defmodule DaProductApp.Acquirer.ReversalConfig do
  @moduledoc """
  Centralized configuration for transaction reversal behavior.
  
  Provides access to all reversal-related timeouts, thresholds, and retry parameters.
  Configuration is read from Application environment (config/*.exs files).
  
  ## Configuration Keys
  
  All configuration is under `:da_product_app, :reversal` application environment.
  
  Example configuration:
  
      config :da_product_app, :reversal,
        stale_transaction_threshold_seconds: 45,
        response_timeout_seconds: 30,
        max_retry_attempts: 3,
        retry_delay_seconds: 60,
        connection_recovery_timeout_seconds: 30,
        startup_cleanup_age_threshold_minutes: 5,
        scheduled_cleanup_interval_minutes: 15,
        automatic_reversal_enabled: false
  
  ## Feature Flags
  
  - `automatic_reversal_enabled` - Master switch for automatic reversal functionality
  - Defaults to `false` for safety, must be explicitly enabled in production
  
  ## Usage
  
      iex> ReversalConfig.response_timeout()
      30
      
      iex> ReversalConfig.automatic_reversal_enabled?()
      false
  """

  @doc """
  Get stale transaction threshold in seconds.
  
  Transactions older than this threshold are considered stale and require reversal.
  Default: 45 seconds
  """
  @spec stale_transaction_threshold :: non_neg_integer()
  def stale_transaction_threshold do
    get_config(:stale_transaction_threshold_seconds, 45)
  end

  @doc """
  Get response timeout in seconds.
  
  Maximum time to wait for response from upstream before marking transaction as timed out.
  Default: 30 seconds
  """
  @spec response_timeout :: non_neg_integer()
  def response_timeout do
    get_config(:response_timeout_seconds, 30)
  end

  @doc """
  Get maximum retry attempts for reversal.
  
  After this many failed reversal attempts, transaction is marked for manual review.
  Default: 3 attempts
  """
  @spec max_retry_attempts :: non_neg_integer()
  def max_retry_attempts do
    get_config(:max_retry_attempts, 3)
  end

  @doc """
  Get base retry delay in seconds.
  
  Base delay used for exponential backoff calculation.
  Default: 60 seconds
  """
  @spec retry_delay_seconds :: non_neg_integer()
  def retry_delay_seconds do
    get_config(:retry_delay_seconds, 60)
  end

  @doc """
  Get connection recovery timeout in seconds.
  
  Time to wait for connection recovery before initiating reversal for affected transactions.
  Default: 30 seconds
  """
  @spec connection_recovery_timeout :: non_neg_integer()
  def connection_recovery_timeout do
    get_config(:connection_recovery_timeout_seconds, 30)
  end

  @doc """
  Get startup cleanup age threshold in minutes.
  
  On application startup, transactions older than this threshold are processed for reversal.
  Default: 5 minutes
  """
  @spec startup_cleanup_age_threshold_minutes :: non_neg_integer()
  def startup_cleanup_age_threshold_minutes do
    get_config(:startup_cleanup_age_threshold_minutes, 5)
  end

  @doc """
  Get scheduled cleanup interval in minutes.
  
  How frequently the ReversalCleanupWorker runs to detect stuck transactions.
  Default: 15 minutes
  """
  @spec scheduled_cleanup_interval_minutes :: non_neg_integer()
  def scheduled_cleanup_interval_minutes do
    get_config(:scheduled_cleanup_interval_minutes, 15)
  end

  @doc """
  Check if automatic reversal is enabled.
  
  Master feature flag for automatic reversal functionality.
  When disabled, reversals must be manually triggered.
  Default: false (for safety)
  """
  @spec automatic_reversal_enabled? :: boolean()
  def automatic_reversal_enabled? do
    get_config(:automatic_reversal_enabled, false)
  end

  @doc """
  Check if cleanup worker is enabled.
  
  Controls whether ReversalCleanupWorker starts as part of supervision tree.
  Default: false (controlled separately from automatic_reversal_enabled)
  """
  @spec cleanup_worker_enabled? :: boolean()
  def cleanup_worker_enabled? do
    get_config(:cleanup_worker_enabled, false)
  end

  @doc """
  Check if retry worker is enabled.
  
  Controls whether retry mechanism is active for failed reversals.
  Default: false
  """
  @spec retry_worker_enabled? :: boolean()
  def retry_worker_enabled? do
    get_config(:retry_worker_enabled, false)
  end

  @doc """
  Check if connection loss handler is enabled.
  
  Controls whether connection loss triggers automatic reversals.
  Default: false
  """
  @spec connection_loss_handler_enabled? :: boolean()
  def connection_loss_handler_enabled? do
    get_config(:connection_loss_handler_enabled, false)
  end

  @doc """
  Calculate exponential backoff delay for retry attempt.
  
  Uses exponential backoff strategy: base_delay * 2^(attempt_number - 1)
  
  ## Examples
  
      iex> ReversalConfig.calculate_backoff_delay(1)
      60  # 60 * 2^0 = 60 seconds
      
      iex> ReversalConfig.calculate_backoff_delay(2)
      120  # 60 * 2^1 = 120 seconds
      
      iex> ReversalConfig.calculate_backoff_delay(3)
      240  # 60 * 2^2 = 240 seconds
  
  ## Parameters
  
    - `attempt_number` - The current retry attempt number (1-based)
  
  ## Returns
  
    Delay in seconds (integer)
  """
  @spec calculate_backoff_delay(non_neg_integer()) :: non_neg_integer()
  def calculate_backoff_delay(attempt_number) when is_integer(attempt_number) and attempt_number > 0 do
    base_delay = retry_delay_seconds()
    # Exponential backoff: base * 2^(attempt - 1)
    (base_delay * :math.pow(2, attempt_number - 1))
    |> round()
  end

  def calculate_backoff_delay(_), do: retry_delay_seconds()

  @doc """
  Get reversal reason code mapping.
  
  Maps reversal reason strings to ISO 8583 response codes.
  
  ## Parameters
  
    - `reason` - Reversal reason string
  
  ## Returns
  
    ISO response code (string)
  """
  @spec map_reason_to_code(String.t()) :: String.t()
  def map_reason_to_code(reason) when is_binary(reason) do
    case reason do
      "TIMEOUT" -> "68"  # Response received too late
      "RESPONSE_TIMEOUT" -> "68"
      "CONNECTION_LOST" -> "91"  # Issuer or switch inoperative
      "STALE_TRANSACTION" -> "68"
      "DB_CREATE_FAILED" -> "96"  # System malfunction
      "DB_DELETE_FAILED" -> "96"
      "STARTUP_CLEANUP" -> "68"
      "ERROR_STATE" -> "96"
      _ -> "68"  # Default: Response received too late
    end
  end

  def map_reason_to_code(_), do: "68"

  @doc """
  Get all configuration values as a map.
  
  Useful for debugging and logging configuration state.
  """
  @spec all_config :: map()
  def all_config do
    %{
      stale_transaction_threshold_seconds: stale_transaction_threshold(),
      response_timeout_seconds: response_timeout(),
      max_retry_attempts: max_retry_attempts(),
      retry_delay_seconds: retry_delay_seconds(),
      connection_recovery_timeout_seconds: connection_recovery_timeout(),
      startup_cleanup_age_threshold_minutes: startup_cleanup_age_threshold_minutes(),
      scheduled_cleanup_interval_minutes: scheduled_cleanup_interval_minutes(),
      automatic_reversal_enabled: automatic_reversal_enabled?(),
      cleanup_worker_enabled: cleanup_worker_enabled?(),
      retry_worker_enabled: retry_worker_enabled?(),
      connection_loss_handler_enabled: connection_loss_handler_enabled?()
    }
  end

  # Private helper to read config with default
  defp get_config(key, default) do
    Application.get_env(:da_product_app, :reversal, [])
    |> Keyword.get(key, default)
  end
end