refactor: define typescript types for OfferCancel Transaction Model (#1512)

* define typescript types for OfferCancel Transaction Model

src/models/transactions/index.ts

@@ -1,5 +1,6 @@
 export * from './transaction'
 export * from './offerCreate'
+export * from './offerCancel'
 export * from './checkCreate'
 export * from './checkCash'
 export * from './checkCancel'

src/models/transactions/offerCancel.ts

@@ -0,0 +1,24 @@
+import { ValidationError } from "../../common/errors"
+import { BaseTransaction, verifyBaseTransaction } from "./common"
+
+export interface OfferCancel extends BaseTransaction {
+    TransactionType: "OfferCancel"
+    OfferSequence: number
+}
+
+/**
+ * Verify the form and type of an OfferCancel at runtime.
+ * 
+ * @param tx - An OfferCancel Transaction
+ * @returns - Void.
+ * @throws - When the OfferCancel is Malformed.
+ */
+ export function verifyOfferCancel(tx: OfferCancel): void {
+    verifyBaseTransaction(tx)
+
+    if (tx.OfferSequence === undefined)
+        throw new ValidationError("OfferCancel: missing field OfferSequence")
+
+    if (typeof tx.OfferSequence !== 'number')
+        throw new ValidationError("OfferCancel: invalid OfferSequence")
+}

src/models/transactions/transaction.ts

@@ -1,13 +1,17 @@
-import Metadata from "../common/metadata";
-import { OfferCreate } from "./offerCreate";
-import { CheckCash } from "./checkCash";
-import { CheckCancel } from "./checkCancel";
-import { CheckCreate } from "./checkCreate";
-import { SignerListSet } from "./signerListSet";
+import Metadata from "../common/metadata"
+import { OfferCreate } from "./offerCreate"
+import { OfferCancel } from "./offerCancel"
+import { CheckCash } from "./checkCash"
+import { CheckCancel } from "./checkCancel"
+import { CheckCreate } from "./checkCreate"
+import { SignerListSet } from "./signerListSet"
 
 export type Transaction =
 //     AccountSet
 //   | AccountDelete
+//   | CheckCancel
+//   | CheckCash
+//   | CheckCreate
        CheckCancel
      | CheckCash
      | CheckCreate
@@ -15,6 +19,7 @@ export type Transaction =
 //   | EscrowCancel
 //   | EscrowCreate
 //   | EscrowFinish
+     | OfferCancel
 //   | OfferCancel
      | OfferCreate
 //   | PaymentTransaction