Grocy printer

Overview

This project provides a label printing solution for Grocy, a self-hosted groceries and household management solution.
It listens for new label requests from the Grocy server and prints them using a CUPS server, specifically targeting Zebra printers.

Code Structure

• product.py
  Defines the Product Pydantic model, representing a Grocy product with attributes such as name, Grocy code, and due date.

• label.py
  Contains utilities for label generation, including ZPL (Zebra Programming Language) template handling.

  • Label and ZPL Pydantic models represent the label content.
  • Functions:
    • load_template(template_file: str): Loads and processes a ZPL template file.
    • generate_label(template: Template, product: Product, name_split: int): Generates a ZPL label for a given product.

• main.py
  The main FastAPI application that:

  • Configures logging and loads configuration from environment variables.
  • Provides endpoints to print labels and product labels:
    • POST /printer/label: Prints a label using provided ZPL content.
    • POST /printer/product: Generates and prints a product label from product data.
  • Handles request validation errors with formatted responses.

Configuration

The application is configured using environment variables, which can be set in the docker-compose.yml file or passed directly to the container:

• CUPS_SERVER: Hostname of the CUPS server (default: cups).
• LINELENGTH: Maximum length for product names on labels (default: 15).
• PRINTER: Name of the target printer/print queue as recognized by CUPS (default: zebra).
• DEV: If set, disables actual printing for development/testing.

You can adjust these variables in the environment section of docker-compose.yml to match your setup.

Deployment

1. Build and Start the Stack
   Run the following command in the project directory to build and start both the application and the CUPS server:

   docker-compose up -d --build

2. Access the CUPS Web Interface
   Once running, open http://localhost:631 in your browser.

   • Login with the credentials specified in docker-compose.yml (default: print/print).
   • Add and configure your Zebra printer using the CUPS interface.

3. Application Endpoints
   The FastAPI application will be available at http://localhost:8000.

   • Use the /printer/label and /printer/product endpoints to print labels.

4. Printer Configuration
   Ensure the printer name in the environment variable PRINTER matches the name configured in CUPS.
   If unsure, you can list available printers in the CUPS interface or by running:

   docker exec -it grocy_printer lpstat -p

5. Volumes and Persistence
   The CUPS container uses Docker volumes (cups_config, cups_services) to persist configuration and printer settings across restarts.

Notes

• The application runs as a non-root user for security.
• The CUPS server is isolated in its own container, and the application communicates with it via the network.
• For USB printers, ensure your Docker host provides access to the relevant devices.