nexfact

^{🌍 Language: 🇩🇪 German →}

	GSF-NexFact A modular system for generating legally compliant electronic invoices (ZUGFeRD/Factur-X). It combines the flexibility of Go with the layout power of LibreOffice and the standards compliance of the Mustang project.

^{GSF stands for Go Small Frameworks — minimalist tools for robust applications.}

Repository

This project is developed and maintained on Codeberg.

Canonical repository:

https://codeberg.org/tiny-frameworks/nexfact

GitHub is an automated mirror of the Codeberg repository:

GitHub mirror:

https://github.com/tiny-frameworks/nexfact

GSF-NexFact

GSF-NexFact is a modular system designed for flexible generating, analyzing, and validating ZUGFeRD and Factur-X e-invoices from JSON data.
It transforms inputs into XML, standard PDFs, or hybrid ZUGFeRD invoices (including attachments) using a file-based architecture with clear conventions (Convention over Configuration).

Architecture & Core Principle: Convention over Configuration

The entire system relies on a strictly file-based data exchange using a defined directory structure (NEXFACT-env). The Go Orchestrator manages state transitions, while specialized workers (running natively or within isolated containers) monitor and process the directories. A standardized RenderJob file acts as the bridge between Go, the LibreOffice Basic macro, and the Mustang engine (Java).

            +-----------------------+
            |  nexfact-orchestrator |
            +-----------+-----------+
                        | (Handles orchestration, transforms
                        |  input-json into internal MasterZugFerd-Struct)
                        v
            +-----------------------+
            |      nexfact-env      | <--- Common state (Directories)
            +-----------+-----------+
                        |
       +----------------+-------------+
       v                              v
+------------------------+     +-----------------------+
|   PDF via LibreOffice  |     |  ZUGFeRD via Mustang  |
|  native or container   |     |  native or container  | (Workers)
+------------------------+     +-----------------------+

Repository Overview, Components (Modules), Documentation

This repository is organized as a multi-module repository:

• api: Core interfaces, types, structs, centralized error handling (e.g., RenderJob, Error, Writer)
• engines: Processing engines (writer), synchronization & worker control
• orchestrator: Control unit, entry point for the Go
• examples: Ready-to-run code examples
• env: Directory structure & configurations
• deployments: Container repos for Docker/Podman (PDF/Mustang)

Helper Modules

• cache: Minimalistic caching module
• logger: Multi-logger (Console/File) based on log/slog

Quick Start & Integration (Go API)

A simple main.go snippet serving as an entry point. This setup utilizes default values:

• The env structure is located right next to the main.go in the current working directory.
• The default seller profile is used (found in env/sellers/default).
• The provider type is set to native (configured in env/system/systm.yaml via zugferd_provider=native and pdf_provider=native).

You can find the documented, working example at examples. You can find the containerized counterpart to this main.go at deployments. You can find a detailed and complex template in the orchestrator.

package main

import (
	"errors"
	"os"
	"os/exec"
	"runtime"

	"codeberg.org/tiny-frameworks/nexfact/api/logger"
	"codeberg.org/tiny-frameworks/nexfact/api/nexerrors"
	"codeberg.org/tiny-frameworks/nexfact/orchestrator"
)

func main() {

	// Required only for the local monorepo example:
	os.Setenv(orchestrator.EnvRootKey, "../env")

	// In production, the orchestrator searches for the env-directory via:
	// 1: orchestrator.NewDefault():
	//   1.1: environment variable: nexfact_ENVROOT, if empty:
	//   1.2: default directory position (env-dir in working directory)
	// 2: orchestrator.New(env-path)

	orch, err := orchestrator.NewDefault()
	if err != nil {
		nexerrors.LogError(logger.Logger, err)
		os.Exit(nexerrors.GetExitCode(err))
	}

	// 2. Execute job (expects JSON payload for the toolchain)
	jsonPayload := jsonJob()
	result, err := orch.RunJsonJob(jsonPayload)
	if err != nil {
		nexerrors.LogError(logger.Logger, err)
		os.Exit(nexerrors.GetExitCode(err))
	}

	logger.Logger.Info("Job succeeded", "JobID:", result.JobID, "OutputPath", result.OutputPath)
	if err := openPDF(result.OutputPath); err != nil {
		nexerrors.LogError(logger.Logger, err)
		os.Exit(nexerrors.GetExitCode(err))
	}
	os.Exit(0)
}

func openPDF(filePath string) error {
	// go-code to open the generated pdf-file	
	// see: examples/main.go
}

func jsonJob() []byte {
	// bytestream for a minimal sample zugferd-invoice
	// see: examples/main.go
}

Organizational & Standards

• Copyright: © 2026 Georg Hagn.
• Repository: codeberg.org/tiny-frameworks/nexfact
• License: Apache License, Version 2.0.

GSF-NexFact is an independent open-source project and is not affiliated with any corporation of a similar name.

Contact & Support

For inquiries, architectural discussions, or security issues, please contact:

📧 georghagn [at] tiny-frameworks.io