assignment/src/main/java/ch/unisg/assignment/assignment/application/port/in/ApplyForTaskUseCase.java

@@ -1,7 +0,0 @@
-package ch.unisg.assignment.assignment.application.port.in;
-
-import ch.unisg.assignment.assignment.domain.Task;
-
-public interface ApplyForTaskUseCase {
-    Task applyForTask(ApplyForTaskCommand applyForTaskCommand);
-}

roster/pom.xml

@@ -56,6 +56,12 @@
 			<version>1.2</version>
 		</dependency>
 
+        <dependency>
+			<groupId>org.eclipse.paho</groupId>
+			<artifactId>org.eclipse.paho.client.mqttv3</artifactId>
+			<version>1.2.5</version>
+		</dependency>
+
         <dependency>
 			<groupId>org.json</groupId>
 			<artifactId>json</artifactId>

roster/src/main/java/ch/unisg/roster/RosterApplication.java

@@ -1,13 +1,13 @@
-package ch.unisg.assignment;
+package ch.unisg.roster;
 
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 
 @SpringBootApplication
-public class AssignmentApplication {
+public class RosterApplication {
 
 	public static void main(String[] args) {
-		SpringApplication.run(AssignmentApplication.class, args);
+		SpringApplication.run(RosterApplication.class, args);
 	}
 
 }

roster/src/main/java/ch/unisg/roster/roster/adapter/common/clients/TapasMqttClient.java

@@ -0,0 +1,94 @@
+package ch.unisg.roster.roster.adapter.common.clients;
+
+import ch.unisg.roster.roster.adapter.in.messaging.mqtt.AuctionEventsMqttDispatcher;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.eclipse.paho.client.mqttv3.*;
+import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;
+
+import java.nio.charset.StandardCharsets;
+import java.util.UUID;
+
+/**
+ * MQTT client for your TAPAS application. This class is defined as a singleton, but it does not have
+ * to be this way. This class is only provided as an example to help you bootstrap your project.
+ * You are welcomed to change this class as you see fit.
+ */
+public class TapasMqttClient {
+    private static final Logger LOGGER = LogManager.getLogger(TapasMqttClient.class);
+
+    private static TapasMqttClient tapasClient = null;
+
+    private MqttClient mqttClient;
+    private final String mqttClientId;
+    private final String brokerAddress;
+
+    private final MessageReceivedCallback messageReceivedCallback;
+
+    private final AuctionEventsMqttDispatcher dispatcher;
+
+    private TapasMqttClient(String brokerAddress, AuctionEventsMqttDispatcher dispatcher) {
+        this.mqttClientId = UUID.randomUUID().toString();
+        this.brokerAddress = brokerAddress;
+
+        this.messageReceivedCallback = new MessageReceivedCallback();
+
+        this.dispatcher = dispatcher;
+    }
+
+    public static synchronized TapasMqttClient getInstance(String brokerAddress,
+            AuctionEventsMqttDispatcher dispatcher) {
+
+        if (tapasClient == null) {
+            tapasClient = new TapasMqttClient(brokerAddress, dispatcher);
+        }
+
+        return tapasClient;
+    }
+
+    public void startReceivingMessages() throws MqttException {
+        mqttClient = new org.eclipse.paho.client.mqttv3.MqttClient(brokerAddress, mqttClientId, new MemoryPersistence());
+        mqttClient.connect();
+        mqttClient.setCallback(messageReceivedCallback);
+
+        subscribeToAllTopics();
+    }
+
+    public void stopReceivingMessages() throws MqttException {
+        mqttClient.disconnect();
+    }
+
+    private void subscribeToAllTopics() throws MqttException {
+        for (String topic : dispatcher.getAllTopics()) {
+            subscribeToTopic(topic);
+        }
+    }
+
+    private void subscribeToTopic(String topic) throws MqttException {
+        mqttClient.subscribe(topic);
+    }
+
+    private void publishMessage(String topic, String payload) throws MqttException {
+        MqttMessage message = new MqttMessage(payload.getBytes(StandardCharsets.UTF_8));
+        mqttClient.publish(topic, message);
+    }
+
+    private class MessageReceivedCallback implements MqttCallback {
+
+        @Override
+        public void connectionLost(Throwable cause) {  }
+
+        @Override
+        public void messageArrived(String topic, MqttMessage message) {
+            LOGGER.info("Received new MQTT message for topic " + topic + ": "
+                + new String(message.getPayload()));
+
+            if (topic != null && !topic.isEmpty()) {
+                dispatcher.dispatchEvent(topic, message);
+            }
+        }
+
+        @Override
+        public void deliveryComplete(IMqttDeliveryToken token) {  }
+    }
+}

roster/src/main/java/ch/unisg/roster/roster/adapter/in/messaging/mqtt/AuctionEventMqttListener.java

@@ -0,0 +1,11 @@
+package ch.unisg.roster.roster.adapter.in.messaging.mqtt;
+
+import org.eclipse.paho.client.mqttv3.MqttMessage;
+
+/**
+ * Abstract MQTT listener for auction-related events
+ */
+public abstract class AuctionEventMqttListener {
+
+    public abstract boolean handleEvent(MqttMessage message);
+}

roster/src/main/java/ch/unisg/roster/roster/adapter/in/messaging/mqtt/AuctionEventsMqttDispatcher.java

@@ -0,0 +1,52 @@
+package ch.unisg.roster.roster.adapter.in.messaging.mqtt;
+
+import org.eclipse.paho.client.mqttv3.*;
+
+import java.util.Hashtable;
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * Dispatches MQTT messages for known topics to associated event listeners. Used in conjunction with
+ * {@link ch.unisg.tapas.auctionhouse.adapter.common.clients.TapasMqttClient}.
+ *
+ * This is where you would define MQTT topics and map them to event listeners (see
+ * {@link AuctionEventsMqttDispatcher#initRouter()}).
+ *
+ * This class is only provided as an example to help you bootstrap the project. You are welcomed to
+ * change this class as you see fit.
+ */
+public class AuctionEventsMqttDispatcher {
+    private final Map<String, AuctionEventMqttListener> router;
+
+    public AuctionEventsMqttDispatcher() {
+        this.router = new Hashtable<>();
+        initRouter();
+    }
+
+    // TODO: Register here your topics and event listener adapters
+    private void initRouter() {
+        router.put("ch/unisg/tapas-group-tutors/executors/added", new ExecutorAddedEventListenerMqttAdapter());
+        router.put("ch/unisg/tapas-group-tutors/executors/removed", new ExecutorRemovedEventListenerMqttAdapter());
+    }
+
+    /**
+     * Returns all topics registered with this dispatcher.
+     *
+     * @return the set of registered topics
+     */
+    public Set<String> getAllTopics() {
+        return router.keySet();
+    }
+
+    /**
+     * Dispatches an event received via MQTT for a given topic.
+     *
+     * @param topic the topic for which the MQTT message was received
+     * @param message the received MQTT message
+     */
+    public void dispatchEvent(String topic, MqttMessage message) {
+        AuctionEventMqttListener listener = router.get(topic);
+        listener.handleEvent(message);
+    }
+}

roster/src/main/java/ch/unisg/roster/roster/adapter/in/messaging/mqtt/ExecutorAddedEventListenerMqttAdapter.java

@@ -0,0 +1,44 @@
+package ch.unisg.roster.roster.adapter.in.messaging.mqtt;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.eclipse.paho.client.mqttv3.MqttMessage;
+
+import ch.unisg.common.valueobject.ExecutorURI;
+import ch.unisg.roster.roster.application.handler.ExecutorAddedHandler;
+import ch.unisg.roster.roster.application.port.in.ExecutorAddedEvent;
+import ch.unisg.roster.roster.domain.valueobject.ExecutorType;
+
+public class ExecutorAddedEventListenerMqttAdapter extends AuctionEventMqttListener {
+    private static final Logger LOGGER = LogManager.getLogger(ExecutorAddedEventListenerMqttAdapter.class);
+
+    @Override
+    public boolean handleEvent(MqttMessage message) {
+        String payload = new String(message.getPayload());
+
+        try {
+            // Note: this messge representation is provided only as an example. You should use a
+            // representation that makes sense in the context of your application.
+            JsonNode data = new ObjectMapper().readTree(payload);
+
+            String taskType = data.get("taskType").asText();
+            String executorId = data.get("executorURI").asText();
+
+            ExecutorAddedEvent executorAddedEvent = new ExecutorAddedEvent(
+                new ExecutorURI(executorId),
+                new ExecutorType(taskType)
+            );
+
+            ExecutorAddedHandler newExecutorHandler = new ExecutorAddedHandler();
+            newExecutorHandler.handleNewExecutorEvent(executorAddedEvent);
+        } catch (JsonProcessingException | NullPointerException e) {
+            LOGGER.error(e.getMessage(), e);
+            return false;
+        }
+
+        return true;
+    }
+}

roster/src/main/java/ch/unisg/roster/roster/adapter/in/messaging/mqtt/ExecutorRemovedEventListenerMqttAdapter.java

@@ -0,0 +1,41 @@
+package ch.unisg.roster.roster.adapter.in.messaging.mqtt;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.eclipse.paho.client.mqttv3.MqttMessage;
+
+import ch.unisg.common.valueobject.ExecutorURI;
+import ch.unisg.roster.roster.application.handler.ExecutorRemovedHandler;
+import ch.unisg.roster.roster.application.port.in.ExecutorRemovedEvent;
+
+public class ExecutorRemovedEventListenerMqttAdapter extends AuctionEventMqttListener {
+    private static final Logger LOGGER = LogManager.getLogger(ExecutorRemovedEventListenerMqttAdapter.class);
+
+    @Override
+    public boolean handleEvent(MqttMessage message) {
+        String payload = new String(message.getPayload());
+
+        try {
+            // Note: this messge representation is provided only as an example. You should use a
+            // representation that makes sense in the context of your application.
+            JsonNode data = new ObjectMapper().readTree(payload);
+
+            String executorId = data.get("executorURI").asText();
+
+            ExecutorRemovedEvent executorRemovedEvent = new ExecutorRemovedEvent(
+                new ExecutorURI(executorId));
+
+            ExecutorRemovedHandler executorRemovedHandler = new ExecutorRemovedHandler();
+            executorRemovedHandler.handleExecutorRemovedEvent(executorRemovedEvent);
+
+        } catch (JsonProcessingException | NullPointerException e) {
+            LOGGER.error(e.getMessage(), e);
+            return false;
+        }
+
+        return true;
+    }
+}

roster/src/main/java/ch/unisg/roster/roster/adapter/in/web/ApplyForTaskController.java

@@ -1,13 +1,13 @@
-package ch.unisg.assignment.assignment.adapter.in.web;
+package ch.unisg.roster.roster.adapter.in.web;
 
 import org.springframework.web.bind.annotation.PostMapping;
 import org.springframework.web.bind.annotation.RequestBody;
 import org.springframework.web.bind.annotation.RestController;
 
-import ch.unisg.assignment.assignment.application.port.in.ApplyForTaskCommand;
+import ch.unisg.roster.roster.application.port.in.ApplyForTaskCommand;
-import ch.unisg.assignment.assignment.application.port.in.ApplyForTaskUseCase;
+import ch.unisg.roster.roster.application.port.in.ApplyForTaskUseCase;
-import ch.unisg.assignment.assignment.domain.ExecutorInfo;
+import ch.unisg.roster.roster.domain.ExecutorInfo;
-import ch.unisg.assignment.assignment.domain.Task;
+import ch.unisg.roster.roster.domain.Task;
 
 @RestController
 public class ApplyForTaskController {

roster/src/main/java/ch/unisg/roster/roster/adapter/in/web/DeleteTaskController.java

@@ -1,4 +1,4 @@
-package ch.unisg.assignment.assignment.adapter.in.web;
+package ch.unisg.roster.roster.adapter.in.web;
 
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
@@ -6,9 +6,9 @@ import org.springframework.web.bind.annotation.DeleteMapping;
 import org.springframework.web.bind.annotation.RequestBody;
 import org.springframework.web.bind.annotation.RestController;
 
-import ch.unisg.assignment.assignment.application.port.in.DeleteTaskCommand;
+import ch.unisg.roster.roster.application.port.in.DeleteTaskCommand;
-import ch.unisg.assignment.assignment.application.port.in.DeleteTaskUseCase;
+import ch.unisg.roster.roster.application.port.in.DeleteTaskUseCase;
-import ch.unisg.assignment.assignment.domain.Task;
+import ch.unisg.roster.roster.domain.Task;
 
 @RestController
 public class DeleteTaskController {

roster/src/main/java/ch/unisg/roster/roster/adapter/in/web/NewTaskController.java

@@ -1,4 +1,4 @@
-package ch.unisg.assignment.assignment.adapter.in.web;
+package ch.unisg.roster.roster.adapter.in.web;
 
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
@@ -6,9 +6,9 @@ import org.springframework.web.bind.annotation.PostMapping;
 import org.springframework.web.bind.annotation.RequestBody;
 import org.springframework.web.bind.annotation.RestController;
 
-import ch.unisg.assignment.assignment.application.port.in.NewTaskCommand;
+import ch.unisg.roster.roster.application.port.in.NewTaskCommand;
-import ch.unisg.assignment.assignment.application.port.in.NewTaskUseCase;
+import ch.unisg.roster.roster.application.port.in.NewTaskUseCase;
-import ch.unisg.assignment.assignment.domain.Task;
+import ch.unisg.roster.roster.domain.Task;
 
 @RestController
 public class NewTaskController {

roster/src/main/java/ch/unisg/roster/roster/adapter/in/web/TaskCompletedController.java

@@ -1,4 +1,4 @@
-package ch.unisg.assignment.assignment.adapter.in.web;
+package ch.unisg.roster.roster.adapter.in.web;
 
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
@@ -6,9 +6,9 @@ import org.springframework.web.bind.annotation.PostMapping;
 import org.springframework.web.bind.annotation.RequestBody;
 import org.springframework.web.bind.annotation.RestController;
 
-import ch.unisg.assignment.assignment.application.port.in.TaskCompletedCommand;
+import ch.unisg.roster.roster.application.port.in.TaskCompletedCommand;
-import ch.unisg.assignment.assignment.application.port.in.TaskCompletedUseCase;
+import ch.unisg.roster.roster.application.port.in.TaskCompletedUseCase;
-import ch.unisg.assignment.assignment.domain.Task;
+import ch.unisg.roster.roster.domain.Task;
 
 @RestController
 public class TaskCompletedController {

roster/src/main/java/ch/unisg/roster/roster/adapter/in/web/WebControllerExceptionHandler.java

@@ -1,4 +1,4 @@
-package ch.unisg.assignment.assignment.adapter.in.web;
+package ch.unisg.roster.roster.adapter.in.web;
 
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;

roster/src/main/java/ch/unisg/roster/roster/adapter/out/web/GetAllExecutorInExecutorPoolByTypeAdapter.java

@@ -1,4 +1,4 @@
-package ch.unisg.assignment.assignment.adapter.out.web;
+package ch.unisg.roster.roster.adapter.out.web;
 
 import java.io.IOException;
 import java.net.URI;
@@ -14,8 +14,8 @@ import org.springframework.context.annotation.Primary;
 import org.springframework.http.HttpStatus;
 import org.springframework.stereotype.Component;
 
-import ch.unisg.assignment.assignment.application.port.out.GetAllExecutorInExecutorPoolByTypePort;
+import ch.unisg.roster.roster.application.port.out.GetAllExecutorInExecutorPoolByTypePort;
-import ch.unisg.assignment.assignment.domain.valueobject.ExecutorType;
+import ch.unisg.roster.roster.domain.valueobject.ExecutorType;
 
 @Component
 @Primary

roster/src/main/java/ch/unisg/roster/roster/adapter/out/web/PublishNewTaskEventAdapter.java

@@ -1,4 +1,4 @@
-package ch.unisg.assignment.assignment.adapter.out.web;
+package ch.unisg.roster.roster.adapter.out.web;
 
 import java.io.IOException;
 import java.net.URI;
@@ -12,8 +12,8 @@ import org.springframework.beans.factory.annotation.Value;
 import org.springframework.context.annotation.Primary;
 import org.springframework.stereotype.Component;
 
-import ch.unisg.assignment.assignment.application.port.out.NewTaskEventPort;
+import ch.unisg.roster.roster.application.port.out.NewTaskEventPort;
-import ch.unisg.assignment.assignment.domain.event.NewTaskEvent;
+import ch.unisg.roster.roster.domain.event.NewTaskEvent;
 
 @Component
 @Primary

roster/src/main/java/ch/unisg/roster/roster/adapter/out/web/PublishTaskAssignedEventAdapter.java

@@ -1,4 +1,4 @@
-package ch.unisg.assignment.assignment.adapter.out.web;
+package ch.unisg.roster.roster.adapter.out.web;
 
 import java.io.IOException;
 import java.net.URI;
@@ -13,8 +13,8 @@ import org.springframework.beans.factory.annotation.Value;
 import org.springframework.context.annotation.Primary;
 import org.springframework.stereotype.Component;
 
-import ch.unisg.assignment.assignment.application.port.out.TaskAssignedEventPort;
+import ch.unisg.roster.roster.application.port.out.TaskAssignedEventPort;
-import ch.unisg.assignment.assignment.domain.event.TaskAssignedEvent;
+import ch.unisg.roster.roster.domain.event.TaskAssignedEvent;
 
 @Component
 @Primary

roster/src/main/java/ch/unisg/roster/roster/adapter/out/web/PublishTaskCompletedEventAdapter.java

@@ -1,4 +1,4 @@
-package ch.unisg.assignment.assignment.adapter.out.web;
+package ch.unisg.roster.roster.adapter.out.web;
 
 import java.io.IOException;
 import java.net.URI;
@@ -13,8 +13,8 @@ import org.springframework.beans.factory.annotation.Value;
 import org.springframework.context.annotation.Primary;
 import org.springframework.stereotype.Component;
 
-import ch.unisg.assignment.assignment.application.port.out.TaskCompletedEventPort;
+import ch.unisg.roster.roster.application.port.out.TaskCompletedEventPort;
-import ch.unisg.assignment.assignment.domain.event.TaskCompletedEvent;
+import ch.unisg.roster.roster.domain.event.TaskCompletedEvent;
 
 @Component
 @Primary

roster/src/main/java/ch/unisg/roster/roster/application/handler/ExecutorAddedHandler.java

@@ -0,0 +1,16 @@
+package ch.unisg.roster.roster.application.handler;
+
+import ch.unisg.roster.roster.application.port.in.ExecutorAddedEvent;
+import ch.unisg.roster.roster.application.port.in.ExecutorAddedEventHandler;
+import ch.unisg.roster.roster.domain.ExecutorRegistry;
+import org.springframework.stereotype.Component;
+
+@Component
+public class ExecutorAddedHandler implements ExecutorAddedEventHandler {
+
+    @Override
+    public boolean handleNewExecutorEvent(ExecutorAddedEvent executorAddedEvent) {
+        return ExecutorRegistry.getInstance().addExecutor(executorAddedEvent.getExecutorType(),
+            executorAddedEvent.getExecutorURI());
+    }
+}

roster/src/main/java/ch/unisg/roster/roster/application/handler/ExecutorRemovedHandler.java

@@ -0,0 +1,19 @@
+package ch.unisg.roster.roster.application.handler;
+
+import ch.unisg.roster.roster.application.port.in.ExecutorRemovedEvent;
+import ch.unisg.roster.roster.application.port.in.ExecutorRemovedEventHandler;
+import ch.unisg.roster.roster.domain.ExecutorRegistry;
+import org.springframework.stereotype.Component;
+
+/**
+ * Handler for executor removed events. It removes the executor from this roster's executor
+ * registry.
+ */
+@Component
+public class ExecutorRemovedHandler implements ExecutorRemovedEventHandler {
+
+    @Override
+    public boolean handleExecutorRemovedEvent(ExecutorRemovedEvent executorRemovedEvent) {
+        return ExecutorRegistry.getInstance().removeExecutor(executorRemovedEvent.getExecutorURI());
+    }
+}

roster/src/main/java/ch/unisg/roster/roster/application/port/in/ApplyForTaskCommand.java

@@ -1,8 +1,8 @@
-package ch.unisg.assignment.assignment.application.port.in;
+package ch.unisg.roster.roster.application.port.in;
 
 import javax.validation.constraints.NotNull;
 
-import ch.unisg.assignment.assignment.domain.valueobject.ExecutorType;
+import ch.unisg.roster.roster.domain.valueobject.ExecutorType;
 import ch.unisg.common.validation.SelfValidating;
 import ch.unisg.common.valueobject.ExecutorURI;
 import lombok.EqualsAndHashCode;

roster/src/main/java/ch/unisg/roster/roster/application/port/in/ApplyForTaskUseCase.java

@@ -0,0 +1,7 @@
+package ch.unisg.roster.roster.application.port.in;
+
+import ch.unisg.roster.roster.domain.Task;
+
+public interface ApplyForTaskUseCase {
+    Task applyForTask(ApplyForTaskCommand applyForTaskCommand);
+}

roster/src/main/java/ch/unisg/roster/roster/application/port/in/DeleteTaskCommand.java

@@ -1,8 +1,8 @@
-package ch.unisg.assignment.assignment.application.port.in;
+package ch.unisg.roster.roster.application.port.in;
 
 import javax.validation.constraints.NotNull;
 
-import ch.unisg.assignment.assignment.domain.valueobject.ExecutorType;
+import ch.unisg.roster.roster.domain.valueobject.ExecutorType;
 import ch.unisg.common.validation.SelfValidating;
 import lombok.EqualsAndHashCode;
 import lombok.Value;

roster/src/main/java/ch/unisg/roster/roster/application/port/in/DeleteTaskUseCase.java

@@ -1,4 +1,4 @@
-package ch.unisg.assignment.assignment.application.port.in;
+package ch.unisg.roster.roster.application.port.in;
 
 public interface DeleteTaskUseCase {
     boolean deleteTask(DeleteTaskCommand deleteTaskCommand);

roster/src/main/java/ch/unisg/roster/roster/application/port/in/ExecutorAddedEvent.java

@@ -0,0 +1,33 @@
+package ch.unisg.roster.roster.application.port.in;
+
+import lombok.Value;
+
+import javax.validation.constraints.NotNull;
+
+import ch.unisg.common.validation.SelfValidating;
+import ch.unisg.common.valueobject.ExecutorURI;
+import ch.unisg.roster.roster.domain.valueobject.ExecutorType;
+
+/**
+ * Event that notifies the auction house that an executor has been added to this TAPAS application.
+ */
+@Value
+public class ExecutorAddedEvent extends SelfValidating<ExecutorAddedEvent> {
+    @NotNull
+    private final ExecutorURI executorURI;
+
+    @NotNull
+    private final ExecutorType executorType;
+
+    /**
+     * Constructs an executor added event.
+     *
+     * @param executorURI the identifier of the executor that was added to this TAPAS application
+     */
+    public ExecutorAddedEvent(ExecutorURI executorURI, ExecutorType executorType) {
+        this.executorURI = executorURI;
+        this.executorType = executorType;
+
+        this.validateSelf();
+    }
+}

roster/src/main/java/ch/unisg/roster/roster/application/port/in/ExecutorAddedEventHandler.java

@@ -0,0 +1,6 @@
+package ch.unisg.roster.roster.application.port.in;
+
+public interface ExecutorAddedEventHandler {
+
+    boolean handleNewExecutorEvent(ExecutorAddedEvent executorAddedEvent);
+}

roster/src/main/java/ch/unisg/roster/roster/application/port/in/ExecutorRemovedEvent.java

@@ -0,0 +1,27 @@
+package ch.unisg.roster.roster.application.port.in;
+
+import lombok.Value;
+
+import javax.validation.constraints.NotNull;
+
+import ch.unisg.common.validation.SelfValidating;
+import ch.unisg.common.valueobject.ExecutorURI;
+
+/**
+ * Event that notifies the auction house that an executor has been removed from this TAPAS application.
+ */
+@Value
+public class ExecutorRemovedEvent extends SelfValidating<ExecutorRemovedEvent> {
+    @NotNull
+    private final ExecutorURI executorURI;
+
+    /**
+     * Constructs an executor removed event.
+     *
+     * @param executorURI the identifier of the executor that was removed from this TAPAS application
+     */
+    public ExecutorRemovedEvent(ExecutorURI executorURI) {
+        this.executorURI = executorURI;
+        this.validateSelf();
+    }
+}

roster/src/main/java/ch/unisg/roster/roster/application/port/in/ExecutorRemovedEventHandler.java

@@ -0,0 +1,6 @@
+package ch.unisg.roster.roster.application.port.in;
+
+public interface ExecutorRemovedEventHandler {
+
+    boolean handleExecutorRemovedEvent(ExecutorRemovedEvent executorRemovedEvent);
+}

roster/src/main/java/ch/unisg/roster/roster/application/port/in/NewTaskCommand.java

@@ -1,8 +1,8 @@
-package ch.unisg.assignment.assignment.application.port.in;
+package ch.unisg.roster.roster.application.port.in;
 
 import javax.validation.constraints.NotNull;
 
-import ch.unisg.assignment.assignment.domain.valueobject.ExecutorType;
+import ch.unisg.roster.roster.domain.valueobject.ExecutorType;
 import ch.unisg.common.validation.SelfValidating;
 import lombok.EqualsAndHashCode;
 import lombok.Value;

roster/src/main/java/ch/unisg/roster/roster/application/port/in/NewTaskUseCase.java

@@ -1,4 +1,4 @@
-package ch.unisg.assignment.assignment.application.port.in;
+package ch.unisg.roster.roster.application.port.in;
 
 public interface NewTaskUseCase {
     boolean addNewTaskToQueue(NewTaskCommand newTaskCommand);

roster/src/main/java/ch/unisg/roster/roster/application/port/in/TaskCompletedCommand.java

@@ -1,4 +1,4 @@
-package ch.unisg.assignment.assignment.application.port.in;
+package ch.unisg.roster.roster.application.port.in;
 
 import javax.validation.constraints.NotNull;
 

roster/src/main/java/ch/unisg/roster/roster/application/port/in/TaskCompletedUseCase.java

@@ -1,4 +1,4 @@
-package ch.unisg.assignment.assignment.application.port.in;
+package ch.unisg.roster.roster.application.port.in;
 
 public interface TaskCompletedUseCase {
     void taskCompleted(TaskCompletedCommand taskCompletedCommand);

roster/src/main/java/ch/unisg/roster/roster/application/port/out/GetAllExecutorInExecutorPoolByTypePort.java

@@ -1,6 +1,6 @@
-package ch.unisg.assignment.assignment.application.port.out;
+package ch.unisg.roster.roster.application.port.out;
 
-import ch.unisg.assignment.assignment.domain.valueobject.ExecutorType;
+import ch.unisg.roster.roster.domain.valueobject.ExecutorType;
 
 public interface GetAllExecutorInExecutorPoolByTypePort {
     /**

roster/src/main/java/ch/unisg/roster/roster/application/port/out/NewTaskEventPort.java

@@ -1,6 +1,6 @@
-package ch.unisg.assignment.assignment.application.port.out;
+package ch.unisg.roster.roster.application.port.out;
 
-import ch.unisg.assignment.assignment.domain.event.NewTaskEvent;
+import ch.unisg.roster.roster.domain.event.NewTaskEvent;
 
 public interface NewTaskEventPort {
     /**

roster/src/main/java/ch/unisg/roster/roster/application/port/out/TaskAssignedEventPort.java

@@ -1,6 +1,6 @@
-package ch.unisg.assignment.assignment.application.port.out;
+package ch.unisg.roster.roster.application.port.out;
 
-import ch.unisg.assignment.assignment.domain.event.TaskAssignedEvent;
+import ch.unisg.roster.roster.domain.event.TaskAssignedEvent;
 
 public interface TaskAssignedEventPort {
     /**

roster/src/main/java/ch/unisg/roster/roster/application/port/out/TaskCompletedEventPort.java

@@ -1,6 +1,6 @@
-package ch.unisg.assignment.assignment.application.port.out;
+package ch.unisg.roster.roster.application.port.out;
 
-import ch.unisg.assignment.assignment.domain.event.TaskCompletedEvent;
+import ch.unisg.roster.roster.domain.event.TaskCompletedEvent;
 
 public interface TaskCompletedEventPort {
     /**

roster/src/main/java/ch/unisg/roster/roster/application/service/ApplyForTaskService.java

@@ -1,15 +1,15 @@
-package ch.unisg.assignment.assignment.application.service;
+package ch.unisg.roster.roster.application.service;
 
 import javax.transaction.Transactional;
 
 import org.springframework.stereotype.Component;
 
-import ch.unisg.assignment.assignment.application.port.in.ApplyForTaskCommand;
+import ch.unisg.roster.roster.application.port.in.ApplyForTaskCommand;
-import ch.unisg.assignment.assignment.application.port.in.ApplyForTaskUseCase;
+import ch.unisg.roster.roster.application.port.in.ApplyForTaskUseCase;
-import ch.unisg.assignment.assignment.application.port.out.TaskAssignedEventPort;
+import ch.unisg.roster.roster.application.port.out.TaskAssignedEventPort;
-import ch.unisg.assignment.assignment.domain.Roster;
+import ch.unisg.roster.roster.domain.Roster;
-import ch.unisg.assignment.assignment.domain.Task;
+import ch.unisg.roster.roster.domain.Task;
-import ch.unisg.assignment.assignment.domain.event.TaskAssignedEvent;
+import ch.unisg.roster.roster.domain.event.TaskAssignedEvent;
 import lombok.RequiredArgsConstructor;
 
 @RequiredArgsConstructor

roster/src/main/java/ch/unisg/roster/roster/application/service/DeleteTaskService.java

@@ -1,12 +1,12 @@
-package ch.unisg.assignment.assignment.application.service;
+package ch.unisg.roster.roster.application.service;
 
 import javax.transaction.Transactional;
 
 import org.springframework.stereotype.Component;
 
-import ch.unisg.assignment.assignment.application.port.in.DeleteTaskCommand;
+import ch.unisg.roster.roster.application.port.in.DeleteTaskCommand;
-import ch.unisg.assignment.assignment.application.port.in.DeleteTaskUseCase;
+import ch.unisg.roster.roster.application.port.in.DeleteTaskUseCase;
-import ch.unisg.assignment.assignment.domain.Roster;
+import ch.unisg.roster.roster.domain.Roster;
 import lombok.RequiredArgsConstructor;
 
 @RequiredArgsConstructor

roster/src/main/java/ch/unisg/roster/roster/application/service/NewTaskService.java

@@ -1,16 +1,16 @@
-package ch.unisg.assignment.assignment.application.service;
+package ch.unisg.roster.roster.application.service;
 
 import javax.transaction.Transactional;
 
 import org.springframework.stereotype.Component;
 
-import ch.unisg.assignment.assignment.application.port.in.NewTaskCommand;
+import ch.unisg.roster.roster.application.port.in.NewTaskCommand;
-import ch.unisg.assignment.assignment.application.port.in.NewTaskUseCase;
+import ch.unisg.roster.roster.application.port.in.NewTaskUseCase;
-import ch.unisg.assignment.assignment.application.port.out.GetAllExecutorInExecutorPoolByTypePort;
+import ch.unisg.roster.roster.application.port.out.NewTaskEventPort;
-import ch.unisg.assignment.assignment.application.port.out.NewTaskEventPort;
+import ch.unisg.roster.roster.domain.ExecutorRegistry;
-import ch.unisg.assignment.assignment.domain.Roster;
+import ch.unisg.roster.roster.domain.Roster;
-import ch.unisg.assignment.assignment.domain.Task;
+import ch.unisg.roster.roster.domain.Task;
-import ch.unisg.assignment.assignment.domain.event.NewTaskEvent;
+import ch.unisg.roster.roster.domain.event.NewTaskEvent;
 import lombok.RequiredArgsConstructor;
 
 @RequiredArgsConstructor
@@ -19,7 +19,6 @@ import lombok.RequiredArgsConstructor;
 public class NewTaskService implements NewTaskUseCase {
 
     private final NewTaskEventPort newTaskEventPort;
-    private final GetAllExecutorInExecutorPoolByTypePort getAllExecutorInExecutorPoolByTypePort;
 
     /**
     *   Checks if we can execute the give task, if yes the task gets added to the task queue and return true.
@@ -29,9 +28,10 @@ public class NewTaskService implements NewTaskUseCase {
     @Override
     public boolean addNewTaskToQueue(NewTaskCommand command) {
 
-        // if (!getAllExecutorInExecutorPoolByTypePort.doesExecutorTypeExist(command.getTaskType())) {
+        ExecutorRegistry executorRegistry = ExecutorRegistry.getInstance();
-        //     return false;
+        if (!executorRegistry.containsTaskType(command.getTaskType())) {
-        // }
+            return false;
+        }
 
         Task task = new Task(command.getTaskID(), command.getTaskType());
 

roster/src/main/java/ch/unisg/roster/roster/application/service/TaskCompletedService.java

@@ -1,14 +1,14 @@
-package ch.unisg.assignment.assignment.application.service;
+package ch.unisg.roster.roster.application.service;
 
 import javax.transaction.Transactional;
 
 import org.springframework.stereotype.Component;
 
-import ch.unisg.assignment.assignment.application.port.in.TaskCompletedCommand;
+import ch.unisg.roster.roster.application.port.in.TaskCompletedCommand;
-import ch.unisg.assignment.assignment.application.port.in.TaskCompletedUseCase;
+import ch.unisg.roster.roster.application.port.in.TaskCompletedUseCase;
-import ch.unisg.assignment.assignment.application.port.out.TaskCompletedEventPort;
+import ch.unisg.roster.roster.application.port.out.TaskCompletedEventPort;
-import ch.unisg.assignment.assignment.domain.Roster;
+import ch.unisg.roster.roster.domain.Roster;
-import ch.unisg.assignment.assignment.domain.event.TaskCompletedEvent;
+import ch.unisg.roster.roster.domain.event.TaskCompletedEvent;
 import lombok.RequiredArgsConstructor;
 
 @RequiredArgsConstructor

roster/src/main/java/ch/unisg/roster/roster/domain/ExecutorInfo.java

@@ -1,6 +1,6 @@
-package ch.unisg.assignment.assignment.domain;
+package ch.unisg.roster.roster.domain;
 
-import ch.unisg.assignment.assignment.domain.valueobject.ExecutorType;
+import ch.unisg.roster.roster.domain.valueobject.ExecutorType;
 import ch.unisg.common.valueobject.ExecutorURI;
 import lombok.Getter;
 import lombok.Setter;

roster/src/main/java/ch/unisg/roster/roster/domain/ExecutorRegistry.java

@@ -0,0 +1,92 @@
+package ch.unisg.roster.roster.domain;
+
+import java.util.*;
+
+import ch.unisg.common.valueobject.ExecutorURI;
+import ch.unisg.roster.roster.domain.valueobject.ExecutorType;
+
+/**
+ * Registry that keeps a track of executors internal to the TAPAS application and the types of tasks
+ * they can achieve. One executor may correspond to multiple task types.
+ * This class is a singleton.
+ */
+public class ExecutorRegistry {
+    private static ExecutorRegistry registry;
+
+    private final Map<ExecutorType, Set<ExecutorURI>> executors;
+
+    private ExecutorRegistry() {
+        this.executors = new Hashtable<>();
+    }
+
+    public static synchronized ExecutorRegistry getInstance() {
+        if (registry == null) {
+            registry = new ExecutorRegistry();
+        }
+
+        return registry;
+    }
+
+    /**
+     * Adds an executor to the registry for a given task type.
+     *
+     * @param taskType the type of the task
+     * @param executorIdentifier the identifier of the executor (can be any string)
+     * @return true unless a runtime exception occurs
+     */
+    public boolean addExecutor(ExecutorType executorType, ExecutorURI executorURI) {
+        Set<ExecutorURI> taskTypeExecs = executors.getOrDefault(executorType,
+            Collections.synchronizedSet(new HashSet<>()));
+
+        taskTypeExecs.add(executorURI);
+        executors.put(executorType, taskTypeExecs);
+
+        return true;
+    }
+
+    /**
+     * Removes an executor from the registry. The executor is disassociated from all known task types.
+     *
+     * @param executorURI the identifier of the executor
+     * @return true unless a runtime exception occurs
+     */
+    public boolean removeExecutor(ExecutorURI executorURI) {
+        Iterator<ExecutorType> iterator = executors.keySet().iterator();
+
+        while (iterator.hasNext()) {
+            ExecutorType executorType = iterator.next();
+            Set<ExecutorURI> set = executors.get(executorType);
+
+            set.remove(executorURI);
+
+            if (set.isEmpty()) {
+                iterator.remove();
+            }
+        }
+
+        return true;
+    }
+
+    /**
+     * Checks if the registry contains an executor for a given task type. Used during task creation
+     * to decide if a task can be executed.
+     *
+     * @param taskType the task type being auctioned
+     * @return
+     */
+    public boolean containsTaskType(ExecutorType taskType) {
+        return executors.containsKey(taskType);
+    }
+
+    /**
+     * Adds a list of executors to current executor list. Should only be used on startup to
+     * add all available executors from the executor pool to the registry.
+     *
+     * @param executors the initial executors
+     * @return
+     */
+    public void init(Map<ExecutorType, Set<ExecutorURI>> executors) {
+        this.executors.putAll(executors);
+    }
+
+}

roster/src/main/java/ch/unisg/roster/roster/domain/Roster.java

@@ -1,4 +1,4 @@
-package ch.unisg.assignment.assignment.domain;
+package ch.unisg.roster.roster.domain;
 
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -6,7 +6,7 @@ import java.util.HashMap;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
-import ch.unisg.assignment.assignment.domain.valueobject.ExecutorType;
+import ch.unisg.roster.roster.domain.valueobject.ExecutorType;
 import ch.unisg.common.valueobject.ExecutorURI;
 
 public class Roster {

roster/src/main/java/ch/unisg/roster/roster/domain/RosterItem.java

@@ -1,4 +1,4 @@
-package ch.unisg.assignment.assignment.domain;
+package ch.unisg.roster.roster.domain;
 
 import ch.unisg.common.valueobject.ExecutorURI;
 import lombok.Getter;

roster/src/main/java/ch/unisg/roster/roster/domain/Task.java

@@ -1,6 +1,6 @@
-package ch.unisg.assignment.assignment.domain;
+package ch.unisg.roster.roster.domain;
 
-import ch.unisg.assignment.assignment.domain.valueobject.ExecutorType;
+import ch.unisg.roster.roster.domain.valueobject.ExecutorType;
 import lombok.Getter;
 import lombok.Setter;
 

roster/src/main/java/ch/unisg/roster/roster/domain/event/NewTaskEvent.java

@@ -1,6 +1,6 @@
-package ch.unisg.assignment.assignment.domain.event;
+package ch.unisg.roster.roster.domain.event;
 
-import ch.unisg.assignment.assignment.domain.valueobject.ExecutorType;
+import ch.unisg.roster.roster.domain.valueobject.ExecutorType;
 
 public class NewTaskEvent {
     public final ExecutorType taskType;

roster/src/main/java/ch/unisg/roster/roster/domain/event/TaskAssignedEvent.java

@@ -1,4 +1,4 @@
-package ch.unisg.assignment.assignment.domain.event;
+package ch.unisg.roster.roster.domain.event;
 
 public class TaskAssignedEvent {
     public final String taskID;

roster/src/main/java/ch/unisg/roster/roster/domain/event/TaskCompletedEvent.java

@@ -1,4 +1,4 @@
-package ch.unisg.assignment.assignment.domain.event;
+package ch.unisg.roster.roster.domain.event;
 
 public class TaskCompletedEvent {
     public final String taskID;

roster/src/main/java/ch/unisg/roster/roster/domain/valueobject/ExecutorType.java

@@ -1,4 +1,4 @@
-package ch.unisg.assignment.assignment.domain.valueobject;
+package ch.unisg.roster.roster.domain.valueobject;
 
 import lombok.Value;
 

roster/src/test/java/ch/unisg/roster/RosterApplicationTests.java

@@ -1,10 +1,10 @@
-package ch.unisg.assignment;
+package ch.unisg.roster;
 
 import org.junit.jupiter.api.Test;
 import org.springframework.boot.test.context.SpringBootTest;
 
 @SpringBootTest
-class AssignmentApplicationTests {
+class RosterApplicationTests {
 
 	@Test
 	void contextLoads() {