refactor: define TicketCreate transaction model (#1547)

- Defines a TypeScript type for TicketCreate
- Provides an optional function to users for verifying a TicketCreate instance at runtime: verifyTicketCreate()
- Adds tests for verifyTicketCreate()

src/models/transactions/index.ts

@@ -5,6 +5,7 @@ export * from './checkCancel'
 export * from './checkCash'
 export * from './checkCreate'
 export * from './signerListSet'
+export * from './ticketCreate'
 export * from './depositPreauth'
 export * from './escrowCancel'
 export * from './escrowFinish'

src/models/transactions/ticketCreate.ts

@@ -0,0 +1,30 @@
+import { ValidationError } from '../../common/errors'
+import { BaseTransaction, verifyBaseTransaction } from './common'
+
+export interface TicketCreate extends BaseTransaction {
+    TransactionType: 'TicketCreate'
+    TicketCount: number
+}
+
+/**
+ * 
+ * @param {TicketCreate} tx A TicketCreate Transaction.
+ * @returns {void}
+ * @throws {ValidationError} When the TicketCreate is malformed.
+ */
+ export function verifyTicketCreate(tx: TicketCreate): void {
+    verifyBaseTransaction(tx)
+    const { TicketCount } = tx
+
+    if (TicketCount === undefined) {
+        throw new ValidationError('TicketCreate: missing field TicketCount')
+    }
+
+    if (typeof TicketCount !== 'number') {
+        throw new ValidationError('TicketCreate: TicketCount must be a number')
+    }
+
+    if (!Number.isInteger(TicketCount) || TicketCount < 1 || TicketCount > 250) {
+        throw new ValidationError('TicketCreate: TicketCount must be an integer from 1 to 250')
+    }
+}

src/models/transactions/transaction.ts

@@ -11,6 +11,7 @@ import { OfferCancel } from "./offerCancel"
 import { OfferCreate } from "./offerCreate"
 import { PaymentTransaction } from "./paymentTransaction"
 import { SignerListSet } from "./signerListSet"
+import { TicketCreate } from "./ticketCreate"
 import { TrustSet } from "./trustSet"
 
 export type Transaction =
@@ -31,7 +32,7 @@ export type Transaction =
 //   | PaymentChannelFund
 //   | SetRegularKey
      | SignerListSet
-//   | TicketCreate
+     | TicketCreate
      | TrustSet
 
 export interface TransactionAndMetadata {