elipl/debug.exs

defmodule Tdd.Debug do
  @moduledoc """
  Provides macros to wrap `def` and `defp` for simple function call/return tracing.
  Logs arguments as a list and return values using `IO.inspect`.
  """

  # --- Agent for Tracing State ---
  @agent_name Tdd.Debug.StateAgent

  def init_agent_if_needed do
    case Process.whereis(@agent_name) do
      nil -> Agent.start_link(fn -> MapSet.new() end, name: @agent_name)
      _pid -> :ok
    end
    :ok
  end

  def add_traced_pid(pid) when is_pid(pid) do
    init_agent_if_needed()
    Agent.update(@agent_name, &MapSet.put(&1, pid))
  end

  def remove_traced_pid(pid) when is_pid(pid) do
    case Process.whereis(@agent_name) do
      nil -> :ok
      agent_pid -> Agent.cast(agent_pid, fn state -> MapSet.delete(state, pid) end)
    end
  end

  def is_pid_traced?(pid) when is_pid(pid) do
    case Process.whereis(@agent_name) do
      nil ->
        false
      agent_pid ->
        try do
          Agent.get(agent_pid, &MapSet.member?(&1, pid), :infinity)
        rescue
          _e in [Exit, ArgumentError] -> false
        end
    end
  end

  # --- Tracing Control Functions ---
  @doc "Enables function call tracing for the current process."
  def enable_tracing do
    pid_to_trace = self()
    add_traced_pid(pid_to_trace)
    ref = Process.monitor(pid_to_trace)

    Process.spawn(fn ->
      receive do
        {:DOWN, ^ref, :process, ^pid_to_trace, _reason} ->
          remove_traced_pid(pid_to_trace)
      after
        3_600_000 -> # 1 hour safety timeout
          remove_traced_pid(pid_to_trace)
      end
    end, [:monitor])
    :ok
  end

  @doc "Disables function call tracing for the current process."
  def disable_tracing do
    remove_traced_pid(self())
    :ok
  end

  @doc "Runs the given 0-arity function with tracing enabled, then disables it."
  def run(fun) when is_function(fun, 0) do
    enable_tracing()
    try do
      fun.()
    after
      disable_tracing()
    end
  end

  # --- Process Dictionary for Call Depth ---
  defp get_depth, do: Process.get(:tdd_debug_depth, 0)
  def increment_depth do
    new_depth = get_depth() + 1
    Process.put(:tdd_debug_depth, new_depth)
    new_depth
  end
  def decrement_depth do
    new_depth = max(0, get_depth() - 1)
    Process.put(:tdd_debug_depth, new_depth)
    new_depth
  end

  # --- Core Macro Logic ---
  defmacro __using__(_opts) do
    quote do
      import Kernel, except: [def: 1, def: 2, defp: 1, defp: 2]
      import Tdd.Debug
      require Tdd.Debug
    end
  end

  @doc false
  defmacro def(call, clauses \\ Keyword.new()) do
    generate_traced_function(:def, call, clauses, __CALLER__)
  end

  @doc false
  defmacro defp(call, clauses \\ Keyword.new()) do
    generate_traced_function(:defp, call, clauses, __CALLER__)
  end
defp is_simple_variable_ast?(ast_node) do
    case ast_node do
    {var_name, _meta, _context} when is_atom(var_name) ->
      var_name != :_
_ -> false 
  end
  end
       defp generate_traced_function(type, call_ast, clauses, caller_env) do
    require Macro # Good practice

    {function_name_ast, meta_call, original_args_patterns_ast_nullable} = call_ast
    original_args_patterns_ast_list = original_args_patterns_ast_nullable || []

    original_body_ast =
      (if Keyword.keyword?(clauses) do
         Keyword.get(clauses, :do, clauses)
       else
         clauses
       end) || quote(do: nil)

    mapped_and_generated_vars_tuples =
      Enum.map(Enum.with_index(original_args_patterns_ast_list), fn {original_pattern_ast, index} ->
        # __td_arg_N__ is for logging, make it hygienic with `nil` context (or __MODULE__)
        td_arg_var = Macro.var(String.to_atom("__td_arg_#{index}__"), nil)

        {final_pattern_for_head, rhs_for_td_arg_assignment} =
          case original_pattern_ast do
            # 1. Ignored variable: `_`
            # AST: {:_, meta, context_module_or_nil}
            {:_, _, _} = underscore_ast ->
              {underscore_ast, quote(do: :__td_ignored_argument__)}

            # 2. Assignment pattern: `var = pattern` or `var = _`
            # AST: {:=, meta, [lhs, rhs_of_assign]}
            {:=, _meta_assign, [lhs_of_assign, _rhs_of_assign]} = assignment_pattern_ast ->
              if is_simple_variable_ast?(lhs_of_assign) do
                {assignment_pattern_ast, lhs_of_assign} # Head uses `var = pattern`, log `var`
              else
                # LHS is complex (e.g., `%{key: v} = pattern`), capture the whole value.
                captured_val_var = Macro.unique_var(String.to_atom("tdc_assign_#{index}"), Elixir)
                new_head_pattern = quote do unquote(captured_val_var) = unquote(assignment_pattern_ast) end
                {new_head_pattern, captured_val_var}
              end

            # 3. Default argument: `pattern_before_default \\ default_value`
            # AST: {:\|, meta, [pattern_before_default, default_value_ast]}
            {:\\, _meta_default, [pattern_before_default, _default_value_ast]} = default_arg_pattern_ast ->
              cond do
                # 3a. `var \\ default`
                is_simple_variable_ast?(pattern_before_default) ->
                  {default_arg_pattern_ast, pattern_before_default}

                # 3b. `(var = inner_pattern) \\ default`
                match?({:=, _, [lhs_inner_assign, _]}, pattern_before_default) and
                    is_simple_variable_ast?(pattern_before_default |> elem(2) |> Enum.at(0)) ->
{:=, _, [lhs_inner_assign, _]}= pattern_before_default
                  # `lhs_inner_assign` is the var on the left of `=`
                  {default_arg_pattern_ast, lhs_inner_assign}

                # 3c. `(complex_pattern) \\ default` or `(_ = inner_pattern) \\ default` etc.
                true ->
                  captured_val_var = Macro.unique_var(String.to_atom("tdc_def_#{index}"), Elixir)
                  new_head_pattern = quote do unquote(captured_val_var) = unquote(default_arg_pattern_ast) end
                  {new_head_pattern, captured_val_var}
              end

            # 4. Simple variable `var` (checked using our helper)
            # or other complex patterns/literals not caught above.
            ast_node ->
              if is_simple_variable_ast?(ast_node) do
                {ast_node, ast_node} # Head uses `var`, log `var`
              else
                # It's a complex pattern (e.g., `%{a:x}`, `[h|t]`) or a literal not assignable to.
                captured_val_var = Macro.unique_var(String.to_atom("tdc_pat_#{index}"), Elixir)
                new_head_pattern = quote do unquote(captured_val_var) = unquote(ast_node) end
                {new_head_pattern, captured_val_var}
              end
          end

        assignment_ast = quote do unquote(td_arg_var) = unquote(rhs_for_td_arg_assignment) end
        {final_pattern_for_head, assignment_ast, td_arg_var}
      end)

    {new_args_patterns_for_head_list, assignments_for_logging_vars_ast_list, generated_vars_to_log_asts} =
      if mapped_and_generated_vars_tuples == [],
        do: {[], [], []},
        else:  mapped_and_generated_vars_tuples |> Enum.map(&Tuple.to_list(&1)) |> Enum.zip()|> Enum.map(&Tuple.to_list(&1))
          |> then(fn [a, b, c] -> {a, b, c} end)
        # Enum.unzip(mapped_and_generated_vars_tuples)

    new_call_ast = {function_name_ast, meta_call, new_args_patterns_for_head_list}

    traced_body_inner_ast =
      quote do
        unquote_splicing(assignments_for_logging_vars_ast_list)

        if Tdd.Debug.is_pid_traced?(self()) do
          current_print_depth = Tdd.Debug.increment_depth()
          indent = String.duplicate("  ", current_print_depth - 1)
          runtime_arg_values = [unquote_splicing(generated_vars_to_log_asts)]

          actual_module_name_str = Atom.to_string(unquote(caller_env.module))

          # The function_name_ast is resolved at macro expansion time.
          # If it's `def foo(...)`, `unquote(function_name_ast)` becomes `:foo`.
          # If `def unquote(name_var)(...)`, it resolves `name_var`.
          resolved_fn_name = unquote(function_name_ast)
          printable_function_name_str =
            if is_atom(resolved_fn_name) do
              Atom.to_string(resolved_fn_name)
            else
              Macro.to_string(resolved_fn_name) # For complex names / operators if AST passed
            end

          IO.puts(
            "#{indent}CALL: #{actual_module_name_str}.#{printable_function_name_str}"
          )
          IO.puts(
            "#{indent}  ARGS: #{inspect(runtime_arg_values)}"
          )

          try do
            result = unquote(original_body_ast)
            _ = Tdd.Debug.decrement_depth()
            IO.puts(
              "#{indent}RETURN from #{actual_module_name_str}.#{printable_function_name_str}: #{inspect(result)}"
            )
            result
          rescue
            exception_class ->
              error_instance = exception_class
              stacktrace = __STACKTRACE__
              _ = Tdd.Debug.decrement_depth()
              IO.puts(
                "#{indent}ERROR in #{actual_module_name_str}.#{printable_function_name_str}: #{inspect(error_instance)}"
              )
              reraise error_instance, stacktrace
          end
        else
          unquote(original_body_ast)
        end
      end

    final_definition_ast =
      quote location: :keep do
        Kernel.unquote(type)(
          unquote(new_call_ast),
          do: unquote(traced_body_inner_ast)
        )
      end

    final_definition_ast
  end

  # --- TDD Graph Printing (Kept as it was, not directly related to call tracing simplification) ---
  @doc "Prints a formatted representation of a TDD graph structure."
  def print_tdd_graph(id, store_module \\ Tdd.Store) do
    IO.puts("--- TDD Graph (ID: #{id}) ---")
    do_print_tdd_node(id, 0, MapSet.new(), store_module)
    IO.puts("------------------------")
  end

  defp do_print_tdd_node(id, indent_level, visited, store_module) do
    prefix = String.duplicate("  ", indent_level)

    if MapSet.member?(visited, id) do
      IO.puts("#{prefix}ID #{id} -> [Seen, recursive link]")
      :ok
    else
      new_visited = MapSet.put(visited, id)
      case store_module.get_node(id) do # Assumes store_module.get_node/1 exists
        {:ok, :true_terminal} -> IO.puts("#{prefix}ID #{id} -> TRUE")
        {:ok, :false_terminal} -> IO.puts("#{prefix}ID #{id} -> FALSE")
        {:ok, {var, y_id, n_id, dc_id}} ->
          IO.puts("#{prefix}ID #{id}: IF #{inspect(var)}")
          IO.puts("#{prefix}  ├─ Yes (to ID #{y_id}):")
          do_print_tdd_node(y_id, indent_level + 2, new_visited, store_module)
          IO.puts("#{prefix}  ├─ No  (to ID #{n_id}):")
          do_print_tdd_node(n_id, indent_level + 2, new_visited, store_module)
          IO.puts("#{prefix}  └─ DC  (to ID #{dc_id}):")
          do_print_tdd_node(dc_id, indent_level + 2, new_visited, store_module)
        {:error, reason} ->
          IO.puts("#{prefix}ID #{id}: ERROR - #{reason}")
      end
    end
  end
end