feat: enhanced dynamic help command with descriptions (fixes #5)

Author: studentpiyush

src/main/java/com/mycmd/commands/HelpCommand.java

@@ -4,6 +4,16 @@
 import com.mycmd.ShellContext;
 import java.util.Map;
 
+/**
+ * Enhanced HelpCommand
+ * --------------------
+ * Dynamically lists all available commands with their descriptions.
+ * 
+ * Features:
+ * - Automatically updates when new commands are added to the registry.
+ * - Displays both command names and short descriptions.
+ * - Supports optional usage help: "help <command>".
+ */
 public class HelpCommand implements Command {
     private final Map<String, Command> commands;
 
@@ -13,9 +23,48 @@ public HelpCommand(Map<String, Command> commands) {
 
     @Override
     public void execute(String[] args, ShellContext context) {
-        System.out.println("Available commands:");
-        for (String key : commands.keySet()) {
-            System.out.println(" - " + key);
+        // Case 1: user asked for detailed help about one command
+        if (args.length > 1) {
+            String cmdName = args[1];
+            Command cmd = commands.get(cmdName);
+
+            if (cmd != null) {
+                System.out.println("\nCommand: " + cmdName);
+                System.out.println("Description: " + cmd.description());
+                if (cmd.usage() != null && !cmd.usage().isEmpty()) {
+                    System.out.println("Usage: " + cmd.usage());
+                } else {
+                    System.out.println("Usage: " + cmdName + " [options]");
+                }
+            } else {
+                System.out.println("No such command: " + cmdName);
+            }
+            return;
+        }
+
+        // Case 2: user just typed 'help'
+        System.out.println("\nMyCMD — Available Commands:\n");
+        for (Map.Entry<String, Command> entry : commands.entrySet()) {
+            String name = entry.getKey();
+            Command cmd = entry.getValue();
+
+            String description = (cmd.description() != null && !cmd.description().isEmpty())
+                    ? cmd.description()
+                    : "No description available";
+
+            System.out.printf("  %-12s : %s%n", name, description);
         }
+
+        System.out.println("\nType 'help <command>' for detailed info about a specific command.\n");
+    }
+
+    @Override
+    public String description() {
+        return "Show list of available commands and their descriptions.";
+    }
+
+    @Override
+    public String usage() {
+        return "help [command]";
     }
-}
+}