "+msg)
+            }
+        }
+    }
+    if (timeout <= 0) {
+      throw new java.lang.AssertionError("Test took too long to complete! Cannot check all schedules as your code is too slow!")
+    }
+  }
+
+  /**
+   * A schedule generator that is based on the context bound
+   */
+  class ScheduleGenerator(numThreads: Int) {
+    val scheduleLength = readWritesPerThread * numThreads
+    val rands = (1 to scheduleLength).map(i => new Random(0xcafe * i)) // random numbers for choosing a thread at each position
+    def schedules(): LazyList[List[Int]] = {
+      var contextSwitches = 0
+      var contexts = List[Int]() // a stack of thread ids in the order of context-switches
+      val remainingOps = MutableMap[Int, Int]()
+      remainingOps ++= (1 to numThreads).map(i => (i, readWritesPerThread)) // num ops remaining in each thread
+      val liveThreads = (1 to numThreads).toSeq.toBuffer
+
+      /**
+       * Updates remainingOps and liveThreads once a thread is chosen for a position in the schedule
+       */
+      def updateState(tid: Int): Unit = {
+        val remOps = remainingOps(tid)
+        if (remOps == 0) {
+          liveThreads -= tid
+        } else {
+          remainingOps += (tid -> (remOps - 1))
+        }
+      }
+      val schedule = rands.foldLeft(List[Int]()){
+        case (acc, r) if contextSwitches < contextSwitchBound =>
+          val tid = liveThreads(r.nextInt(liveThreads.size))
+          contexts match {
+            case prev :: tail if prev != tid => // we have a new context switch here
+              contexts  +:= tid
+              contextSwitches += 1
+            case prev :: tail =>
+            case _ => // init case
+              contexts +:= tid
+          }
+          updateState(tid)
+          acc :+ tid
+        case (acc, _) => // here context-bound has been reached so complete the schedule without any more context switches
+          if(!contexts.isEmpty) {
+            contexts = contexts.dropWhile(remainingOps(_) == 0)
+          }
+          val tid = contexts match {
+            case top :: tail => top
+            case _ => liveThreads(0)  // here, there has to be threads that have not even started
+          }
+          updateState(tid)
+          acc :+ tid
+      }
+      schedule #:: schedules()
+    }
+  }
+}

src/main/scala/pubsub/instrumentation/TestUtils.scala

@@ -0,0 +1,19 @@
+package instrumentation
+
+import scala.concurrent._
+import scala.concurrent.duration._
+import scala.concurrent.ExecutionContext.Implicits.global
+
+object TestUtils {
+  def failsOrTimesOut[T](action: => T): Boolean = {
+    val asyncAction = Future {
+      action
+    }
+    try {
+      Await.result(asyncAction, 2000.millisecond)
+    } catch {
+      case _: Throwable => return true
+    }
+    return false
+  }
+}

src/main/scala/pubsub/network/TCPReader.scala

@@ -0,0 +1,32 @@
+package pubsub.network
+
+import java.net.Socket
+
+import pubsub.Client
+import pubsub.collection.BoundedBuffer
+import pubsub.command._
+
+class TCPReader(id: Int, socket: Socket, buffer: BoundedBuffer[Command]) {
+  val client = new Client(socket, id)
+  val reader = new CommandReader(socket.getInputStream(), client)
+
+  def read(): Unit = {
+    client.sayHello()
+    println(s"New client: ${client.name}")
+    while(client.isConnected) {
+
+      reader.fetchCommand() match {
+        case c: EndOfClient =>
+          buffer.put(c)
+          println(c)
+          client.sayGoodbye()
+          client.close()
+        case _: MalformedCommand =>
+          client.invalidPreviousCommand()
+        case command =>
+          println(command)
+          buffer.put(command)
+      }
+    }
+  }
+}

src/test/scala/pubsub/BoundedBufferSuite.scala

@@ -0,0 +1,43 @@
+package pubsub
+
+import scala.concurrent._
+import scala.concurrent.duration._
+import scala.concurrent.ExecutionContext.Implicits.global
+import scala.collection.mutable.HashMap
+import pubsub.collection._
+import org.junit._
+import org.junit.Assert.assertEquals
+
+import instrumentation._
+import instrumentation.Stats._
+import TestHelper._
+import TestUtils._
+
+class BoundedBufferSuite {
+  @Test def `Should work in a sequential setting`: Unit = {
+    testSequential[(Int, Int, Int, Int)]{ sched =>
+      val buffer = new SchedulableBoundedBuffer[Int](4, sched)
+      buffer.put(1)
+      buffer.put(2)
+      buffer.put(3)
+      buffer.put(4)
+      (buffer.take(),
+      buffer.take(),
+      buffer.take(),
+      buffer.take())
+    }{ tuple =>
+      (tuple == (1, 2, 3, 4), s"Expected (1, 2, 3, 4) got $tuple")
+    }
+  }
+
+  @Test def `Should work when Thread 1: 'put(1)', Thread 2: 'take' and a buffer of size 1`: Unit = {
+    testManySchedules(2, sched => {
+      val prodCons = new SchedulableBoundedBuffer[Int](1, sched)
+      (List(() => prodCons.put(1), () => prodCons.take()),
+       args => (args(1) == 1, s"expected 1 your 'take' implementation returned ${args(1)}"))
+    })
+  }
+
+
+  @Rule def individualTestTimeout = new org.junit.rules.Timeout(400 * 1000)
+}