pinchflat/AGENTS.md

Agent Guidelines for Pinchflat

Guidelines for AI agents working on this Elixir/Phoenix codebase.

Project Overview

Pinchflat is a self-hosted media management app using:

• Backend: Elixir 1.17+, Phoenix 1.7, Ecto with SQLite
• Frontend: Phoenix LiveView, Tailwind CSS, esbuild
• Background Jobs: Oban
• Testing: ExUnit with Mox for mocking

Build/Lint/Test Commands

# Enter Nix dev shell (required for tooling)
nix develop

# Run all checks (compile, format, credo, tests, sobelow, prettier)
mix check

# Run tests only
mix test

# Run a single test file
mix test test/pinchflat/media_test.exs

# Run a specific test by line number
mix test test/pinchflat/media_test.exs:42

# Run tests matching a pattern
mix test --only describe:"list_media_items"

# Format Elixir code
mix format

# Run Credo linter
mix credo

# Security analysis
mix sobelow --config

# Format JS/CSS/YAML/JSON
yarn run lint:fix

Code Style Guidelines

Module Structure

Follow this order in modules:

1. @moduledoc - required for all public modules
2. use/import/alias/require statements
3. Module attributes (@allowed_fields, @impl, etc.)
4. Public functions with @doc
5. Private functions

defmodule Pinchflat.Media do
  @moduledoc """
  The Media context.
  """

  import Ecto.Query, warn: false
  use Pinchflat.Media.MediaQuery

  alias Pinchflat.Repo
  alias Pinchflat.Media.MediaItem

  @doc """
  Returns the list of media_items.
  """
  def list_media_items do
    Repo.all(MediaItem)
  end

  defp some_private_function do
    # ...
  end
end

Imports and Aliases

• Use alias for frequently used modules
• Prefer explicit imports: import Ecto.Query, warn: false
• Group aliases alphabetically
• Use alias __MODULE__ for self-reference in schemas

Naming Conventions

• Modules: PascalCase matching file path (Pinchflat.Media.MediaItem)
• Functions: snake*case with verb prefixes (get*, list*, create*, update*, delete*)
• Predicate functions: end with ? (pending_download?/1)
• Private functions: prefix with do_ for wrapper pattern (do_delete_media_files)
• Workers: suffix with Worker (MediaDownloadWorker)
• Fixtures: suffix with _fixture (media_item_fixture)

Formatting

• Line length: 120 characters max
• Use mix format - config in .formatter.exs
• Prettier for JS/CSS/YAML/JSON

Return Types

Document returns in @doc:

@doc """
Creates a media_item.

Returns {:ok, %MediaItem{}} | {:error, %Ecto.Changeset{}}
"""
def create_media_item(attrs) do
  # ...
end

Error Handling

• Use {:ok, result} / {:error, reason} tuples
• Use ! suffix for functions that raise (get_media_item!/1)
• Pattern match on error tuples explicitly
• Rescue specific exceptions when needed:

def perform(%Oban.Job{args: %{"id" => id}}) do
  # ...
rescue
  Ecto.NoResultsError -> Logger.info("Record not found")
  Ecto.StaleEntryError -> Logger.info("Record stale")
end

Oban Workers

defmodule Pinchflat.Downloading.MediaDownloadWorker do
  @moduledoc false

  use Oban.Worker,
    queue: :media_fetching,
    priority: 5,
    unique: [period: :infinity, states: [:available, :scheduled, :retryable, :executing]],
    tags: ["media_item", "show_in_dashboard"]

  @impl Oban.Worker
  def perform(%Oban.Job{args: %{"id" => id} = args}) do
    # Return :ok, {:ok, result}, {:error, reason}, or {:snooze, seconds}
  end
end

Testing Patterns

Use Pinchflat.DataCase for database tests:

defmodule Pinchflat.MediaTest do
  use Pinchflat.DataCase

  import Pinchflat.MediaFixtures
  import Pinchflat.SourcesFixtures

  alias Pinchflat.Media

  describe "list_media_items/0" do
    test "returns all media_items" do
      media_item = media_item_fixture()
      assert Media.list_media_items() == [media_item]
    end
  end
end

Mocking with Mox

Mocks are defined in test/test_helper.exs:

• YtDlpRunnerMock - yt-dlp commands
• HTTPClientMock - HTTP requests
• UserScriptRunnerMock - user scripts
• AppriseRunnerMock - notifications

test "calls user script" do
  expect(UserScriptRunnerMock, :run, fn :media_deleted, data ->
    assert data.id == media_item.id
    {:ok, "", 0}
  end)

  Media.delete_media_item(media_item, delete_files: true)
end

Test Fixtures

Create fixtures in test/support/fixtures/:

def media_item_fixture(attrs \\ %{}) do
  {:ok, media_item} =
    attrs
    |> Enum.into(%{
      media_id: Faker.String.base64(12),
      title: Faker.Commerce.product_name(),
      source_id: source_fixture().id
    })
    |> Pinchflat.Media.create_media_item()

  media_item
end

Test Helpers

From Pinchflat.TestingHelperMethods:

• now/0 - current UTC datetime
• now_minus/2 - datetime in past (now_minus(5, :days))
• now_plus/2 - datetime in future
• assert_changed/2 - verify state change

Project Structure

lib/
  pinchflat/           # Business logic contexts
    media/             # Media context (MediaItem, queries)
    sources/           # Source context
    downloading/       # Download workers and helpers
    yt_dlp/            # yt-dlp integration
  pinchflat_web/       # Phoenix web layer
test/
  pinchflat/           # Context tests
  pinchflat_web/       # Controller/LiveView tests
  support/
    fixtures/          # Test data factories
    data_case.ex       # Database test setup
    conn_case.ex       # HTTP test setup

Pre-commit Hooks

Lefthook runs on commit:

• prettier - JS/CSS/YAML/JSON formatting
• mix format - Elixir formatting
• typos - spell checking
• actionlint - GitHub Actions validation

Bypass if needed: git commit --no-verify -m "message"