text: export class SingularPurchase {
      constructor(revenue, currency) {
          this._values = {
              r: revenue,
              pcc: currency,
              is_revenue_event: true
          };
      }
  
      getPurchaseValues() {
          return this._values;
      }
  }
  
  export class SingularIOSPurchase extends SingularPurchase {
      constructor(revenue, currency, productId, transactionId, receipt) {
          super(revenue, currency);
          this._values = {
              ...this._values,
              pk: productId,
              pti: transactionId,
              ptr: receipt,
          };
      }
  }
  
  export class SingularAndroidPurchase extends SingularPurchase {
      constructor(revenue, currency, receipt, signature) {
          super(revenue, currency);
          this._values = {
              ...this._values,
              receipt: receipt,
              receipt_signature: signature,
              ptr: receipt,
          };
      }
  }
  