codicil

defmodule Codicil.FileWatcher do
  # Watches file system for deletions and retires modules when source files are deleted.
  #
  # Subscribes to the Codicil.FsWatcher FileSystem process that is managed by the
  # supervision tree.
  @moduledoc false
  use GenServer

  alias Codicil.Functions
  alias Codicil.Modules

  # BOILERPLATE & INITIALIZATION

  def start_link(_opts) do
    GenServer.start_link(__MODULE__, [], name: __MODULE__)
  end

  @impl true
  def init([]) do
    # Subscribe to the FileSystem process managed by the supervision tree
    FileSystem.subscribe(Codicil.FsWatcher)

    {:ok, %{}}
  end

  # ROUTER

  @impl true
  def handle_info({:file_event, _watcher_pid, {path, events}}, state) do
    if Path.extname(path) in [".ex", ".exs"] do
      cond do
        # File was deleted or removed - retire modules
        :deleted in events or :removed in events ->
          retire_modules_for_path(path)

        # File was created or modified - trigger recompilation
        :created in events or :modified in events ->
          recompile_file(path)

        true ->
          :ok
      end
    end

    {:noreply, state}
  end

  def handle_info({:file_event, _watcher_pid, :stop}, state) do
    {:noreply, state}
  end

  # HELPER FUNCTIONS

  defp retire_modules_for_path(path) do
    # Get all modules associated with this file path
    modules = Modules.list_by_path(path)

    for module <- modules do
      module_atom = String.to_atom(module.id)

      # If this is a .ex file, purge and delete the compiled module from BEAM
      if Path.extname(path) == ".ex" do
        :code.purge(module_atom)
        :code.delete(module_atom)
      end

      # Mark the module for deletion (preserves data for potential rename)
      Modules.mark_for_deletion(module)
    end

    # Mark all functions at this path for deletion
    functions = Functions.list_by_path(path)

    for function <- functions do
      Functions.mark_for_deletion(function)
    end
  end

  defp recompile_file(path) do
    # Compile the file - this will trigger the tracer which will update the database
    Code.compile_file(path)
  rescue
    # Ignore compilation errors - let the user handle them
    _ -> :ok
  end
end