This is a Docker-based MQTT client that listens for print requests, generates vet drug prescription labels, and prints them using a Brother QL printer.

Setup

Configure the environment variables in .env:
- MQTT_HOST: MQTT broker hostname
- MQTT_PORT: MQTT broker port
- MQTT_TOPIC_SUB: Topic to subscribe for print requests
- MQTT_TOPIC_PUB_STATUS: Topic to publish status messages (success and errors)
- PRINTER_DEVICE: Printer device path (e.g., /dev/usb/lp0)
- PRINTER_MODEL: Printer model (e.g., QL-800)
- LABEL_SIZE_DEFAULT: Default label size (e.g., 29x90)
Build and run with Docker Compose:
```
docker-compose up --build
```

MQTT Message Format

The client subscribes to the configured topic and expects JSON messages like:

{
  "template_id": "vet_label",
  "label_size": "29x90",
  "variables": {
    "practice_name": "Many Tears Animal Rescue",
    "animal_name": "Rosie 468837",
    "drug_name": "Amoxicillin 50mg",
    "dosage": "1 tablet twice daily with food",
    "quantity": "14 tablets",
    "vet_initials": "Frank Molina"
  },
  "test": false
}

template_id: Identifier for the label template (currently only "vet_label" supported)
label_size: Size of the label (passed to brother-ql)
variables: Key-value pairs for label content
test: If true, saves PNG to /app/output/ instead of printing

Error Handling

Any errors during processing are published to the error topic as JSON:

{
  "error": "Error message",
  "original_payload": "{original message}"
}

Adding New Templates

To add new label templates, edit templates.py and add to the TEMPLATES dict.