gh-1612 - ExtractWalkVertex and test added

core/data/src/main/java/uk/gov/gchq/gaffer/data/graph/function/walk/ExtractWalkVertex.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2017 Crown Copyright
+ *
+ * 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.
+ */
+package uk.gov.gchq.gaffer.data.graph.function.walk;
+
+import com.google.common.collect.Iterables;
+
+import uk.gov.gchq.gaffer.data.graph.Walk;
+import uk.gov.gchq.koryphe.function.KorypheFunction;
+
+public class ExtractWalkVertex extends KorypheFunction<Walk, Object> {
+    @Override
+    public Object apply(final Walk walk) {
+        if (null == walk) {
+            throw new IllegalArgumentException("Walk cannot be null");
+        }
+        return Iterables.get(walk.getEntities().get(0), 0).getVertex();
+    }
+}

core/data/src/test/java/uk/gov/gchq/gaffer/data/graph/function/walk/ExtractWalkVertexTest.java

@@ -0,0 +1,73 @@
+/*
+ * Copyright 2017 Crown Copyright
+ *
+ * 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.
+ */
+package uk.gov.gchq.gaffer.data.graph.function.walk;
+
+import org.junit.Test;
+
+import uk.gov.gchq.gaffer.commonutil.TestGroups;
+import uk.gov.gchq.gaffer.data.element.Edge;
+import uk.gov.gchq.gaffer.data.element.Entity;
+import uk.gov.gchq.gaffer.data.graph.Walk;
+
+import java.util.function.Function;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+public class ExtractWalkVertexTest {
+    private static final Edge EDGE_AB = new Edge.Builder().group(TestGroups.EDGE).source("A").dest("B").directed(true).build();
+    private static final Edge EDGE_BC = new Edge.Builder().group(TestGroups.EDGE).source("B").dest("C").directed(true).build();
+    private static final Edge EDGE_CA = new Edge.Builder().group(TestGroups.EDGE).source("C").dest("A").directed(true).build();
+
+    private static final Entity ENTITY_A = new Entity.Builder().group(TestGroups.ENTITY).vertex("A").build();
+    private static final Entity ENTITY_B = new Entity.Builder().group(TestGroups.ENTITY).vertex("B").build();
+    private static final Entity ENTITY_C = new Entity.Builder().group(TestGroups.ENTITY).vertex("C").build();
+
+    @Test
+    public void shouldReturnVertexFromWalkObject() {
+        // Given
+        final Function<Walk, Object> function = new ExtractWalkVertex();
+        final Walk walk = new Walk.Builder()
+                .entity(ENTITY_A)
+                .edge(EDGE_AB)
+                .entity(ENTITY_B)
+                .edge(EDGE_BC)
+                .entity(ENTITY_C)
+                .edge(EDGE_CA)
+                .entity(ENTITY_A)
+                .build();
+
+        // When
+        final Object result = function.apply(walk);
+
+        // Then
+        assertEquals("A", result);
+    }
+
+    @Test
+    public void shouldThrowIAEForNullInput() {
+        // Given
+        final Function<Walk, Object> function = new ExtractWalkVertex();
+        final Walk walk = null;
+
+        // When / Then
+        try {
+            function.apply(walk);
+        } catch (final IllegalArgumentException e) {
+            assertTrue(e.getMessage().contains("Walk cannot be null"));
+        }
+    }
+}