Elixir Project

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# Elixir Development Instructions (2025)

_Last updated: October 2025_

- Always use the fetch tool to look up the latest Elixir documentation: https://elixir-lang.org/docs.html
- Use Elixir 1.15+ for new projects
- Leverage functional programming patterns and immutability
- Use Phoenix framework for web applications
- Implement OTP principles for fault-tolerant systems
- Follow Elixir style guide and naming conventions

**Core Principles:**

- Embrace immutability - data cannot be changed
- Use pattern matching for control flow and function dispatch
- Implement pipe operator |> for data transformation pipelines
- Use atoms for constant values and keys
- Follow functional programming principles
- Understand processes and message passing

**Phoenix Framework:**

- Use Phoenix 1.7+ with LiveView for real-time web apps
- Implement context-based architecture
- Use Ecto for database operations
- Leverage channels for WebSocket communication
- Use generators for scaffolding (mix phx.gen)
- Implement proper routing with Phoenix Router

**Pattern Matching:**

- Use pattern matching in function heads
- Implement guard clauses for additional conditions
- Match on data structures for destructuring
- Use = operator for matching, not assignment
- Pattern match in case and with expressions

**Concurrency:**

- Use processes for concurrent operations (spawn, Task)
- Implement GenServer for stateful processes
- Use Supervisor for fault tolerance
- Leverage Task.async for concurrent operations
- Implement proper message passing between processes

**Ecto (Database):**

- Use Ecto schemas for data validation
- Implement changesets for data validation and casting
- Use Ecto Query for database queries
- Leverage Ecto migrations for schema changes
- Implement associations (belongs_to, has_many)

**Error Handling:**

- Use {:ok, result} and {:error, reason} tuples
- Implement with expressions for happy path
- Use case for pattern matching on results
- Let it crash - embrace OTP supervision
- Use try/rescue sparingly

**LiveView:**

- Use Phoenix LiveView for real-time server-rendered apps
- Implement mount and handle_event callbacks
- Use assigns for state management
- Leverage PubSub for real-time updates
- Implement form handling with changesets

**Testing:**

- Use ExUnit for testing
- Write doctests for function documentation
- Implement proper test setup with setup/setup_all
- Use Mox for mocking
- Test GenServers and processes properly

**Performance:**

- Use ETS for in-memory storage
- Implement caching strategies
- Leverage BEAM's concurrency model
- Use :telemetry for monitoring
- Profile with :observer and :fprof

**Summary:**

> For all Elixir work, always use the fetch tool to look up the latest documentation from https://elixir-lang.org/docs.html. Build scalable, fault-tolerant applications with functional programming.