/**
 * Copyright (C) 2018 Adrien Hopkins
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
package test.java;

import static org.junit.Assert.assertEquals;

import java.util.Random;
import java.util.concurrent.ThreadLocalRandom;

import org.junit.Test;
import org.unitConverter.dimension.StandardDimensions;
import org.unitConverter.math.DecimalComparison;
import org.unitConverter.unit.BaseUnit;
import org.unitConverter.unit.LinearUnit;
import org.unitConverter.unit.SI;
import org.unitConverter.unit.SIPrefix;
import org.unitConverter.unit.Unit;

/**
 * Testing the various Unit classes. This is NOT part of this program's public API.
 * 
 * @author Adrien Hopkins
 * @since 2018-12-22
 * @since v0.1.0
 */
public class UnitTest {
	/** A random number generator */
	private static final Random rng = ThreadLocalRandom.current();

	@Test
	public void testAdditionAndSubtraction() {
		final LinearUnit inch = SI.METRE.times(0.0254);
		final LinearUnit foot = SI.METRE.times(0.3048);

		assertEquals(inch.plus(foot), SI.METRE.times(0.3302));
		assertEquals(foot.minus(inch), SI.METRE.times(0.2794));
	}

	@Test
	public void testBaseUnitExclusives() {
		// this test should have a compile error if I am doing something wrong
		final BaseUnit metrePerSecondSquared = SI.METRE.dividedBy(SI.SECOND.toExponent(2));

		assertEquals(metrePerSecondSquared, SI.SI.getBaseUnit(StandardDimensions.ACCELERATION));
	}

	@Test
	public void testConversion() {
		final BaseUnit metre = SI.METRE;
		final Unit inch = metre.times(0.0254);

		assertEquals(1.9, inch.convertTo(metre, 75), 0.01);

		// try random stuff
		for (int i = 0; i < 1000; i++) {
			// initiate random values
			final double conversionFactor = rng.nextDouble() * 1000000;
			final double testValue = rng.nextDouble() * 1000000;
			final double expected = testValue * conversionFactor;

			// test
			final Unit unit = SI.METRE.times(conversionFactor);
			final double actual = unit.convertToBase(testValue);

			assertEquals(actual, expected, expected * DecimalComparison.DOUBLE_EPSILON);
		}
	}

	@Test
	public void testEquals() {
		final BaseUnit metre = SI.METRE;
		final Unit meter = SI.SI.getBaseUnit(StandardDimensions.LENGTH);

		assertEquals(metre, meter);
	}

	@Test
	public void testMultiplicationAndDivision() {
		// test unit-times-unit multiplication
		final LinearUnit generatedJoule = SI.KILOGRAM.times(SI.METRE.toExponent(2)).dividedBy(SI.SECOND.toExponent(2));
		final LinearUnit actualJoule = SI.SI.getBaseUnit(StandardDimensions.ENERGY);

		assertEquals(generatedJoule, actualJoule);

		// test multiplication by conversion factors
		final LinearUnit kilometre = SI.METRE.times(1000);
		final LinearUnit hour = SI.SECOND.times(3600);
		final LinearUnit generatedKPH = kilometre.dividedBy(hour);

		final LinearUnit actualKPH = SI.SI.getBaseUnit(StandardDimensions.VELOCITY).dividedBy(3.6);

		assertEquals(generatedKPH, actualKPH);
	}

	@Test
	public void testPrefixes() {
		final LinearUnit generatedKilometre = SI.METRE.withPrefix(SIPrefix.KILO);
		final LinearUnit actualKilometre = SI.METRE.times(1000);

		assertEquals(generatedKilometre, actualKilometre);
	}
}