SEP-31: make sure we get the amount_in from GET /transactions before …

…sending the stellar payment (#275)

### What

Make sure we get the `amount_in` from `GET /transactions` before sending the stellar payment.

### Why

To be consistent with stellar/stellar-protocol#1203.

packages/demo-wallet-client/src/ducks/sep31Send.ts

@@ -21,6 +21,7 @@ import {
   pollTransactionUntilComplete,
 } from "demo-wallet-shared/build/methods/sep31Send";
 import { checkTomlForFields } from "demo-wallet-shared/build/methods/checkTomlForFields";
+import { Sep31GetTransaction } from "demo-wallet-shared/build/types/types";
 
 import {
   Asset,
@@ -324,15 +325,20 @@ export const submitSep31SendTransactionAction = createAsyncThunk<
       });
 
       // Poll transaction until ready
-      await pollTransactionUntilReady({
+      const getSep31Tx: Sep31GetTransaction = await pollTransactionUntilReady({
         sendServer,
         transactionId: postResponse.transactionId,
         token,
       });
 
+      const amountIn = getSep31Tx?.transaction?.amount_in;
+      if (amountIn === undefined) {
+        throw new Error(`"amount_in" is missing from the GET /transaction response`);
+      }
+
       // Send payment
       await sendPayment({
-        amount: amount.amount,
+        amount: amountIn,
         assetCode,
         assetIssuer,
         receiverAddress: postResponse.receiverAddress,

packages/demo-wallet-shared/methods/sep31Send/pollTransactionUntilReady.ts

@@ -1,5 +1,5 @@
 import { log } from "../../helpers/log";
-import { TransactionStatus } from "../../types/types";
+import { TransactionStatus, Sep31GetTransaction } from "../../types/types";
 
 export const pollTransactionUntilReady = async ({
   sendServer,
@@ -15,6 +15,7 @@ export const pollTransactionUntilReady = async ({
   });
 
   let transactionStatus;
+  let resultJson: Sep31GetTransaction = {};
 
   while (transactionStatus !== TransactionStatus.PENDING_SENDER) {
     log.request({ title: `GET \`/transactions/${transactionId}\`` });
@@ -32,14 +33,16 @@ export const pollTransactionUntilReady = async ({
     }
 
     // eslint-disable-next-line no-await-in-loop
-    const resultJson = await result.json();
+    resultJson = await result.json();
     log.response({
       title: `GET \`/transactions/${transactionId}\``,
       body: resultJson,
     });
-    transactionStatus = resultJson.transaction.status;
+    transactionStatus = resultJson.transaction?.status;
 
     // eslint-disable-next-line no-await-in-loop
     await new Promise((resolve) => setTimeout(resolve, 2000));
   }
+
+  return resultJson;
 };

packages/demo-wallet-shared/types/types.ts

@@ -277,6 +277,30 @@ export interface Sep31SendInitialState {
   status: ActionStatus | undefined;
 }
 
+export interface Sep31GetTransaction {
+  transaction?: {
+    id: string;
+    status: string;
+    status_eta?: number;
+    amount_in?: string;
+    amount_in_asset?: string;
+    amount_out?: string;
+    amount_out_asset?: string;
+    amount_fee?: string;
+    amount_fee_asset?: string;
+    stellar_account_id: string;
+    stellar_memo_type: string;
+    stellar_memo: string;
+    started_at?: string;
+    completed_at?: string;
+    stellar_transaction_id?: string;
+    external_transaction_id?: string;
+    refunded?: boolean;
+    required_info_message?: string;
+    required_info_updates?: any;
+  };
+}
+
 export interface Setting {
   [key: string]: any;
 }