Add ApiUtils to facilitate looping over features

A number of places in the code (common & drools-pdp) loop over
features, giving each provider a chance to act on something.
Created a common method in a new ApiUtils class to faciliate
it.
Renamed to FeatureApiUtils per review comment.

Change-Id: I0c2cf0f33854cb5b6921b394f64de498a6234909
Issue-ID: POLICY-1968
Signed-off-by: Jim Hahn <jrh3@att.com>

2 files changed, 143 insertions, 0 deletions

diff --git a/utils/src/main/java/org/onap/policy/common/utils/services/FeatureApiUtils.java b/utils/src/main/java/org/onap/policy/common/utils/services/FeatureApiUtils.java
new file mode 100644
index 00000000..e88361ea
--- /dev/null
+++ b/utils/src/main/java/org/onap/policy/common/utils/services/FeatureApiUtils.java
@@ -0,0 +1,61 @@
+/*
+ * ============LICENSE_START=======================================================
+ * ONAP
+ * ================================================================================
+ * Copyright (C) 2019 AT&T Intellectual Property. All rights reserved.
+ * ================================================================================
+ * Licensed 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.
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.common.utils.services;
+
+import java.util.List;
+import java.util.function.BiConsumer;
+import java.util.function.Predicate;
+
+/**
+ * Utilities for use with "feature APIs".
+ */
+public class FeatureApiUtils {
+
+    private FeatureApiUtils() {
+        // do nothing
+    }
+
+    /**
+     * Applies a function on each feature provider, stopping as soon as one returns true.
+     *
+     * @param providers list of feature providers
+     * @param predicate function to be applied to each provider
+     * @param handleEx function to handle any exception generated by the predicate
+     *        (typically, by logging the message)
+     * @return {@code true} if one of the providers returned {@code true}, {@code false}
+     *         otherwise
+     */
+    public static <T> boolean apply(List<T> providers, Predicate<T> predicate,
+                    BiConsumer<T,Exception> handleEx) {
+
+        for (T feature : providers) {
+            try {
+                if (predicate.test(feature)) {
+                    return true;
+                }
+            } catch (RuntimeException e) {
+                handleEx.accept(feature, e);
+            }
+        }
+
+        return false;
+    }
+}
diff --git a/utils/src/test/java/org/onap/policy/common/utils/services/FeatureApiUtilsTest.java b/utils/src/test/java/org/onap/policy/common/utils/services/FeatureApiUtilsTest.java
new file mode 100644
index 00000000..232d3409
--- /dev/null
+++ b/utils/src/test/java/org/onap/policy/common/utils/services/FeatureApiUtilsTest.java
@@ -0,0 +1,82 @@
+/*-
+ * ============LICENSE_START=======================================================
+ * ONAP
+ * ================================================================================
+ * Copyright (C) 2019 AT&T Intellectual Property. All rights reserved.
+ * ================================================================================
+ * Licensed 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.
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.common.utils.services;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import java.util.Arrays;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.function.Predicate;
+import org.junit.Before;
+import org.junit.Test;
+
+public class FeatureApiUtilsTest {
+    private static final String HANDLED = "handled";
+
+    private MyPred pred;
+    private List<String> tried;
+    private List<String> errors;
+
+    /**
+     * Initializes fields.
+     */
+    @Before
+    public void setUp() {
+        tried = new LinkedList<>();
+        errors = new LinkedList<>();
+        pred = new MyPred();
+    }
+
+    @Test
+    public void testApplyFeatureTrue() {
+        assertTrue(FeatureApiUtils.apply(Arrays.asList("exceptT0", "falseT1", HANDLED, "falseT2", HANDLED), pred,
+            (str, ex) -> errors.add(str)));
+
+        assertEquals("[exceptT0, falseT1, handled]", tried.toString());
+        assertEquals("[exceptT0]", errors.toString());
+    }
+
+    @Test
+    public void testApplyFeatureFalse() {
+        List<String> lst = Arrays.asList("falseF1", "exceptF2", "falseF3");
+
+        assertFalse(FeatureApiUtils.apply(lst, pred, (str,ex) -> errors.add(str)));
+        assertEquals(lst.toString(), tried.toString());
+        assertEquals("[exceptF2]", errors.toString());
+    }
+
+    private class MyPred implements Predicate<String> {
+
+        @Override
+        public boolean test(String data) {
+            tried.add(data);
+
+            if (data.startsWith("except")) {
+                throw new IllegalArgumentException("expected exception");
+            }
+
+            return data.equals(HANDLED);
+        }
+    }
+}