FINERACT-2181: Introduce Loop guard to avoid endless loops

fineract-core/src/main/java/org/apache/fineract/util/LoopContext.java

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+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.fineract.util;
+
+public interface LoopContext {}

fineract-core/src/main/java/org/apache/fineract/util/LoopGuard.java

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+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.fineract.util;
+
+import java.util.function.Predicate;
+
+/**
+ * Loop Guard is a utility solution to avoid endless loops
+ *
+ * Example: LoopGuard.runSafeDoWhileLoop(500, () -> { // loop body }, () -> conditions() );
+ */
+public final class LoopGuard {
+
+    private LoopGuard() {}
+
+    public interface LoopBody<T extends LoopContext> {
+
+        void execute(T context);
+    }
+
+    public static <T extends LoopContext> void runSafeDoWhileLoop(int maxIterations, T context, Predicate<T> condition, LoopBody<T> body) {
+        int count = 0;
+        do {
+            if (++count > maxIterations) {
+                throw new IllegalStateException("Loop exceeded " + maxIterations + " iterations. Possible infinite loop.");
+            }
+            body.execute(context);
+        } while (condition.test(context));
+    }
+
+    public static <T extends LoopContext> void runSafeWhileLoop(int maxIterations, T context, Predicate<T> condition, LoopBody<T> body) {
+        int count = 0;
+        while (condition.test(context)) {
+            if (++count > maxIterations) {
+                throw new IllegalStateException("Loop exceeded " + maxIterations + " iterations. Possible infinite loop.");
+            }
+            body.execute(context);
+        }
+    }
+}

fineract-core/src/test/java/org/apache/fineract/util/LoopGuardTest.java

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+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.fineract.util;
+
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.Predicate;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+
+public class LoopGuardTest {
+
+    static class TestContext implements LoopContext {
+
+        int iteration;
+    }
+
+    @ParameterizedTest
+    // target value, max iterations
+    @CsvSource({ "3, 5", //
+            "5, 6", //
+            "2, 10", //
+            "2, 2", //
+    })
+    void testSafeDoWhileLoopExecutesCorrectly(int targetValue, int maxIterations) {
+        TestContext context = new TestContext();
+
+        Predicate<TestContext> condition = ctx -> ctx.iteration < targetValue;
+        LoopGuard.LoopBody<TestContext> body = ctx -> ctx.iteration++;
+
+        LoopGuard.runSafeDoWhileLoop(maxIterations, context, condition, body);
+
+        Assertions.assertEquals(targetValue, context.iteration);
+    }
+
+    @ParameterizedTest
+    // target value, max iterations
+    @CsvSource({ "2, 5", //
+            "4, 5", //
+            "6, 10", //
+            "2, 2" //
+    })
+    void testSafeWhileLoopExecutesCorrectly(int targetValue, int maxIterations) {
+        TestContext context = new TestContext();
+
+        Predicate<TestContext> condition = ctx -> ctx.iteration < targetValue;
+        LoopGuard.LoopBody<TestContext> body = ctx -> ctx.iteration++;
+
+        LoopGuard.runSafeWhileLoop(maxIterations, context, condition, body);
+
+        Assertions.assertEquals(targetValue, context.iteration);
+    }
+
+    @ParameterizedTest
+    // max iterations
+    @CsvSource({ "10", //
+            "5", //
+            "1", //
+            "0", //
+            "-1" //
+    })
+    void testSafeDoWhileLoopThrowsOnExceedingMaxIterations(int maxIterations) {
+        TestContext context = new TestContext();
+
+        Predicate<TestContext> condition = ctx -> true; // infinite
+        LoopGuard.LoopBody<TestContext> body = ctx -> ctx.iteration++;
+
+        IllegalStateException exception = Assertions.assertThrows(IllegalStateException.class,
+                () -> LoopGuard.runSafeDoWhileLoop(maxIterations, context, condition, body));
+
+        Assertions.assertTrue(exception.getMessage().contains("Loop exceeded " + maxIterations));
+    }
+
+    @ParameterizedTest
+    // max iterations
+    @CsvSource({ "10", //
+            "3", //
+            "2" //
+    })
+    void testSafeWhileLoopThrowsOnExceedingMaxIterations(int maxIterations) {
+        TestContext context = new TestContext();
+
+        Predicate<TestContext> condition = ctx -> true; // infinite
+        LoopGuard.LoopBody<TestContext> body = ctx -> ctx.iteration++;
+
+        IllegalStateException exception = Assertions.assertThrows(IllegalStateException.class,
+                () -> LoopGuard.runSafeWhileLoop(maxIterations, context, condition, body));
+
+        Assertions.assertTrue(exception.getMessage().contains("Loop exceeded " + maxIterations));
+    }
+
+    @Test
+    void testSafeDoWhileLoopRunsAtLeastOnce() {
+        TestContext context = new TestContext();
+        AtomicInteger counter = new AtomicInteger();
+
+        Predicate<TestContext> condition = ctx -> false;
+        LoopGuard.LoopBody<TestContext> body = ctx -> counter.incrementAndGet();
+
+        LoopGuard.runSafeDoWhileLoop(3, context, condition, body);
+
+        Assertions.assertEquals(1, counter.get(), "Do-while loop should execute at least once");
+    }
+
+    @Test
+    void testSafeWhileLoopSkipsIfConditionFalseInitially() {
+        TestContext context = new TestContext();
+        AtomicInteger counter = new AtomicInteger();
+
+        Predicate<TestContext> condition = ctx -> false;
+        LoopGuard.LoopBody<TestContext> body = ctx -> counter.incrementAndGet();
+
+        LoopGuard.runSafeWhileLoop(3, context, condition, body);
+
+        Assertions.assertEquals(0, counter.get(), "While loop should skip execution if condition is false");
+    }
+}