Invoice Ninja is a full-featured open-source invoicing and billing platform designed for small to medium businesses. It handles the complete lifecycle of invoices, quotes, credits, purchase orders, payments, and expenses. The system supports multi-tenant SaaS and self-hosted deployments with per-company database isolation, and integrates with over 20 payment gateways (Stripe, PayPal, Mollie, GoCardless, etc.). It provides client and vendor portals for self-service, along with extensive reporting, CSV export, and e-invoicing capabilities (Peppol, Verifactu, France e-reporting). The application follows a monolithic MVC architecture built on a custom PHP framework (Illuminate) similar to Laravel. It uses an event-driven architecture with domain events and listeners for side effects (email, webhooks, activity logging). Background jobs are queued for async processing. The frontend uses Blade templates, Livewire components, and a separate React app for some admin panels. The API is RESTful with OpenAPI documentation. Key entry points are HTTP controllers under app/Http/Controllers, with request validation classes. Core data flows involve creating entities through factories, persisting via repositories, and triggering events that listeners handle. Payment flows go through abstract payment drivers that encapsulate gateway-specific logic. The system also includes extensive reporting, CSV export, and e-invoicing (Peppol, Verifactu, France e-reporting). External dependencies include a relational database (MySQL/PostgreSQL), Redis for caching and queues, Elasticsearch for search, and various third-party APIs for payment processing, tax calculation (ZipTax), bank integration (Nordigen, Yodlee), email delivery (Mailgun, Postmark, Brevo), and e-invoicing gateways (Storecove, Qvalia).
This repository is a curated collection of code implementations, cheat sheets, and study resources for software engineering (SDE) interview preparation. It contains hundreds of independently written C++, Python, and C files covering fundamental data structures (arrays, linked lists, stacks, queues, trees, graphs) and algorithms (sorting, searching, dynamic programming, greedy, backtracking, string algorithms, etc.). The repo also includes problem sheets from popular SDE preparation resources (Striver's SDE Sheet, Love Babbar DSA Sheet), competitive programming patterns, and notes on core subjects like DBMS, OS, and CN. It is primarily a reference/learning resource rather than a cohesive application or data pipeline; the code is not packaged as a library and lacks tests, build systems, or dependency management. Many files are standalone textbook-style implementations. While the breadth is impressive, the depth and consistency of quality vary significantly across contributions, and the repository appears to be in a stale maintenance state with no recent meaningful code updates.
This repository is a curated list of interesting open source projects organized by programming language. It contains markdown files with links and descriptions for each language. There is no application code, data pipelines, or analytical models. It serves as a reference directory for developers seeking open source projects to contribute to or learn from. The repository is well-maintained with recent updates and a large community following.