# Implementation Plan: Cancel Event

**Branch**: `016-cancel-event` | **Date**: 2026-03-12 | **Spec**: [spec.md](spec.md)
**Input**: Feature specification from `/specs/016-cancel-event/spec.md`

## Summary

Allow organizers to permanently cancel events via a bottom sheet UI. Cancelled events display a red banner to visitors and block new RSVPs. Implementation adds a `PATCH /events/{eventToken}` endpoint, extends the Event entity with `cancelled` and `cancellationReason` fields, and reuses the existing `BottomSheet.vue` component for the cancel interaction.

## Technical Context

**Language/Version**: Java 25 (backend), TypeScript 5.9 (frontend)
**Primary Dependencies**: Spring Boot 3.5.x, Vue 3, Vue Router 5, openapi-fetch, openapi-typescript
**Storage**: PostgreSQL (JPA via Spring Data, Liquibase migrations)
**Testing**: JUnit (backend), Vitest (frontend unit), Playwright + MSW (frontend E2E)
**Target Platform**: Self-hosted Linux server, mobile-first PWA
**Project Type**: Web application (REST API + SPA)
**Performance Goals**: N/A — simple state transition, no performance-critical path
**Constraints**: Privacy by design (no analytics/tracking), WCAG AA, mobile-first
**Scale/Scope**: Single new endpoint, 2 new DB columns, 1 view extension

## Constitution Check

*GATE: Must pass before Phase 0 research. Re-check after Phase 1 design.*

| Principle | Status | Notes |
|-----------|--------|-------|
| I. Privacy by Design | PASS | No new data collection beyond organizer-provided reason. No analytics. |
| II. Test-Driven Methodology | PASS | TDD enforced: tests before implementation, E2E mandatory for both user stories. |
| III. API-First Development | PASS | OpenAPI spec updated first, types generated before implementation. `example:` fields included. |
| IV. Simplicity & Quality | PASS | Minimal change: 2 columns, 1 endpoint, reuse existing BottomSheet. No over-engineering. |
| V. Dependency Discipline | PASS | No new dependencies required. |
| VI. Accessibility | PASS | Reuses accessible BottomSheet component. Banner uses semantic HTML + ARIA. |

**Gate result: PASS** — no violations.

## Project Structure

### Documentation (this feature)

```text
specs/016-cancel-event/
├── plan.md              # This file
├── spec.md              # Feature specification
├── research.md          # Phase 0 output — design decisions
├── data-model.md        # Phase 1 output — entity changes
├── quickstart.md        # Phase 1 output — implementation overview
├── contracts/           # Phase 1 output — API contract additions
│   └── patch-event-endpoint.yaml
└── tasks.md             # Phase 2 output (/speckit.tasks command)
```

### Source Code (repository root)

```text
backend/
├── src/main/java/de/fete/
│   ├── domain/model/Event.java                          # + cancelled, cancellationReason, cancel()
│   ├── application/service/EventService.java            # + CancelEventUseCase implementation
│   ├── adapter/in/web/EventController.java              # + cancelEvent endpoint
│   └── adapter/out/persistence/
│       ├── EventJpaEntity.java                          # + cancelled, cancellation_reason columns
│       └── EventPersistenceAdapter.java                 # + mapper updates
├── src/main/resources/
│   ├── openapi/api.yaml                                 # + cancel endpoint, request/response schemas
│   └── db/changelog/004-add-cancellation-columns.xml    # New migration
└── src/test/java/de/fete/                               # Unit + integration tests

frontend/
├── src/
│   └── views/EventDetailView.vue                        # + cancel button, bottom sheet, banner
└── e2e/                                                 # E2E tests for both user stories
```

**Structure Decision**: Web application (Option 2) — matches existing project layout with `backend/` and `frontend/` at repository root.

## Complexity Tracking

> No violations — table not applicable.