defmodule AssertBoundary do
  @moduledoc """
  ExUnit assertion helpers for testing module dependency boundaries.

  AssertBoundary uses Erlang's `:xref` to analyze BEAM bytecode and verify
  that module dependencies respect architectural boundaries. This lets you
  enforce that your runtime and verification pipelines don't leak into each
  other, that your domain layer stays independent, or any other structural
  invariant your architecture requires.

  ## Usage

      defmodule MyApp.BoundaryTest do
        use ExUnit.Case, async: true
        use AssertBoundary, app: :my_app

        test "web layer doesn't touch repo internals", %{boundary: boundary} do
          refute_calls(boundary, from: ~r/^MyApp\\.Web/, to: ~r/^MyApp\\.Repo\\.Internal/)
        end

        test "domain has restricted dependencies", %{boundary: boundary} do
          assert_boundary(boundary,
            modules: ~r/^MyApp\\.Domain/,
            allow: [~r/^MyApp\\.Schema/]
          )
        end
      end

  `use AssertBoundary, app: :my_app` does three things:

  1. Imports `AssertBoundary.Assertions` (`refute_calls/2`, `assert_calls/2`, `assert_boundary/2`).
  2. Adds a `setup_all` that builds the dependency graph for the given app.
  3. Makes the graph available as `%{boundary: graph}` in test context.
  """

  alias AssertBoundary.Graph

  @doc false
  defmacro __using__(opts) do
    quote do
      import AssertBoundary.Assertions
      import AssertBoundary.Graph, only: [under: 1]

      setup_all do
        %{boundary: AssertBoundary.graph(unquote(opts))}
      end
    end
  end

  @doc """
  Builds a dependency graph for the given application.

  Accepts a keyword list with an `:app` key, or an atom directly.

  ## Examples

      graph = AssertBoundary.graph(app: :my_app)
      graph = AssertBoundary.graph(:my_app)
  """
  @spec graph(atom() | keyword()) :: Graph.t()
  def graph(opts) when is_list(opts) do
    app = Keyword.fetch!(opts, :app)
    Graph.build(app)
  end

  def graph(app) when is_atom(app) do
    Graph.build(app)
  end
end