SimplCalCon

A multi-tenant CalDAV / CardDAV server with a REST API and a Blazor WebAssembly web UI — store and synchronise calendar entries (events & tasks) and contacts across your devices (phones, tablets, computers), plus edit, view, share, import/export and back them up from the browser.

Built on .NET 10 with Clean Architecture and EF Core, running on PostgreSQL or SQLite (both are first-class production databases — every feature works on both).

🧪 A showcase

This repository is a showcase of how a senior, AI-driven software developer can design and build a complex, production-shaped system in a remarkably short period of time — a full CalDAV/CardDAV protocol stack, a REST API, a web client, multi-tenancy, sharing/ACLs, scheduling, data portability, and Docker/Kubernetes packaging, developed collaboratively and incrementally, with an Architecture Decision Record behind every choice.

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Features

• CalDAV & CardDAV (in-house protocol layer) — syncs with Apple Calendar/Contacts, Thunderbird, iOS, DAVx5, and other standard clients, with WebDAV-Push so DAVx5 gets pushed changes instead of polling.
• REST API — HATEOAS envelopes, RFC 7807 problem details, ETag/If-Match concurrency, JSON.
• Blazor WebAssembly web UI — calendars (list + month/week grid with recurring events), contacts (master-detail), import/export, sharing, trash & version history, profile & contact photos, with live updates (SignalR) so changes and invitations appear without a reload.
• Multi-tenancy with platform / tenant admins and full ACL sharing.
• Authentication — OIDC (auth code + PKCE) for web/REST; per-device app passwords for DAV.
• Data portability — per-collection import/export, account takeout, direct Google export .zip import (recreating the original calendars), and revocable read-only subscription feeds (.ics/webcal) that any client — including Microsoft Outlook — can subscribe to.
• Scheduling — attendees, free/busy, and RFC 6638 iTIP with web invitations (accept / tentative / decline) and email iMIP to and from external attendees (per-tenant SMTP out; inbound via a REST endpoint or IMAP polling).

See docs/spec.md for the full specification and docs/adr/ for the decision records.

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Quick start (Docker Compose)

The whole demo runs from the single docker-compose.yaml at the repository root — under Docker (docker compose) or Podman (podman compose):

docker compose up --build -d

Then open http://localhost:9080 and sign in with a seeded demo account:

Account	Email	Password
Platform admin	admin@simplcalcon.local	ChangeMe-Platform-2026
Demo-tenant admin	admin@demo.local	ChangeMe-Demo-2026

Native (Apple) CalDAV/CardDAV clients reach the server over HTTPS at https://localhost (a Caddy TLS proxy on port 443). Full walkthrough — running the stack, connecting native clients, and the optional pgAdmin — is in the user & operator manual.

The Compose stack ships in Development / demo configuration (ephemeral keys, demo seeding, throwaway credentials). It is not for production — see below.

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Production installation

The demo Compose file is for local/demo use. For a real deployment:

• Container image: published to ghcr.io/hebelconsulting/simplcalcon on GitHub Container Registry — full multi-arch (amd64 + arm64) on v* release tags, amd64 for main. The app listens on port 9080. Pull and run a release:

  docker pull ghcr.io/hebelconsulting/simplcalcon:0.1.0
  docker run -p 9080:9080 \
    -e ASPNETCORE_ENVIRONMENT=Production \
    -e SimplCalCon__Database__Provider=Sqlite \
    -e SimplCalCon__Database__ConnectionString="Data Source=/data/simplcalcon.db" \
    -v simplcalcon-data:/data \
    ghcr.io/hebelconsulting/simplcalcon:0.1.0

  Tags: 0.1.0 (exact), 0.1 (minor), main (latest main), and sha-<commit>. Production also needs the OIDC certificates and SimplCalCon:SpaClient:BaseUrl below.

• Kubernetes (Helm): a chart lives at deploy/helm/simplcalcon — Deployment with startup/liveness/readiness probes and a non-root security context, a Service on 9080, a config Secret, an optional Ingress, and a mount hook for the OIDC certificates.

• Database: choose the provider with SimplCalCon:Database:Provider (Postgres or Sqlite) and supply the connection string; point it at a managed/persistent database.

• Certificates: production requires OIDC signing + encryption certificates from config and fails fast without them (Development uses ephemeral in-memory keys).

• Environment: set ASPNETCORE_ENVIRONMENT=Production, and set SimplCalCon:SpaClient:BaseUrl to the origin the web UI is served from (the SPA's OIDC redirect must match it).

• Health: /health/live (liveness) and /health/ready (readiness) are anonymous.

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Documentation

• User & operator manual — running the stack, connecting native clients, pgAdmin.
• Specification — the full functional/architectural spec.
• Architecture Decision Records — the rationale behind every decision.
• CLAUDE.md — how the repository is structured and operated.

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Tech stack

.NET 10 · ASP.NET Core · EF Core (PostgreSQL + SQLite) · OpenIddict · Blazor WebAssembly · Serilog · Ical.Net / FolkerKinzel.VCards · xUnit · Stryker.NET (mutation testing) · Docker / Podman · Helm · Caddy.

License

Licensed under the Apache License 2.0 — see LICENSE.