One-way synchronization from CalDAV to Google Calendar
Intelligent change detection:
- Adds new events
- Updates modified events
- Removes deleted events
Local state management to track synchronized events
Detailed logging of synchronization activities
Rate limiting to prevent API throttling
Error handling with failed events tracking

Prerequisites

1. Python Environment

Python 3.10 or higher
Poetry for dependency management

2. CalDAV Server Details

You'll need:

CalDAV server URL
Username
Password
Calendar name to synchronize

3. Google Calendar Setup

To interact with the Google Calendar API, follow these steps:

Go to the Google Cloud Console.
Create a new project or select an existing one.
Enable the Google Calendar API for the project.
Create OAuth 2.0 credentials:
- Go to APIs & Services > Credentials.
- Click Create Credentials > OAuth Client ID.
- Configure the consent screen (if not already done).
- Select Desktop App as the application type.
- Download the credentials.json file.
Place the credentials.json file in the project directory.

Installation

Clone the repository:

git clone https://gitlab.com/rogs/caldav2google.git
cd caldav2google

Install dependencies:
```
poetry install
```

Create .env file:

CALDAV_URL=https://your-caldav-server.com
CALDAV_USERNAME=your_username
CALDAV_PASSWORD=your_password
CALDAV_CALENDAR_NAME=your_calendar_name
GOOGLE_CALENDAR_NAME=target_google_calendar_name

Usage

Activate virtual environment:
```
poetry shell
```
Run synchronization:
```
python main.py
```

On first run:

Browser opens for Google OAuth authentication
Grant requested calendar permissions
Token is saved locally for future use

Project Structure

src/
├── auth_google.py        # Google Calendar authentication
├── caldav_client.py      # CalDAV server interactions
├── main.py               # Main synchronization script
├── sync_logic.py         # Core synchronization logic
pyproject.toml            # Project configuration
env.example               # Environment variables example file
.env                      # Environment variables 
README.md                 # README instructions
credentials.json          # Google OAuth credentials
token.pickle              # Stored Google token
calendar_sync.json        # Local sync state

Configuration Files

credentials.json

Downloaded from Google Cloud Console (required)

.env

CALDAV_URL=https://caldav.example.com
CALDAV_USERNAME=user
CALDAV_PASSWORD=pass
CALDAV_CALENDAR_NAME=My Calendar
GOOGLE_CALENDAR_NAME=CalDAV Events

calendar_sync.json

Automatically maintained by the script to track synchronization state.

Error Handling

The script provides robust error handling:

Failed events are tracked and reported
Rate limiting prevents API throttling
Detailed error messages for troubleshooting
Synchronization state preserved on failure

Troubleshooting

Authentication Issues

Google Calendar

Error: Invalid client credentials
- Verify credentials.json is correctly downloaded and placed
- Ensure OAuth consent screen is configured
Error: Token has been expired or revoked
- Delete token.pickle
- Re-run script to authenticate

CalDAV

Error: Could not connect to server
- Check URL format and accessibility
- Verify network connectivity
- Confirm server SSL certificate if using HTTPS

Synchronization Issues

Error: Calendar not found
- Verify calendar names in .env
- Check calendar visibility/permissions
Error: Failed to add/update events
- Check event data formatting
- Verify calendar write permissions
- Review API quotas and limits

Development

Pre-commit Hooks

poetry run pre-commit install

Contributing

Fork the repository
Create feature branch
Commit changes
Push to branch
Submit pull request

Please:

Follow existing code style
Add tests for new features
Update documentation
Run pre-commit hooks

License

GNU General Public License v3.0 or later

Credits

Built with:

caldav - CalDAV client library
google-api-python-client - Google Calendar API
python-dotenv - Environment management
Poetry - Dependency management