Implement cancel-event feature (016)

Add PATCH /events/{eventToken} endpoint for organizers to cancel events,
cancellation banner for visitors, and RSVP rejection on cancelled events.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/src/main/java/de/fete/adapter/in/web/EventController.java

@@ -8,6 +8,7 @@ import de.fete.adapter.in.web.model.CreateRsvpRequest;
 import de.fete.adapter.in.web.model.CreateRsvpResponse;
 import de.fete.adapter.in.web.model.GetAttendeesResponse;
 import de.fete.adapter.in.web.model.GetEventResponse;
+import de.fete.adapter.in.web.model.PatchEventRequest;
 import de.fete.application.service.EventNotFoundException;
 import de.fete.application.service.InvalidTimezoneException;
 import de.fete.domain.model.CreateEventCommand;
@@ -22,6 +23,7 @@ import de.fete.domain.port.in.CreateEventUseCase;
 import de.fete.domain.port.in.CreateRsvpUseCase;
 import de.fete.domain.port.in.GetAttendeesUseCase;
 import de.fete.domain.port.in.GetEventUseCase;
+import de.fete.domain.port.in.UpdateEventUseCase;
 import java.time.DateTimeException;
 import java.time.ZoneId;
 import java.util.List;
@@ -40,6 +42,7 @@ public class EventController implements EventsApi {
   private final CancelRsvpUseCase cancelRsvpUseCase;
   private final CountAttendeesByEventUseCase countAttendeesByEventUseCase;
   private final GetAttendeesUseCase getAttendeesUseCase;
+  private final UpdateEventUseCase updateEventUseCase;
 
   /** Creates a new controller with the given use cases. */
   public EventController(
@@ -48,13 +51,15 @@ public class EventController implements EventsApi {
       CreateRsvpUseCase createRsvpUseCase,
       CancelRsvpUseCase cancelRsvpUseCase,
       CountAttendeesByEventUseCase countAttendeesByEventUseCase,
-      GetAttendeesUseCase getAttendeesUseCase) {
+      GetAttendeesUseCase getAttendeesUseCase,
+      UpdateEventUseCase updateEventUseCase) {
     this.createEventUseCase = createEventUseCase;
     this.getEventUseCase = getEventUseCase;
     this.createRsvpUseCase = createRsvpUseCase;
     this.cancelRsvpUseCase = cancelRsvpUseCase;
     this.countAttendeesByEventUseCase = countAttendeesByEventUseCase;
     this.getAttendeesUseCase = getAttendeesUseCase;
+    this.updateEventUseCase = updateEventUseCase;
   }
 
   @Override
@@ -97,10 +102,23 @@ public class EventController implements EventsApi {
     response.setLocation(event.getLocation());
     response.setAttendeeCount(
         (int) countAttendeesByEventUseCase.countByEvent(evtToken));
+    response.setCancelled(event.isCancelled());
+    response.setCancellationReason(event.getCancellationReason());
 
     return ResponseEntity.ok(response);
   }
 
+  @Override
+  public ResponseEntity<Void> patchEvent(
+      UUID eventToken, UUID organizerToken, PatchEventRequest request) {
+    updateEventUseCase.cancelEvent(
+        new EventToken(eventToken),
+        new OrganizerToken(organizerToken),
+        request.getCancelled(),
+        request.getCancellationReason());
+    return ResponseEntity.noContent().build();
+  }
+
   @Override
   public ResponseEntity<GetAttendeesResponse> getAttendees(
       UUID eventToken, UUID organizerToken) {

backend/src/main/java/de/fete/adapter/in/web/GlobalExceptionHandler.java

@@ -1,5 +1,7 @@
 package de.fete.adapter.in.web;
 
+import de.fete.application.service.EventAlreadyCancelledException;
+import de.fete.application.service.EventCancelledException;
 import de.fete.application.service.EventExpiredException;
 import de.fete.application.service.EventNotFoundException;
 import de.fete.application.service.ExpiryDateBeforeEventException;
@@ -75,6 +77,32 @@ public class GlobalExceptionHandler extends ResponseEntityExceptionHandler {
         .body(problemDetail);
   }
 
+  /** Handles attempt to cancel an already cancelled event. */
+  @ExceptionHandler(EventAlreadyCancelledException.class)
+  public ResponseEntity<ProblemDetail> handleEventAlreadyCancelled(
+      EventAlreadyCancelledException ex) {
+    ProblemDetail problemDetail = ProblemDetail.forStatusAndDetail(
+        HttpStatus.CONFLICT, ex.getMessage());
+    problemDetail.setTitle("Event Already Cancelled");
+    problemDetail.setType(URI.create("urn:problem-type:event-already-cancelled"));
+    return ResponseEntity.status(HttpStatus.CONFLICT)
+        .contentType(MediaType.APPLICATION_PROBLEM_JSON)
+        .body(problemDetail);
+  }
+
+  /** Handles RSVP on cancelled event. */
+  @ExceptionHandler(EventCancelledException.class)
+  public ResponseEntity<ProblemDetail> handleEventCancelled(
+      EventCancelledException ex) {
+    ProblemDetail problemDetail = ProblemDetail.forStatusAndDetail(
+        HttpStatus.CONFLICT, ex.getMessage());
+    problemDetail.setTitle("Event Cancelled");
+    problemDetail.setType(URI.create("urn:problem-type:event-cancelled"));
+    return ResponseEntity.status(HttpStatus.CONFLICT)
+        .contentType(MediaType.APPLICATION_PROBLEM_JSON)
+        .body(problemDetail);
+  }
+
   /** Handles RSVP on expired event. */
   @ExceptionHandler(EventExpiredException.class)
   public ResponseEntity<ProblemDetail> handleEventExpired(

backend/src/main/java/de/fete/adapter/out/persistence/EventJpaEntity.java

@@ -46,6 +46,12 @@ public class EventJpaEntity {
   @Column(name = "created_at", nullable = false)
   private OffsetDateTime createdAt;
 
+  @Column(name = "cancelled", nullable = false)
+  private boolean cancelled;
+
+  @Column(name = "cancellation_reason", length = 2000)
+  private String cancellationReason;
+
   /** Returns the internal database ID. */
   public Long getId() {
     return id;
@@ -145,4 +151,24 @@ public class EventJpaEntity {
   public void setCreatedAt(OffsetDateTime createdAt) {
     this.createdAt = createdAt;
   }
+
+  /** Returns whether the event is cancelled. */
+  public boolean isCancelled() {
+    return cancelled;
+  }
+
+  /** Sets the cancelled flag. */
+  public void setCancelled(boolean cancelled) {
+    this.cancelled = cancelled;
+  }
+
+  /** Returns the cancellation reason. */
+  public String getCancellationReason() {
+    return cancellationReason;
+  }
+
+  /** Sets the cancellation reason. */
+  public void setCancellationReason(String cancellationReason) {
+    this.cancellationReason = cancellationReason;
+  }
 }

backend/src/main/java/de/fete/adapter/out/persistence/EventPersistenceAdapter.java

@@ -48,6 +48,8 @@ public class EventPersistenceAdapter implements EventRepository {
     entity.setLocation(event.getLocation());
     entity.setExpiryDate(event.getExpiryDate());
     entity.setCreatedAt(event.getCreatedAt());
+    entity.setCancelled(event.isCancelled());
+    entity.setCancellationReason(event.getCancellationReason());
     return entity;
   }
 
@@ -63,6 +65,8 @@ public class EventPersistenceAdapter implements EventRepository {
     event.setLocation(entity.getLocation());
     event.setExpiryDate(entity.getExpiryDate());
     event.setCreatedAt(entity.getCreatedAt());
+    event.setCancelled(entity.isCancelled());
+    event.setCancellationReason(entity.getCancellationReason());
     return event;
   }
 }

backend/src/main/java/de/fete/application/service/EventAlreadyCancelledException.java

@@ -0,0 +1,12 @@
+package de.fete.application.service;
+
+import java.util.UUID;
+
+/** Thrown when attempting to cancel an event that is already cancelled. */
+public class EventAlreadyCancelledException extends RuntimeException {
+
+  /** Creates a new exception for the given event token. */
+  public EventAlreadyCancelledException(UUID eventToken) {
+    super("Event is already cancelled: " + eventToken);
+  }
+}

backend/src/main/java/de/fete/application/service/EventCancelledException.java

@@ -0,0 +1,12 @@
+package de.fete.application.service;
+
+import java.util.UUID;
+
+/** Thrown when an RSVP is attempted on a cancelled event. */
+public class EventCancelledException extends RuntimeException {
+
+  /** Creates a new exception for the given event token. */
+  public EventCancelledException(UUID eventToken) {
+    super("Event is cancelled: " + eventToken);
+  }
+}

backend/src/main/java/de/fete/application/service/EventService.java

@@ -6,16 +6,18 @@ import de.fete.domain.model.EventToken;
 import de.fete.domain.model.OrganizerToken;
 import de.fete.domain.port.in.CreateEventUseCase;
 import de.fete.domain.port.in.GetEventUseCase;
+import de.fete.domain.port.in.UpdateEventUseCase;
 import de.fete.domain.port.out.EventRepository;
 import java.time.Clock;
 import java.time.LocalDate;
 import java.time.OffsetDateTime;
 import java.util.Optional;
 import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
 
 /** Application service implementing event creation and retrieval. */
 @Service
-public class EventService implements CreateEventUseCase, GetEventUseCase {
+public class EventService implements CreateEventUseCase, GetEventUseCase, UpdateEventUseCase {
 
   private static final int EXPIRY_DAYS_AFTER_EVENT = 7;
 
@@ -50,4 +52,29 @@ public class EventService implements CreateEventUseCase, GetEventUseCase {
   public Optional<Event> getByEventToken(EventToken eventToken) {
     return eventRepository.findByEventToken(eventToken);
   }
+
+  @Transactional
+  @Override
+  public void cancelEvent(
+      EventToken eventToken, OrganizerToken organizerToken,
+      Boolean cancelled, String reason) {
+    if (!Boolean.TRUE.equals(cancelled)) {
+      return;
+    }
+
+    Event event = eventRepository.findByEventToken(eventToken)
+        .orElseThrow(() -> new EventNotFoundException(eventToken.value()));
+
+    if (!event.getOrganizerToken().equals(organizerToken)) {
+      throw new InvalidOrganizerTokenException();
+    }
+
+    if (event.isCancelled()) {
+      throw new EventAlreadyCancelledException(eventToken.value());
+    }
+
+    event.setCancelled(true);
+    event.setCancellationReason(reason);
+    eventRepository.save(event);
+  }
 }

backend/src/main/java/de/fete/application/service/RsvpService.java

@@ -42,6 +42,10 @@ public class RsvpService
     Event event = eventRepository.findByEventToken(eventToken)
         .orElseThrow(() -> new EventNotFoundException(eventToken.value()));
 
+    if (event.isCancelled()) {
+      throw new EventCancelledException(eventToken.value());
+    }
+
     if (!event.getExpiryDate().isAfter(LocalDate.now(clock))) {
       throw new EventExpiredException(eventToken.value());
     }

backend/src/main/java/de/fete/domain/model/Event.java

@@ -17,6 +17,8 @@ public class Event {
   private String location;
   private LocalDate expiryDate;
   private OffsetDateTime createdAt;
+  private boolean cancelled;
+  private String cancellationReason;
 
   /** Returns the internal database ID. */
   public Long getId() {
@@ -117,4 +119,24 @@ public class Event {
   public void setCreatedAt(OffsetDateTime createdAt) {
     this.createdAt = createdAt;
   }
+
+  /** Returns whether the event has been cancelled. */
+  public boolean isCancelled() {
+    return cancelled;
+  }
+
+  /** Sets the cancelled flag. */
+  public void setCancelled(boolean cancelled) {
+    this.cancelled = cancelled;
+  }
+
+  /** Returns the cancellation reason, if any. */
+  public String getCancellationReason() {
+    return cancellationReason;
+  }
+
+  /** Sets the cancellation reason. */
+  public void setCancellationReason(String cancellationReason) {
+    this.cancellationReason = cancellationReason;
+  }
 }

backend/src/main/java/de/fete/domain/port/in/UpdateEventUseCase.java

@@ -0,0 +1,13 @@
+package de.fete.domain.port.in;
+
+import de.fete.domain.model.EventToken;
+import de.fete.domain.model.OrganizerToken;
+
+/** Inbound port for updating an event. */
+public interface UpdateEventUseCase {
+
+  /** Cancels the event identified by the given token. */
+  void cancelEvent(
+      EventToken eventToken, OrganizerToken organizerToken,
+      Boolean cancelled, String reason);
+}

backend/src/main/resources/db/changelog/004-add-cancellation-columns.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<databaseChangeLog
+    xmlns="http://www.liquibase.org/xml/ns/dbchangelog"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog
+        http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-latest.xsd">
+
+    <changeSet id="004-add-cancellation-columns" author="fete">
+        <addColumn tableName="events">
+            <column name="cancelled" type="BOOLEAN" defaultValueBoolean="false">
+                <constraints nullable="false"/>
+            </column>
+            <column name="cancellation_reason" type="VARCHAR(2000)"/>
+        </addColumn>
+    </changeSet>
+
+</databaseChangeLog>

backend/src/main/resources/db/changelog/db.changelog-master.xml

@@ -9,5 +9,6 @@
     <include file="db/changelog/001-create-events-table.xml"/>
     <include file="db/changelog/002-add-timezone-column.xml"/>
     <include file="db/changelog/003-create-rsvps-table.xml"/>
+    <include file="db/changelog/004-add-cancellation-columns.xml"/>
 
 </databaseChangeLog>

backend/src/main/resources/openapi/api.yaml

@@ -184,6 +184,58 @@ paths:
               schema:
                 $ref: "#/components/schemas/ProblemDetail"
 
+    patch:
+      operationId: patchEvent
+      summary: Update an event (currently cancel)
+      description: |
+        Partial update of an event resource. Currently the only supported operation
+        is cancellation (setting cancelled to true). Requires the organizer token.
+        Cancellation is irreversible.
+      tags:
+        - events
+      parameters:
+        - name: eventToken
+          in: path
+          required: true
+          schema:
+            type: string
+            format: uuid
+          description: Public event token
+        - name: organizerToken
+          in: query
+          required: true
+          schema:
+            type: string
+            format: uuid
+          description: Organizer token for authorization
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              $ref: "#/components/schemas/PatchEventRequest"
+      responses:
+        "204":
+          description: Event updated successfully
+        "403":
+          description: Invalid organizer token
+          content:
+            application/problem+json:
+              schema:
+                $ref: "#/components/schemas/ProblemDetail"
+        "404":
+          description: Event not found
+          content:
+            application/problem+json:
+              schema:
+                $ref: "#/components/schemas/ProblemDetail"
+        "409":
+          description: Event is already cancelled
+          content:
+            application/problem+json:
+              schema:
+                $ref: "#/components/schemas/ProblemDetail"
+
 components:
   schemas:
     CreateEventRequest:
@@ -252,6 +304,7 @@ components:
         - dateTime
         - timezone
         - attendeeCount
+        - cancelled
       properties:
         eventToken:
           type: string
@@ -284,6 +337,31 @@ components:
           minimum: 0
           description: Number of confirmed attendees (attending=true)
           example: 12
+        cancelled:
+          type: boolean
+          description: Whether the event has been cancelled
+          example: false
+        cancellationReason:
+          type:
+            - string
+            - "null"
+          description: Reason for cancellation, if provided
+          example: null
+
+    PatchEventRequest:
+      type: object
+      required:
+        - cancelled
+      properties:
+        cancelled:
+          type: boolean
+          description: Set to true to cancel the event (irreversible)
+          example: true
+        cancellationReason:
+          type: string
+          maxLength: 2000
+          description: Optional cancellation reason
+          example: "Unfortunately the venue is no longer available."
 
     CreateRsvpRequest:
       type: object

backend/src/test/java/de/fete/adapter/in/web/EventControllerIntegrationTest.java

@@ -3,6 +3,7 @@ package de.fete.adapter.in.web;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.delete;
 import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.patch;
 import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.post;
 import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.content;
 import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.jsonPath;
@@ -21,6 +22,7 @@ import de.fete.adapter.out.persistence.RsvpJpaRepository;
 import java.time.LocalDate;
 import java.time.OffsetDateTime;
 import java.time.ZoneOffset;
+import java.util.Map;
 import java.util.UUID;
 import org.junit.jupiter.api.Test;
 import org.springframework.beans.factory.annotation.Autowired;
@@ -431,6 +433,147 @@ class EventControllerIntegrationTest {
         .andExpect(jsonPath("$.attendeeCount").value(1));
   }
 
+  // --- Cancel Event tests ---
+
+  @Test
+  void cancelEventReturns204AndPersists() throws Exception {
+    EventJpaEntity event = seedEvent(
+        "Cancel Me", null, "Europe/Berlin", null, LocalDate.now().plusDays(30));
+
+    var body = Map.of(
+        "cancelled", true,
+        "cancellationReason", "Venue closed");
+
+    mockMvc.perform(patch("/api/events/" + event.getEventToken()
+            + "?organizerToken=" + event.getOrganizerToken())
+            .contentType(MediaType.APPLICATION_JSON)
+            .content(objectMapper.writeValueAsString(body)))
+        .andExpect(status().isNoContent());
+
+    EventJpaEntity persisted = jpaRepository
+        .findByEventToken(event.getEventToken()).orElseThrow();
+    assertThat(persisted.isCancelled()).isTrue();
+    assertThat(persisted.getCancellationReason()).isEqualTo("Venue closed");
+  }
+
+  @Test
+  void cancelEventWithoutReasonReturns204() throws Exception {
+    EventJpaEntity event = seedEvent(
+        "Cancel No Reason", null, "Europe/Berlin", null, LocalDate.now().plusDays(30));
+
+    var body = Map.of("cancelled", true);
+
+    mockMvc.perform(patch("/api/events/" + event.getEventToken()
+            + "?organizerToken=" + event.getOrganizerToken())
+            .contentType(MediaType.APPLICATION_JSON)
+            .content(objectMapper.writeValueAsString(body)))
+        .andExpect(status().isNoContent());
+
+    EventJpaEntity persisted = jpaRepository
+        .findByEventToken(event.getEventToken()).orElseThrow();
+    assertThat(persisted.isCancelled()).isTrue();
+    assertThat(persisted.getCancellationReason()).isNull();
+  }
+
+  @Test
+  void cancelEventWithWrongOrganizerTokenReturns403() throws Exception {
+    EventJpaEntity event = seedEvent(
+        "Wrong Token", null, "Europe/Berlin", null, LocalDate.now().plusDays(30));
+
+    var body = Map.of("cancelled", true);
+
+    mockMvc.perform(patch("/api/events/" + event.getEventToken()
+            + "?organizerToken=" + UUID.randomUUID())
+            .contentType(MediaType.APPLICATION_JSON)
+            .content(objectMapper.writeValueAsString(body)))
+        .andExpect(status().isForbidden())
+        .andExpect(content().contentTypeCompatibleWith("application/problem+json"))
+        .andExpect(jsonPath("$.type").value("urn:problem-type:invalid-organizer-token"));
+
+    assertThat(jpaRepository.findByEventToken(event.getEventToken())
+        .orElseThrow().isCancelled()).isFalse();
+  }
+
+  @Test
+  void cancelEventNotFoundReturns404() throws Exception {
+    var body = Map.of("cancelled", true);
+
+    mockMvc.perform(patch("/api/events/" + UUID.randomUUID()
+            + "?organizerToken=" + UUID.randomUUID())
+            .contentType(MediaType.APPLICATION_JSON)
+            .content(objectMapper.writeValueAsString(body)))
+        .andExpect(status().isNotFound())
+        .andExpect(content().contentTypeCompatibleWith("application/problem+json"))
+        .andExpect(jsonPath("$.type").value("urn:problem-type:event-not-found"));
+  }
+
+  @Test
+  void cancelAlreadyCancelledEventReturns409() throws Exception {
+    EventJpaEntity event = seedCancelledEvent("Already Cancelled");
+
+    var body = Map.of("cancelled", true);
+
+    mockMvc.perform(patch("/api/events/" + event.getEventToken()
+            + "?organizerToken=" + event.getOrganizerToken())
+            .contentType(MediaType.APPLICATION_JSON)
+            .content(objectMapper.writeValueAsString(body)))
+        .andExpect(status().isConflict())
+        .andExpect(content().contentTypeCompatibleWith("application/problem+json"))
+        .andExpect(jsonPath("$.type").value("urn:problem-type:event-already-cancelled"));
+  }
+
+  @Test
+  void getEventReturnsCancelledFields() throws Exception {
+    EventJpaEntity event = seedCancelledEvent("Weather Event");
+
+    mockMvc.perform(get("/api/events/" + event.getEventToken()))
+        .andExpect(status().isOk())
+        .andExpect(jsonPath("$.cancelled").value(true))
+        .andExpect(jsonPath("$.cancellationReason").value("Cancelled"));
+  }
+
+  @Test
+  void getEventReturnsNotCancelledByDefault() throws Exception {
+    EventJpaEntity event = seedEvent(
+        "Active Event", null, "Europe/Berlin", null, LocalDate.now().plusDays(30));
+
+    mockMvc.perform(get("/api/events/" + event.getEventToken()))
+        .andExpect(status().isOk())
+        .andExpect(jsonPath("$.cancelled").value(false))
+        .andExpect(jsonPath("$.cancellationReason").doesNotExist());
+  }
+
+  @Test
+  void createRsvpOnCancelledEventReturns409() throws Exception {
+    EventJpaEntity event = seedCancelledEvent("Cancelled RSVP");
+    long countBefore = rsvpJpaRepository.count();
+
+    var request = new CreateRsvpRequest().name("Late Guest");
+
+    mockMvc.perform(post("/api/events/" + event.getEventToken() + "/rsvps")
+            .contentType(MediaType.APPLICATION_JSON)
+            .content(objectMapper.writeValueAsString(request)))
+        .andExpect(status().isConflict())
+        .andExpect(content().contentTypeCompatibleWith("application/problem+json"))
+        .andExpect(jsonPath("$.type").value("urn:problem-type:event-cancelled"));
+
+    assertThat(rsvpJpaRepository.count()).isEqualTo(countBefore);
+  }
+
+  private EventJpaEntity seedCancelledEvent(String title) {
+    var entity = new EventJpaEntity();
+    entity.setEventToken(UUID.randomUUID());
+    entity.setOrganizerToken(UUID.randomUUID());
+    entity.setTitle(title);
+    entity.setDateTime(OffsetDateTime.of(2026, 6, 15, 20, 0, 0, 0, ZoneOffset.ofHours(2)));
+    entity.setTimezone("Europe/Berlin");
+    entity.setExpiryDate(LocalDate.now().plusDays(30));
+    entity.setCreatedAt(OffsetDateTime.now());
+    entity.setCancelled(true);
+    entity.setCancellationReason("Cancelled");
+    return jpaRepository.save(entity);
+  }
+
   private UUID seedRsvpAndGetToken(EventJpaEntity event, String name) {
     var rsvp = new RsvpJpaEntity();
     UUID token = UUID.randomUUID();

backend/src/test/java/de/fete/application/service/EventServiceCancelTest.java

@@ -0,0 +1,138 @@
+package de.fete.application.service;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import de.fete.application.service.EventAlreadyCancelledException;
+import de.fete.domain.model.Event;
+import de.fete.domain.model.EventToken;
+import de.fete.domain.model.OrganizerToken;
+import de.fete.domain.port.out.EventRepository;
+import java.time.Clock;
+import java.time.Instant;
+import java.time.LocalDate;
+import java.time.ZoneId;
+import java.util.Optional;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.ArgumentCaptor;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+@ExtendWith(MockitoExtension.class)
+class EventServiceCancelTest {
+
+  private static final ZoneId ZONE = ZoneId.of("Europe/Berlin");
+  private static final Instant FIXED_INSTANT =
+      LocalDate.of(2026, 3, 5).atStartOfDay(ZONE).toInstant();
+  private static final Clock FIXED_CLOCK = Clock.fixed(FIXED_INSTANT, ZONE);
+
+  @Mock
+  private EventRepository eventRepository;
+
+  private EventService eventService;
+
+  @BeforeEach
+  void setUp() {
+    eventService = new EventService(eventRepository, FIXED_CLOCK);
+  }
+
+  @Test
+  void cancelEventDelegatesToDomainAndSaves() {
+    EventToken eventToken = EventToken.generate();
+    OrganizerToken organizerToken = OrganizerToken.generate();
+    var event = new Event();
+    event.setEventToken(eventToken);
+    event.setOrganizerToken(organizerToken);
+    event.setCancelled(false);
+
+    when(eventRepository.findByEventToken(eventToken))
+        .thenReturn(Optional.of(event));
+    when(eventRepository.save(any(Event.class)))
+        .thenAnswer(invocation -> invocation.getArgument(0));
+
+    eventService.cancelEvent(eventToken, organizerToken, true, "Venue unavailable");
+
+    ArgumentCaptor<Event> captor = ArgumentCaptor.forClass(Event.class);
+    verify(eventRepository).save(captor.capture());
+    assertThat(captor.getValue().isCancelled()).isTrue();
+    assertThat(captor.getValue().getCancellationReason()).isEqualTo("Venue unavailable");
+  }
+
+  @Test
+  void cancelEventWithNullReason() {
+    EventToken eventToken = EventToken.generate();
+    OrganizerToken organizerToken = OrganizerToken.generate();
+    var event = new Event();
+    event.setEventToken(eventToken);
+    event.setOrganizerToken(organizerToken);
+    event.setCancelled(false);
+
+    when(eventRepository.findByEventToken(eventToken))
+        .thenReturn(Optional.of(event));
+    when(eventRepository.save(any(Event.class)))
+        .thenAnswer(invocation -> invocation.getArgument(0));
+
+    eventService.cancelEvent(eventToken, organizerToken, true, null);
+
+    ArgumentCaptor<Event> captor = ArgumentCaptor.forClass(Event.class);
+    verify(eventRepository).save(captor.capture());
+    assertThat(captor.getValue().isCancelled()).isTrue();
+    assertThat(captor.getValue().getCancellationReason()).isNull();
+  }
+
+  @Test
+  void cancelEventThrows404WhenNotFound() {
+    EventToken eventToken = EventToken.generate();
+    OrganizerToken organizerToken = OrganizerToken.generate();
+
+    when(eventRepository.findByEventToken(eventToken))
+        .thenReturn(Optional.empty());
+
+    assertThatThrownBy(() -> eventService.cancelEvent(eventToken, organizerToken, true, null))
+        .isInstanceOf(EventNotFoundException.class);
+
+    verify(eventRepository, never()).save(any());
+  }
+
+  @Test
+  void cancelEventThrows403WhenWrongOrganizerToken() {
+    EventToken eventToken = EventToken.generate();
+    OrganizerToken correctToken = OrganizerToken.generate();
+    var event = new Event();
+    event.setEventToken(eventToken);
+    event.setOrganizerToken(correctToken);
+
+    when(eventRepository.findByEventToken(eventToken))
+        .thenReturn(Optional.of(event));
+
+    final OrganizerToken wrongToken = OrganizerToken.generate();
+    assertThatThrownBy(() -> eventService.cancelEvent(eventToken, wrongToken, true, null))
+        .isInstanceOf(InvalidOrganizerTokenException.class);
+
+    verify(eventRepository, never()).save(any());
+  }
+
+  @Test
+  void cancelEventThrows409WhenAlreadyCancelled() {
+    EventToken eventToken = EventToken.generate();
+    OrganizerToken organizerToken = OrganizerToken.generate();
+    var event = new Event();
+    event.setEventToken(eventToken);
+    event.setOrganizerToken(organizerToken);
+    event.setCancelled(true);
+
+    when(eventRepository.findByEventToken(eventToken))
+        .thenReturn(Optional.of(event));
+
+    assertThatThrownBy(() -> eventService.cancelEvent(eventToken, organizerToken, true, null))
+        .isInstanceOf(EventAlreadyCancelledException.class);
+
+    verify(eventRepository, never()).save(any());
+  }
+}