Merge pull request #33 from davidalves04/17-create-dashboardserver-process

Dashboard Server Implementation

main/src/main/java/sd/IntersectionProcess.java

@@ -171,6 +171,29 @@ public class IntersectionProcess {
         System.out.println("  Routing configured.");
     }
 
+    /**
+     * Requests permission for a traffic light to turn green.
+     * Blocks until permission is granted (no other light is green).
+     * 
+     * @param direction The direction requesting green light
+     */
+    public void requestGreenLight(String direction) {
+        trafficCoordinationLock.lock();
+        currentGreenDirection = direction;
+    }
+    
+    /**
+     * Releases the green light permission, allowing another light to turn green.
+     * 
+     * @param direction The direction releasing green light
+     */
+    public void releaseGreenLight(String direction) {
+        if (direction.equals(currentGreenDirection)) {
+            currentGreenDirection = null;
+            trafficCoordinationLock.unlock();
+        }
+    }
+    
     /**
      * Starts all traffic light threads.
      */

main/src/main/java/sd/dashboard/DashboardClientHandler.java

@@ -0,0 +1,110 @@
+package sd.dashboard;
+
+import java.io.IOException;
+import java.net.Socket;
+
+import sd.model.MessageType;
+import sd.protocol.MessageProtocol;
+import sd.protocol.SocketConnection;
+
+/**
+ * Processes statistics messages from a single client connection.
+ * Runs in a separate thread per client.
+ */
+public class DashboardClientHandler implements Runnable {
+    
+    private final Socket clientSocket;
+    private final DashboardStatistics statistics;
+    
+    public DashboardClientHandler(Socket clientSocket, DashboardStatistics statistics) {
+        this.clientSocket = clientSocket;
+        this.statistics = statistics;
+    }
+    
+    @Override
+    public void run() {
+        String clientInfo = clientSocket.getInetAddress().getHostAddress() + ":" + clientSocket.getPort();
+        
+        try (SocketConnection connection = new SocketConnection(clientSocket)) {
+            System.out.println("[Handler] Started handling client: " + clientInfo);
+            
+            while (!Thread.currentThread().isInterrupted()) {
+                try {
+                    MessageProtocol message = connection.receiveMessage();
+                    
+                    if (message == null) {
+                        System.out.println("[Handler] Client disconnected: " + clientInfo);
+                        break;
+                    }
+                    
+                    processMessage(message);
+                    
+                } catch (ClassNotFoundException e) {
+                    System.err.println("[Handler] Unknown message class from " + clientInfo + ": " + e.getMessage());
+                } catch (IOException e) {
+                    System.out.println("[Handler] Connection error with " + clientInfo + ": " + e.getMessage());
+                    break;
+                }
+            }
+            
+        } catch (IOException e) {
+            System.err.println("[Handler] Error initializing connection with " + clientInfo + ": " + e.getMessage());
+        } finally {
+            try {
+                if (!clientSocket.isClosed()) {
+                    clientSocket.close();
+                }
+            } catch (IOException e) {
+                System.err.println("[Handler] Error closing socket for " + clientInfo + ": " + e.getMessage());
+            }
+        }
+    }
+    
+    private void processMessage(MessageProtocol message) {
+        if (message.getType() != MessageType.STATS_UPDATE) {
+            System.out.println("[Handler] Ignoring non-statistics message type: " + message.getType());
+            return;
+        }
+        
+        String senderId = message.getSourceNode();
+        Object payload = message.getPayload();
+        
+        System.out.println("[Handler] Received STATS_UPDATE from: " + senderId);
+        
+        if (payload instanceof StatsUpdatePayload stats) {
+            updateStatistics(senderId, stats);
+        } else {
+            System.err.println("[Handler] Unknown payload type: " + 
+                (payload != null ? payload.getClass().getName() : "null"));
+        }
+    }
+    
+    private void updateStatistics(String senderId, StatsUpdatePayload stats) {
+        if (stats.getTotalVehiclesGenerated() >= 0) {
+            statistics.updateVehiclesGenerated(stats.getTotalVehiclesGenerated());
+        }
+        
+        if (stats.getTotalVehiclesCompleted() >= 0) {
+            statistics.updateVehiclesCompleted(stats.getTotalVehiclesCompleted());
+        }
+        
+        if (stats.getTotalSystemTime() >= 0) {
+            statistics.addSystemTime(stats.getTotalSystemTime());
+        }
+        
+        if (stats.getTotalWaitingTime() >= 0) {
+            statistics.addWaitingTime(stats.getTotalWaitingTime());
+        }
+        
+        if (senderId.startsWith("Cr") || senderId.startsWith("E")) {
+            statistics.updateIntersectionStats(
+                senderId,
+                stats.getIntersectionArrivals(),
+                stats.getIntersectionDepartures(),
+                stats.getIntersectionQueueSize()
+            );
+        }
+        
+        System.out.println("[Handler] Successfully updated statistics from: " + senderId);
+    }
+}

main/src/main/java/sd/dashboard/DashboardServer.java

@@ -0,0 +1,148 @@
+package sd.dashboard;
+
+import java.io.IOException;
+import java.net.ServerSocket;
+import java.net.Socket;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import sd.config.SimulationConfig;
+
+/**
+ * Aggregates and displays real-time statistics from all simulation processes.
+ * Uses a thread pool to handle concurrent client connections.
+ */
+public class DashboardServer {
+    
+    private final int port;
+    private final DashboardStatistics statistics;
+    private final ExecutorService clientHandlerPool;
+    private final AtomicBoolean running;
+    private ServerSocket serverSocket;
+    
+    public static void main(String[] args) {
+        System.out.println("=".repeat(60));
+        System.out.println("DASHBOARD SERVER - DISTRIBUTED TRAFFIC SIMULATION");
+        System.out.println("=".repeat(60));
+        
+        try {
+            // Load configuration
+            String configFile = args.length > 0 ? args[0] : "src/main/resources/simulation.properties";
+            System.out.println("Loading configuration from: " + configFile);
+            
+            SimulationConfig config = new SimulationConfig(configFile);
+            DashboardServer server = new DashboardServer(config);
+            
+            // Start the server
+            System.out.println("\n" + "=".repeat(60));
+            server.start();
+            
+            // Keep running until interrupted
+            Runtime.getRuntime().addShutdownHook(new Thread(() -> {
+                System.out.println("\n\nShutdown signal received...");
+                server.stop();
+            }));
+            
+            // Display statistics periodically
+            server.displayLoop();
+            
+        } catch (IOException e) {
+            System.err.println("Failed to start Dashboard Server: " + e.getMessage());
+            System.exit(1);
+        }
+    }
+    
+    public DashboardServer(SimulationConfig config) {
+        this.port = config.getDashboardPort();
+        this.statistics = new DashboardStatistics();
+        this.clientHandlerPool = Executors.newFixedThreadPool(10);
+        this.running = new AtomicBoolean(false);
+    }
+    
+    public void start() throws IOException {
+        if (running.get()) {
+            System.out.println("Dashboard Server is already running.");
+            return;
+        }
+        
+        serverSocket = new ServerSocket(port);
+        running.set(true);
+        
+        System.out.println("Dashboard Server started on port " + port);
+        System.out.println("Waiting for statistics updates from simulation processes...");
+        System.out.println("=".repeat(60));
+        
+        Thread acceptThread = new Thread(this::acceptConnections, "DashboardServer-Accept");
+        acceptThread.setDaemon(false);
+        acceptThread.start();
+    }
+    
+    private void acceptConnections() {
+        while (running.get()) {
+            try {
+                Socket clientSocket = serverSocket.accept();
+                System.out.println("[Connection] New client connected: " + 
+                    clientSocket.getInetAddress().getHostAddress() + ":" + clientSocket.getPort());
+                
+                clientHandlerPool.execute(new DashboardClientHandler(clientSocket, statistics));
+                
+            } catch (IOException e) {
+                if (running.get()) {
+                    System.err.println("[Error] Failed to accept client connection: " + e.getMessage());
+                }
+            }
+        }
+    }
+    
+    @SuppressWarnings("BusyWait")
+    private void displayLoop() {
+        final long DISPLAY_INTERVAL_MS = 5000;
+        
+        while (running.get()) {
+            try {
+                Thread.sleep(DISPLAY_INTERVAL_MS);
+                displayStatistics();
+            } catch (InterruptedException e) {
+                Thread.currentThread().interrupt();
+                break;
+            }
+        }
+    }
+    
+    public void displayStatistics() {
+        System.out.println("\n" + "=".repeat(60));
+        System.out.println("REAL-TIME SIMULATION STATISTICS");
+        System.out.println("=".repeat(60));
+        statistics.display();
+        System.out.println("=".repeat(60));
+    }
+    
+    public void stop() {
+        if (!running.get()) {
+            return;
+        }
+        
+        System.out.println("\nStopping Dashboard Server...");
+        running.set(false);
+        
+        try {
+            if (serverSocket != null && !serverSocket.isClosed()) {
+                serverSocket.close();
+            }
+        } catch (IOException e) {
+            System.err.println("Error closing server socket: " + e.getMessage());
+        }
+        
+        clientHandlerPool.shutdownNow();
+        System.out.println("Dashboard Server stopped.");
+    }
+    
+    public DashboardStatistics getStatistics() {
+        return statistics;
+    }
+    
+    public boolean isRunning() {
+        return running.get();
+    }
+}

main/src/main/java/sd/dashboard/DashboardStatistics.java

@@ -0,0 +1,214 @@
+package sd.dashboard;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicLong;
+
+import sd.model.VehicleType;
+
+/**
+ * Thread-safe storage for aggregated simulation statistics.
+ * Uses atomic types and concurrent collections for lock-free updates.
+ */
+public class DashboardStatistics {
+    
+    private final AtomicInteger totalVehiclesGenerated;
+    private final AtomicInteger totalVehiclesCompleted;
+    private final AtomicLong totalSystemTime;
+    private final AtomicLong totalWaitingTime;
+    
+    private final Map<String, IntersectionStats> intersectionStats;
+    private final Map<VehicleType, AtomicInteger> vehicleTypeCount;
+    private final Map<VehicleType, AtomicLong> vehicleTypeWaitTime;
+    
+    private volatile long lastUpdateTime;
+    
+    public DashboardStatistics() {
+        this.totalVehiclesGenerated = new AtomicInteger(0);
+        this.totalVehiclesCompleted = new AtomicInteger(0);
+        this.totalSystemTime = new AtomicLong(0);
+        this.totalWaitingTime = new AtomicLong(0);
+        
+        this.intersectionStats = new ConcurrentHashMap<>();
+        this.vehicleTypeCount = new ConcurrentHashMap<>();
+        this.vehicleTypeWaitTime = new ConcurrentHashMap<>();
+        
+        for (VehicleType type : VehicleType.values()) {
+            vehicleTypeCount.put(type, new AtomicInteger(0));
+            vehicleTypeWaitTime.put(type, new AtomicLong(0));
+        }
+        
+        this.lastUpdateTime = System.currentTimeMillis();
+    }
+    
+    public void updateVehiclesGenerated(int count) {
+        totalVehiclesGenerated.set(count);
+        updateTimestamp();
+    }
+    
+    public void incrementVehiclesGenerated() {
+        totalVehiclesGenerated.incrementAndGet();
+        updateTimestamp();
+    }
+    
+    public void updateVehiclesCompleted(int count) {
+        totalVehiclesCompleted.set(count);
+        updateTimestamp();
+    }
+    
+    public void incrementVehiclesCompleted() {
+        totalVehiclesCompleted.incrementAndGet();
+        updateTimestamp();
+    }
+    
+    public void addSystemTime(long timeMs) {
+        totalSystemTime.addAndGet(timeMs);
+        updateTimestamp();
+    }
+    
+    public void addWaitingTime(long timeMs) {
+        totalWaitingTime.addAndGet(timeMs);
+        updateTimestamp();
+    }
+    
+    public void updateVehicleTypeStats(VehicleType type, int count, long waitTimeMs) {
+        vehicleTypeCount.get(type).set(count);
+        vehicleTypeWaitTime.get(type).set(waitTimeMs);
+        updateTimestamp();
+    }
+    
+    public void incrementVehicleType(VehicleType type) {
+        vehicleTypeCount.get(type).incrementAndGet();
+        updateTimestamp();
+    }
+    
+    public void updateIntersectionStats(String intersectionId, int arrivals, 
+                                       int departures, int currentQueueSize) {
+        intersectionStats.compute(intersectionId, (id, stats) -> {
+            if (stats == null) {
+                stats = new IntersectionStats(intersectionId);
+            }
+            stats.updateStats(arrivals, departures, currentQueueSize);
+            return stats;
+        });
+        updateTimestamp();
+    }
+    
+    private void updateTimestamp() {
+        lastUpdateTime = System.currentTimeMillis();
+    }
+    
+    public int getTotalVehiclesGenerated() {
+        return totalVehiclesGenerated.get();
+    }
+    
+    public int getTotalVehiclesCompleted() {
+        return totalVehiclesCompleted.get();
+    }
+    
+    public double getAverageSystemTime() {
+        int completed = totalVehiclesCompleted.get();
+        if (completed == 0) return 0.0;
+        return (double) totalSystemTime.get() / completed;
+    }
+    
+    public double getAverageWaitingTime() {
+        int completed = totalVehiclesCompleted.get();
+        if (completed == 0) return 0.0;
+        return (double) totalWaitingTime.get() / completed;
+    }
+    
+    public int getVehicleTypeCount(VehicleType type) {
+        return vehicleTypeCount.get(type).get();
+    }
+    
+    public double getAverageWaitingTimeByType(VehicleType type) {
+        int count = vehicleTypeCount.get(type).get();
+        if (count == 0) return 0.0;
+        return (double) vehicleTypeWaitTime.get(type).get() / count;
+    }
+    
+    public IntersectionStats getIntersectionStats(String intersectionId) {
+        return intersectionStats.get(intersectionId);
+    }
+    
+    public Map<String, IntersectionStats> getAllIntersectionStats() {
+        return new HashMap<>(intersectionStats);
+    }
+    
+    public long getLastUpdateTime() {
+        return lastUpdateTime;
+    }
+    
+    public void display() {
+        System.out.println("\n--- GLOBAL STATISTICS ---");
+        System.out.printf("Total Vehicles Generated: %d%n", getTotalVehiclesGenerated());
+        System.out.printf("Total Vehicles Completed: %d%n", getTotalVehiclesCompleted());
+        System.out.printf("Vehicles In Transit: %d%n", 
+            getTotalVehiclesGenerated() - getTotalVehiclesCompleted());
+        System.out.printf("Average System Time: %.2f ms%n", getAverageSystemTime());
+        System.out.printf("Average Waiting Time: %.2f ms%n", getAverageWaitingTime());
+        
+        System.out.println("\n--- VEHICLE TYPE STATISTICS ---");
+        for (VehicleType type : VehicleType.values()) {
+            int count = getVehicleTypeCount(type);
+            double avgWait = getAverageWaitingTimeByType(type);
+            System.out.printf("%s: %d vehicles, avg wait: %.2f ms%n", 
+                type, count, avgWait);
+        }
+        
+        System.out.println("\n--- INTERSECTION STATISTICS ---");
+        if (intersectionStats.isEmpty()) {
+            System.out.println("(No data received yet)");
+        } else {
+            for (IntersectionStats stats : intersectionStats.values()) {
+                stats.display();
+            }
+        }
+        
+        System.out.printf("%nLast Update: %tT%n", lastUpdateTime);
+    }
+    
+    public static class IntersectionStats {
+        private final String intersectionId;
+        private final AtomicInteger totalArrivals;
+        private final AtomicInteger totalDepartures;
+        private final AtomicInteger currentQueueSize;
+        
+        public IntersectionStats(String intersectionId) {
+            this.intersectionId = intersectionId;
+            this.totalArrivals = new AtomicInteger(0);
+            this.totalDepartures = new AtomicInteger(0);
+            this.currentQueueSize = new AtomicInteger(0);
+        }
+        
+        public void updateStats(int arrivals, int departures, int queueSize) {
+            this.totalArrivals.set(arrivals);
+            this.totalDepartures.set(departures);
+            this.currentQueueSize.set(queueSize);
+        }
+        
+        public String getIntersectionId() {
+            return intersectionId;
+        }
+        
+        public int getTotalArrivals() {
+            return totalArrivals.get();
+        }
+        
+        public int getTotalDepartures() {
+            return totalDepartures.get();
+        }
+        
+        public int getCurrentQueueSize() {
+            return currentQueueSize.get();
+        }
+        
+        public void display() {
+            System.out.printf("%s: Arrivals=%d, Departures=%d, Queue=%d%n",
+                intersectionId, getTotalArrivals(), getTotalDepartures(), getCurrentQueueSize());
+        }
+    }
+}

main/src/main/java/sd/dashboard/StatsMessage.java

@@ -0,0 +1,48 @@
+package sd.dashboard;
+
+import sd.model.MessageType;
+import sd.protocol.MessageProtocol;
+
+/**
+ * Message wrapper for sending statistics to the dashboard.
+ */
+public class StatsMessage implements MessageProtocol {
+    
+    private static final long serialVersionUID = 1L;
+    
+    private final String sourceNode;
+    private final String destinationNode;
+    private final StatsUpdatePayload payload;
+    
+    public StatsMessage(String sourceNode, StatsUpdatePayload payload) {
+        this.sourceNode = sourceNode;
+        this.destinationNode = "DashboardServer";
+        this.payload = payload;
+    }
+    
+    @Override
+    public MessageType getType() {
+        return MessageType.STATS_UPDATE;
+    }
+    
+    @Override
+    public Object getPayload() {
+        return payload;
+    }
+    
+    @Override
+    public String getSourceNode() {
+        return sourceNode;
+    }
+    
+    @Override
+    public String getDestinationNode() {
+        return destinationNode;
+    }
+    
+    @Override
+    public String toString() {
+        return String.format("StatsMessage[from=%s, to=%s, payload=%s]", 
+            sourceNode, destinationNode, payload);
+    }
+}

main/src/main/java/sd/dashboard/StatsUpdatePayload.java

@@ -0,0 +1,121 @@
+package sd.dashboard;
+
+import java.io.Serializable;
+import java.util.HashMap;
+import java.util.Map;
+
+import sd.model.VehicleType;
+
+/**
+ * Data transfer object for statistics updates to the dashboard.
+ * Use -1 for fields not being updated in this message.
+ */
+public class StatsUpdatePayload implements Serializable {
+    
+    private static final long serialVersionUID = 1L;
+    
+    private int totalVehiclesGenerated = -1;
+    private int totalVehiclesCompleted = -1;
+    private long totalSystemTime = -1;
+    private long totalWaitingTime = -1;
+    
+    private int intersectionArrivals = 0;
+    private int intersectionDepartures = 0;
+    private int intersectionQueueSize = 0;
+    
+    private Map<VehicleType, Integer> vehicleTypeCounts;
+    private Map<VehicleType, Long> vehicleTypeWaitTimes;
+    
+    public StatsUpdatePayload() {
+        this.vehicleTypeCounts = new HashMap<>();
+        this.vehicleTypeWaitTimes = new HashMap<>();
+    }
+    
+    public int getTotalVehiclesGenerated() {
+        return totalVehiclesGenerated;
+    }
+    
+    public int getTotalVehiclesCompleted() {
+        return totalVehiclesCompleted;
+    }
+    
+    public long getTotalSystemTime() {
+        return totalSystemTime;
+    }
+    
+    public long getTotalWaitingTime() {
+        return totalWaitingTime;
+    }
+    
+    public int getIntersectionArrivals() {
+        return intersectionArrivals;
+    }
+    
+    public int getIntersectionDepartures() {
+        return intersectionDepartures;
+    }
+    
+    public int getIntersectionQueueSize() {
+        return intersectionQueueSize;
+    }
+    
+    public Map<VehicleType, Integer> getVehicleTypeCounts() {
+        return vehicleTypeCounts;
+    }
+    
+    public Map<VehicleType, Long> getVehicleTypeWaitTimes() {
+        return vehicleTypeWaitTimes;
+    }
+    
+    public StatsUpdatePayload setTotalVehiclesGenerated(int totalVehiclesGenerated) {
+        this.totalVehiclesGenerated = totalVehiclesGenerated;
+        return this;
+    }
+    
+    public StatsUpdatePayload setTotalVehiclesCompleted(int totalVehiclesCompleted) {
+        this.totalVehiclesCompleted = totalVehiclesCompleted;
+        return this;
+    }
+    
+    public StatsUpdatePayload setTotalSystemTime(long totalSystemTime) {
+        this.totalSystemTime = totalSystemTime;
+        return this;
+    }
+    
+    public StatsUpdatePayload setTotalWaitingTime(long totalWaitingTime) {
+        this.totalWaitingTime = totalWaitingTime;
+        return this;
+    }
+    
+    public StatsUpdatePayload setIntersectionArrivals(int intersectionArrivals) {
+        this.intersectionArrivals = intersectionArrivals;
+        return this;
+    }
+    
+    public StatsUpdatePayload setIntersectionDepartures(int intersectionDepartures) {
+        this.intersectionDepartures = intersectionDepartures;
+        return this;
+    }
+    
+    public StatsUpdatePayload setIntersectionQueueSize(int intersectionQueueSize) {
+        this.intersectionQueueSize = intersectionQueueSize;
+        return this;
+    }
+    
+    public StatsUpdatePayload setVehicleTypeCounts(Map<VehicleType, Integer> vehicleTypeCounts) {
+        this.vehicleTypeCounts = vehicleTypeCounts;
+        return this;
+    }
+    
+    public StatsUpdatePayload setVehicleTypeWaitTimes(Map<VehicleType, Long> vehicleTypeWaitTimes) {
+        this.vehicleTypeWaitTimes = vehicleTypeWaitTimes;
+        return this;
+    }
+    
+    @Override
+    public String toString() {
+        return String.format("StatsUpdatePayload[generated=%d, completed=%d, arrivals=%d, departures=%d, queueSize=%d]",
+            totalVehiclesGenerated, totalVehiclesCompleted, intersectionArrivals, 
+            intersectionDepartures, intersectionQueueSize);
+    }
+}

main/src/main/java/sd/engine/TrafficLightThread.java

@@ -29,7 +29,6 @@ public class TrafficLightThread implements Runnable {
 
     @Override
     public void run() {
-        // Capture the current thread reference
         this.currentThread = Thread.currentThread();
         this.running = true;
         System.out.println("[" + light.getId() + "] Traffic light thread started.");
@@ -37,6 +36,10 @@ public class TrafficLightThread implements Runnable {
         try {
             while (running && !Thread.currentThread().isInterrupted()) {
                 
+                // Request permission to turn green (blocks until granted)
+                process.requestGreenLight(light.getDirection());
+                
+                try {
                     // --- GREEN Phase ---
                     light.changeState(TrafficLightState.GREEN);
                     System.out.println("[" + light.getId() + "] State: GREEN");
@@ -54,12 +57,16 @@ public class TrafficLightThread implements Runnable {
                     light.changeState(TrafficLightState.RED);
                     System.out.println("[" + light.getId() + "] State: RED");
                     
+                } finally {
+                    // Always release the green light permission
+                    process.releaseGreenLight(light.getDirection());
+                }
+                
                 // Wait for red duration
                 Thread.sleep((long) (light.getRedTime() * 1000));
             }
         } catch (InterruptedException e) {
             System.out.println("[" + light.getId() + "] Traffic light thread interrupted.");
-            // Restore interrupt status
             Thread.currentThread().interrupt();
         } finally {
             this.running = false;

main/src/test/java/sd/TrafficLightCoordinationTest.java

@@ -1,18 +1,18 @@
 package sd;
 
-import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.AfterEach;
-import org.junit.jupiter.api.BeforeEach;
-
-import sd.model.TrafficLight;
-import sd.model.TrafficLightState;
-
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.concurrent.atomic.AtomicInteger;
 
-import static org.junit.jupiter.api.Assertions.*;
+import org.junit.jupiter.api.AfterEach;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import sd.model.TrafficLight;
+import sd.model.TrafficLightState;
 
 /**
  * Test class to verify traffic light coordination within an intersection.
@@ -108,7 +108,7 @@ public class TrafficLightCoordinationTest {
         assertTrue(maxGreenSimultaneously.get() <= 1, 
             "At most ONE light should be GREEN at any time. Found: " + maxGreenSimultaneously.get());
         
-        System.out.println("\n✅ Traffic light coordination working correctly!");
+        System.out.println("\nTraffic light coordination working correctly!");
     }
 
     /**

main/src/test/java/sd/dashboard/DashboardTest.java

@@ -0,0 +1,164 @@
+package sd.dashboard;
+
+import org.junit.jupiter.api.AfterEach;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import sd.config.SimulationConfig;
+import sd.model.VehicleType;
+
+/**
+ * Unit tests for Dashboard Server components.
+ */
+class DashboardTest {
+    
+    private DashboardStatistics statistics;
+    
+    @BeforeEach
+    void setUp() {
+        statistics = new DashboardStatistics();
+    }
+    
+    @AfterEach
+    void tearDown() {
+        statistics = null;
+    }
+    
+    @Test
+    void testInitialStatistics() {
+        assertEquals(0, statistics.getTotalVehiclesGenerated(), 
+            "Initial vehicles generated should be 0");
+        assertEquals(0, statistics.getTotalVehiclesCompleted(), 
+            "Initial vehicles completed should be 0");
+        assertEquals(0.0, statistics.getAverageSystemTime(), 
+            "Initial average system time should be 0.0");
+        assertEquals(0.0, statistics.getAverageWaitingTime(), 
+            "Initial average waiting time should be 0.0");
+    }
+    
+    @Test
+    void testVehicleCounters() {
+        statistics.incrementVehiclesGenerated();
+        assertEquals(1, statistics.getTotalVehiclesGenerated());
+        
+        statistics.updateVehiclesGenerated(10);
+        assertEquals(10, statistics.getTotalVehiclesGenerated());
+        
+        statistics.incrementVehiclesCompleted();
+        assertEquals(1, statistics.getTotalVehiclesCompleted());
+    }
+    
+    @Test
+    void testAverageCalculations() {
+        // Add 3 completed vehicles with known times
+        statistics.updateVehiclesCompleted(3);
+        statistics.addSystemTime(3000); // 3000ms total
+        statistics.addWaitingTime(1500); // 1500ms total
+        
+        assertEquals(1000.0, statistics.getAverageSystemTime(), 0.01,
+            "Average system time should be 1000ms");
+        assertEquals(500.0, statistics.getAverageWaitingTime(), 0.01,
+            "Average waiting time should be 500ms");
+    }
+    
+    @Test
+    void testVehicleTypeStatistics() {
+        statistics.incrementVehicleType(VehicleType.LIGHT);
+        statistics.incrementVehicleType(VehicleType.LIGHT);
+        statistics.incrementVehicleType(VehicleType.HEAVY);
+        
+        assertEquals(2, statistics.getVehicleTypeCount(VehicleType.LIGHT));
+        assertEquals(1, statistics.getVehicleTypeCount(VehicleType.HEAVY));
+        assertEquals(0, statistics.getVehicleTypeCount(VehicleType.BIKE));
+    }
+    
+    @Test
+    void testIntersectionStatistics() {
+        statistics.updateIntersectionStats("Cr1", 10, 8, 2);
+        
+        DashboardStatistics.IntersectionStats stats = 
+            statistics.getIntersectionStats("Cr1");
+        
+        assertNotNull(stats, "Intersection stats should not be null");
+        assertEquals("Cr1", stats.getIntersectionId());
+        assertEquals(10, stats.getTotalArrivals());
+        assertEquals(8, stats.getTotalDepartures());
+        assertEquals(2, stats.getCurrentQueueSize());
+    }
+    
+    @Test
+    void testMultipleIntersections() {
+        statistics.updateIntersectionStats("Cr1", 10, 8, 2);
+        statistics.updateIntersectionStats("Cr2", 15, 12, 3);
+        statistics.updateIntersectionStats("Cr3", 5, 5, 0);
+        
+        assertEquals(3, statistics.getAllIntersectionStats().size(),
+            "Should have 3 intersections");
+    }
+    
+    @Test
+    void testStatsUpdatePayload() {
+        StatsUpdatePayload payload = new StatsUpdatePayload()
+            .setTotalVehiclesGenerated(50)
+            .setTotalVehiclesCompleted(20)
+            .setIntersectionArrivals(30)
+            .setIntersectionDepartures(25)
+            .setIntersectionQueueSize(5);
+        
+        assertEquals(50, payload.getTotalVehiclesGenerated());
+        assertEquals(20, payload.getTotalVehiclesCompleted());
+        assertEquals(30, payload.getIntersectionArrivals());
+        assertEquals(25, payload.getIntersectionDepartures());
+        assertEquals(5, payload.getIntersectionQueueSize());
+    }
+    
+    @Test
+    void testStatsMessage() {
+        StatsUpdatePayload payload = new StatsUpdatePayload()
+            .setIntersectionArrivals(10);
+        
+        StatsMessage message = new StatsMessage("Cr1", payload);
+        
+        assertEquals("Cr1", message.getSourceNode());
+        assertEquals("DashboardServer", message.getDestinationNode());
+        assertEquals(sd.model.MessageType.STATS_UPDATE, message.getType());
+        assertNotNull(message.getPayload());
+    }
+    
+    @Test
+    void testThreadSafety() throws InterruptedException {
+        // Test concurrent updates
+        Thread t1 = new Thread(() -> {
+            for (int i = 0; i < 100; i++) {
+                statistics.incrementVehiclesGenerated();
+            }
+        });
+        
+        Thread t2 = new Thread(() -> {
+            for (int i = 0; i < 100; i++) {
+                statistics.incrementVehiclesGenerated();
+            }
+        });
+        
+        t1.start();
+        t2.start();
+        t1.join();
+        t2.join();
+        
+        assertEquals(200, statistics.getTotalVehiclesGenerated(),
+            "Concurrent increments should total 200");
+    }
+    
+    @Test
+    void testDashboardServerCreation() throws Exception {
+        SimulationConfig config = new SimulationConfig("simulation.properties");
+        DashboardServer server = new DashboardServer(config);
+        
+        assertNotNull(server, "Server should be created successfully");
+        assertNotNull(server.getStatistics(), "Statistics should be initialized");
+        assertFalse(server.isRunning(), "Server should not be running initially");
+    }
+}