# Baïkal Calendar Sync

An incremental CalDAV sync service that keeps your Baïkal calendar in sync with an Outlook ICS feed — with zero downtime and near-instant sync times.

## Features

- **Incremental Delta Sync**: Only adds, updates, or deletes events that actually changed
- **Zero Downtime**: Adds/updates events before deleting removed ones — calendar never goes empty
- **Smart Change Detection**: ETag check first, SHA-256 fallback. Skips sync when nothing changed
- **Stable Event Hashing**: Ignores volatile fields (DTSTAMP, LAST-MODIFIED) to avoid false updates
- **Automatic Backoff**: Exponential retry on failures (1m, 2m, 4m... max 30m)
- **Health Endpoint**: Built-in `/health` and `/metrics` (Prometheus-compatible) on port 8081
- **Graceful Shutdown**: SIGTERM/SIGINT handlers finish current sync before exiting
- **Docker Ready**: Includes `Dockerfile`, `docker-compose.yml`, and HEALTHCHECK

## Prerequisites

- Docker & Docker Compose installed
- An existing Baïkal instance
- An Outlook ICS link

## Configuration (Environment Variables)

| Variable | Description | Default |
| :--- | :--- | :--- |
| `ICS_URL` | The public ICS URL of your Outlook calendar. | **Required** |
| `BAIKAL_URL` | The URL to your Baïkal calendar. | **Required** |
| `BAIKAL_USER` | Your Baïkal username. | **Required** |
| `BAIKAL_PASS` | Your Baïkal password. | **Required** |
| `SYNC_FREQUENCY` | How often to sync **in minutes**. | `5` |
| `CALENDAR_ID` | Optional calendar ID to match against. | — |

## Quick Start

1. **Clone or download** this repository.
2. **Create a `.env` file** (optional but recommended):

    ```bash
    ICS_URL="https://outlook.office365.com/owa/calendar/your-calendar.ics"
    BAIKAL_URL="https://your-baikal.com/dav.php/calendars/user/calendar-id/"
    BAIKAL_USER="your-username"
    BAIKAL_PASS="your-password"
    SYNC_FREQUENCY=5
    ```

3. **Run with Docker Compose**:

    ```bash
    docker compose up -d
    ```

4. **Check Logs**:

    ```bash
    docker compose logs -f baikal-sync
    ```

5. **Check Health**:

    ```bash
    curl http://localhost:8081/health
    curl http://localhost:8081/metrics
    ```

## Building & Publishing

1. **Build**:
    ```bash
    docker build -t lagortinez/baikal-sync:latest .
    ```

2. **Push**:
    ```bash
    docker push lagortinez/baikal-sync:latest
    ```