3 files changed, 70 insertions, 3 deletions
diff --git a/src/main/java/simulator/VSMain.java b/src/main/java/simulator/VSMain.java
index 02f3e20..5718b72 100644
--- a/src/main/java/simulator/VSMain.java
+++ b/src/main/java/simulator/VSMain.java
@@ -51,6 +51,21 @@ public class VSMain {
     }
 
     /**
+     * Resolves the initial simulation filename from the CLI arguments.
+     *
+     * @param args the arguments passed to main
+     *
+     * @return the first non-blank argument, or null if none was provided
+     */
+    static String resolveStartupSimulationFile(String[] args) {
+        if (args == null || args.length == 0 || args[0] == null)
+            return null;
+
+        String filename = args[0].trim();
+        return filename.isEmpty() ? null : filename;
+    }
+
+    /**
      * The main method.
      *
      * @param args the arguments
@@ -69,14 +84,18 @@ public class VSMain {
         javax.swing.JPopupMenu.setDefaultLightWeightPopupEnabled(false);
         VSPrefs prefs = VSDefaultPrefs.init();
         VSRegisteredEvents.init(prefs);
-        
+        VSMain.prefs = prefs;
+
         // Wait for splash screen to finish before showing main window
         try {
             Thread.sleep(3000);
         } catch (InterruptedException e) {
             Thread.currentThread().interrupt();
         }
-        
-        new VSMain(prefs);
+
+        VSSimulatorFrame simulatorFrame = new VSSimulatorFrame(prefs, null);
+        String startupSimulationFile = resolveStartupSimulationFile(args);
+        if (startupSimulationFile != null)
+            simulatorFrame.openAndStartSimulator(startupSimulationFile);
     }
 }
diff --git a/src/main/java/simulator/VSSimulatorFrame.java b/src/main/java/simulator/VSSimulatorFrame.java
index 3cf4e91..818bea9 100644
--- a/src/main/java/simulator/VSSimulatorFrame.java
+++ b/src/main/java/simulator/VSSimulatorFrame.java
@@ -504,6 +504,7 @@ public class VSSimulatorFrame extends VSFrame {
         tabbedPane.addTab(prefs.getString("lang.simulator")
                           + " " + simulator.getSimulatorNum(), simulator);
         tabbedPane.setSelectedComponent(simulator);
+        currentSimulator = simulator;
 
         if (simulators.size() == 1) {
             menuEdit.setEnabled(true);
@@ -576,6 +577,9 @@ public class VSSimulatorFrame extends VSFrame {
      * Starts the current simulator
      */
     public void startCurrentSimulator() {
+        if (currentSimulator == null)
+            return;
+
         VSMenuItemStates menuItemState =
             currentSimulator.getMenuItemStates();
         menuItemState.setStart(false);
@@ -587,6 +591,23 @@ public class VSSimulatorFrame extends VSFrame {
     }
 
     /**
+     * Opens the given simulator file and starts playback if load succeeds.
+     *
+     * @param filename the simulation file to open
+     *
+     * @return the loaded simulator, or null if loading failed
+     */
+    public VSSimulator openAndStartSimulator(String filename) {
+        VSSerialize serialize = new VSSerialize();
+        VSSimulator simulator = serialize.openSimulator(filename, this);
+
+        if (simulator != null)
+            startCurrentSimulator();
+
+        return simulator;
+    }
+
+    /**
      * Pauses the current simulator
      */
     public void pauseCurrentSimulator() {
diff --git a/src/test/java/simulator/VSMainTest.java b/src/test/java/simulator/VSMainTest.java
new file mode 100644
index 0000000..5d4fb8b
--- /dev/null
+++ b/src/test/java/simulator/VSMainTest.java
@@ -0,0 +1,27 @@
+package simulator;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+import org.junit.jupiter.api.Test;
+
+public class VSMainTest {
+    @Test
+    void resolveStartupSimulationFileReturnsNullForMissingArgs() {
+        assertNull(VSMain.resolveStartupSimulationFile(null));
+        assertNull(VSMain.resolveStartupSimulationFile(new String[0]));
+        assertNull(VSMain.resolveStartupSimulationFile(new String[] {""}));
+        assertNull(VSMain.resolveStartupSimulationFile(new String[] {"   "}));
+    }
+
+    @Test
+    void resolveStartupSimulationFileUsesFirstArgument() {
+        assertEquals("saved-simulations/raft.dat",
+                     VSMain.resolveStartupSimulationFile(
+                         new String[] {"saved-simulations/raft.dat"}));
+        assertEquals("saved-simulations/raft.dat",
+                     VSMain.resolveStartupSimulationFile(
+                         new String[] {"  saved-simulations/raft.dat  ",
+                                       "ignored"}));
+    }
+}