Created reducer that determines closest location ProjectSWGCore#150

src/main/java/com/projectswg/holocore/resources/support/data/location/ClosestLocationReducer.java

@@ -0,0 +1,50 @@
+package com.projectswg.holocore.resources.support.data.location;
+
+import com.projectswg.common.data.location.Location;
+import com.projectswg.common.data.location.Terrain;
+
+import java.util.function.BinaryOperator;
+
+/**
+ * Reducer that determines the Location that is closest to a given base Location.
+ */
+public class ClosestLocationReducer implements BinaryOperator<Location> {
+
+	private final Location baseLocation;
+
+	public ClosestLocationReducer(Location baseLocation) {
+		this.baseLocation = baseLocation;
+	}
+
+	@Override
+	public Location apply(Location location1, Location location2) {
+		Terrain terrainBase = baseLocation.getTerrain();
+		Terrain terrain1 = location1.getTerrain();
+		Terrain terrain2 = location2.getTerrain();
+		boolean terrain1Match = terrainBase == terrain1;
+		boolean terrain2Match = terrainBase == terrain2;
+
+		if (!terrain1Match && !terrain2Match) {
+			// Given locations are both located on different planets
+			return null;
+		}
+
+		if (terrain1Match && !terrain2Match) {
+			// Location 1 is a best fit since it has the same terrain as the base location while location 2 doesn't
+			return location1;
+		} else if (!terrain1Match) {
+			// Location 2 is a best fit since it has the same terrain as the base location while location 1 doesn't
+			return location2;
+		}
+
+		// location1 and location2 are on same terrain as baseLocation. Let's perform a distance check.
+		double location1Distance = baseLocation.flatDistanceTo(location1);
+		double location2Distance = baseLocation.flatDistanceTo(location2);
+
+		if (location1Distance > location2Distance) {
+			return location2;    // Location 2 is closest to the player - return location2
+		} else {
+			return location1;    // Location 1 is closest to the player or both locations are equally close - return location1
+		}
+	}
+}

src/test/java/com/projectswg/holocore/resources/support/data/location/TestClosestLocationReducer.java

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+package com.projectswg.holocore.resources.support.data.location;
+
+import com.projectswg.common.data.location.Location;
+import com.projectswg.common.data.location.Terrain;
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+
+public class TestClosestLocationReducer {
+
+	private ClosestLocationReducer reducer;
+
+	@Before
+	public void setup() {
+		Location base = Location.builder()
+				.setTerrain(Terrain.TATOOINE)
+				.setX(100)
+				.setZ(-100)
+				.build();
+		reducer = new ClosestLocationReducer(base);
+	}
+
+	/**
+	 * Verifies that the terrain check can return neither of the given locations if both are on different planets
+	 */
+	@Test
+	public void testBothLocationsDifferentPlanet() {
+		Location loc1 = Location.builder()
+				.setTerrain(Terrain.DANTOOINE)
+				.setX(100)
+				.setZ(-100)
+				.build();
+
+		Location loc2 = Location.builder()
+				.setTerrain(Terrain.DANTOOINE)
+				.setX(900)
+				.setZ(-900)
+				.build();
+
+		Location reduced = reducer.apply(loc1, loc2);
+
+		assertNull("Null should be the result when reducing locations not located on the same planet as the base location", reduced);
+	}
+
+	/**
+	 * Verifies that the distance check works when all locations are on the same planet
+	 */
+	@Test
+	public void testBothLocationsSamePlanet() {
+		Location closest = Location.builder()
+				.setTerrain(Terrain.TATOOINE)
+				.setX(110)
+				.setZ(-110)
+				.build();
+
+		Location farthest = Location.builder()
+				.setTerrain(Terrain.TATOOINE)
+				.setX(900)
+				.setZ(-900)
+				.build();
+
+		Location reduced = reducer.apply(closest, farthest);
+
+		assertEquals("The location closest to the base location should be the reduced location", closest, reduced);
+	}
+
+	/**
+	 * Verifies that the distance check only matters if on the same terrain
+	 */
+	@Test
+	public void testOneLocationOnDifferentPlanet() {
+		Location base = Location.builder()
+				.setTerrain(Terrain.TATOOINE)
+				.setX(100)
+				.setZ(-100)
+				.build();
+		ClosestLocationReducer reducer = new ClosestLocationReducer(base);
+
+		Location closestDifferentPlanet = Location.builder()
+				.setTerrain(Terrain.DANTOOINE)
+				.setX(110)
+				.setZ(-110)
+				.build();
+
+		Location farthestSamePlanet = Location.builder()
+				.setTerrain(Terrain.TATOOINE)
+				.setX(900)
+				.setZ(-900)
+				.build();
+
+		Location reduced = reducer.apply(closestDifferentPlanet, farthestSamePlanet);
+
+		assertEquals("The location on the same planet should be picked even if it's furthest away from the X Y Z coordinates", farthestSamePlanet, reduced);
+	}
+
+}