payment-circle: polish responses and code (#88)

### What

Code polishes and small fixes. Changes details:
* Add `CircleWallet.defaultCapabilities()` and `CircleWallet.merchantAccountCapabilities()` to avoid hardcoding the capabilities every time.
* Update Account default `balances` and `unsettledBalances` values to null, so the JSON response works better when we don't have the balances. Otherwise, returning an empty list passes the impression the balances are empty when that might not be the case.
* Fix paginated responses cursors.
* Updated docs on how to get the bank deposit instructions.
* Solve warnings
* Update `CirclePaymentServiceTest` to reduce code repetition and standardize method names.
* Add all Circle asset names to the `CircleAsset` class, so we don't need to hardcode the string names.

core/src/main/java/org/stellar/anchor/paymentservice/Account.java

@@ -24,14 +24,14 @@ public class Account {
    */
   @NonNull public Account.Capabilities capabilities;
 
-  @NonNull public List<Balance> balances = new ArrayList<>();
+  @Nullable public List<Balance> balances;
 
   /**
    * The list of not-yet-available balances that are expected to settle shortly. These balances
    * could be cancelled or returned, in which cases they may never become available in the user
    * account.
    */
-  @NonNull public List<Balance> unsettledBalances = new ArrayList<>();
+  @Nullable public List<Balance> unsettledBalances;
 
   public Account(
       @NonNull PaymentNetwork paymentNetwork,

docs/payment-circle.md

@@ -157,7 +157,7 @@ Usage:
 // CircleWallet->CircleWallet
 Account source = new Account(PaymentNetwork.CIRCLE, "1000066041", Account.Capabilities(PaymentNetwork.CIRCLE, PaymentNetwork.STELLAR));
 Account destination = new Account(PaymentNetwork.CIRCLE, "1000067536", Account.Capabilities(PaymentNetwork.CIRCLE, PaymentNetwork.STELLAR));
-String currencyName = "circle:USD";
+String currencyName = CircleAsset.circleUSD();
 Payment payment = service.sendPayment(source, destination, currencyName, BigDecimal.valueOf(0.91)).block();
 System.out.println(payment);
 
@@ -172,7 +172,7 @@ System.out.println(payment);
 Account source = new Account(PaymentNetwork.CIRCLE, "1000066041", Account.Capabilities(PaymentNetwork.CIRCLE, PaymentNetwork.STELLAR));
 // The bank wire account should have been created in advance directly in Circle
 Account destination = new Account(PaymentNetwork.BANK_WIRE, "6c87da10-feb8-484f-822c-2083ed762d25", "[email protected]", Account.Capabilities());
-String currencyName = "iso4217:USD";
+String currencyName = CircleAsset.fiatUSD();
 Payment payment = service.sendPayment(source, destination, currencyName, BigDecimal.valueOf(0.91)).block();
 System.out.println(payment);
 ```
@@ -186,17 +186,17 @@ Usage:
 
 ```java
 // Deposit requirements to receive CircleWallet<-CircleWallet payments
-DepositRequirements config = DepositRequirements("1000066041", null, PaymentNetwork.CIRCLE, "circle:USD");
+DepositRequirements config = DepositRequirements("1000066041", PaymentNetwork.CIRCLE, CircleAsset.circleUSD());
 DepositInstructions instructions = service.getDepositInstructions(config).block();
 System.out.println(instructions);
 
 // Deposit requirements to receive CircleWallet<-Stellar payments
-DepositRequirements config = DepositRequirements("1000066041", null, PaymentNetwork.STELLAR, "circle:USD");
+DepositRequirements config = DepositRequirements("1000066041", PaymentNetwork.STELLAR, CircleAsset.circleUSD());
 DepositInstructions instructions = service.getDepositInstructions(config).block();
 System.out.println(instructions);
 
 // Deposit requirements to receive CircleWallet<-BankWire payments
-DepositRequirements config = DepositRequirements("1000066041", null, PaymentNetwork.BANK_WIRE, "circle:USD");
+DepositRequirements config = DepositRequirements("1000066041", null, PaymentNetwork.BANK_WIRE, "a4e76642-81c5-47ca-9229-ebd64efd74a7", CircleAsset.circleUSD());
 DepositInstructions instructions = service.getDepositInstructions(config).block();
 System.out.println(instructions);
 ```

payment-circle/src/main/java/org/stellar/anchor/paymentservice/circle/CirclePaymentService.java

@@ -15,6 +15,7 @@
 import org.stellar.anchor.paymentservice.circle.model.*;
 import org.stellar.anchor.paymentservice.circle.model.request.CircleSendTransactionRequest;
 import org.stellar.anchor.paymentservice.circle.model.response.*;
+import org.stellar.anchor.paymentservice.circle.util.CircleAsset;
 import org.stellar.anchor.paymentservice.circle.util.NettyHttpClient;
 import org.stellar.sdk.Network;
 import reactor.core.publisher.Mono;
@@ -335,7 +336,7 @@ public Mono<PaymentHistory> getAccountPaymentHistory(
     String afterTransfer = null, afterPayout = null, afterPayment = null;
     if (beforeCursor != null) {
       String[] beforeCursors = beforeCursor.split(":");
-      if (beforeCursors.length < 2) {
+      if (beforeCursors.length < 3) {
         throw new HttpException(400, "invalid before cursor");
       }
       beforeTransfer = beforeCursors[0];
@@ -344,7 +345,7 @@ public Mono<PaymentHistory> getAccountPaymentHistory(
     }
     if (afterCursor != null) {
       String[] afterCursors = afterCursor.split(":");
-      if (afterCursors.length < 2) {
+      if (afterCursors.length < 3) {
         throw new HttpException(400, "invalid after cursor");
       }
       afterTransfer = afterCursors[0];
@@ -361,31 +362,30 @@ public Mono<PaymentHistory> getAccountPaymentHistory(
         .map(
             args -> {
               String distributionAccId = args.getT1();
-              Account account =
-                  new Account(
-                      PaymentNetwork.CIRCLE,
-                      accountID,
-                      new Account.Capabilities(PaymentNetwork.CIRCLE, PaymentNetwork.STELLAR));
-              account.capabilities.set(
-                  PaymentNetwork.BANK_WIRE, distributionAccId.equals(account.id));
+              boolean isMerchantAccount = distributionAccId.equals(accountID);
+              Account.Capabilities capabilities =
+                  isMerchantAccount
+                      ? CircleWallet.merchantAccountCapabilities()
+                      : CircleWallet.defaultCapabilities();
+              Account account = new Account(PaymentNetwork.CIRCLE, accountID, capabilities);
 
               PaymentHistory transfersHistory =
                   args.getT2().toPaymentHistory(pageSize, account, distributionAccId);
               PaymentHistory payoutsHistory = args.getT3().toPaymentHistory(pageSize, account);
               PaymentHistory paymentsHistory = args.getT4().toPaymentHistory(pageSize, account);
               PaymentHistory result = new PaymentHistory(account);
 
-              String befTransfer = transfersHistory.getBeforeCursor();
-              String befPayout = payoutsHistory.getBeforeCursor();
-              String befPayment = paymentsHistory.getBeforeCursor();
-              if (befTransfer != null || befPayout != null || befPayment != null) {
+              String befTransfer = Objects.toString(transfersHistory.getBeforeCursor(), "");
+              String befPayout = Objects.toString(payoutsHistory.getBeforeCursor(), "");
+              String befPayment = Objects.toString(paymentsHistory.getBeforeCursor(), "");
+              if (!befTransfer.isEmpty() || !befPayout.isEmpty() || !befPayment.isEmpty()) {
                 result.setBeforeCursor(befTransfer + ":" + befPayout + ":" + befPayment);
               }
 
-              String aftTransfer = transfersHistory.getAfterCursor();
-              String aftPayout = payoutsHistory.getAfterCursor();
-              String aftPayment = paymentsHistory.getAfterCursor();
-              if (aftTransfer != null || aftPayout != null || aftPayment != null) {
+              String aftTransfer = Objects.toString(transfersHistory.getAfterCursor(), "");
+              String aftPayout = Objects.toString(payoutsHistory.getAfterCursor(), "");
+              String aftPayment = Objects.toString(paymentsHistory.getAfterCursor(), "");
+              if (!aftTransfer.isEmpty() || !aftPayout.isEmpty() || !aftPayment.isEmpty()) {
                 result.setAfterCursor(aftTransfer + ":" + aftPayout + ":" + aftPayment);
               }
 
@@ -444,6 +444,13 @@ private void validateSendPaymentInput(
       throw new HttpException(
           400, "the currency to be sent must contain the destination network schema");
     }
+    if (!CircleAsset.isSupported(currencyName, stellarNetwork)) {
+      throw new HttpException(
+          400,
+          String.format(
+              "the only supported currencies are %s, %s and %s.",
+              "circle:USD", "iso4217:USD", CircleAsset.stellarUSDC(stellarNetwork)));
+    }
   }
 
   /**
@@ -546,14 +553,17 @@ private void updatePaymentWireCapability(Payment payment, String distributionAcc
     Boolean isSourceWireEnabled =
         sourceAcc.paymentNetwork.equals(PaymentNetwork.BANK_WIRE)
             || distributionAccountId.equals(sourceAcc.id);
-    sourceAcc.capabilities.set(PaymentNetwork.BANK_WIRE, isSourceWireEnabled);
+    sourceAcc.capabilities.getReceive().put(PaymentNetwork.BANK_WIRE, isSourceWireEnabled);
 
     // fill destination account level
     Account destinationAcc = payment.getDestinationAccount();
     Boolean isDestinationWireEnabled =
         destinationAcc.paymentNetwork.equals(PaymentNetwork.BANK_WIRE)
             || distributionAccountId.equals(destinationAcc.id);
-    destinationAcc.capabilities.set(PaymentNetwork.BANK_WIRE, isDestinationWireEnabled);
+    destinationAcc
+        .capabilities
+        .getReceive()
+        .put(PaymentNetwork.BANK_WIRE, isDestinationWireEnabled);
   }
 
   /**
@@ -577,10 +587,7 @@ public Mono<Payment> sendPayment(
     // validate input
     validateSendPaymentInput(sourceAccount, destinationAccount, currencyName);
 
-    String rawCurrencyName =
-        currencyName.replace(destinationAccount.paymentNetwork.getCurrencyPrefix() + ":", "");
-    CircleBalance circleBalance =
-        new CircleBalance(rawCurrencyName, amount.toString(), stellarNetwork);
+    CircleBalance circleBalance = new CircleBalance("USD", amount.toString(), stellarNetwork);
 
     switch (destinationAccount.paymentNetwork) {
       case CIRCLE:
@@ -675,7 +682,7 @@ private void validateDepositRequirements(@NonNull DepositRequirements config)
       throw new HttpException(400, "beneficiary account id cannot be empty");
     }
 
-    if (!"circle:USD".equals(config.getBeneficiaryCurrencyName())) {
+    if (!CircleAsset.circleUSD().equals(config.getBeneficiaryCurrencyName())) {
       throw new HttpException(
           400, "the only receiving currency in a circle account is \"circle:USD\"");
     }

payment-circle/src/main/java/org/stellar/anchor/paymentservice/circle/model/CircleBalance.java

@@ -28,8 +28,7 @@ public CircleBalance(@NonNull String currency, @NonNull String amount) {
 
   public Balance toBalance(@NonNull PaymentNetwork destinationPaymentNetwork) {
     String currencyName = destinationPaymentNetwork.getCurrencyPrefix() + ":" + currency;
-    if (currencyName.equals("stellar:USD"))
-      currencyName = destinationPaymentNetwork.getCurrencyPrefix() + ":" + stellarUSDC();
+    if (currencyName.equals("stellar:USD")) currencyName = stellarUSDC();
 
     return new Balance(amount, currencyName);
   }

payment-circle/src/main/java/org/stellar/anchor/paymentservice/circle/model/CircleBlockchainAddress.java

@@ -28,16 +28,14 @@ public CircleBlockchainAddress(
 
   public DepositInstructions toDepositInstructions(
       String beneficiaryAccountId, Network stellarNetwork) {
-    String intermediaryCurrencyName =
-        PaymentNetwork.STELLAR.getCurrencyPrefix() + ":" + CircleAsset.stellarUSDC(stellarNetwork);
     return new DepositInstructions(
         beneficiaryAccountId,
         null,
         PaymentNetwork.CIRCLE,
         address,
         addressTag,
         PaymentNetwork.STELLAR,
-        intermediaryCurrencyName,
+        CircleAsset.stellarUSDC(stellarNetwork),
         null);
   }
 }

payment-circle/src/main/java/org/stellar/anchor/paymentservice/circle/model/CircleTransactionParty.java

@@ -87,14 +87,13 @@ public Account toAccount(@Nullable String distributionAccountId) {
             new Account.Capabilities(PaymentNetwork.STELLAR));
 
       case WALLET:
-        Account account =
-            new Account(
-                PaymentNetwork.CIRCLE,
-                id,
-                new Account.Capabilities(PaymentNetwork.CIRCLE, PaymentNetwork.STELLAR));
-        boolean isWireEnabled = distributionAccountId != null && distributionAccountId.equals(id);
-        account.capabilities.set(PaymentNetwork.BANK_WIRE, isWireEnabled);
-        return account;
+        boolean isMerchantAccount =
+            distributionAccountId != null && distributionAccountId.equals(id);
+        Account.Capabilities capabilities =
+            isMerchantAccount
+                ? CircleWallet.merchantAccountCapabilities()
+                : CircleWallet.defaultCapabilities();
+        return new Account(PaymentNetwork.CIRCLE, id, capabilities);
 
       case WIRE:
         return new Account(

payment-circle/src/main/java/org/stellar/anchor/paymentservice/circle/model/CircleWallet.java

@@ -1,11 +1,13 @@
 package org.stellar.anchor.paymentservice.circle.model;
 
+import java.util.ArrayList;
 import java.util.List;
 import java.util.stream.Collectors;
 import lombok.Data;
 import org.stellar.anchor.paymentservice.Account;
 import org.stellar.anchor.paymentservice.DepositInstructions;
 import org.stellar.anchor.paymentservice.PaymentNetwork;
+import org.stellar.anchor.paymentservice.circle.util.CircleAsset;
 
 @Data
 public class CircleWallet {
@@ -15,25 +17,33 @@ public class CircleWallet {
   String description;
   List<CircleBalance> balances;
 
-  public CircleWallet() {}
-
   public CircleWallet(String walletId) {
     this.walletId = walletId;
   }
 
   public Account.Capabilities getCapabilities() {
+    return "merchant".equals(type) ? merchantAccountCapabilities() : defaultCapabilities();
+  }
+
+  public static Account.Capabilities defaultCapabilities() {
     Account.Capabilities capabilities =
         new Account.Capabilities(PaymentNetwork.CIRCLE, PaymentNetwork.STELLAR);
-    capabilities.set(PaymentNetwork.BANK_WIRE, "merchant".equals(type));
+    capabilities.getSend().put(PaymentNetwork.BANK_WIRE, true);
     return capabilities;
   }
 
+  public static Account.Capabilities merchantAccountCapabilities() {
+    return new Account.Capabilities(
+        PaymentNetwork.CIRCLE, PaymentNetwork.STELLAR, PaymentNetwork.BANK_WIRE);
+  }
+
   public Account toAccount() {
     Account account = new Account(PaymentNetwork.CIRCLE, walletId, description, getCapabilities());
     account.setBalances(
         balances.stream()
             .map(circleBalance -> circleBalance.toBalance(PaymentNetwork.CIRCLE))
             .collect(Collectors.toList()));
+    account.setUnsettledBalances(new ArrayList<>());
     return account;
   }
 
@@ -45,7 +55,7 @@ public DepositInstructions toDepositInstructions() {
         walletId,
         null,
         PaymentNetwork.CIRCLE,
-        "circle:USD",
+        CircleAsset.circleUSD(),
         null);
   }
 }

payment-circle/src/main/java/org/stellar/anchor/paymentservice/circle/model/CircleWireDepositInstructions.java

@@ -5,6 +5,7 @@
 import lombok.Data;
 import org.stellar.anchor.paymentservice.DepositInstructions;
 import org.stellar.anchor.paymentservice.PaymentNetwork;
+import org.stellar.anchor.paymentservice.circle.util.CircleAsset;
 import org.stellar.sdk.responses.GsonSingleton;
 import shadow.com.google.common.reflect.TypeToken;
 import shadow.com.google.gson.Gson;
@@ -45,7 +46,7 @@ public DepositInstructions toDepositInstructions(String beneficiaryAccountId) {
         trackingRef,
         null,
         PaymentNetwork.BANK_WIRE,
-        "iso4217:USD",
+        CircleAsset.fiatUSD(),
         originalResponse);
   }
 }

payment-circle/src/main/java/org/stellar/anchor/paymentservice/circle/model/request/CircleSendTransactionRequest.java

@@ -21,7 +21,6 @@ public static CircleSendTransactionRequest forTransfer(
     CircleSendTransactionRequest req = new CircleSendTransactionRequest();
     req.source = source;
     req.destination = destination;
-    if (amount.stellarUSDC().equals(amount.getCurrency())) amount.setCurrency("USD");
     req.amount = amount;
     req.idempotencyKey = idempotencyKey;
     return req;

payment-circle/src/main/java/org/stellar/anchor/paymentservice/circle/util/CircleAsset.java

@@ -1,14 +1,29 @@
 package org.stellar.anchor.paymentservice.circle.util;
 
+import java.util.List;
 import org.stellar.sdk.Network;
 import reactor.util.annotation.NonNull;
 
 public class CircleAsset {
   @NonNull
   public static String stellarUSDC(Network stellarNetwork) {
     if (stellarNetwork == org.stellar.sdk.Network.PUBLIC)
-      return "USDC:GA5ZSEJYB37JRC5AVCIA5MOP4RHTM335X2KGX3IHOJAPP5RE34K4KZVN";
+      return "stellar:USDC:GA5ZSEJYB37JRC5AVCIA5MOP4RHTM335X2KGX3IHOJAPP5RE34K4KZVN";
 
-    return "USDC:GBBD47IF6LWK7P7MDEVSCWR7DPUWV3NY3DTQEVFL4NAT4AQH3ZLLFLA5";
+    return "stellar:USDC:GBBD47IF6LWK7P7MDEVSCWR7DPUWV3NY3DTQEVFL4NAT4AQH3ZLLFLA5";
+  }
+
+  public static String circleUSD() {
+    return "circle:USD";
+  }
+
+  public static String fiatUSD() {
+    return "iso4217:USD";
+  }
+
+  public static boolean isSupported(String currencyName, Network stellarNetwork) {
+    return List.of(
+            CircleAsset.circleUSD(), CircleAsset.fiatUSD(), CircleAsset.stellarUSDC(stellarNetwork))
+        .contains(currencyName);
   }
 }