Add flexible amount verification using predicates

Author: satran004

quicktx/src/main/java/com/bloxbean/cardano/client/quicktx/verifiers/OutputAmountVerifier.java

@@ -8,6 +8,7 @@
 import com.bloxbean.cardano.client.util.Tuple;
 
 import java.math.BigInteger;
+import java.util.function.Predicate;
 
 import static com.bloxbean.cardano.client.common.CardanoConstants.LOVELACE;
 
@@ -18,6 +19,8 @@ public class OutputAmountVerifier implements Verifier {
 
     private final String address;
     private final Amount amount;
+    private final Predicate<Amount> predicate;
+    private final String unit;
     private final String customMsg;
 
     /**
@@ -29,19 +32,43 @@ public class OutputAmountVerifier implements Verifier {
     public OutputAmountVerifier(String address, Amount amount, String customMsg) {
         this.address = address;
         this.amount = amount;
+        this.unit = amount.getUnit();
+        this.predicate = null;
+        this.customMsg = customMsg;
+    }
+
+    /**
+     * Constructor to create an OutputAmountVerifier instance with a specific unit and predicate for validation.
+     * This verifier is used to verify the output amount for a given address.
+     *
+     * @param address the address for which the output amount is to be verified
+     * @param unit the unit of the amount to be verified
+     * @param predicate a predicate to define the condition for amount verification
+     * @param customMsg a custom message to throw in case of verification failure
+     */
+    public OutputAmountVerifier(String address, String unit, Predicate<Amount> predicate, String customMsg) {
+        this.address = address;
+        this.amount = null;
+        this.unit = unit;
+        this.predicate = predicate;
         this.customMsg = customMsg;
     }
 
     @Override
     public void verify(Transaction txn) throws VerifierException {
-        if (LOVELACE.equals(amount.getUnit())) {
+        if (LOVELACE.equals(unit)) {
             BigInteger lovelaceAmt = txn.getBody()
                     .getOutputs().stream()
                     .filter(o -> o.getAddress().equals(address))
                     .map(o -> o.getValue().getCoin())
                     .reduce(BigInteger.ZERO, (amount1, amount2) -> amount1.add(amount2));
 
-            if (lovelaceAmt.compareTo(amount.getQuantity()) != 0) {
+            if (predicate != null) {
+                if (!predicate.test(Amount.lovelace(lovelaceAmt))) {
+                    String expectedMsg = formatExceptionMessage(customMsg, address, unit, lovelaceAmt);
+                    throw new VerifierException(expectedMsg);
+                }
+            } else if (lovelaceAmt.compareTo(amount.getQuantity()) != 0) {
                 String expectedMsg = formatExceptionMessage(customMsg, address, amount, lovelaceAmt);
                 throw new VerifierException(expectedMsg);
             }
@@ -57,8 +84,13 @@ public void verify(Transaction txn) throws VerifierException {
                     }).map(assetTuple -> assetTuple._2.getValue())
                     .reduce(BigInteger.ZERO, (amount1, amount2) -> amount1.add(amount2));
 
-            String expectedMsg = formatExceptionMessage(customMsg, address, amount, assetAmount);
-            if (assetAmount.compareTo(amount.getQuantity()) != 0) {
+            if (predicate != null) {
+                if (!predicate.test(Amount.asset(amount.getUnit(), assetAmount))) {
+                    String expectedMsg = formatExceptionMessage(customMsg, address, unit, assetAmount);
+                    throw new VerifierException(expectedMsg);
+                }
+            } else if (assetAmount.compareTo(amount.getQuantity()) != 0) {
+                String expectedMsg = formatExceptionMessage(customMsg, address, amount, assetAmount);
                 throw new VerifierException(expectedMsg);
             }
         }
@@ -72,4 +104,13 @@ private String formatExceptionMessage(String customMsg, String address, Amount e
 
         return expectedMsg;
     }
+
+    private String formatExceptionMessage(String customMsg, String address, String unit, BigInteger actualAmount) {
+        String expectedMsg = String.format("Amount for  address %s and unit %s doesn't match the condition. Actual amount: %s",
+                 address, unit, actualAmount);
+        if(customMsg != null)
+            expectedMsg = customMsg + ".\n" + expectedMsg;
+
+        return expectedMsg;
+    }
 }