# CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

## Development Commands

### Frontend Development
- `trunk serve` - Start frontend development server at http://localhost:8080
- `trunk build --release` - Build frontend for production
- `cargo check` - Check frontend code compilation

### Backend Development
- `cargo run --manifest-path=backend/Cargo.toml` - Start backend server at http://localhost:3000
- `cargo check --manifest-path=backend/Cargo.toml` - Check backend code compilation

### Full Development Setup
1. Start backend: `cargo run --manifest-path=backend/Cargo.toml`
2. Start frontend: `trunk serve` (in project root)
3. Access application at http://localhost:8080

## Architecture Overview

This is a full-stack calendar application with a Rust WebAssembly frontend and Rust backend, featuring CalDAV integration for calendar synchronization.

### Frontend (Yew WebAssembly)
- **Entry Point**: `src/app.rs` - Main application component with routing and state management
- **Models**: `src/models/ical.rs` - RFC 5545-compliant iCalendar data structures (VEvent, VTodo, etc.)
- **Services**: `src/services/calendar_service.rs` - HTTP client for backend API calls
- **Components**: `src/components/` - UI components including calendar views, modals, and forms
- **Views**: Month view (`month_view.rs`) and week view (`week_view.rs`) with drag-and-drop event modification

### Backend (Axum)
- **Entry Point**: `backend/src/main.rs` - HTTP server with CORS and routing
- **Handlers**: `backend/src/handlers.rs` - API endpoints for calendar operations
- **CalDAV Integration**: `backend/src/calendar.rs` - CalDAV client for server synchronization
- **Authentication**: `backend/src/auth.rs` - JWT token management

### Key Data Flow
1. Frontend makes HTTP requests to backend API (`/api/*` endpoints)
2. Backend authenticates requests and proxies to CalDAV servers
3. Data uses RFC 5545 VEvent structures throughout the system
4. Events support recurrence (RRULE), exceptions (EXDATE), and timezone conversion

### Event Management Features
- **Series Updates**: Events can be updated as "entire series" (`update_series`) or "this and future events" (`this_and_future`)
- **Drag and Drop**: Week/month views support dragging events to new times with automatic timezone conversion
- **Recurring Events**: Full RRULE support with UNTIL dates and exception handling
- **Timezone Handling**: Local time in UI, UTC for storage and API calls

### Important Implementation Details
- All event data uses RFC 5545-compliant VEvent structures (not legacy CalendarEvent)
- Frontend converts local times to UTC before sending to backend
- API expects `HH:MM` time format (not `HH:MM:SS`)
- Recurrence modifications create new series with UNTIL dates on original events
- Event UIDs are preserved across updates for CalDAV compatibility

### Build Configuration
- Frontend built with Trunk (see `Trunk.toml`)
- Backend API URL: `http://localhost:3000/api` (configurable via `BACKEND_API_URL`)
- Frontend serves on port 8080, backend on port 3000

### Dependencies
- **Frontend**: Yew, chrono, serde, web-sys, gloo-storage
- **Backend**: Axum, tokio, reqwest, ical, jsonwebtoken
- **Shared**: RFC 5545 iCalendar structures, UUID generation