📆 CalendarAPI

CalendarAPI is a service that parses iCal files and exposes their content via gRPC or a REST API. It uses Viper for configuration, which supports runtime reloads.

⚙️ Features

• ✅ Parse iCal (.ics) files from URLs or local files
• ✅ Exposes events via REST and gRPC APIs
• ✅ Built-in rule engine for relabeling, filtering, and skipping events
• ✅ Supports hot configuration reloads (with Viper)
• ✅ HomeAssistant Add-On to easily host CalendarAPI on your Home Assistant

Configuration

Server config

server:
  server: ""      # ! Does not support changing at runtime
  httpPort: 8080  # ! Does not support changing at runtime
  grpcPort: 50051 # ! Does not support changing at runtime
  debug: false    # Control if debug logs are printed
  refresh: 5m     # how often are the calendars refreshed? Must be parsable by time.ParseDuration()

Calendar config

It is possible to add multiple iCal calendar feeds to pull multiple calendars from multiple sources. ical files can be read either from a URL or from a local file

calendars:
  calendar1:
    from: file
    ical: ./path/to/calender1.ics
  calendar2:
    from: url
    ical: www.example.com/calendar/calendar.ics

Rules config

Rules allow you to filter events, or apply re-labeling. Rules are evaluated in the order of which they are specified in. The rule-evaluation stops after the event matches the first rule.

Relabel

The rule below matches if the Title of your calendar event contains the string 1:1 and then sets the display message to 1:1 as well as marking the event as important

rules:
  - name: "1:1s"
    key: "title"
    contains:
      - "1:1"
    relabelConfig:
      message: "1:1"
      important: true

Skip rules

If a rule specifies skip: true then each calendar event that matches this rule is excluded from the API responses. Below are examples to skip all day and non-blocking events:

rules:
  - name: "Skip all day events"
    key: "all_day"
    contains:
      - "true"
    skip: true

  - name: "Skip non-blocking events"
    key: "busy"
    contains:
      - "Free"
    skip: true

Wildcard matching

You can use * as a wildcard to match everything. If key uses the wildcard, it will search all fields. This is useful for catch-all rules that allow all other events that did not match previous rules to be included in the API responses.

rules:
  - name: "Allow everything else"
    key: "*"
    important: false
    contains:
      - "*"

Development

Prerequisites

• Go 1.24+
• Docker (for building and running containers)

Building

To build the project, run:

go build -o calendarapi main.go

Running

To run the project, execute:

./calendarapi

Docker

To build and run the Docker container, use the following commands:

docker build -t calendarapi .
docker run -p 8080:8080 -p 50051:50051 calendarapi

Testing

To run tests, use:

go test ./...

Contributing

Contributions are welcome! Please open an issue or submit a pull request.

License

This project is licensed under the MIT License. See the LICENSE file for details.