defmodule ActorSimulation.GeneratorMetadata do
  @moduledoc """
  Utilities for tracking which test file/function generated an HTML report.

  This helps maintain traceability between generated reports and their source code.
  """

  @doc """
  Extracts generator metadata from the current stack trace.

  Returns a map with `:test_file`, `:test_name`, and `:generator_function` keys,
  or `nil` if not called from a test.

  ## Example

      metadata = GeneratorMetadata.from_stacktrace()
      # => %{
      #   test_file: "test/mermaid_report_test.exs",
      #   test_name: "generates pipeline report",
      #   generator_function: "ActorSimulation.MermaidReportGenerator.generate_report/2"
      # }
  """
  def from_stacktrace do
    # Get the stack trace
    stacktrace = Process.info(self(), :current_stacktrace) |> elem(1)

    # Find test info and generator function from stacktrace
    test_info = find_test_info(stacktrace)
    generator_function = find_generator_function(stacktrace)

    if test_info do
      Map.put(test_info, :generator_function, generator_function)
    else
      nil
    end
  end

  @doc """
  Generates an HTML comment with generator metadata.

  ## Example

      comment = GeneratorMetadata.to_html_comment(metadata)
      # => "<!--\\n  Generated by: test/mermaid_report_test.exs\\n  Test: generates pipeline report\\n  Generator: ActorSimulation.MermaidReportGenerator.generate_report/2\\n-->\\n"
  """
  def to_html_comment(metadata) when is_map(metadata) do
    generator_line =
      if metadata[:generator_function] do
        "  Generator: #{metadata.generator_function}\n"
      else
        ""
      end

    """
    <!--
      Generated by: #{metadata.test_file}
      Test: #{metadata.test_name}
    #{generator_line}-->
    """
  end

  def to_html_comment(nil), do: ""

  # Private functions

  defp find_test_info(stacktrace) do
    stacktrace
    |> Enum.find_value(fn {_module, function, _arity, location} ->
      # Match ExUnit test functions
      if is_atom(function) && String.starts_with?(Atom.to_string(function), "test ") do
        test_file = Keyword.get(location, :file, "unknown")
        test_name = function |> Atom.to_string() |> String.replace_prefix("test ", "")
        %{test_file: test_file, test_name: test_name}
      else
        nil
      end
    end)
  end

  defp find_generator_function(stacktrace) do
    # Look for known generator modules in the stacktrace
    generator_modules = [
      ActorSimulation.MermaidReportGenerator,
      ActorSimulation.OMNeTPPGenerator,
      ActorSimulation.CAFGenerator,
      ActorSimulation.PonyGenerator,
      ActorSimulation.PhonyGenerator,
      ActorSimulation.VlingoGenerator
    ]

    stacktrace
    |> Enum.find_value(fn {module, function, arity, _location} ->
      if module in generator_modules do
        "#{inspect(module)}.#{function}/#{arity}"
      else
        nil
      end
    end) || "unknown"
  end
end