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package org.scijava.ops.image.topology.eulerCharacteristic;

import static org.scijava.ops.image.topology.eulerCharacteristic.TestHelper.drawCube;
import static org.junit.jupiter.api.Assertions.assertEquals;

import org.scijava.ops.image.AbstractOpTest;
import net.imglib2.RandomAccess;
import net.imglib2.img.Img;
import net.imglib2.img.array.ArrayImgs;
import net.imglib2.type.logic.BitType;
import net.imglib2.type.numeric.real.DoubleType;

import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.Test;

/**
 * Tests for the {@link EulerCharacteristic26NFloating} class
 *
 * @author Richard Domander (Royal Veterinary College, London)
 */
public class EulerCharacteristic26NFloatingTest extends AbstractOpTest {

	@Test
	public void testConforms() throws AssertionError {
		final Img<BitType> img = ArrayImgs.bits(3, 3);

		final DoubleType result = new DoubleType();
		Assertions.assertThrows(IllegalArgumentException.class, () -> {
			ops.op("topology.eulerCharacteristic26NFloating").input(img).output(
				result).compute();
		});
	}

	/**
	 * Test with a single voxel (=solid cube) that floats in the middle of a 3x3x3
	 * space
	 * <p>
	 * Here χ = β_0 - β_1 + β_2 = 1 - 0 + 0 = 1.<br>
	 * The formula χ = vertices - edges + faces for surfaces of polyhedra doesn't
	 * apply because the cuboid is solid.
	 * </p>
	 */
	@Test
	public void testCube() throws Exception {
		final Img<BitType> img = drawCube(1, 1, 1, 1);

		final DoubleType result = new DoubleType();
		ops.op("topology.eulerCharacteristic26NFloating").input(img).output(result)
			.compute();

		assertEquals(1.0, result.get(), 1e-12,
			"Euler characteristic (χ) is incorrect");
	}

	/**
	 * Test with a single voxel (=solid cube) in a 1x1x1 space
	 * <p>
	 * In this op result shouldn't differ from {@link #testCube} because space is
	 * zero extended
	 * </p>
	 */
	@Test
	public void testEdgeCube() throws Exception {
		final Img<BitType> img = drawCube(1, 1, 1, 0);

		final DoubleType result = new DoubleType();
		ops.op("topology.eulerCharacteristic26NFloating").input(img).output(result)
			.compute();

		assertEquals(1.0, result.get(), 1e-12,
			"Euler characteristic (χ) is incorrect");
	}

	/**
	 * Test with a cube that has a cavity inside
	 * <p>
	 * Here χ = β_0 - β_1 + β_2 = 1 - 0 + 1 = 2
	 * </p>
	 */
	@Test
	public void testHollowCube() throws Exception {
		final Img<BitType> img = drawCube(3, 3, 3, 1);
		final RandomAccess<BitType> access = img.randomAccess();

		// Add cavity
		access.setPosition(new long[] { 2, 2, 2 });
		access.get().setZero();

		final DoubleType result = new DoubleType();
		ops.op("topology.eulerCharacteristic26NFloating").input(img).output(result)
			.compute();

		assertEquals(2.0, result.get(), 1e-12,
			"Euler characteristic (χ) is incorrect");
	}

	/**
	 * Test with a cube that has a "handle"
	 * <p>
	 * Here χ = β_0 - β_1 + β_2 = 1 - 1 + 0 = 0
	 * </p>
	 */
	@Test
	public void testHandleCube() throws Exception {
		final Img<BitType> cube = drawCube(9, 9, 9, 5);
		final RandomAccess<BitType> access = cube.randomAccess();

		// Draw a handle on the front xy-face of the cuboid
		access.setPosition(9, 0);
		access.setPosition(6, 1);
		access.setPosition(4, 2);
		access.get().setOne();
		access.setPosition(3, 2);
		access.get().setOne();
		access.setPosition(7, 1);
		access.get().setOne();
		access.setPosition(8, 1);
		access.get().setOne();
		access.setPosition(4, 2);
		access.get().setOne();

		final DoubleType result = new DoubleType();
		ops.op("topology.eulerCharacteristic26NFloating").input(cube).output(result)
			.compute();

		assertEquals(0.0, result.get(), 1e-12,
			"Euler characteristic (χ) is incorrect");
	}
}
