From 2183c591bfbcf56252980ee24c449d80301cbda7 Mon Sep 17 00:00:00 2001
From: Lars Simon Winzer <lars.winzer@stud.unibas.ch>
Date: Wed, 4 Mar 2026 11:23:39 +0100
Subject: [PATCH] Add: Main, ClientApp, and ServerApp classes for application
 entry point with primitive input validation

---
 .../ch/unibas/dmi/dbis/cs108/casono/Main.java | 42 +++++++++++++++++++
 .../dbis/cs108/casono/client/ClientApp.java   | 14 +++++++
 .../dbis/cs108/casono/server/ServerApp.java   |  8 ++++
 3 files changed, 64 insertions(+)
 create mode 100644 src/main/java/ch/unibas/dmi/dbis/cs108/casono/Main.java
 create mode 100644 src/main/java/ch/unibas/dmi/dbis/cs108/casono/client/ClientApp.java
 create mode 100644 src/main/java/ch/unibas/dmi/dbis/cs108/casono/server/ServerApp.java

diff --git a/src/main/java/ch/unibas/dmi/dbis/cs108/casono/Main.java b/src/main/java/ch/unibas/dmi/dbis/cs108/casono/Main.java
new file mode 100644
index 0000000..d1890db
--- /dev/null
+++ b/src/main/java/ch/unibas/dmi/dbis/cs108/casono/Main.java
@@ -0,0 +1,42 @@
+package ch.unibas.dmi.dbis.cs108.casono;
+
+import ch.unibas.dmi.dbis.cs108.casono.client.ClientApp;
+import ch.unibas.dmi.dbis.cs108.casono.server.ServerApp;
+
+public final class Main {
+
+    public static void main(String[] args) {
+        if (!isValid(args)) {
+            printUsage();
+            System.exit(1);
+        }
+
+        switch (args[0]) {
+            case "server" -> ServerApp.start(args[1]);
+            case "client" -> ClientApp.start(args[1]);
+            default -> {
+                printUsage();
+                System.exit(1);
+            }
+        }
+    }
+
+    private static boolean isValid(String[] args) {
+        if (args.length != 2) {
+            return false;
+        }
+
+        return switch (args[0]) {
+            case "server", "client" -> true;
+            default -> false;
+        };
+    }
+
+    private static void printUsage() {
+        System.err.println("""
+            Usage:
+              java -jar xyz.jar server <listenPort>
+              java -jar xyz.jar client <serverIp>:<serverPort>
+            """);
+    }
+}
diff --git a/src/main/java/ch/unibas/dmi/dbis/cs108/casono/client/ClientApp.java b/src/main/java/ch/unibas/dmi/dbis/cs108/casono/client/ClientApp.java
new file mode 100644
index 0000000..2c17a37
--- /dev/null
+++ b/src/main/java/ch/unibas/dmi/dbis/cs108/casono/client/ClientApp.java
@@ -0,0 +1,14 @@
+package ch.unibas.dmi.dbis.cs108.casono.client;
+
+public class ClientApp {
+    public static void start(String arg) {
+        String[] parts = arg.split(":", 2);
+        if (parts.length != 2) {
+            throw new IllegalArgumentException("Address must be in format <ip>:<port>.");
+        }
+        String host = parts[0];
+        int port = Integer.parseInt(parts[1]);
+
+        System.out.println("You've selected the client. It will connect port " + port + " at host " + host);
+    }
+}
diff --git a/src/main/java/ch/unibas/dmi/dbis/cs108/casono/server/ServerApp.java b/src/main/java/ch/unibas/dmi/dbis/cs108/casono/server/ServerApp.java
new file mode 100644
index 0000000..1004cd7
--- /dev/null
+++ b/src/main/java/ch/unibas/dmi/dbis/cs108/casono/server/ServerApp.java
@@ -0,0 +1,8 @@
+package ch.unibas.dmi.dbis.cs108.casono.server;
+
+public class ServerApp {
+    public static void start(String arg) {
+        int port = Integer.parseInt(arg);
+        System.out.println("You've selected the server. It will accept connections at port" + port);
+    }
+}