Init

2025-09-16 23:05:31 +02:00
commit adb8ef9c83
30 changed files with 1422 additions and 0 deletions
--- a/build.gradle
+++ b/build.gradle
@@ -0,0 +1,40 @@
+plugins {
+	id 'java'
+	id 'org.springframework.boot' version '3.5.3'
+	id 'io.spring.dependency-management' version '1.1.7'
+}
+
+group = 'de.w665'
+version = '0.0.1-SNAPSHOT'
+
+java {
+	toolchain {
+		languageVersion = JavaLanguageVersion.of(21)
+	}
+}
+
+configurations {
+	compileOnly {
+		extendsFrom annotationProcessor
+	}
+}
+
+repositories {
+	mavenCentral()
+}
+
+dependencies {
+	implementation 'org.springframework.boot:spring-boot-starter-actuator'
+	implementation 'org.springframework.boot:spring-boot-starter-web'
+	implementation 'org.springframework.boot:spring-boot-starter-websocket'
+	implementation 'org.springframework.boot:spring-boot-starter-data-jpa'
+	implementation 'com.h2database:h2'
+	compileOnly 'org.projectlombok:lombok'
+	annotationProcessor 'org.projectlombok:lombok'
+	testImplementation 'org.springframework.boot:spring-boot-starter-test'
+	testRuntimeOnly 'org.junit.platform:junit-platform-launcher'
+}
+
+tasks.named('test') {
+	useJUnitPlatform()
+}
--- a/gradle/wrapper/gradle-wrapper.jar
+++ b/gradle/wrapper/gradle-wrapper.jar
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -0,0 +1,7 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.14.2-bin.zip
+networkTimeout=10000
+validateDistributionUrl=true
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
--- a/251
+++ b/251
@@ -0,0 +1,251 @@
+#!/bin/sh
+
+#
+# Copyright © 2015-2021 the original authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+##############################################################################
+#
+#   Gradle start up script for POSIX generated by Gradle.
+#
+#   Important for running:
+#
+#   (1) You need a POSIX-compliant shell to run this script. If your /bin/sh is
+#       noncompliant, but you have some other compliant shell such as ksh or
+#       bash, then to run this script, type that shell name before the whole
+#       command line, like:
+#
+#           ksh Gradle
+#
+#       Busybox and similar reduced shells will NOT work, because this script
+#       requires all of these POSIX shell features:
+#         * functions;
+#         * expansions «$var», «${var}», «${var:-default}», «${var+SET}»,
+#           «${var#prefix}», «${var%suffix}», and «$( cmd )»;
+#         * compound commands having a testable exit status, especially «case»;
+#         * various built-in commands including «command», «set», and «ulimit».
+#
+#   Important for patching:
+#
+#   (2) This script targets any POSIX shell, so it avoids extensions provided
+#       by Bash, Ksh, etc; in particular arrays are avoided.
+#
+#       The "traditional" practice of packing multiple parameters into a
+#       space-separated string is a well documented source of bugs and security
+#       problems, so this is (mostly) avoided, by progressively accumulating
+#       options in "$@", and eventually passing that to Java.
+#
+#       Where the inherited environment variables (DEFAULT_JVM_OPTS, JAVA_OPTS,
+#       and GRADLE_OPTS) rely on word-splitting, this is performed explicitly;
+#       see the in-line comments for details.
+#
+#       There are tweaks for specific operating systems such as AIX, CygWin,
+#       Darwin, MinGW, and NonStop.
+#
+#   (3) This script is generated from the Groovy template
+#       https://github.com/gradle/gradle/blob/HEAD/platforms/jvm/plugins-application/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       within the Gradle project.
+#
+#       You can find Gradle at https://github.com/gradle/gradle/.
+#
+##############################################################################
+
+# Attempt to set APP_HOME
+
+# Resolve links: $0 may be a link
+app_path=$0
+
+# Need this for daisy-chained symlinks.
+while
+    APP_HOME=${app_path%"${app_path##*/}"}  # leaves a trailing /; empty if no leading path
+    [ -h "$app_path" ]
+do
+    ls=$( ls -ld "$app_path" )
+    link=${ls#*' -> '}
+    case $link in             #(
+      /*)   app_path=$link ;; #(
+      *)    app_path=$APP_HOME$link ;;
+    esac
+done
+
+# This is normally unused
+# shellcheck disable=SC2034
+APP_BASE_NAME=${0##*/}
+# Discard cd standard output in case $CDPATH is set (https://github.com/gradle/gradle/issues/25036)
+APP_HOME=$( cd -P "${APP_HOME:-./}" > /dev/null && printf '%s\n' "$PWD" ) || exit
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD=maximum
+
+warn () {
+    echo "$*"
+} >&2
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+} >&2
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "$( uname )" in                #(
+  CYGWIN* )         cygwin=true  ;; #(
+  Darwin* )         darwin=true  ;; #(
+  MSYS* | MINGW* )  msys=true    ;; #(
+  NONSTOP* )        nonstop=true ;;
+esac
+
+CLASSPATH="\\\"\\\""
+
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD=$JAVA_HOME/jre/sh/java
+    else
+        JAVACMD=$JAVA_HOME/bin/java
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD=java
+    if ! command -v java >/dev/null 2>&1
+    then
+        die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+fi
+
+# Increase the maximum file descriptors if we can.
+if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
+    case $MAX_FD in #(
+      max*)
+        # In POSIX sh, ulimit -H is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
+        MAX_FD=$( ulimit -H -n ) ||
+            warn "Could not query maximum file descriptor limit"
+    esac
+    case $MAX_FD in  #(
+      '' | soft) :;; #(
+      *)
+        # In POSIX sh, ulimit -n is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
+        ulimit -n "$MAX_FD" ||
+            warn "Could not set maximum file descriptor limit to $MAX_FD"
+    esac
+fi
+
+# Collect all arguments for the java command, stacking in reverse order:
+#   * args from the command line
+#   * the main class name
+#   * -classpath
+#   * -D...appname settings
+#   * --module-path (only if needed)
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and GRADLE_OPTS environment variables.
+
+# For Cygwin or MSYS, switch paths to Windows format before running java
+if "$cygwin" || "$msys" ; then
+    APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
+    CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )
+
+    JAVACMD=$( cygpath --unix "$JAVACMD" )
+
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    for arg do
+        if
+            case $arg in                                #(
+              -*)   false ;;                            # don't mess with options #(
+              /?*)  t=${arg#/} t=/${t%%/*}              # looks like a POSIX filepath
+                    [ -e "$t" ] ;;                      #(
+              *)    false ;;
+            esac
+        then
+            arg=$( cygpath --path --ignore --mixed "$arg" )
+        fi
+        # Roll the args list around exactly as many times as the number of
+        # args, so each arg winds up back in the position where it started, but
+        # possibly modified.
+        #
+        # NB: a `for` loop captures its iteration list before it begins, so
+        # changing the positional parameters here affects neither the number of
+        # iterations, nor the values presented in `arg`.
+        shift                   # remove old arg
+        set -- "$@" "$arg"      # push replacement arg
+    done
+fi
+
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Collect all arguments for the java command:
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and optsEnvironmentVar are not allowed to contain shell fragments,
+#     and any embedded shellness will be escaped.
+#   * For example: A user cannot expect ${Hostname} to be expanded, as it is an environment variable and will be
+#     treated as '${Hostname}' itself on the command line.
+
+set -- \
+        "-Dorg.gradle.appname=$APP_BASE_NAME" \
+        -classpath "$CLASSPATH" \
+        -jar "$APP_HOME/gradle/wrapper/gradle-wrapper.jar" \
+        "$@"
+
+# Stop when "xargs" is not available.
+if ! command -v xargs >/dev/null 2>&1
+then
+    die "xargs is not available"
+fi
+
+# Use "xargs" to parse quoted args.
+#
+# With -n1 it outputs one arg per line, with the quotes and backslashes removed.
+#
+# In Bash we could simply go:
+#
+#   readarray ARGS < <( xargs -n1 <<<"$var" ) &&
+#   set -- "${ARGS[@]}" "$@"
+#
+# but POSIX shell has neither arrays nor command substitution, so instead we
+# post-process each arg (as a line of input to sed) to backslash-escape any
+# character that might be a shell metacharacter, then use eval to reverse
+# that process (while maintaining the separation between arguments), and wrap
+# the whole thing up as a single "set" statement.
+#
+# This will of course break if any of these variables contains a newline or
+# an unmatched quote.
+#
+
+eval "set -- $(
+        printf '%s\n' "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" |
+        xargs -n1 |
+        sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; ' |
+        tr '\n' ' '
+    )" '"$@"'
+
+exec "$JAVACMD" "$@"
--- a/gradlew.bat
+++ b/gradlew.bat
@@ -0,0 +1,94 @@
+@rem
+@rem Copyright 2015 the original author or authors.
+@rem
+@rem Licensed under the Apache License, Version 2.0 (the "License");
+@rem you may not use this file except in compliance with the License.
+@rem You may obtain a copy of the License at
+@rem
+@rem      https://www.apache.org/licenses/LICENSE-2.0
+@rem
+@rem Unless required by applicable law or agreed to in writing, software
+@rem distributed under the License is distributed on an "AS IS" BASIS,
+@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@rem See the License for the specific language governing permissions and
+@rem limitations under the License.
+@rem
+@rem SPDX-License-Identifier: Apache-2.0
+@rem
+
+@if "%DEBUG%"=="" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%"=="" set DIRNAME=.
+@rem This is normally unused
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Resolve any "." and ".." in APP_HOME to make it shorter.
+for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if %ERRORLEVEL% equ 0 goto execute
+
+echo. 1>&2
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH. 1>&2
+echo. 1>&2
+echo Please set the JAVA_HOME variable in your environment to match the 1>&2
+echo location of your Java installation. 1>&2
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto execute
+
+echo. 1>&2
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME% 1>&2
+echo. 1>&2
+echo Please set the JAVA_HOME variable in your environment to match the 1>&2
+echo location of your Java installation. 1>&2
+
+goto fail
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=
+
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" -jar "%APP_HOME%\gradle\wrapper\gradle-wrapper.jar" %*
+
+:end
+@rem End local scope for the variables with windows NT shell
+if %ERRORLEVEL% equ 0 goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+set EXIT_CODE=%ERRORLEVEL%
+if %EXIT_CODE% equ 0 set EXIT_CODE=1
+if not ""=="%GRADLE_EXIT_CONSOLE%" exit %EXIT_CODE%
+exit /b %EXIT_CODE%
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega
--- a/settings.gradle
+++ b/settings.gradle
@@ -0,0 +1 @@
+rootProject.name = 'testing'
--- a/src/main/java/de/w665/testing/TestingApplication.java
+++ b/src/main/java/de/w665/testing/TestingApplication.java
@@ -0,0 +1,13 @@
+package de.w665.testing;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class TestingApplication {
+
+	public static void main(String[] args) {
+		SpringApplication.run(TestingApplication.class, args);
+	}
+
+}
--- a/src/main/java/de/w665/testing/config/UsernameHandshakeInterceptor.java
+++ b/src/main/java/de/w665/testing/config/UsernameHandshakeInterceptor.java
@@ -0,0 +1,37 @@
+package de.w665.testing.config;
+
+import org.springframework.http.server.ServerHttpRequest;
+import org.springframework.http.server.ServerHttpResponse;
+import org.springframework.web.socket.WebSocketHandler;
+import org.springframework.web.socket.server.HandshakeInterceptor;
+
+import java.net.URI;
+import java.util.List;
+import java.util.Map;
+
+public class UsernameHandshakeInterceptor implements HandshakeInterceptor {
+    @Override
+    public boolean beforeHandshake(ServerHttpRequest request, ServerHttpResponse response, WebSocketHandler wsHandler, Map<String, Object> attributes) {
+        URI uri = request.getURI();
+        String query = uri.getQuery();
+        if (query != null) {
+            for (String pair : query.split("&")) {
+                String[] kv = pair.split("=", 2);
+                if (kv.length == 2 && kv[0].equals("token")) {
+                    attributes.put("token", kv[1]);
+                }
+            }
+        }
+        // Also check headers (not used by SockJS handshake, but harmless)
+        List<String> header = request.getHeaders().get("X-Auth-Token");
+        if (header != null && !header.isEmpty()) {
+            attributes.put("token", header.getFirst());
+        }
+        return true;
+    }
+
+    @Override
+    public void afterHandshake(ServerHttpRequest request, ServerHttpResponse response, WebSocketHandler wsHandler, Exception exception) {
+        // no-op
+    }
+}
--- a/src/main/java/de/w665/testing/config/UsernamePrincipalHandshakeHandler.java
+++ b/src/main/java/de/w665/testing/config/UsernamePrincipalHandshakeHandler.java
@@ -0,0 +1,34 @@
+package de.w665.testing.config;
+
+import de.w665.testing.service.TokenService;
+import org.springframework.http.server.ServerHttpRequest;
+import org.springframework.web.socket.WebSocketHandler;
+import org.springframework.web.socket.server.support.DefaultHandshakeHandler;
+
+import java.security.Principal;
+import java.util.Map;
+import java.util.Optional;
+import java.util.UUID;
+
+public class UsernamePrincipalHandshakeHandler extends DefaultHandshakeHandler {
+    private final TokenService tokenService;
+
+    public UsernamePrincipalHandshakeHandler(TokenService tokenService) {
+        this.tokenService = tokenService;
+    }
+
+    @Override
+    protected Principal determineUser(ServerHttpRequest request,
+                                      WebSocketHandler wsHandler,
+                                      Map<String, Object> attributes) {
+        Object tokenObj = attributes.get("token");
+        String token = tokenObj != null ? tokenObj.toString() : null;
+        if (token == null) {
+            // Anonymous session (reject by generating random, effectively not mapped to any user)
+            return () -> "anon-" + UUID.randomUUID();
+        }
+        Optional<String> user = tokenService.resolveUsername(token);
+        return user.<Principal>map(name -> () -> name)
+                .orElseGet(() -> (()-> "anon-" + UUID.randomUUID()));
+    }
+}
--- a/src/main/java/de/w665/testing/config/WebSocketConfig.java
+++ b/src/main/java/de/w665/testing/config/WebSocketConfig.java
@@ -0,0 +1,34 @@
+package de.w665.testing.config;
+
+import org.springframework.context.annotation.Configuration;
+import org.springframework.messaging.simp.config.MessageBrokerRegistry;
+import org.springframework.web.socket.config.annotation.EnableWebSocketMessageBroker;
+import org.springframework.web.socket.config.annotation.StompEndpointRegistry;
+import org.springframework.web.socket.config.annotation.WebSocketMessageBrokerConfigurer;
+import de.w665.testing.service.TokenService;
+
+@Configuration
+@EnableWebSocketMessageBroker
+public class WebSocketConfig implements WebSocketMessageBrokerConfigurer {
+    private final TokenService tokenService;
+
+    public WebSocketConfig(TokenService tokenService) {
+        this.tokenService = tokenService;
+    }
+
+    @Override
+    public void configureMessageBroker(MessageBrokerRegistry config) {
+        config.enableSimpleBroker("/topic", "/queue");
+        config.setApplicationDestinationPrefixes("/app");
+        config.setUserDestinationPrefix("/user");
+    }
+
+    @Override
+    public void registerStompEndpoints(StompEndpointRegistry registry) {
+        registry.addEndpoint("/ws")
+                .setAllowedOriginPatterns("*")
+                .addInterceptors(new UsernameHandshakeInterceptor())
+                .setHandshakeHandler(new UsernamePrincipalHandshakeHandler(tokenService))
+                .withSockJS();
+    }
+}
--- a/src/main/java/de/w665/testing/controller/AuthController.java
+++ b/src/main/java/de/w665/testing/controller/AuthController.java
@@ -0,0 +1,40 @@
+package de.w665.testing.controller;
+
+import de.w665.testing.dto.SignupRequest;
+import de.w665.testing.dto.SignupResponse;
+import de.w665.testing.service.PresenceService;
+import de.w665.testing.service.TokenService;
+import de.w665.testing.service.UserService;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.*;
+
+import java.util.Set;
+
+@RestController
+@RequestMapping("/api")
+public class AuthController {
+    private final UserService userService;
+    private final PresenceService presenceService;
+    private final TokenService tokenService;
+
+    public AuthController(UserService userService, PresenceService presenceService, TokenService tokenService) {
+        this.userService = userService;
+        this.presenceService = presenceService;
+        this.tokenService = tokenService;
+    }
+
+    @PostMapping("/signup")
+    public ResponseEntity<?> signup(@RequestBody SignupRequest request) {
+        try {
+            String token = userService.signup(request.getUsername());
+            return ResponseEntity.ok(new SignupResponse(request.getUsername().trim().toLowerCase(), token));
+        } catch (IllegalArgumentException ex) {
+            return ResponseEntity.status(409).body(ex.getMessage());
+        }
+    }
+
+    @GetMapping("/online")
+    public Set<String> online() {
+        return presenceService.getOnlineUsers();
+    }
+}
--- a/src/main/java/de/w665/testing/controller/WebSocketChatController.java
+++ b/src/main/java/de/w665/testing/controller/WebSocketChatController.java
@@ -0,0 +1,29 @@
+package de.w665.testing.controller;
+
+import de.w665.testing.dto.ChatMessage;
+import de.w665.testing.dto.SendMessageCommand;
+import org.springframework.messaging.handler.annotation.MessageMapping;
+import org.springframework.messaging.handler.annotation.Payload;
+import org.springframework.messaging.simp.SimpMessagingTemplate;
+import org.springframework.stereotype.Controller;
+
+import java.security.Principal;
+
+@Controller
+public class WebSocketChatController {
+    private final SimpMessagingTemplate messagingTemplate;
+
+    public WebSocketChatController(SimpMessagingTemplate messagingTemplate) {
+        this.messagingTemplate = messagingTemplate;
+    }
+
+    @MessageMapping("/chat/send")
+    public void send(@Payload SendMessageCommand cmd, Principal principal) {
+        if (principal == null || cmd.getRoomId() == null || cmd.getRoomId().isBlank() || cmd.getContent() == null || cmd.getContent().isBlank()) {
+            return;
+        }
+        String sender = principal.getName();
+        ChatMessage msg = ChatMessage.of(cmd.getRoomId(), sender, cmd.getContent());
+        messagingTemplate.convertAndSend("/topic/room." + cmd.getRoomId(), msg);
+    }
+}
--- a/src/main/java/de/w665/testing/controller/WebSocketInviteController.java
+++ b/src/main/java/de/w665/testing/controller/WebSocketInviteController.java
@@ -0,0 +1,45 @@
+package de.w665.testing.controller;
+
+import de.w665.testing.dto.AcceptInviteCommand;
+import de.w665.testing.dto.DeclineInviteCommand;
+import de.w665.testing.dto.InviteCommand;
+import de.w665.testing.service.InviteService;
+import org.springframework.messaging.handler.annotation.MessageMapping;
+import org.springframework.messaging.handler.annotation.Payload;
+import org.springframework.stereotype.Controller;
+
+import java.security.Principal;
+
+@Controller
+public class WebSocketInviteController {
+    private final InviteService inviteService;
+
+    public WebSocketInviteController(InviteService inviteService) {
+        this.inviteService = inviteService;
+    }
+
+    @MessageMapping("/invite/send")
+    public void sendInvite(@Payload InviteCommand cmd, Principal principal) {
+        if (principal == null) return;
+        String from = principal.getName();
+        if (cmd.getTo() == null || cmd.getTo().isBlank()) return;
+        if (from.equalsIgnoreCase(cmd.getTo())) return;
+        inviteService.sendInvite(from, cmd.getTo().trim().toLowerCase());
+    }
+
+    @MessageMapping("/invite/accept")
+    public void acceptInvite(@Payload AcceptInviteCommand cmd, Principal principal) {
+        if (principal == null) return;
+        String recipient = principal.getName();
+        if (cmd.getInviter() == null || cmd.getInviter().isBlank()) return;
+        inviteService.acceptInvite(recipient, cmd.getInviter().trim().toLowerCase());
+    }
+
+    @MessageMapping("/invite/decline")
+    public void declineInvite(@Payload DeclineInviteCommand cmd, Principal principal) {
+        if (principal == null) return;
+        String recipient = principal.getName();
+        if (cmd.getInviter() == null || cmd.getInviter().isBlank()) return;
+        inviteService.declineInvite(recipient, cmd.getInviter().trim().toLowerCase());
+    }
+}
--- a/src/main/java/de/w665/testing/dto/AcceptInviteCommand.java
+++ b/src/main/java/de/w665/testing/dto/AcceptInviteCommand.java
@@ -0,0 +1,13 @@
+package de.w665.testing.dto;
+
+public class AcceptInviteCommand {
+    private String inviter;
+
+    public String getInviter() {
+        return inviter;
+    }
+
+    public void setInviter(String inviter) {
+        this.inviter = inviter;
+    }
+}
--- a/src/main/java/de/w665/testing/dto/ChatMessage.java
+++ b/src/main/java/de/w665/testing/dto/ChatMessage.java
@@ -0,0 +1,55 @@
+package de.w665.testing.dto;
+
+import java.time.Instant;
+
+public class ChatMessage {
+    private String roomId;
+    private String sender;
+    private String content;
+    private long timestamp;
+
+    public ChatMessage() {}
+
+    public ChatMessage(String roomId, String sender, String content, long timestamp) {
+        this.roomId = roomId;
+        this.sender = sender;
+        this.content = content;
+        this.timestamp = timestamp;
+    }
+
+    public static ChatMessage of(String roomId, String sender, String content) {
+        return new ChatMessage(roomId, sender, content, Instant.now().toEpochMilli());
+    }
+
+    public String getRoomId() {
+        return roomId;
+    }
+
+    public void setRoomId(String roomId) {
+        this.roomId = roomId;
+    }
+
+    public String getSender() {
+        return sender;
+    }
+
+    public void setSender(String sender) {
+        this.sender = sender;
+    }
+
+    public String getContent() {
+        return content;
+    }
+
+    public void setContent(String content) {
+        this.content = content;
+    }
+
+    public long getTimestamp() {
+        return timestamp;
+    }
+
+    public void setTimestamp(long timestamp) {
+        this.timestamp = timestamp;
+    }
+}
--- a/src/main/java/de/w665/testing/dto/DeclineInviteCommand.java
+++ b/src/main/java/de/w665/testing/dto/DeclineInviteCommand.java
@@ -0,0 +1,13 @@
+package de.w665.testing.dto;
+
+public class DeclineInviteCommand {
+    private String inviter;
+
+    public String getInviter() {
+        return inviter;
+    }
+
+    public void setInviter(String inviter) {
+        this.inviter = inviter;
+    }
+}
--- a/src/main/java/de/w665/testing/dto/InviteCommand.java
+++ b/src/main/java/de/w665/testing/dto/InviteCommand.java
@@ -0,0 +1,13 @@
+package de.w665.testing.dto;
+
+public class InviteCommand {
+    private String to;
+
+    public String getTo() {
+        return to;
+    }
+
+    public void setTo(String to) {
+        this.to = to;
+    }
+}
--- a/src/main/java/de/w665/testing/dto/InviteEvent.java
+++ b/src/main/java/de/w665/testing/dto/InviteEvent.java
@@ -0,0 +1,63 @@
+package de.w665.testing.dto;
+
+public class InviteEvent {
+    public enum Type { INVITE, ACCEPT, DECLINE }
+
+    private Type type;
+    private String from;
+    private String to;
+    private String roomId; // present when type == ACCEPT
+
+    public InviteEvent() {}
+
+    public InviteEvent(Type type, String from, String to, String roomId) {
+        this.type = type;
+        this.from = from;
+        this.to = to;
+        this.roomId = roomId;
+    }
+
+    public static InviteEvent invite(String from, String to) {
+        return new InviteEvent(Type.INVITE, from, to, null);
+    }
+
+    public static InviteEvent accept(String from, String to, String roomId) {
+        return new InviteEvent(Type.ACCEPT, from, to, roomId);
+    }
+
+    public static InviteEvent decline(String from, String to) {
+        return new InviteEvent(Type.DECLINE, from, to, null);
+    }
+
+    public Type getType() {
+        return type;
+    }
+
+    public void setType(Type type) {
+        this.type = type;
+    }
+
+    public String getFrom() {
+        return from;
+    }
+
+    public void setFrom(String from) {
+        this.from = from;
+    }
+
+    public String getTo() {
+        return to;
+    }
+
+    public void setTo(String to) {
+        this.to = to;
+    }
+
+    public String getRoomId() {
+        return roomId;
+    }
+
+    public void setRoomId(String roomId) {
+        this.roomId = roomId;
+    }
+}
--- a/src/main/java/de/w665/testing/dto/SendMessageCommand.java
+++ b/src/main/java/de/w665/testing/dto/SendMessageCommand.java
@@ -0,0 +1,22 @@
+package de.w665.testing.dto;
+
+public class SendMessageCommand {
+    private String roomId;
+    private String content;
+
+    public String getRoomId() {
+        return roomId;
+    }
+
+    public void setRoomId(String roomId) {
+        this.roomId = roomId;
+    }
+
+    public String getContent() {
+        return content;
+    }
+
+    public void setContent(String content) {
+        this.content = content;
+    }
+}
--- a/src/main/java/de/w665/testing/dto/SignupRequest.java
+++ b/src/main/java/de/w665/testing/dto/SignupRequest.java
@@ -0,0 +1,13 @@
+package de.w665.testing.dto;
+
+public class SignupRequest {
+    private String username;
+
+    public String getUsername() {
+        return username;
+    }
+
+    public void setUsername(String username) {
+        this.username = username;
+    }
+}
--- a/src/main/java/de/w665/testing/dto/SignupResponse.java
+++ b/src/main/java/de/w665/testing/dto/SignupResponse.java
@@ -0,0 +1,29 @@
+package de.w665.testing.dto;
+
+public class SignupResponse {
+    private String username;
+    private String token;
+
+    public SignupResponse() {}
+
+    public SignupResponse(String username, String token) {
+        this.username = username;
+        this.token = token;
+    }
+
+    public String getUsername() {
+        return username;
+    }
+
+    public void setUsername(String username) {
+        this.username = username;
+    }
+
+    public String getToken() {
+        return token;
+    }
+
+    public void setToken(String token) {
+        this.token = token;
+    }
+}
--- a/src/main/java/de/w665/testing/service/ChatRoomService.java
+++ b/src/main/java/de/w665/testing/service/ChatRoomService.java
@@ -0,0 +1,28 @@
+package de.w665.testing.service;
+
+import org.springframework.stereotype.Service;
+
+import java.util.Map;
+import java.util.Optional;
+import java.util.concurrent.ConcurrentHashMap;
+
+@Service
+public class ChatRoomService {
+    // key: canonicalPair(userA,userB) -> roomId
+    private final Map<String, String> pairToRoom = new ConcurrentHashMap<>();
+
+    public String getOrCreateRoom(String userA, String userB) {
+        String key = canonicalPair(userA, userB);
+        return pairToRoom.computeIfAbsent(key, k -> "room-" + Math.abs(k.hashCode()));
+    }
+
+    public Optional<String> getRoomIfExists(String userA, String userB) {
+        return Optional.ofNullable(pairToRoom.get(canonicalPair(userA, userB)));
+    }
+
+    private String canonicalPair(String a, String b) {
+        String u1 = a.toLowerCase();
+        String u2 = b.toLowerCase();
+        return (u1.compareTo(u2) <= 0) ? (u1 + "|" + u2) : (u2 + "|" + u1);
+    }
+}
--- a/src/main/java/de/w665/testing/service/InviteService.java
+++ b/src/main/java/de/w665/testing/service/InviteService.java
@@ -0,0 +1,48 @@
+package de.w665.testing.service;
+
+import de.w665.testing.dto.InviteEvent;
+import org.springframework.messaging.simp.SimpMessagingTemplate;
+import org.springframework.stereotype.Service;
+
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+
+@Service
+public class InviteService {
+    private final SimpMessagingTemplate messagingTemplate;
+    private final ChatRoomService chatRoomService;
+
+    // recipient -> set of inviters
+    private final Map<String, Set<String>> pending = new ConcurrentHashMap<>();
+
+    public InviteService(SimpMessagingTemplate messagingTemplate, ChatRoomService chatRoomService) {
+        this.messagingTemplate = messagingTemplate;
+        this.chatRoomService = chatRoomService;
+    }
+
+    public void sendInvite(String from, String to) {
+        pending.computeIfAbsent(to, k -> ConcurrentHashMap.newKeySet()).add(from);
+        InviteEvent event = InviteEvent.invite(from, to);
+        messagingTemplate.convertAndSendToUser(to, "/queue/invites", event);
+    }
+
+    public void acceptInvite(String recipient, String inviter) {
+        Set<String> inviters = pending.getOrDefault(recipient, ConcurrentHashMap.newKeySet());
+        if (inviters.remove(inviter)) {
+            String room = chatRoomService.getOrCreateRoom(inviter, recipient);
+            InviteEvent acceptForInviter = InviteEvent.accept(recipient, inviter, room);
+            InviteEvent acceptForRecipient = InviteEvent.accept(inviter, recipient, room);
+            messagingTemplate.convertAndSendToUser(inviter, "/queue/invites", acceptForInviter);
+            messagingTemplate.convertAndSendToUser(recipient, "/queue/invites", acceptForRecipient);
+        }
+    }
+
+    public void declineInvite(String recipient, String inviter) {
+        Set<String> inviters = pending.getOrDefault(recipient, ConcurrentHashMap.newKeySet());
+        if (inviters.remove(inviter)) {
+            InviteEvent declineForInviter = InviteEvent.decline(recipient, inviter);
+            messagingTemplate.convertAndSendToUser(inviter, "/queue/invites", declineForInviter);
+        }
+    }
+}
--- a/src/main/java/de/w665/testing/service/PresenceService.java
+++ b/src/main/java/de/w665/testing/service/PresenceService.java
@@ -0,0 +1,54 @@
+package de.w665.testing.service;
+
+import org.springframework.messaging.simp.SimpMessagingTemplate;
+import org.springframework.stereotype.Service;
+
+import java.util.Collections;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.stream.Collectors;
+
+@Service
+public class PresenceService {
+    private final SimpMessagingTemplate messagingTemplate;
+
+    // sessionId -> username
+    private final Map<String, String> sessionToUser = new ConcurrentHashMap<>();
+    // username -> session count
+    private final Map<String, Integer> userSessionCounts = new ConcurrentHashMap<>();
+
+    public PresenceService(SimpMessagingTemplate messagingTemplate) {
+        this.messagingTemplate = messagingTemplate;
+    }
+
+    public void userConnected(String sessionId, String username) {
+        sessionToUser.put(sessionId, username);
+        userSessionCounts.merge(username, 1, Integer::sum);
+        broadcastOnlineUsers();
+    }
+
+    public void userDisconnected(String sessionId) {
+        String username = sessionToUser.remove(sessionId);
+        if (username != null) {
+            userSessionCounts.computeIfPresent(username, (u, count) -> {
+                int next = count - 1;
+                return next <= 0 ? null : next;
+            });
+            broadcastOnlineUsers();
+        }
+    }
+
+    public Set<String> getOnlineUsers() {
+        return Collections.unmodifiableSet(
+                userSessionCounts.entrySet().stream()
+                        .filter(e -> e.getValue() != null && e.getValue() > 0)
+                        .map(Map.Entry::getKey)
+                        .collect(Collectors.toSet())
+        );
+    }
+
+    public void broadcastOnlineUsers() {
+        messagingTemplate.convertAndSend("/topic/online-users", getOnlineUsers());
+    }
+}
--- a/src/main/java/de/w665/testing/service/TokenService.java
+++ b/src/main/java/de/w665/testing/service/TokenService.java
@@ -0,0 +1,35 @@
+package de.w665.testing.service;
+
+import org.springframework.stereotype.Service;
+
+import java.security.SecureRandom;
+import java.util.Base64;
+import java.util.Map;
+import java.util.Optional;
+import java.util.concurrent.ConcurrentHashMap;
+
+@Service
+public class TokenService {
+    private final Map<String, String> tokenToUser = new ConcurrentHashMap<>();
+    private final SecureRandom random = new SecureRandom();
+
+    public String createTokenForUsername(String username) {
+        String token = generateToken();
+        tokenToUser.put(token, username);
+        return token;
+    }
+
+    public Optional<String> resolveUsername(String token) {
+        return Optional.ofNullable(tokenToUser.get(token));
+    }
+
+    public void invalidate(String token) {
+        tokenToUser.remove(token);
+    }
+
+    private String generateToken() {
+        byte[] bytes = new byte[32];
+        random.nextBytes(bytes);
+        return Base64.getUrlEncoder().withoutPadding().encodeToString(bytes);
+    }
+}
--- a/src/main/java/de/w665/testing/service/UserService.java
+++ b/src/main/java/de/w665/testing/service/UserService.java
@@ -0,0 +1,41 @@
+package de.w665.testing.service;
+
+import org.springframework.stereotype.Service;
+
+import java.util.Collections;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+
+@Service
+public class UserService {
+    private final TokenService tokenService;
+    private final Map<String, String> usernameToToken = new ConcurrentHashMap<>();
+
+    public UserService(TokenService tokenService) {
+        this.tokenService = tokenService;
+    }
+
+    public synchronized String signup(String username) {
+        String normalized = normalize(username);
+        if (usernameToToken.containsKey(normalized)) {
+            throw new IllegalArgumentException("Username already taken");
+        }
+        String token = tokenService.createTokenForUsername(normalized);
+        usernameToToken.put(normalized, token);
+        return token;
+    }
+
+    public Optional<String> getTokenFor(String username) {
+        return Optional.ofNullable(usernameToToken.get(normalize(username)));
+    }
+
+    public Set<String> getAllRegisteredUsers() {
+        return Collections.unmodifiableSet(usernameToToken.keySet());
+    }
+
+    private String normalize(String username) {
+        return username.trim().toLowerCase();
+    }
+}
--- a/src/main/java/de/w665/testing/ws/WebSocketPresenceEventListener.java
+++ b/src/main/java/de/w665/testing/ws/WebSocketPresenceEventListener.java
@@ -0,0 +1,54 @@
+package de.w665.testing.ws;
+
+import de.w665.testing.service.PresenceService;
+import org.springframework.context.event.EventListener;
+import org.springframework.messaging.simp.stomp.StompHeaderAccessor;
+import org.springframework.stereotype.Component;
+import org.springframework.web.socket.messaging.SessionConnectEvent;
+import org.springframework.web.socket.messaging.SessionConnectedEvent;
+import org.springframework.web.socket.messaging.SessionDisconnectEvent;
+
+import java.security.Principal;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+
+@Component
+public class WebSocketPresenceEventListener {
+    private final PresenceService presenceService;
+    private final Set<String> connectedSessions = ConcurrentHashMap.newKeySet();
+
+    public WebSocketPresenceEventListener(PresenceService presenceService) {
+        this.presenceService = presenceService;
+    }
+
+    @EventListener
+    public void handleWebSocketConnectListener(SessionConnectEvent event) {
+        StompHeaderAccessor sha = StompHeaderAccessor.wrap(event.getMessage());
+        Principal p = sha.getUser();
+        String sessionId = sha.getSessionId();
+        if (p != null && sessionId != null && connectedSessions.add(sessionId)) {
+            presenceService.userConnected(sessionId, p.getName());
+        }
+    }
+
+    @EventListener
+    public void handleWebSocketConnectedListener(SessionConnectedEvent event) {
+        StompHeaderAccessor sha = StompHeaderAccessor.wrap(event.getMessage());
+        Principal p = sha.getUser();
+        String sessionId = sha.getSessionId();
+        if (p != null && sessionId != null && connectedSessions.add(sessionId)) {
+            presenceService.userConnected(sessionId, p.getName());
+        }
+    }
+
+    @EventListener
+    public void handleWebSocketDisconnectListener(SessionDisconnectEvent event) {
+        String sessionId = event.getSessionId();
+        if (sessionId != null && connectedSessions.remove(sessionId)) {
+            presenceService.userDisconnected(sessionId);
+        } else {
+            // Even if we didn't mark it as connected (edge cases), attempt to notify presence
+            presenceService.userDisconnected(sessionId);
+        }
+    }
+}
--- a/src/main/resources/application.properties
+++ b/src/main/resources/application.properties
@@ -0,0 +1,17 @@
+spring.application.name=testing
+
+# H2 Database configuration
+spring.datasource.url=jdbc:h2:mem:testdb
+spring.datasource.driverClassName=org.h2.Driver
+spring.datasource.username=sa
+spring.datasource.password=password
+spring.h2.console.enabled=true
+spring.h2.console.path=/h2-console
+
+# JPA configuration
+spring.jpa.database-platform=org.hibernate.dialect.H2Dialect
+spring.jpa.hibernate.ddl-auto=create-drop
+spring.jpa.show-sql=true
+
+# Server configuration
+server.port=8080
--- a/src/main/resources/static/index.html
+++ b/src/main/resources/static/index.html
@@ -0,0 +1,286 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <meta charset="UTF-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1.0">
+  <title>Simple Chat</title>
+  <style>
+    body { font-family: system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, sans-serif; margin: 0; background: #0f172a; color: #e2e8f0; }
+    header { padding: 16px; background: #111827; display: flex; justify-content: space-between; align-items: center; }
+    header h1 { margin: 0; font-size: 18px; }
+    .container { display: grid; grid-template-columns: 300px 1fr; gap: 16px; padding: 16px; height: calc(100vh - 64px); box-sizing: border-box; }
+    .panel { background: #1f2937; border-radius: 8px; padding: 12px; overflow: hidden; display: flex; flex-direction: column; }
+    .panel h2 { margin: 0 0 8px 0; font-size: 14px; color: #93c5fd; }
+    .row { display: flex; gap: 8px; align-items: center; }
+    input, button, select { padding: 8px 10px; border-radius: 6px; border: 1px solid #374151; background: #0b1220; color: #e5e7eb; }
+    button { cursor: pointer; background: #2563eb; border: none; }
+    button.secondary { background: #374151; }
+    button:disabled { background: #1f2937; cursor: not-allowed; }
+    ul { list-style: none; padding: 0; margin: 0; overflow: auto; }
+    li { padding: 8px; border-bottom: 1px solid #374151; display: flex; align-items: center; justify-content: space-between; gap: 8px; }
+    .badge { background: #10b981; color: #052e1a; border-radius: 999px; padding: 2px 8px; font-size: 12px; }
+    .chat { display: grid; grid-template-rows: 1fr auto; gap: 8px; height: 100%; }
+    .messages { background: #0b1220; border-radius: 8px; padding: 8px; overflow: auto; border: 1px solid #1f2937; }
+    .msg { margin: 6px 0; }
+    .msg .sender { font-weight: 600; color: #60a5fa; margin-right: 6px; }
+    .system { color: #9ca3af; font-style: italic; }
+    .rooms { display: flex; gap: 6px; flex-wrap: wrap; margin-bottom: 8px; }
+    .pill { padding: 6px 10px; border-radius: 999px; background: #0b1220; border: 1px solid #374151; cursor: pointer; }
+    .pill.active { background: #1d4ed8; border-color: #1d4ed8; }
+    .invite { display: flex; gap: 6px; align-items: center; }
+    .footer { color: #9ca3af; font-size: 12px; }
+  </style>
+  <script src="https://cdn.jsdelivr.net/npm/sockjs-client@1.6.1/dist/sockjs.min.js"></script>
+  <script src="https://cdn.jsdelivr.net/npm/stompjs@2.3.3/lib/stomp.min.js"></script>
+</head>
+<body>
+<header>
+  <h1>Simple Chat</h1>
+  <div id="me" class="footer"></div>
+</header>
+<div class="container">
+  <div class="panel">
+    <h2>Sign up</h2>
+    <div class="row" style="margin-bottom:8px;">
+      <input id="username" placeholder="username (a-z, 0-9)" />
+      <button id="signupBtn">Sign up</button>
+    </div>
+    <div class="footer">After signup, a WebSocket connection is created. Your online status will be visible to others.</div>
+
+    <h2 style="margin-top:16px;">Online users</h2>
+    <ul id="users"></ul>
+  </div>
+  <div class="panel">
+    <h2>Chat</h2>
+    <div class="rooms" id="rooms"></div>
+    <div class="chat">
+      <div class="messages" id="messages"></div>
+      <div class="row">
+        <input id="messageInput" placeholder="Type a message..." style="flex:1" />
+        <button id="sendBtn" disabled>Send</button>
+      </div>
+    </div>
+  </div>
+</div>
+
+<script>
+(function(){
+  const state = {
+    username: localStorage.getItem('username') || '',
+    token: localStorage.getItem('token') || '',
+    client: null,
+    connected: false,
+    online: new Set(),
+    rooms: {}, // roomId -> { participants: [a,b], messages: [] }
+    activeRoom: null,
+    subscribedRooms: new Set(),
+  };
+
+  const els = {
+    username: document.getElementById('username'),
+    signupBtn: document.getElementById('signupBtn'),
+    users: document.getElementById('users'),
+    messages: document.getElementById('messages'),
+    messageInput: document.getElementById('messageInput'),
+    sendBtn: document.getElementById('sendBtn'),
+    rooms: document.getElementById('rooms'),
+    me: document.getElementById('me'),
+  };
+
+  function setMe() {
+    if (state.username) {
+      els.me.textContent = `Signed in as ${state.username}`;
+    } else {
+      els.me.textContent = 'Not signed in';
+    }
+  }
+
+  function api(path, options={}){
+    return fetch(path, {
+      headers: { 'Content-Type': 'application/json' },
+      ...options,
+    }).then(r => {
+      if (!r.ok) return r.text().then(t => Promise.reject(new Error(t||r.statusText)));
+      const ct = r.headers.get('content-type')||'';
+      if (ct.includes('application/json')) return r.json();
+      return r.text();
+    });
+  }
+
+  function renderUsers(){
+    els.users.innerHTML = '';
+    const arr = Array.from(state.online).filter(u => u !== state.username).sort();
+    if (!arr.length) {
+      const li = document.createElement('li');
+      li.innerHTML = '<span class="system">No other users online</span>';
+      els.users.appendChild(li);
+      return;
+    }
+    arr.forEach(u => {
+      const li = document.createElement('li');
+      const span = document.createElement('span');
+      span.textContent = u;
+      const btn = document.createElement('button');
+      btn.textContent = 'Invite';
+      btn.onclick = () => sendInvite(u);
+      li.appendChild(span);
+      li.appendChild(btn);
+      els.users.appendChild(li);
+    });
+  }
+
+  function renderRooms(){
+    els.rooms.innerHTML = '';
+    Object.entries(state.rooms).forEach(([roomId, room]) => {
+      const pill = document.createElement('div');
+      pill.className = 'pill' + (state.activeRoom === roomId ? ' active' : '');
+      const other = room.participants.find(p => p !== state.username) || 'room';
+      pill.textContent = other;
+      pill.onclick = () => setActiveRoom(roomId);
+      els.rooms.appendChild(pill);
+    });
+  }
+
+  function renderMessages(){
+    els.messages.innerHTML = '';
+    const room = state.rooms[state.activeRoom];
+    if (!room) {
+      const d = document.createElement('div');
+      d.className = 'system';
+      d.textContent = 'No active room. Send or accept an invite to start chatting.';
+      els.messages.appendChild(d);
+      els.sendBtn.disabled = true;
+      return;
+    }
+    els.sendBtn.disabled = false;
+    room.messages.forEach(m => {
+      const div = document.createElement('div');
+      div.className = 'msg';
+      const sender = document.createElement('span');
+      sender.className = 'sender';
+      sender.textContent = m.sender + ':';
+      const content = document.createElement('span');
+      content.textContent = ' ' + m.content;
+      div.appendChild(sender);
+      div.appendChild(content);
+      els.messages.appendChild(div);
+    });
+    els.messages.scrollTop = els.messages.scrollHeight;
+  }
+
+  function setActiveRoom(roomId){
+    state.activeRoom = roomId;
+    renderRooms();
+    renderMessages();
+  }
+
+  function upsertRoom(roomId, participants){
+    if (!state.rooms[roomId]) {
+      state.rooms[roomId] = { participants: participants || [], messages: [] };
+      if (!state.activeRoom) setActiveRoom(roomId);
+    }
+  }
+
+  function connectWebSocket(){
+    if (!state.token) return;
+    const sock = new SockJS(`/ws?token=${encodeURIComponent(state.token)}`);
+    const client = Stomp.over(sock);
+    client.debug = () => {};
+    client.connect({}, () => {
+      state.client = client;
+      state.connected = true;
+      // Online users topic
+      client.subscribe('/topic/online-users', msg => {
+        try{ const set = new Set(JSON.parse(msg.body)); state.online = set; renderUsers(); } catch(e){}
+      });
+      // Invite queue (user-specific)
+      client.subscribe('/user/queue/invites', msg => {
+        const ev = JSON.parse(msg.body);
+        if (ev.type === 'INVITE') {
+          const accept = confirm(`${ev.from} invited you to chat. Accept?`);
+          if (accept) {
+            client.send('/app/invite/accept', {}, JSON.stringify({ inviter: ev.from }));
+          } else {
+            client.send('/app/invite/decline', {}, JSON.stringify({ inviter: ev.from }));
+          }
+        } else if (ev.type === 'ACCEPT') {
+          // Both sides receive ACCEPT with roomId
+          upsertRoom(ev.roomId, [ev.from, ev.to]);
+          subscribeRoom(ev.roomId);
+        } else if (ev.type === 'DECLINE') {
+          alert(`${ev.from} declined your invite.`);
+        }
+      });
+      // Get initial online users
+      refreshOnline();
+    }, (err) => {
+      console.error('WS error', err);
+      state.connected = false;
+      setTimeout(connectWebSocket, 2000);
+    });
+  }
+
+  function subscribeRoom(roomId){
+    if (!state.client) return;
+    if (state.subscribedRooms.has(roomId)) return;
+    state.subscribedRooms.add(roomId);
+    state.client.subscribe(`/topic/room.${roomId}`, msg => {
+      const chat = JSON.parse(msg.body);
+      upsertRoom(chat.roomId);
+      state.rooms[chat.roomId].messages.push(chat);
+      renderMessages();
+    });
+  }
+
+  function sendInvite(to){
+    if (!state.client) return;
+    state.client.send('/app/invite/send', {}, JSON.stringify({ to }));
+    alert(`Invite sent to ${to}`);
+  }
+
+  function sendMessage(){
+    const roomId = state.activeRoom;
+    const content = els.messageInput.value.trim();
+    if (!content || !roomId || !state.client) return;
+    state.client.send('/app/chat/send', {}, JSON.stringify({ roomId, content }));
+    els.messageInput.value = '';
+  }
+
+  function refreshOnline(){
+    api('/api/online').then(list => {
+      state.online = new Set(list);
+      renderUsers();
+    }).catch(()=>{});
+  }
+
+  function signup(){
+    const raw = els.username.value.trim().toLowerCase();
+    const username = raw.replace(/[^a-z0-9_-]/g, '');
+    if (!username) { alert('Please enter a username'); return; }
+    api('/api/signup', { method: 'POST', body: JSON.stringify({ username }) })
+      .then(res => {
+        state.username = res.username;
+        state.token = res.token;
+        localStorage.setItem('username', state.username);
+        localStorage.setItem('token', state.token);
+        setMe();
+        connectWebSocket();
+        refreshOnline();
+      })
+      .catch(err => alert('Signup failed: ' + err.message));
+  }
+
+  // Init
+  setMe();
+  if (state.username && state.token) {
+    connectWebSocket();
+    refreshOnline();
+  }
+
+  els.signupBtn.addEventListener('click', signup);
+  els.messageInput.addEventListener('keydown', (e)=>{ if (e.key === 'Enter') sendMessage(); });
+  els.sendBtn.addEventListener('click', sendMessage);
+})();
+</script>
+</body>
+</html>
--- a/src/test/java/de/w665/testing/TestingApplicationTests.java
+++ b/src/test/java/de/w665/testing/TestingApplicationTests.java
@@ -0,0 +1,13 @@
+package de.w665.testing;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.boot.test.context.SpringBootTest;
+
+@SpringBootTest
+class TestingApplicationTests {
+
+	@Test
+	void contextLoads() {
+	}
+
+}