# CLAUDE.md

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

## Project Overview

This is a Docker-based Dynamic DNS client for Hetzner DNS (and 50+ other providers) using **[qmcgaw/ddns-updater](https://github.com/qdm12/ddns-updater)** - a universal, production-ready DDNS solution with web UI.

**Core Components:**
- `docker-compose.yml`: Service configuration using qmcgaw/ddns-updater image
- `data/config.json`: DDNS configuration (domains, tokens, providers)
- `config.json.example`: Configuration template for Hetzner setup

## Development Commands

### Docker Operations

**Start the service:**
```bash
docker-compose up -d
```

**View logs:**
```bash
docker-compose logs -f
```

**Restart service:**
```bash
docker-compose restart
```

**Stop service:**
```bash
docker-compose down
```

**Check status:**
```bash
docker-compose ps
```

### Configuration Management

**Create initial config:**
```bash
mkdir -p data
cp config.json.example data/config.json
# Edit data/config.json with your credentials
```

**Validate config JSON:**
```bash
cat data/config.json | jq .
```

**Get Hetzner Zone ID via API:**
```bash
curl -H "Auth-API-Token: YOUR_TOKEN" https://dns.hetzner.com/api/v1/zones
```

### Web UI

**Access Web UI:**
Open browser to `http://localhost:8000`

The Web UI shows:
- Current IP status
- Last update timestamp
- Update history
- Errors and warnings
- Per-domain status

## Architecture

### Application Flow

1. **Initialization**: Load configuration from `data/config.json`
2. **Main Loop**:
   - Get current public IP (IPv4/IPv6)
   - Compare with DNS records for each configured domain
   - Update DNS if IP has changed
   - Wait for configured period (default: 5 minutes)
   - Repeat

### Configuration Structure

Configuration is in JSON format at `data/config.json`:

```json
{
  "settings": [
    {
      "provider": "hetzner",
      "zone_identifier": "zone_id",
      "domain": "example.com",
      "host": "@",
      "ttl": 60,
      "token": "api_token",
      "ip_version": "ipv4"
    }
  ]
}
```

**Key Parameters:**
- `provider`: DNS provider name (hetzner, cloudflare, duckdns, etc.)
- `zone_identifier`: Hetzner DNS Zone ID
- `domain`: Base domain name
- `host`: Subdomain or `@` for root
- `ttl`: Time-to-live in seconds
- `token`: Hetzner API token with DNS edit permissions
- `ip_version`: `ipv4`, `ipv6`, or `ipv4 or ipv6`

### Multi-Domain Support

Add multiple entries in the `settings` array to manage multiple domains or subdomains.

### Environment Variables

Optional variables in `.env`:
- `PERIOD`: Update check interval (default: 5m)
- `LOG_LEVEL`: Logging verbosity (debug, info, warning, error)

## Versioning Strategy

This project uses a simplified versioning scheme:
- **0.1**: Large changes (new features, breaking changes)
- **0.0.1**: Small changes (bugfixes, minor improvements)
- **1.x**: Major releases (only by explicit instruction)

**When making changes:**
1. Update `CHANGELOG.md` with the change description
2. Increment version according to change size
3. Work in feature branches, merge to main when ready

## Key Files

- `docker-compose.yml`: Service definition using qmcgaw/ddns-updater
- `config.json.example`: Template for Hetzner configuration
- `data/config.json`: Active configuration (not in git)
- `.env.example`: Optional environment variables template
- `CHANGELOG.md`: Version history

## Security Notes

- API token is sensitive - never commit `data/config.json` or `.env`
- Container runs with minimal privileges
- Only ports 8000 (web UI) exposed
- Use HTTPS reverse proxy for production deployments
- API token should have minimal required permissions (DNS read/write only)

## Troubleshooting

**View Web UI status:**
```bash
# Open http://localhost:8000 in browser
```

**Check container logs:**
```bash
docker-compose logs --tail=50 -f
```

**Validate configuration:**
```bash
# Check JSON syntax
cat data/config.json | jq .
```

**Test API connectivity:**
```bash
# List zones
curl -H "Auth-API-Token: YOUR_TOKEN" https://dns.hetzner.com/api/v1/zones

# List records for a zone
curl -H "Auth-API-Token: YOUR_TOKEN" "https://dns.hetzner.com/api/v1/records?zone_id=ZONE_ID"
```

**Debug mode:**
Set `LOG_LEVEL=debug` in `.env` and restart container.

**Container won't start:**
- Check `docker-compose logs`
- Verify `data/config.json` exists and is valid JSON
- Check port 8000 is not in use

## Provider Migration

To switch from Hetzner to another provider:
1. Check [supported providers](https://github.com/qdm12/ddns-updater#providers)
2. Update `provider` field in `data/config.json`
3. Adjust provider-specific fields
4. Restart: `docker-compose restart`

No code changes needed - just configuration!

## Upstream Documentation

- [DDNS-Updater GitHub](https://github.com/qdm12/ddns-updater)
- [Hetzner Configuration Guide](https://github.com/qdm12/ddns-updater/blob/master/docs/hetzner.md)
- [All Supported Providers](https://github.com/qdm12/ddns-updater#providers)