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What is Kontrak Backend?

Kontrak Backend is a powerful Node.js-based REST API that automates the generation of employment contracts and related documents. Built with Express and TypeScript, it streamlines the contract creation process by transforming employee data into professionally formatted PDF documents.

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Key Features

Multi-Contract Support

Generate three types of employment contracts: Planilla (standard), Part Time, and Subsidio (substitution)

Batch Processing

Process up to 50 employees at once and download all contracts in a single ZIP file

Automated PDF Generation

Uses Puppeteer and pdf-lib to generate high-quality, legally compliant contract PDFs

Data Validation

Built-in Zod schemas validate employee data to ensure accuracy and completeness

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Who Should Use Kontrak Backend?

This system is ideal for:
  • HR Departments: Automate repetitive contract generation tasks
  • Staffing Agencies: Handle large volumes of employee onboarding
  • Legal Teams: Ensure consistent, compliant employment documentation
  • System Integrators: Build employee management systems with contract generation capabilities

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Core Capabilities

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Contract Types

Kontrak Backend supports three distinct contract types, each with specific requirements:
Standard full-time employment contracts with complete benefits and long-term engagement.Required Fields:
  • Employee personal information (name, DNI, address)
  • Position and salary details
  • Contract dates (entry and end date)
  • Subdivision or parking assignment

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Document Generation

For each employee, the system automatically generates:
  1. Employment Contract: Main contract document based on contract type
  2. Data Processing Agreement: Personal data treatment consent (GDPR compliance)
  3. Annexes: Additional documentation and forms
All documents are bundled together in an organized ZIP structure.

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Architecture Overview

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Technology Stack

{
  "dependencies": {
    "express": "^5.1.0",
    "typescript": "^5.9.3",
    "zod": "^4.1.12",
    "puppeteer": "^24.34.0",
    "pdf-lib": "^1.17.1",
    "handlebars": "^4.7.8",
    "archiver": "^7.0.1"
  }
}
Core Technologies:
  • Express 5.1: Modern web framework for API endpoints
  • TypeScript 5.9: Type-safe development with latest features
  • Zod 4.1: Runtime type validation and schema definition
  • Puppeteer 24: Headless Chrome for PDF generation
  • pdf-lib: PDF manipulation and generation
  • Archiver: ZIP file creation for batch downloads

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Project Structure

src/
├── controllers/          # Request handlers
│   ├── contract.controller.ts
│   └── addendum.controller.ts
├── services/            # Business logic
│   ├── contract.service.ts
│   ├── pdf-generator.service.ts
│   └── validation.service.ts
├── validators/          # Zod schemas
│   └── employee.validator.ts
├── middlewares/         # Express middlewares
│   ├── error-handle.middleware.ts
│   └── schema-validator.middleware.ts
├── types/              # TypeScript interfaces
│   ├── employees.interface.ts
│   └── contract.interface.ts
├── template/           # Contract templates
│   └── contracts.ts
└── config/             # Configuration
    └── index.ts

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API Endpoints

Kontrak Backend exposes a RESTful API with the following main endpoints:
EndpointMethodDescription
/GETHealth check and API information
/api/healthGETServer health status
/api/contracts/download-zipPOSTGenerate and download contracts as ZIP
/api/contracts/previewPOSTPreview a single contract PDF
All contract generation endpoints require validated employee data according to the Zod schemas defined in src/validators/employee.validator.ts.

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Data Flow

  1. Request Reception: Client sends employee data to the API
  2. Validation: Data is validated against Zod schemas
  3. Processing: Contract service processes each employee
  4. PDF Generation: Puppeteer generates PDFs from HTML templates
  5. Bundling: Documents are organized and archived
  6. Response: ZIP file is streamed back to the client

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Next Steps

Quick Start

Get up and running in 5 minutes

Installation

Detailed installation instructions

API Reference

Complete API documentation

Configuration

Configure your environment

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