Invoice Generator with German Localization and Web Interface

This invoice generator application includes German localization for businesses operating in Germany or German-speaking regions, and features a web-based interface for easier invoice generation.

Key Updates

Major Architectural Improvements

• Reorganized Codebase: The entire codebase has been restructured following proper Go project practices with cmd, internal, and pkg directories
• Decoupled Dependencies: Interfaces for all services to improve testability and maintainability
• Fixed WebUI Issues: Resolved issues with tax exemption checkbox, footer settings, and company name display

Features

• Command-line and web-based interfaces
• German localization (labels, date format, VAT)
• Euro (€) as default currency with support for other currencies
• Configurable invoice details via JSON/YAML files
• PDF generation with proper layout
• Dynamic positioning to handle various content lengths
• Support for extended invoice numbers with suffix
• Automatic file naming based on invoice ID
• Nextcloud integration for file sharing
• Tax exemption support (Kleinunternehmer-Regelung)
• Environment variable configuration support
• Proper service/handler separation for business logic

Installation

Build from Source

1. Clone the repository:

   git clone https://github.com/cougz/invoice.git
   cd invoice

2. Build the application:

   go build -o invoice ./cmd/invoice

3. (Optional) Install to your PATH:

   go install ./cmd/invoice

This will create the invoice executable that you can run from the command line.

Web Interface

The invoice generator includes a web server that provides a browser-based interface for creating invoices.

Starting the Web Server

./invoice web [--config config/web_config.json]

The web server will start on port 8080 by default (configurable). Access the interface by opening http://localhost:8080 in your browser.

Web Configuration

Configure the web server by creating a config/web_config.json file:

{
  "port": 8080,
  "nextcloudUrl": "https://your-nextcloud-server.com",
  "nextcloudShare": "/s/your-share-id",
  "uploadScript": "./cloudsend.sh"
}

Environment Variables

You can also configure the application using environment variables:

INVOICE_WEB_PORT=8080 INVOICE_TAX_RATE=0.19 ./invoice web

Nextcloud Integration

The web interface supports uploading and viewing generated invoices directly to a Nextcloud share. To use this feature:

1. Configure your Nextcloud settings in config/web_config.json
2. Make sure the cloudsend.sh script is executable (chmod +x cloudsend.sh)
3. After generating an invoice, click "Upload to Nextcloud" to share it

Command-Line Usage

Basic German Invoice

./invoice generate --from "Meine Firma GmbH" \
    --to "Kunde GmbH" \
    --item "Beratungsleistung" --quantity 10 --rate 120 \
    --tax 0.19 \
    --note "Zahlbar innerhalb von 14 Tagen ohne Abzug."

Using Invoice Number Suffix

./invoice generate --id "2023001" --id-suffix "-R1" \
    --from "Meine Firma GmbH" \
    --to "Kunde GmbH" \
    --item "Software-Lizenz" --quantity 1 --rate 499 \
    --tax 0.19

Using Configuration Files

Save repeated information with JSON / YAML:

{
    "logo": "/path/to/logo.png",
    "from": "Meine Firma GmbH\nMusterstraße 123\n10115 Berlin",
    "tax": 0.19,
    "currency": "EUR",
    "note": "Bitte überweisen Sie den Betrag innerhalb von 14 Tagen.",
    "footer": {
      "companyName": "Meine Firma GmbH",
      "registrationInfo": "Amtsgericht Berlin, HRB 123456",
      "vatId": "USt-IdNr. DE123456789",
      "address": "Musterstraße 123",
      "city": "Berlin",
      "zip": "10115",
      "phone": "+49 30 1234567",
      "email": "info@meinefirma.de",
      "website": "www.meinefirma.de",
      "bankName": "Sparkasse Berlin",
      "bankIban": "DE12 3456 7890 1234 5678 90",
      "bankBic": "BELADEBEXXX"
    }
}

Generate a new invoice by importing the configuration file:

./invoice generate --import config/data.json \
    --to "Kunde GmbH\nKundenweg 42\n80331 München" \
    --item "Support-Paket" --quantity 1 --rate 299

Currency Management

The invoice generator supports custom currency configurations through JSON files.

List Available Currencies

View all available currencies and their symbols:

./invoice currency list

Export Currency Configuration

Export the current currency configuration to a JSON file:

./invoice currency export my_currencies.json

Custom Currency Configuration

Create or modify a currency configuration file (currency_config.json or config/currency.json):

{
  "symbols": {
    "USD": "$",
    "EUR": "€",
    "GBP": "£",
    "CHF": "CHF",
    "CAD": "C$",
    "AUD": "A$",
    "CUSTOM": "¤"
  }
}

The application will automatically load currency symbols from any of these locations:

• currency_config.json in the current directory
• config/currency.json in the current directory
• ~/.config/invoice/currency.json in the user's home directory

Code Structure

The application follows a clean architecture pattern:

/invoice
├── cmd/                      # Command-line applications
│   └── invoice/              # Main application
│       └── main.go           # Entry point
├── internal/                 # Private application code
│   ├── models/               # Data models
│   │   ├── invoice.go        # Invoice data structures
│   │   └── config.go         # Configuration models
│   ├── handlers/             # Request handlers
│   │   └── web.go            # Web interface handlers
│   ├── services/             # Business logic
│   │   ├── pdf/              # PDF generation
│   │   │   └── renderer.go   # PDF rendering logic
│   │   ├── currency/         # Currency handling
│   │   │   └── service.go    # Currency service
│   │   ├── invoice/          # Invoice generation
│   │   │   └── service.go    # Invoice service
│   │   └── storage/          # Data persistence (future use)
│   └── config/               # Config handling
│       └── loader.go         # Configuration loading
├── pkg/                      # Public libraries
│   └── templates/            # Invoice templates (future use)
├── web/                      # Web assets and templates
│   ├── templates/            # HTML templates (future use)
│   └── static/               # Static assets
│       └── css/              # CSS stylesheets
└── config/                   # Configuration files
    ├── currency.json         # Currency configuration
    └── web_config.json       # Web server configuration

Future Improvements

The codebase now supports further improvements:

1. Adding proper unit and integration tests
2. Implementing database storage for invoices
3. Adding authentication and user management
4. Creating customizable PDF templates
5. Implementing a RESTful API
6. Internationalization and additional localization support