Fix incorrect maxTradeLimit assignment from Offer

- Make all PaymentMethod constructors private
- Use PaymentMethod.getPaymentMethodById in Offer for getting the
PaymentMethod. This change a bit the context as now we always create the
PaymentMethod from the actual code base in contrast to the data which
have been used when creating the offer. As our fields as final and must
not change in software updates it should have no issues but we have to
keep that in mind to not alter the default values.
- Added a runtimeException in case the maxTradeLimit does not match one
of our default values.
- Use PaymentMethod.getDummyPaymentMethod(GUIUtil.SHOW_ALL_FLAG)
instead of new PaymentMethod(GUIUtil.SHOW_ALL_FLAG))

core/src/main/java/bisq/core/offer/Offer.java

@@ -314,9 +314,7 @@ public class Offer implements NetworkPayload, PersistablePayload {
     }
 
     public PaymentMethod getPaymentMethod() {
-        return new PaymentMethod(offerPayload.getPaymentMethodId(),
-                offerPayload.getMaxTradePeriod(),
-                Coin.valueOf(offerPayload.getMaxTradeLimit()));
+        return PaymentMethod.getPaymentMethodById(offerPayload.getPaymentMethodId());
     }
 
     // utils

core/src/main/java/bisq/core/payment/payload/PaymentMethod.java

@@ -56,6 +56,8 @@ public final class PaymentMethod implements PersistablePayload, Comparable {
     // We initialize very early before reading persisted data. We will apply later the limit from the DAO param
     // but that can be only done after the dao is initialized. The default values will be used for deriving the
     // risk factor so the relation between the risk categories stays the same as with the default values.
+    // We must not change those values as it could lead to invalid offers if amount becomes lower then new trade limit.
+    // Increasing might be ok, but needs more thought as well...
     private static final Coin DEFAULT_TRADE_LIMIT_VERY_LOW_RISK = Coin.parseCoin("1");
     private static final Coin DEFAULT_TRADE_LIMIT_LOW_RISK = Coin.parseCoin("0.5");
     private static final Coin DEFAULT_TRADE_LIMIT_MID_RISK = Coin.parseCoin("0.25");
@@ -115,6 +117,8 @@ public final class PaymentMethod implements PersistablePayload, Comparable {
     public static PaymentMethod PROMPT_PAY;
     public static PaymentMethod ADVANCED_CASH;
 
+    // The limit and duration assignment must not be changed as that could break old offers (if amount would be higher
+    // than new trade limit) and violate the maker expectation when he created the offer (duration).
     @Getter
     private final static List<PaymentMethod> paymentMethods = new ArrayList<>(Arrays.asList(
             // EUR
@@ -177,6 +181,10 @@ public final class PaymentMethod implements PersistablePayload, Comparable {
         });
     }
 
+    public static PaymentMethod getDummyPaymentMethod(String id) {
+        return new PaymentMethod(id, 0, Coin.ZERO);
+    }
+
 
     ///////////////////////////////////////////////////////////////////////////////////////////
     // Instance fields
@@ -184,6 +192,9 @@ public final class PaymentMethod implements PersistablePayload, Comparable {
 
     @Getter
     private final String id;
+
+    // Must not change as old offers would get a new period then and that would violate the makers "contract" or
+    // expectation when he created the offer.
     @Getter
     private final long maxTradePeriod;
 
@@ -207,14 +218,14 @@ public final class PaymentMethod implements PersistablePayload, Comparable {
      * @param maxTradePeriod The min. period a trader need to wait until he gets displayed the contact form for opening a dispute.
      * @param maxTradeLimit  The max. allowed trade amount in Bitcoin for that payment method (depending on charge back risk)
      */
-    public PaymentMethod(String id, long maxTradePeriod, Coin maxTradeLimit) {
+    private PaymentMethod(String id, long maxTradePeriod, Coin maxTradeLimit) {
         this.id = id;
         this.maxTradePeriod = maxTradePeriod;
         this.maxTradeLimit = maxTradeLimit.value;
     }
 
     // Used for dummy entries in payment methods list (SHOW_ALL)
-    public PaymentMethod(String id) {
+    private PaymentMethod(String id) {
         this(id, 0, Coin.ZERO);
     }
 
@@ -263,8 +274,10 @@ public final class PaymentMethod implements PersistablePayload, Comparable {
             riskFactor = 2;
         else if (maxTradeLimit == DEFAULT_TRADE_LIMIT_MID_RISK.value)
             riskFactor = 4;
-        else
+        else if (maxTradeLimit == DEFAULT_TRADE_LIMIT_HIGH_RISK.value)
             riskFactor = 8;
+        else
+            throw new RuntimeException("maxTradeLimit is not matching one of our default values. maxTradeLimit=" + Coin.valueOf(maxTradeLimit).toFriendlyString());
 
         TradeLimits tradeLimits = TradeLimits.getINSTANCE();
         checkNotNull(tradeLimits, "tradeLimits must not be null");

core/src/test/java/bisq/core/payment/ReceiptPredicatesTest.java

@@ -94,7 +94,7 @@ public class ReceiptPredicatesTest {
 
     @Test
     public void testIsEqualPaymentMethods() {
-        final PaymentMethod method = new PaymentMethod("1");
+        PaymentMethod method = PaymentMethod.getDummyPaymentMethod("1");
 
         Offer offer = mock(Offer.class);
         when(offer.getPaymentMethod()).thenReturn(method);

desktop/src/main/java/bisq/desktop/main/offer/offerbook/OfferBookViewModel.java

@@ -117,7 +117,7 @@ class OfferBookViewModel extends ActivatableViewModel {
 
     // If id is empty string we ignore filter (display all methods)
 
-    PaymentMethod selectedPaymentMethod = new PaymentMethod(GUIUtil.SHOW_ALL_FLAG);
+    PaymentMethod selectedPaymentMethod = PaymentMethod.getDummyPaymentMethod(GUIUtil.SHOW_ALL_FLAG);
 
     private boolean isTabSelected;
     final BooleanProperty showAllTradeCurrenciesProperty = new SimpleBooleanProperty(true);
@@ -329,7 +329,7 @@ class OfferBookViewModel extends ActivatableViewModel {
 
     ObservableList<PaymentMethod> getPaymentMethods() {
         ObservableList<PaymentMethod> list = FXCollections.observableArrayList(PaymentMethod.getPaymentMethods());
-        list.add(0, new PaymentMethod(GUIUtil.SHOW_ALL_FLAG));
+        list.add(0, PaymentMethod.getDummyPaymentMethod(GUIUtil.SHOW_ALL_FLAG));
         return list;
     }