Handle Fast iOS SDK Events

/// The outcome of the Fast checkout flow.
public enum FastEventType: Int {
  /// Emitted when the order has been submitted through Fast Checkout.
  case orderCreated = 0
  /// Emitted when the order has changed while inside the Fast Checkout.
  case orderUpdated = 1
  /// Emitted when the order has been finalized from inside Fast Checkout,
  /// either when the post-purchase order batching window times out or
  /// when Fast Checkout is manually dismissed.
  case orderCompleted = 2
  /// Emitted when the order has been cancelled from inside Fast Checkout
  case orderCancelled = 3
  /// Emitted when checkout has failed with an error.
  case orderFailed = 4
  /// Emitted at SDK exit
  case closed = 5
}

public enum FastEventInfoKey: String {
  case error
  case purchaseInfo
}

// Purchase details for an order.
@objc public class PurchaseInfo: NSObject {
  // The ID of a purchase as represented in the seller's backend platform.
  @objc public let platformId: String
  // The purchase total, including tax, shipping, and discounts.
  @objc public let revenue: String
  // Total taxes for this purchase.
  @objc public let tax: String
  // Cost of shipping for this purchase.
  @objc public let shipping: String
  // The 3-character ISO 4217 currency code for the purchase.
  @objc public let countryCode: String
  // Coupon, if any, included in this purchase.
  @objc public let coupon: String?
  // Time of checkout.
  @objc public let checkoutTime: Date?
  // The items included in this purchase.
  @objc public let items: [PurchaseItem]
}

/// Object describing a product that is part of a purchase.
@objc public class PurchaseItem: NSObject {
  /// The ID of a product as represented in the seller's backend platform.
  @objc public let platformId: String
  /// The ID of a product variant as represented in the seller's backend platform.
  @objc public let platformVariantId: String?
  /// The price of a product (not including discounts, tax, etc.).
  @objc public let price: String
  /// The name of a product as displayed to the user.
  @objc public let name: String
  /// The 3-character ISO 4217 currency code for the item.
  @objc public let countryCode: String
  /// The number of this item that was included in a purchase.
  @objc public let quantity: Int
  /// Any coupon applied to this product.
  @objc public let coupon: String?
}