defmodule DaProductApp.Repo.Migrations.CreateInterchangeRates do
  use Ecto.Migration

  @moduledoc """
  Interchange rate master table — Mercury's cost per transaction from card schemes.

  Used in Settlement MIS to calculate Mercury's cost and profitability at
  transaction level (spec requirement: interchange rates in Settlement MIS).

  If actual interchange is not received from YSP for a transaction, the system
  falls back to this master table to estimate cost using card_type_id + scheme.

  Data source: Interchange table from YSP (pending — table created now).
  """

  def change do
    create table(:interchange_rates) do
      add :card_type_id, :bigint, null: false,
          comment: "shukria_mms card_types.id"
      add :card_type_code, :string, size: 50,
          comment: "Denormalized for display"
      add :scheme_name, :string, size: 30,
          comment: "VISA | MASTERCARD | AMEX | UNIONPAY"
      add :rate_percentage, :decimal, precision: 8, scale: 4, null: false
      add :fixed_fee, :decimal, precision: 10, scale: 2, null: false, default: 0
      add :effective_from, :date
      add :effective_to, :date
      add :status, :integer, null: false, default: 1,
          comment: "1 = active, 0 = inactive"
      add :notes, :text
      add :inserted_at, :naive_datetime, null: false
      add :updated_at, :naive_datetime, null: false
    end

    create index(:interchange_rates, [:card_type_id])
    create index(:interchange_rates, [:scheme_name])
    create index(:interchange_rates, [:effective_from, :effective_to])
    create index(:interchange_rates, [:status])
  end
end