Professional Invoice Management System

Overview

This is a Flask-based invoice management system designed to provide professional invoice generation and management capabilities. The application features a modern web interface with a purple gradient theme, database persistence using SQLAlchemy, and comprehensive invoice tracking functionality.

User Preferences

Preferred communication style: Simple, everyday language.

System Architecture

Backend Architecture

• Framework: Flask web framework with SQLAlchemy ORM
• Database: SQLite for development (configurable to PostgreSQL via DATABASE_URL environment variable)
• Models: Company, Client, Invoice, and LineItem entities with proper relationships
• Session Management: Flask sessions with configurable secret key
• Deployment: WSGI-ready with ProxyFix middleware for production deployment

Frontend Architecture

• Template Engine: Jinja2 templating with base template inheritance
• CSS Framework: Bootstrap 5 with custom CSS styling
• UI Theme: Purple gradient design (#4f46e5 → #7c3aed) with smooth animations
• Icons: Font Awesome integration
• JavaScript: Vanilla JS for dynamic functionality and form interactions
• PDF Generation: html2pdf.js library for invoice PDF export

Database Schema

The system uses a relational database with the following key entities:

• Company: Stores business information (name, address, contact details, tax ID)
• Client: Customer information with contact details
• Invoice: Core invoice data with financial calculations and status tracking
• LineItem: Individual invoice line items (implied from routes but not fully shown in models.py)

Key Components

Core Pages

1. Create Invoice (/create-invoice): Dynamic invoice creation with live preview
2. Company Settings (/company-settings): Business profile management
3. Invoice History (/invoice-history): Invoice tracking with search and filtering

Data Management

• Invoice Numbering: Unique invoice number generation
• Status Tracking: Pending, Paid, Overdue status management
• Financial Calculations: Automatic subtotal, tax, and total calculations
• Date Management: Issue date and due date tracking

User Interface Features

• Responsive Design: Mobile-friendly layout using Bootstrap grid system
• Animation Effects: Slide-in animations and hover effects
• Interactive Elements: Dynamic form fields and real-time calculations
• Search & Filter: Invoice history filtering by status and search terms
• Statistics Dashboard: Revenue and invoice count summaries

Data Flow

1. Invoice Creation Flow:

   • User selects/creates company information
   • Enters client details
   • Adds line items with automatic calculation updates
   • Generates PDF for download or email

2. Data Persistence:

   • Form data auto-saves to localStorage for user experience
   • Database persistence through SQLAlchemy ORM
   • Relationship mapping between companies, clients, and invoices

3. Invoice Management:

   • Status updates trigger recalculation of statistics
   • Search functionality queries across invoice numbers and client names
   • Historical data provides business insights

External Dependencies

Python Libraries

• Flask: Web framework and routing
• Flask-SQLAlchemy: Database ORM and management
• Werkzeug: WSGI utilities and proxy handling

Frontend Libraries

• Bootstrap 5: CSS framework for responsive design
• Font Awesome: Icon library for UI elements
• html2pdf.js: Client-side PDF generation

Development Tools

• SQLite: Default database for development
• Logging: Built-in Python logging for debugging

Deployment Strategy

Environment Configuration

• Database: Configurable via DATABASE_URL environment variable
• Security: Session secret via SESSION_SECRET environment variable
• Connection Pooling: SQLAlchemy engine optimization for production

Production Considerations

• WSGI Deployment: Ready for deployment with ProxyFix middleware
• Database Migration: Automatic table creation on startup
• Static Assets: Organized static file structure for CDN deployment
• Error Handling: Comprehensive logging and error management

Scalability Features

• Database Agnostic: Easy migration from SQLite to PostgreSQL
• Session Management: Stateless design for horizontal scaling
• Asset Optimization: Modular CSS and JavaScript for performance

The application follows a traditional MVC pattern with clear separation of concerns, making it maintainable and extensible for additional features like payment integration, email notifications, or multi-tenant support.