Merge pull request #103 from A248/master

Solve #100

SaneEconomyCore/src/main/java/org/appledash/saneeconomy/economy/EconomyManager.java

@@ -30,6 +30,8 @@ public class EconomyManager {
     private final EconomyStorageBackend backend;
     private final String serverAccountName;
     
+    private static final BigDecimal REQUIRED_BALANCE_ACCURACY = new BigDecimal("0.0001");
+
     public EconomyManager(ISaneEconomy saneEconomy, Currency currency, EconomyStorageBackend backend, String serverAccountName) {
         this.saneEconomy = saneEconomy;
         this.currency = currency;
@@ -84,8 +86,25 @@ public class EconomyManager {
      * @return True if they have requiredBalance or more, false otherwise
      */
     public boolean hasBalance(Economable targetPlayer, BigDecimal requiredBalance) {
-        return (EconomableConsole.isConsole(targetPlayer)) || (this.getBalance(targetPlayer).compareTo(requiredBalance) >= 0);
+        return (EconomableConsole.isConsole(targetPlayer)) || (hasBalance(this.getBalance(targetPlayer), requiredBalance));
+    }
     
+    /**
+     * Compare account balance and required balance to a reasonable degree of accuracy. <br>
+     * <b>Visible for testing</b>
+     * 
+     * @param accountBalance account balance
+     * @param requiredBalance required balance
+     * @return true if the account has the required balance to some degree of accuracy, false otherwise
+     */
+    public boolean hasBalance(BigDecimal accountBalance, BigDecimal requiredBalance) {
+    	if (accountBalance.compareTo(requiredBalance) >= 0) {
+    		return true;
+    	}
+    	// Must compare to degree of accuracy
+    	// See https://github.com/AppleDash/SaneEconomy/issues/100
+    	BigDecimal difference = requiredBalance.subtract(accountBalance);
+		return difference.compareTo(REQUIRED_BALANCE_ACCURACY) < 0; // difference < PRECISION
     }
 
     /**

SaneEconomyCore/src/test/java/org/appledash/saneeconomy/test/EconomyManagerTest.java

@@ -18,6 +18,7 @@ import org.junit.Test;
 import java.math.BigDecimal;
 import java.text.DecimalFormat;
 import java.util.*;
+import java.util.concurrent.ThreadLocalRandom;
 import java.util.stream.Collectors;
 
 /**
@@ -117,4 +118,25 @@ public class EconomyManagerTest {
 
         return true;
     }
+    
+    @Test
+    public void testHasRequiredBalance() {
+    	for (int n = 0; n < 20; n++) { // in the absence of Junit 5's @RepeatedTest
+    		
+    		BigDecimal bigDecimal = randomBigDecimal();
+			// We MUST modify the BigDecimal in some way otherwise the test will always succeed
+    		// See https://github.com/AppleDash/SaneEconomy/issues/100
+			for (int m = 0; m < 20; m++) {
+				bigDecimal = bigDecimal.add(randomBigDecimal()).subtract(randomBigDecimal());
+			}
+			//
+    		
+			Assert.assertTrue("Account must have required balance despite loss of precision (repeat " + n + ")",
+					economyManager.hasBalance(bigDecimal, new BigDecimal(bigDecimal.doubleValue())));
+    	}
+    }
+    
+	private static BigDecimal randomBigDecimal() {
+		return new BigDecimal(ThreadLocalRandom.current().nextDouble());
+	}
 }