caldav-forwarder

Polls a public iCal (.ics) feed on a schedule and forwards each event to a work email as a stripped-down "Busy" calendar hold — details removed, time blocked.

Flow

EventBridge Scheduler ──> Poller Lambda ──fetch+parse+diff──> DynamoDB (STATE + OUTBOX, atomic)
                                                                     │ stream (NEW_IMAGE)
                                                                     ▼
                                                              EventBridge Pipe
                                                     (filter: INSERT + SK "OUTBOX#")
                                                                     ▼
                                                              SQS (+ DLQ)
                                                                     ▼
                                                          Consumer Lambda ──iMIP──> SES ──> work email

• Recurring events keep their RRULE (one recurring hold).
• Birthdays/anniversaries are skipped.
• Removed or STATUS:CANCELLED events emit a METHOD:CANCEL to delete the hold.
• Holds are SUMMARY:Busy, TRANSP:OPAQUE, CLASS:PRIVATE — no location/description.

Both functions run on the python3.14 runtime. The consumer is idempotent (Powertools DynamoDB idempotency) so SQS at-least-once redelivery never sends a duplicate invite, and both Lambdas opt into the updated AWS SDK retry behavior (AWS_NEW_RETRIES_2026).

Develop

uv sync
uv run ruff check . && uv run ruff format --check .
uv run ty check
uv run pytest -q

Deploy

OrganizerEmail must be a verified SES identity (and DestEmail too, in the SES sandbox).

Real deploy parameters live in samconfig.toml, which is gitignored — keep your feed URL and emails out of version control:

cp samconfig.example.toml samconfig.toml
$EDITOR samconfig.toml           # fill in SourceIcalUrl / OrganizerEmail / DestEmail
make deploy-guided               # first deploy (writes back to samconfig.toml)
make deploy                      # subsequent deploys

SourceIcalUrl accepts webcal:// iCloud share links (normalized to https://).

Configuration

Parameter	Purpose
SourceIcalUrl	Public HTTPS iCal feed to poll.
OrganizerEmail	SES-verified sender / invite ORGANIZER.
DestEmail	Work address receiving holds (invite ATTENDEE).
ScheduleExpression	Poll frequency (default rate(15 minutes)).