defmodule CPSolver.Propagator.Variable do
  alias CPSolver.Variable
  alias CPSolver.Propagator

  @propagator_events Propagator.propagator_events()

  @variable_op_results_key :variable_op_results
  defdelegate domain(var), to: Variable
  defdelegate size(var), to: Variable
  defdelegate min(var), to: Variable
  defdelegate max(var), to: Variable
  defdelegate fixed?(var), to: Variable
  defdelegate contains?(var, val), to: Variable

  def remove(var, val) do
    wrap(:remove, var, val)
  end

  def removeAbove(var, val) do
    wrap(:removeAbove, var, val)
  end

  def removeBelow(var, val) do
    wrap(:removeBelow, var, val)
  end

  def fix(var, val) do
    wrap(:fix, var, val)
  end

  def set_propagate_on(%Variable{} = var, propagator_event)
      when propagator_event in @propagator_events do
    Map.put(var, :propagate_on, propagator_event)
  end

  defp wrap(op, var, val) do
    save_in_dict(var, apply(Variable, op, [var, val]))
  end

  defp save_in_dict(var, result) do
    result
    |> tap(fn
      :fail ->
        Process.put(@variable_op_results_key, {:fail, var.id})

      _ ->
        case get_variable_ops() do
          {:fail, _var} ->
            :fail

          current ->
            Process.put(@variable_op_results_key, Map.put(current, var.id, result))
        end
    end)
  end

  def get_variable_ops() do
    Process.get(@variable_op_results_key, Map.new())
  end

  def reset_variable_ops() do
    Process.delete(@variable_op_results_key)
  end

  def plus(:fail, _) do
    :fail
  end

  def plus(_, :fail) do
    :fail
  end

  def plus(a, b) do
    a + b
  end
end