FaxMeMaybe

Send me a TODO at remind.deadpackets.pw and it prints on a thermal printer on my desk.

It is a reminder system that is over-engineered on purpose. The idea comes from Laurie Hérault's article A thermal receipt printer cured my procrastination and a Coding With Lewis video. I built it to learn Cloudflare Workers, message queues, headless rendering and a little hardware in one silly project.

A real ticket from the end-to-end test.

How it works

flowchart LR
  Form[Web form or API] --> Worker[Cloudflare Worker]
  Apps[Todoist apps] -- webhook --> Worker
  Worker <--> Todoist[(Todoist)]
  Worker -- print job --> Queue[[Cloudflare Queue]] --> Worker
  Worker -- render at 576 px --> Browser[Browser Rendering]
  Worker -- PNG --> R2[(R2)]
  Worker -- R2 key --> SQS[[SQS FIFO]]
  SQS --> Pi[Raspberry Pi] --> Printer[Thermal printer]

Loading

1. Someone fills in the form, or something calls POST /api/todos. My n8n email parser and a Linear automation both use the API.
2. The Worker creates the task in Todoist and replies. Todoist is my real task list, so I manage everything in its apps.
3. A print job goes on a Cloudflare Queue. The Worker's queue consumer opens /todo-ticket in Cloudflare's headless browser at 576 px (80 mm paper), takes a screenshot of the ticket and stores the PNG in R2.
4. It puts the R2 key on an SQS FIFO queue.
5. A Raspberry Pi polls the queue, downloads the PNG and prints it with python-escpos.
6. When the task is done, I scan the QR code on the ticket. It opens the task in the Todoist app, and I tick it off there.

Tasks that I add in the Todoist apps print too. Todoist webhooks tell the Worker when a task is added, completed or deleted. Every new task prints unless it has the noprint label, and the stats on the site count tickets printed, done and still on the desk.

Repository layout

fax-me-maybe-server/          Cloudflare Worker (Hono) and the React app
  src/worker/index.ts         API, ticket rendering, Todoist webhook
  src/worker/services/        Todoist client
  src/react-app/App.tsx       The form
  src/react-app/Ticket.tsx    The ticket, used by the print render and the live preview
fax-me-maybe-client/          Raspberry Pi queue consumer (Docker image on GHCR)
e2e/ticket_e2e.py             End-to-end print check
PRODUCT.md                    Who the app is for and its design principles
VERSION                       Major.minor version; CI adds the build number

Setup

Worker

You need a Cloudflare account with Workers, D1, R2, Queues and Browser Rendering, a Todoist account and an AWS SQS FIFO queue.

cd fax-me-maybe-server
npm install
npx wrangler queues create faxmemaybe-print
npx wrangler d1 migrations apply faxmemaybe-db --remote
npx wrangler secret put TODOIST_API_TOKEN    # repeat for every secret below
npm run deploy

Secret	Purpose
TODOIST_API_TOKEN	Todoist API token (Settings → Integrations → Developer)
TODOIST_WEBHOOK_SECRET	Client secret of your Todoist app, used to verify webhooks
HONO_API_KEY	Key for the admin endpoints and to skip the rate limit
AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, AWS_REGION	Credentials that can send to the queue
SQS_QUEUE_URL	The FIFO queue URL

wrangler.json also sets TODOIST_PROJECT_NAME, TIMEZONE (the time zone printed on tickets) and VERSION (set by CI). For local development, put the secrets in .dev.vars and run npm run dev.

Todoist webhook

This makes tasks added in the Todoist apps print.

1. Create an app in the Todoist App Console.
2. Set the webhook callback URL to https://<your domain>/api/webhooks/todoist and select the item:added, item:completed and item:deleted events.
3. Todoist sends webhooks only for accounts that authorized the app, so run the app's OAuth flow once with your own account.
4. Run npx wrangler secret put TODOIST_WEBHOOK_SECRET with the app's client secret.

Raspberry Pi client

Run ghcr.io/deadpackets/fax-me-maybe-client with fax-me-maybe-client/docker-compose.yml. Its .env needs SQS_QUEUE_URL, AWS_REGION, AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY and TICKETS_BUCKET_URL (the public URL of the R2 bucket). The container needs USB access to the printer.

API

POST /api/todos is public and allows 10 requests a minute per IP. Requests with a valid X-API-KEY header skip the limit.

Field	Required	Notes
todo	Yes	Up to 64 characters
importance	Yes	1 (low) to 5 (critical)
description	No	Up to 500 characters. Saved in Todoist, not printed
dueDate	No	Natural language, like next friday at 2pm
from	No	Up to 40 characters
labels	No	Names of existing Todoist labels
source	No	Free text, saved in the task description

curl -X POST https://remind.deadpackets.pw/api/todos \
  -H "Content-Type: application/json" \
  -d '{"todo": "Review the new feature", "importance": 3, "dueDate": "tomorrow at 5pm", "from": "API User"}'

The response comes back when the task is saved in Todoist. The ticket prints from a Cloudflare Queue, which retries a failed print 3 times. A print that still fails shows only in the Worker logs.

Other endpoints:

• Public: GET /api/todos/stats, GET /api/labels, GET /api/health
• With X-API-KEY: GET /api/todos, PATCH /api/todos/:id/incomplete, DELETE /api/todos/:id
• POST /api/first-bloods prints a "First Blood" receipt for CTF events.

Testing

The end-to-end check sends a real TODO through the whole pipeline and prints a real ticket. It checks that the PNG is exactly 576 px wide and that the QR code opens the Todoist task.

FAXMEMAYBE_API_KEY=... uv run e2e/ticket_e2e.py https://remind.deadpackets.pw

Run it against production. The queue consumer runs only on the deployed version, so a version preview URL can queue a ticket but never prints it.

It writes ticket.png and report.json to e2e/artifacts/<timestamp>/. With FAXMEMAYBE_API_KEY set, it deletes the test task afterwards.

Credits

• Laurie Hérault, for the original idea
• Coding With Lewis, for the video that started this build
• python-escpos, for the printer driver

MIT licensed. See LICENSE.