documents/docs/networking/commands/protocol-document.md

@@ -43,6 +43,13 @@ This document describes the protocol for client-server communication in our appl
     - [Error Response](#error-response-5)
     - [Example Request](#example-request-3)
     - [Example Response](#example-response-3)
+  - [LIST\_USERS command](#list_users-command)
+    - [Required pre-execution checks](#required-pre-execution-checks-4)
+    - [Request Parameters](#request-parameters-4)
+    - [Success Response](#success-response-4)
+    - [Error Response](#error-response-6)
+    - [Example Request](#example-request-4)
+    - [Example Response](#example-response-4)
 
 <!-- Please see the comments for copy ‚ n' paste ready examples -->
 
@@ -287,3 +294,51 @@ LOGOUT
 +OK
 END
 ```
+
+## LIST_USERS command
+The `LIST_USERS` command is used to retrieve a list of all currently logged-in users.
+
+### Required pre-execution checks
+None.
+
+### Request Parameters
+No parameters.
+
+### Success Response
+| Field   | Type               | Description                              |
+| :------ | :----------------- | :--------------------------------------- |
+| `USERS` | `Collection<User>` | Collection of all users currently online |
+
+| Fields of `User` | Type                                                                    | Description                                                           |
+| :--------------- | :---------------------------------------------------------------------- | :-------------------------------------------------------------------- |
+| `USERNAME`       | `String`                                                                | Username of the newly created user, can differ from the requested one |
+| `ID`             | [`UUID`](https://docs.oracle.com/javase/8/docs/api/java/util/UUID.html) | The ID of the created user                                            |
+
+
+### Error Response
+None.
+
+### Example Request
+```
+LIST_USERS
+```
+
+### Example Response
+```
++OK
+  USERS
+    USER
+      USERNAME=Lars_001
+      ID=56765d0f-8cd3-4eec-91b2-7e36265c1a5d
+    END
+    USER
+      USERNAME=Lars_002
+      ID=b7bbd9b3-0d49-4c92-8306-b1c8506d2ff0
+    END
+    USER
+      USERNAME=Lars
+      ID=982bc78e-547f-495a-a821-433a3603f92c
+    END
+  END
+END
+```

src/main/java/ch/unibas/dmi/dbis/cs108/casono/server/ServerApp.java

@@ -3,6 +3,9 @@ package ch.unibas.dmi.dbis.cs108.casono.server;
 import ch.unibas.dmi.dbis.cs108.casono.server.app.commands.check_nick.CheckUsernameHandler;
 import ch.unibas.dmi.dbis.cs108.casono.server.app.commands.check_nick.CheckUsernameParser;
 import ch.unibas.dmi.dbis.cs108.casono.server.app.commands.check_nick.CheckUsernameRequest;
+import ch.unibas.dmi.dbis.cs108.casono.server.app.commands.list_users.ListUsersHandler;
+import ch.unibas.dmi.dbis.cs108.casono.server.app.commands.list_users.ListUsersParser;
+import ch.unibas.dmi.dbis.cs108.casono.server.app.commands.list_users.ListUsersRequest;
 import ch.unibas.dmi.dbis.cs108.casono.server.app.commands.login.LoginHandler;
 import ch.unibas.dmi.dbis.cs108.casono.server.app.commands.login.LoginParser;
 import ch.unibas.dmi.dbis.cs108.casono.server.app.commands.login.LoginRequest;
@@ -106,5 +109,9 @@ public class ServerApp {
         parserDispatcher.register("LOGOUT", new LogoutParser());
         commandRouter.register(
                 LogoutRequest.class, new LogoutHandler(responseDispatcher, userRegistry));
+
+        parserDispatcher.register("LIST_USERS", new ListUsersParser());
+        commandRouter.register(
+                ListUsersRequest.class, new ListUsersHandler(responseDispatcher, userRegistry));
     }
 }

src/main/java/ch/unibas/dmi/dbis/cs108/casono/server/app/commands/list_users/ListUsersHandler.java

@@ -0,0 +1,40 @@
+package ch.unibas.dmi.dbis.cs108.casono.server.app.commands.list_users;
+
+import ch.unibas.dmi.dbis.cs108.casono.server.domain.user.User;
+import ch.unibas.dmi.dbis.cs108.casono.server.domain.user.UserRegistry;
+import ch.unibas.dmi.dbis.cs108.casono.server.network.command.execution.CommandHandler;
+import ch.unibas.dmi.dbis.cs108.casono.server.network.protocol.response.dispatcher.ResponseDispatcher;
+import java.util.Collection;
+
+/**
+ * Handles {@link ListUsersRequest}s by retrieving all users from the {@link UserRegistry} and
+ * dispatching a {@link ListUsersResponse} containing the list of users.
+ */
+public class ListUsersHandler extends CommandHandler<ListUsersRequest> {
+    private final UserRegistry userRegistry;
+
+    /**
+     * Creates a new handler for listing all users
+     *
+     * @param responseDispatcher the dispatcher used to send the response
+     * @param userRegistry the registry used to look up existing users
+     */
+    public ListUsersHandler(ResponseDispatcher responseDispatcher, UserRegistry userRegistry) {
+        super(responseDispatcher);
+        this.userRegistry = userRegistry;
+    }
+
+    /**
+     * Executes the list users request
+     *
+     * <p>All users are retrieved from the {@link UserRegistry} and returned in a {@link
+     * ListUsersResponse}.
+     *
+     * @param request the request to execute
+     */
+    @Override
+    public void execute(ListUsersRequest request) {
+        Collection<User> users = userRegistry.getAllUsers();
+        responseDispatcher.dispatch(new ListUsersResponse(request.getContext(), users));
+    }
+}

src/main/java/ch/unibas/dmi/dbis/cs108/casono/server/app/commands/list_users/ListUsersParser.java

@@ -0,0 +1,18 @@
+package ch.unibas.dmi.dbis.cs108.casono.server.app.commands.list_users;
+
+import ch.unibas.dmi.dbis.cs108.casono.server.network.command.parsing.CommandParser;
+import ch.unibas.dmi.dbis.cs108.casono.server.network.protocol.request.PrimitiveRequest;
+
+/** Parses a primitive request into a {@link ListUsersRequest}. */
+public class ListUsersParser implements CommandParser<ListUsersRequest> {
+    /**
+     * Parses a primitive request into a ListUsersRequest.
+     *
+     * @param primitiveRequest the request to parse
+     * @return the created {@link ListUsersRequest}
+     */
+    @Override
+    public ListUsersRequest parse(PrimitiveRequest primitiveRequest) {
+        return new ListUsersRequest(primitiveRequest.context());
+    }
+}

src/main/java/ch/unibas/dmi/dbis/cs108/casono/server/app/commands/list_users/ListUsersRequest.java

@@ -0,0 +1,17 @@
+package ch.unibas.dmi.dbis.cs108.casono.server.app.commands.list_users;
+
+import ch.unibas.dmi.dbis.cs108.casono.server.network.protocol.request.Request;
+import ch.unibas.dmi.dbis.cs108.casono.server.network.protocol.request.RequestContext;
+
+/** Request implementation used to retrieve all existing users from the server. */
+public class ListUsersRequest extends Request {
+    /**
+     * Constructs a new ListUsersRequest with the given context
+     *
+     * @param context the {@link RequestContext} containing information for responding to the
+     *     request
+     */
+    public ListUsersRequest(RequestContext context) {
+        super(context);
+    }
+}

src/main/java/ch/unibas/dmi/dbis/cs108/casono/server/app/commands/list_users/ListUsersResponse.java

@@ -0,0 +1,35 @@
+package ch.unibas.dmi.dbis.cs108.casono.server.app.commands.list_users;
+
+import ch.unibas.dmi.dbis.cs108.casono.server.domain.user.User;
+import ch.unibas.dmi.dbis.cs108.casono.server.network.protocol.request.RequestContext;
+import ch.unibas.dmi.dbis.cs108.casono.server.network.protocol.response.SuccessResponse;
+import ch.unibas.dmi.dbis.cs108.casono.server.network.protocol.response.builder.ResponseBody;
+import java.util.Collection;
+
+/** Response containing a list of all active users on the server */
+public class ListUsersResponse extends SuccessResponse {
+    /**
+     * Creates a new ListUsersResponse containing the given list of users
+     *
+     * @param context the {@link RequestContext} associated with the request
+     * @param users the collection of users currently active on the server
+     */
+    public ListUsersResponse(RequestContext context, Collection<User> users) {
+        super(
+                context,
+                ResponseBody.builder()
+                        .block(
+                                "USERS",
+                                users_block -> {
+                                    for (User user : users) {
+                                        users_block.block(
+                                                "USER",
+                                                user_block -> {
+                                                    user_block.param("USERNAME", user.getName());
+                                                    user_block.param("ID", user.getId().value());
+                                                });
+                                    }
+                                })
+                        .build());
+    }
+}