Install and use Usage Rules

requires a further cleanup of CLAUDE.md

CLAUDE.md

@@ -245,3 +245,150 @@ Security
 - Protect against common web vulnerabilities (XSS, CSRF, SQL injection).
 
 Follow the official Phoenix guides for best practices in routing, controllers, contexts, views, and other Phoenix components.
+
+<!-- usage-rules-start -->
+<!-- usage-rules-header -->
+# Usage Rules
+
+**IMPORTANT**: Consult these usage rules early and often when working with the packages listed below. 
+Before attempting to use any of these packages or to discover if you should use them, review their 
+usage rules to understand the correct patterns, conventions, and best practices.
+<!-- usage-rules-header-end -->
+
+<!-- igniter-start -->
+## igniter usage
+_A code generation and project patching framework
+_
+
+[igniter usage rules](deps/igniter/usage-rules.md)
+<!-- igniter-end -->
+<!-- usage_rules-start -->
+## usage_rules usage
+_A dev tool for Elixir projects to gather LLM usage rules from dependencies
+_
+
+## Using Usage Rules
+
+Many packages have usage rules, which you should *thoroughly* consult before taking any
+action. These usage rules contain guidelines and rules *directly from the package authors*.
+They are your best source of knowledge for making decisions.
+
+## Modules & functions in the current app and dependencies
+
+When looking for docs for modules & functions that are dependencies of the current project,
+or for Elixir itself, use `mix usage_rules.docs`
+
+```
+# Search a whole module
+mix usage_rules.docs Enum
+
+# Search a specific function
+mix usage_rules.docs Enum.zip
+
+# Search a specific function & arity
+mix usage_rules.docs Enum.zip/1
+```
+
+
+## Searching Documentation
+
+You should also consult the documentation of any tools you are using, early and often. The best 
+way to accomplish this is to use the `usage_rules.search_docs` mix task. Once you have
+found what you are looking for, use the links in the search results to get more detail. For example:
+
+```
+# Search docs for all packages in the current application, including Elixir
+mix usage_rules.search_docs Enum.zip
+
+# Search docs for specific packages
+mix usage_rules.search_docs Req.get -p req
+
+# Search docs for multi-word queries
+mix usage_rules.search_docs "making requests" -p req
+
+# Search only in titles (useful for finding specific functions/modules)
+mix usage_rules.search_docs "Enum.zip" --query-by title
+```
+
+
+<!-- usage_rules-end -->
+<!-- usage_rules:elixir-start -->
+## usage_rules:elixir usage
+# Elixir Core Usage Rules
+
+## Pattern Matching
+- Use pattern matching over conditional logic when possible
+- Prefer to match on function heads instead of using `if`/`else` or `case` in function bodies
+
+## Error Handling
+- Use `{:ok, result}` and `{:error, reason}` tuples for operations that can fail
+- Avoid raising exceptions for control flow
+- Use `with` for chaining operations that return `{:ok, _}` or `{:error, _}`
+
+## Common Mistakes to Avoid
+- Elixir has no `return` statement, nor early returns. The last expression in a block is always returned.
+- Don't use `Enum` functions on large collections when `Stream` is more appropriate
+- Avoid nested `case` statements - refactor to a single `case`, `with` or separate functions
+- Don't use `String.to_atom/1` on user input (memory leak risk)
+- Lists and enumerables cannot be indexed with brackets. Use pattern matching or `Enum` functions
+- Prefer `Enum` functions like `Enum.reduce` over recursion
+- When recursion is necessary, prefer to use pattern matching in function heads for base case detection
+- Using the process dictionary is typically a sign of unidiomatic code
+- Only use macros if explicitly requested
+- There are many useful standard library functions, prefer to use them where possible
+
+## Function Design
+- Use guard clauses: `when is_binary(name) and byte_size(name) > 0`
+- Prefer multiple function clauses over complex conditional logic
+- Name functions descriptively: `calculate_total_price/2` not `calc/2`
+- Predicate function names should not start with `is` and should end in a question mark. 
+- Names like `is_thing` should be reserved for guards
+
+## Data Structures
+- Use structs over maps when the shape is known: `defstruct [:name, :age]`
+- Prefer keyword lists for options: `[timeout: 5000, retries: 3]`
+- Use maps for dynamic key-value data
+- Prefer to prepend to lists `[new | list]` not `list ++ [new]`
+
+## Mix Tasks
+
+- Use `mix help` to list available mix tasks
+- Use `mix help task_name` to get docs for an individual task
+- Read the docs and options fully before using tasks
+
+## Testing
+- Run tests in a specific file with `mix test test/my_test.exs` and a specific test 
+  with the line number `mix test path/to/test.exs:123`
+- Limit the number of failed tests with `mix test --max-failures n`
+- Use `@tag` to tag specific tests, and `mix test --only tag` to run only those tests
+- Use `assert_raise` for testing expected exceptions: `assert_raise ArgumentError, fn -> invalid_function() end`
+
+<!-- usage_rules:elixir-end -->
+<!-- usage_rules:otp-start -->
+## usage_rules:otp usage
+# OTP Usage Rules
+
+## GenServer Best Practices
+- Keep state simple and serializable
+- Handle all expected messages explicitly
+- Use `handle_continue/2` for post-init work
+- Implement proper cleanup in `terminate/2` when necessary
+
+## Process Communication
+- Use `GenServer.call/3` for synchronous requests expecting replies
+- Use `GenServer.cast/2` for fire-and-forget messages.
+- When in doubt, us `call` over `cast`, to ensure back-pressure
+- Set appropriate timeouts for `call/3` operations
+
+## Fault Tolerance
+- Set up processes such that they can handle crashing and being restarted by supervisors
+- Use `:max_restarts` and `:max_seconds` to prevent restart loops
+
+## Task and Async
+- Use `Task.Supervisor` for better fault tolerance
+- Handle task failures with `Task.yield/2` or `Task.shutdown/2`
+- Set appropriate task timeouts
+- Use `Task.async_stream/3` for concurrent enumeration with back-pressure
+
+<!-- usage_rules:otp-end -->
+<!-- usage-rules-end -->

mise.toml

@@ -118,6 +118,16 @@ depends = [
 description = 'Install dependencies and setup the database'
 run = ['mix setup']
 
+# AI
+
+[tasks."usage-rules:sync"]
+run = """
+mix usage_rules.sync CLAUDE.md --all \
+  --inline usage_rules:all \
+  --link-to-folder deps \
+  --remove-missing
+"""
+
 # PRODUCTION
 
 [tasks."prod:console"]

mix.exs

@@ -72,6 +72,7 @@ defmodule MusicLibrary.MixProject do
 
       # Dev tooling
       {:igniter, "~> 0.6", only: [:dev, :test]},
+      {:usage_rules, "~> 0.1", only: [:dev]},
       {:phoenix_live_reload, "~> 1.2", only: :dev},
       {:esbuild, "~> 0.8", runtime: Mix.env() == :dev},
       {:tailwind, "~> 0.3", runtime: Mix.env() == :dev},

mix.lock

@@ -69,6 +69,7 @@
   "thousand_island": {:hex, :thousand_island, "1.3.14", "ad45ebed2577b5437582bcc79c5eccd1e2a8c326abf6a3464ab6c06e2055a34a", [:mix], [{:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "d0d24a929d31cdd1d7903a4fe7f2409afeedff092d277be604966cd6aa4307ef"},
   "tidewave": {:hex, :tidewave, "0.2.0", "e98378803e535d3035138e4b354dcfca26b7f862fd44cffef5aa697b814c0b0b", [:mix], [{:circular_buffer, "~> 0.4 or ~> 1.0", [hex: :circular_buffer, repo: "hexpm", optional: false]}, {:igniter, ">= 0.5.47 and < 1.0.0-0", [hex: :igniter, repo: "hexpm", optional: true]}, {:jason, "~> 1.4", [hex: :jason, repo: "hexpm", optional: false]}, {:plug, "~> 1.17", [hex: :plug, repo: "hexpm", optional: false]}, {:req, "~> 0.5", [hex: :req, repo: "hexpm", optional: false]}], "hexpm", "6ad11829f4600cd69955ffc66935e6456b775fea095172147244ba6f65986735"},
   "time_zone_info": {:hex, :time_zone_info, "0.7.8", "5b0e2b6b4af7b7526ef519dfd919d9d89d493a7b5e12a07434f2760dd5fe8be0", [:mix], [{:castore, "~> 1.0", [hex: :castore, repo: "hexpm", optional: true]}, {:mint, "~> 1.0", [hex: :mint, repo: "hexpm", optional: true]}, {:nimble_parsec, "~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "307d3fab87679e80888ce39fdfcf44a8fd6189cefc2fca3a83fb5c1097efa40e"},
+  "usage_rules": {:hex, :usage_rules, "0.1.21", "5869383bd23ffc1ee499eb00614106b36fb1f554a17706e27cb84725e72d925a", [:mix], [{:igniter, ">= 0.6.6 and < 1.0.0-0", [hex: :igniter, repo: "hexpm", optional: true]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}, {:req, "~> 0.5", [hex: :req, repo: "hexpm", optional: false]}], "hexpm", "5d2eadd4e7506c0ef995ca05362ac54ace7e6d2311d391cbb678a85f3095eeb0"},
   "vix": {:hex, :vix, "0.35.0", "f6319b715e3b072e53eba456a21af5f2ff010a7a7b19b884600ea98a0609b18c", [:make, :mix], [{:cc_precompiler, "~> 0.1.4 or ~> 0.2", [hex: :cc_precompiler, repo: "hexpm", optional: false]}, {:elixir_make, "~> 0.7.3 or ~> 0.8", [hex: :elixir_make, repo: "hexpm", optional: false]}, {:kino, "~> 0.7", [hex: :kino, repo: "hexpm", optional: true]}], "hexpm", "a3e80067a89d0631b6cf2b93594e03c1b303a2c7cddbbdd28040750d521984e5"},
   "websock": {:hex, :websock, "0.5.3", "2f69a6ebe810328555b6fe5c831a851f485e303a7c8ce6c5f675abeb20ebdadc", [:mix], [], "hexpm", "6105453d7fac22c712ad66fab1d45abdf049868f253cf719b625151460b8b453"},
   "websock_adapter": {:hex, :websock_adapter, "0.5.8", "3b97dc94e407e2d1fc666b2fb9acf6be81a1798a2602294aac000260a7c4a47d", [:mix], [{:bandit, ">= 0.6.0", [hex: :bandit, repo: "hexpm", optional: true]}, {:plug, "~> 1.14", [hex: :plug, repo: "hexpm", optional: false]}, {:plug_cowboy, "~> 2.6", [hex: :plug_cowboy, repo: "hexpm", optional: true]}, {:websock, "~> 0.5", [hex: :websock, repo: "hexpm", optional: false]}], "hexpm", "315b9a1865552212b5f35140ad194e67ce31af45bcee443d4ecb96b5fd3f3782"},