A web-based todo application built with Flix and HTMX that demonstrates effect-oriented programming principles.

This project showcases how to build a web application using Flix's algebraic effects and handlers to cleanly separate pure business logic from side effects. The architecture demonstrates effect-oriented programming where:

• Pure business logic resides in the functional core
• Side effects are captured by algebraic effects
• Effect handlers manage the imperative shell
• All mutable state is scoped using regions

The application follows effect-oriented design principles:

Effects:

• TodoStorage - Data persistence operations
• TodoView - UI rendering operations
• TodoConfig - Configuration access

Handlers:

• TodoStorageHandler - Manages in-memory state using regions
• TodoViewHandler - Renders HTML components
• TodoConfigHandler - Provides initial configuration

Pure Core:

• TodoService - Business logic (validation, CRUD operations)
• Todo - Domain types and operations
• View components - Pure HTML generation functions

• Create, read, update, and delete todos
• Filter todos by status (all, active, completed)
• Clear completed todos
• Persistent state during session
• Responsive web interface with HTMX

• Backend: Flix with built-in HTTP server
• Frontend: HTMX for dynamic updates
• Styling: CSS for responsive design
• Memory Management: Region-based scoped memory

1. Ensure you have Flix installed (requires Java 21+)
2. Clone this repository
3. Run: flix run
4. Open http://localhost:8080 in your browser

• Effect-Oriented Programming: Separation of pure and effectful code
• Algebraic Effects: User-defined effects with handlers
• Region-Based Memory: Safe mutable memory management
• Functional Core, Imperative Shell: Clean architecture pattern
• Type and Effect Safety: Compile-time guarantees about side effects

This example illustrates how effect-oriented programming enables building maintainable web applications with clear separation of concerns and strong safety guarantees.