defmodule TradeMachine.GMGradeV2.Pillars.CapFlexibility.CurrentCapPosition do
  @moduledoc """
  Scores AVC's Current Cap Position metric from a validated `CapState` snapshot.

  The financial zone and dollar cushions are engine-owned facts. This module
  only normalizes the applicable cushion by the season's salary cap and applies
  AVC's five scoring curves, including their intentional threshold cliffs.
  """

  alias TradeMachine.GMGradeV2.ModelVersion
  alias TradeMachine.GMGradeV2.Result.MetricResult

  @doc "Returns the full-precision Current Cap Position metric result."
  @spec score(map()) :: MetricResult.t()
  def score(%{
        season: season,
        financial_zone: zone,
        thresholds: thresholds,
        cushions: cushions
      }) do
    salary_cap = thresholds |> Map.fetch!(season) |> Map.fetch!(:salary_cap)
    score = zone_score(zone, cushions, salary_cap)

    %MetricResult{
      key: :current_cap_position,
      version: ModelVersion.model_version(),
      score: score,
      inputs: %{salary_cap: salary_cap},
      supporting: Map.put(cushions, :financial_zone, zone),
      explanation:
        "Current Cap Position scores the #{label(zone)} zone using its engine-calculated " <>
          "threshold cushion relative to the season's salary cap."
    }
  end

  @doc "Applies AVC's financial-zone curve to engine-calculated cushions."
  @spec zone_score(atom(), map(), pos_integer()) :: float()
  def zone_score(:below_cap, cushions, salary_cap) do
    60.0 + min(40.0, ratio(cushions.cap_room, salary_cap) * 200.0)
  end

  def zone_score(:over_cap_below_tax, cushions, salary_cap) do
    50.0 + min(10.0, ratio(cushions.tax_cushion, salary_cap) * 100.0)
  end

  def zone_score(:taxpayer_below_first_apron, cushions, salary_cap) do
    30.0 + min(20.0, ratio(cushions.first_apron_cushion, salary_cap) * 200.0)
  end

  def zone_score(:between_aprons, cushions, salary_cap) do
    10.0 + min(20.0, ratio(cushions.second_apron_cushion, salary_cap) * 200.0)
  end

  def zone_score(:above_second_apron, cushions, salary_cap) do
    max(0.0, 10.0 - ratio(cushions.second_apron_excess, salary_cap) * 200.0)
  end

  defp ratio(amount, salary_cap)
       when is_number(amount) and amount >= 0 and is_number(salary_cap) and salary_cap > 0,
       do: amount / salary_cap

  defp label(:below_cap), do: "below-cap"
  defp label(:over_cap_below_tax), do: "over-cap, below-tax"
  defp label(:taxpayer_below_first_apron), do: "taxpayer, below-first-apron"
  defp label(:between_aprons), do: "between-aprons"
  defp label(:above_second_apron), do: "above-second-apron"
end