---name: backend-developmentdescription: Guidelines for backend development in C++ and Elixir/Phoenix, covering modern language features, best practices, and production-ready patterns.---

Backend Development

You are an expert in backend development with C++ and Elixir/Phoenix.

C++ Development

Naming Conventions

• Use PascalCase for classes and structs
• Use camelCase for variables and methods
• Use SCREAMING_SNAKE_CASE for constants and macros

Memory Management

• Prefer smart pointers (std::unique_ptr, std::shared_ptr) over raw pointers
• Use std::unique_ptr for exclusive ownership
• Use std::shared_ptr only when shared ownership is required
• Implement RAII for all resource management
• Avoid unnecessary heap allocations

Modern C++ Features

• Use auto for type inference where it improves readability
• Leverage range-based for loops
• Use std::optional for values that may not exist
• Use std::variant for type-safe unions
• Apply structured bindings for cleaner code
• Use std::move for move semantics

Error Handling

• Use exceptions for error handling
• Define custom exception types for domain-specific errors
• Catch exceptions at appropriate boundaries
• Ensure exception safety in all code

Best Practices

• Enforce const-correctness throughout
• Avoid C-style casts; use static_cast, dynamic_cast, etc.
• Write unit tests with Google Test or Catch2
• Document with Doxygen comments

Elixir and Phoenix Best Practices

Core Philosophy

• Follow domain-driven design with PragDave philosophy
• Use functional programming with explicit error handling
• Embrace the "let it crash" principle

Code Organization

• Organize code around business domains using Phoenix contexts
• Keep contexts focused on single domains
• Use bounded contexts to prevent coupling
• Implement clear public APIs for each context

Pattern Matching and Control Flow

• Use pattern matching extensively for data extraction
• Apply "railway-oriented programming" with with statements
• Chain operations cleanly with the pipe operator
• Handle all pattern match cases explicitly

Error Handling

• Return tagged tuples ({:ok, result} or {:error, reason})
• Use with statements to chain fallible operations
• Implement proper supervision trees
• Handle expected errors explicitly

Phoenix Contexts

• Group related functionality in contexts
• Define clear boundaries between contexts
• Use contexts as the API layer for business logic
• Keep controllers thin, delegate to contexts

LiveView

• Use LiveView as primary UI technology
• Implement function components for reusable UI
• Handle events in LiveView modules
• Manage state appropriately in assigns

Data Validation

• Validate at boundaries using Ecto.Changeset
• Use changesets even outside database contexts
• Define clear validation rules
• Return helpful error messages