code: /*
   * #%L
   * Simmetrics Core
   * %%
   * Copyright (C) 2014 - 2016 Simmetrics Authors
   * %%
   * 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.
   * #L%
   */
  
  package org.simmetrics;
  
  import static com.google.common.primitives.Floats.max;
  import static java.lang.String.format;
  import static org.hamcrest.CoreMatchers.not;
  import static org.junit.Assert.assertEquals;
  import static org.junit.Assert.assertThat;
  import static org.junit.Assert.assertTrue;
  import static org.junit.Assert.fail;
  import static org.simmetrics.matchers.ImplementsToString.implementsToString;
  import static org.simmetrics.matchers.ToStringContainsSimpleClassName.toStringContainsSimpleClassName;
  
  import org.junit.Before;
  import org.junit.Test;
  
  
  @SuppressWarnings("javadoc")
  public abstract class DistanceTest<K> {
  
  	protected static class TestCase<K> {
  		protected final K a;
  		protected final K b;
  		protected final float distance;
  
  		public TestCase(float distance, K a, K b) {
  			this.a = a;
  			this.b = b;
  			this.distance = distance;
  		}
  	}
  
  	private static final float DEFAULT_DELTA = 0.0001f;
  
  	private static <K> boolean testCoincidence(Distance<K> distance, K a, K b) {
  		return distance.distance(a, b) != 0.0f || a.equals(b);
  	}
  
  	private static <K> void testNullPointerException(Distance<K> distance, K a,
  			K b) {
  		try {
  			distance.distance(null, b);
  			fail("Distance should have thrown a null pointer exception for the first argument");
  		} catch (NullPointerException ignored) {
  			// Ignored
  		}
  
  		try {
  			distance.distance(a, null);
  			fail("Distance should have thrown a null pointer exception for the second argument");
  		} catch (NullPointerException ignored) {
  			// Ignored
  		}
  
  		try {
  			distance.distance(null, null);
  			fail("Distance should have thrown a null pointer exception for either argument");
  		} catch (NullPointerException ignored) {
  			// Ignored
  		}
  	}
  
  	private static <K> void testRange(Distance<K> metric, K a, K b) {
  		float similarity = metric.distance(a, b);
  		String message1 = String.format(
  				"Distance %s-%s %f must be non-negative", a, b, similarity);
  		assertTrue(message1, 0.0f <= similarity);
  	}
  
  	private static <K> void testReflexive(Distance<K> metric, K a, float delta) {
  		assertEquals(0.0f, metric.distance(a, a), delta);
  	}
  
  	private static <K> void testDistance(Distance<K> metric, K a, K b,
  			float expected, float delta) {
  		float similarity = metric.distance(a, b);
  		String message = String.format("\"%s\" vs \"%s\"", a, b);
  		assertEquals(message, expected, similarity, delta);
  	}
  
  	private static <K> boolean testSubadditivity(Distance<K> metric, K a, K b,
  			K c) {
  
  		float ab = metric.distance(a, b);
  		float ac = metric.distance(a, c);
  		float bc = metric.distance(b, c);
  		return (ab == 0.0f || ac == 0.0f || bc == 0.0f || 2 * max(ab, ac, bc) <= ab
  				+ ac + bc);
  	}
  
  	private static <K> void testSymmetric(Distance<K> metric, K a, K b,
  			float delta) {
  		float distance = metric.distance(a, b);
  		float distanceReversed = metric.distance(b, a);
  
  		String message = String.format(
  				"Distance relation \"%s\" vs \"%s\" must be symmetric", a, b);
  		assertEquals(message, distanceReversed, distance, delta);
  
  	}
  
  	protected float delta;
  
  	protected Distance<K> metric;
  
  	protected TestCase<K>[] tests;
  
  	protected float getDelta() {
  		return DEFAULT_DELTA;
  	}
  
  	protected abstract K getEmpty();
  
  	protected abstract Distance<K> getMetric();
  
  	protected abstract TestCase<K>[] getTests();
  
  	protected boolean satisfiesCoincidence() {
  		return true;
  	}
  
  	protected boolean satisfiesSubadditivity() {
  		return true;
  	}
  	
  	protected boolean toStringIncludesSimpleClassName(){
  		return true;
  	}
  
  	@Before
  	public final void setUp() throws Exception {
  		this.delta = getDelta();
  		this.metric = getMetric();
  		this.tests = getTests();
  	}
  
  	@Test
  	public final void empty() {
  		assertEquals(0.0f, metric.distance(getEmpty(), getEmpty()), delta);
  	}
  
  	@Test
  	public final void nullPointerException() {
  		for (TestCase<K> t : tests) {
  			testNullPointerException(metric, t.a, t.b);
  		}
  	}
  
  	@Test
  	public final void coincidence() {
  		if (satisfiesCoincidence()) {
  			for (TestCase<K> t : tests) {
  				assertTrue(
  						format("coincidence did not hold for %s and %s", t.a,
  								t.b), testCoincidence(metric, t.a, t.b));
  			}
  		} else {
  			for (TestCase<K> t : tests) {
  				if (!testCoincidence(metric, t.a, t.b)) {
  					return;
  				}
  			}
  			fail("no counter example for the coincidence property was found");
  		}
  	}
  
  	@Test
  	public final void subadditivity() {
  		if (satisfiesSubadditivity()) {
  			for (TestCase<K> n : tests) {
  				for (TestCase<K> m : tests) {
  					assertTrue(
  							format("triangle ineqaulity must hold for %s, %s, %s",
  									n.a, n.b, m.a),
  							testSubadditivity(metric, n.a, n.b, m.a));
  					assertTrue(
  							format("triangle ineqaulity must hold for %s, %s, %s",
  									n.a, n.b, m.b),
  							testSubadditivity(metric, n.a, n.b, m.b));
  				}
  			}
  		} else {
  			for (TestCase<K> n : tests) {
  				for (TestCase<K> m : tests) {
  					if (!testSubadditivity(metric, n.a, n.b, m.a)
  							|| !testSubadditivity(metric, n.a, n.b, m.b)) {
  						return;
  					}
  				}
  			}
  			fail("no counter example for the subadditive property was found");
  		}
  	}
  
  	@Test
  	public final void range() {
  		for (TestCase<K> t : tests) {
  			testRange(metric, t.a, t.b);
  		}
  	}
  
  	@Test
  	public final void reflexive() {
  		for (TestCase<K> t : tests) {
  			testReflexive(metric, t.a, delta);
  			testReflexive(metric, t.b, delta);
  		}
  	}
  
  	@Test
  	public final void distance() {
  		for (TestCase<K> t : tests) {
  			testDistance(metric, t.a, t.b, t.distance, delta);
  		}
  	}
  
  	public final void generateDistance() {
  		for (TestCase<K> t : tests) {
  			System.out.println(format("new T<>(%1.4ff, \"%s\", \"%s\"),",
  					metric.distance(t.a, t.b), t.a, t.b));
  		}
  	}
  
  	@Test
  	public final void symmetric() {
  		for (TestCase<K> t : tests) {
  			testSymmetric(metric, t.a, t.b, delta);
  		}
  	}
  
  	@Test
  	public final void shouldImplementToString() {
  		assertThat(metric, implementsToString());
  	}
  	
  	@Test
  	public final void shouldContainSimpleClassNameToString() {
  		if(toStringIncludesSimpleClassName()){
  			assertThat(metric, toStringContainsSimpleClassName());
  		} else {
  			assertThat(metric, not(toStringContainsSimpleClassName()));	
  		}
  	}
  
  }
  