feat: update structure

cs2030s/labs/Lab1/ServiceEndEvent.java

@@ -0,0 +1,58 @@
+/**
+ * The ServiceEndEvent is an Event which handles the end of a service.
+ * It handles freeing the counter and also generating a departure event
+ * 
+ * @author Yadunand Prem
+ * @version CS2030S AY22/23 Semester 2
+ */
+class ServiceEndEvent extends Event {
+
+  private ServiceCounter counter;
+  private Customer customer;
+  private Shop shop;
+
+  public ServiceEndEvent(double time, Customer customer, Shop shop, ServiceCounter counter) {
+    super(time);
+    this.customer = customer;
+    this.shop = shop;
+    this.counter = counter;
+  }
+
+  @Override
+  public String toString() {
+    return super.toString()
+        + String.format(": %s service done (by %s)", this.customer, this.counter);
+  }
+
+  @Override
+  public Event[] simulate() {
+    // if there are customers in the counter queue, they will be serviced next.
+    // Customers in the shop queue will then be added to the counter queue
+    if (!this.counter.isQueueEmpty()) {
+      Customer serviceCustomer = this.counter.leaveQueue();
+
+      if (!this.shop.isQueueEmpty()) {
+        return new Event[] {
+            new DepartureEvent(this.getTime(), this.customer),
+            new ServiceBeginEvent(this.getTime(), serviceCustomer, this.shop, this.counter),
+            new JoinCounterQueueEvent(this.getTime(), this.shop.leaveQueue(), counter)
+        };
+      }
+      return new Event[] {
+          new DepartureEvent(this.getTime(), this.customer),
+          new ServiceBeginEvent(this.getTime(), serviceCustomer, this.shop, this.counter),
+      };
+    }
+    // There can also be the case where the counter queue may be empty but there are
+    // customers in the shop queue.
+    if (!this.shop.isQueueEmpty()) {
+      return new Event[] {
+          new DepartureEvent(this.getTime(), this.customer),
+          new ServiceBeginEvent(this.getTime(), this.shop.leaveQueue(), this.shop, this.counter),
+      };
+    }
+    // else there are no more customers in the queue, and the counter can be freed
+    this.counter.free();
+    return new Event[] { new DepartureEvent(this.getTime(), this.customer) };
+  }
+}