/**
 * Copyright (C) 2020 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 sevenUnits.unit;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import sevenUnits.math.ObjectProduct;

/**
 * A combination of units, like "5 foot + 7 inch". All but the last units should
 * have a whole number value associated with them.
 *
 * @since 2020-10-02
 */
public final class MultiUnit extends Unitlike<List<Double>> {
	/**
	 * Creates a {@code MultiUnit} from its units. It will not have a name or
	 * symbol.
	 *
	 * @since 2020-10-03
	 */
	public static final MultiUnit of(LinearUnit... units) {
		return of(Arrays.asList(units));
	}
	
	/**
	 * Creates a {@code MultiUnit} from its units. It will not have a name or
	 * symbol.
	 *
	 * @since 2020-10-03
	 */
	public static final MultiUnit of(List<LinearUnit> units) {
		if (units.size() < 1)
			throw new IllegalArgumentException("Must have at least one unit");
		final ObjectProduct<BaseUnit> unitBase = units.get(0).getBase();
		for (final LinearUnit unit : units) {
			if (!unitBase.equals(unit.getBase()))
				throw new IllegalArgumentException(
						"All units must have the same base.");
		}
		return new MultiUnit(new ArrayList<>(units), unitBase, NameSymbol.EMPTY);
	}
	
	/**
	 * The units that make up this value.
	 */
	private final List<LinearUnit> units;
	
	/**
	 * Creates a {@code MultiUnit}.
	 *
	 * @since 2020-10-03
	 */
	private MultiUnit(List<LinearUnit> units, ObjectProduct<BaseUnit> unitBase,
			NameSymbol ns) {
		super(unitBase, ns);
		this.units = units;
	}
	
	@Override
	protected List<Double> convertFromBase(double value) {
		final List<Double> values = new ArrayList<>(this.units.size());
		double temp = value;
		
		for (final LinearUnit unit : this.units.subList(0,
				this.units.size() - 1)) {
			values.add(Math.floor(temp / unit.getConversionFactor()));
			temp %= unit.getConversionFactor();
		}
		
		values.add(this.units.size() - 1,
				this.units.get(this.units.size() - 1).convertFromBase(temp));
		
		return values;
	}
	
	/**
	 * Converts a value expressed in this unitlike form to a value expressed in
	 * {@code other}.
	 * 
	 * @implSpec If conversion is possible, this implementation returns
	 *           {@code other.convertFromBase(this.convertToBase(value))}.
	 *           Therefore, overriding either of those methods will change the
	 *           output of this method.
	 * 				
	 * @param other unit to convert to
	 * @param value value to convert
	 * @return converted value
	 * @since 2020-10-03
	 * @throws IllegalArgumentException if {@code other} is incompatible for
	 *                                  conversion with this unitlike form (as
	 *                                  tested by {@link Unit#canConvertTo}).
	 * @throws NullPointerException     if other is null
	 */
	public final <U extends Unitlike<V>, V> V convertTo(U other,
			double... values) {
		final List<Double> valueList = new ArrayList<>(values.length);
		for (final double d : values) {
			valueList.add(d);
		}
		
		return this.convertTo(other, valueList);
	}
	
	/**
	 * Converts a value expressed in this unitlike form to a value expressed in
	 * {@code other}.
	 * 
	 * @implSpec If conversion is possible, this implementation returns
	 *           {@code other.convertFromBase(this.convertToBase(value))}.
	 *           Therefore, overriding either of those methods will change the
	 *           output of this method.
	 * 				
	 * @param other unit to convert to
	 * @param value value to convert
	 * @return converted value
	 * @since 2020-10-03
	 * @throws IllegalArgumentException if {@code other} is incompatible for
	 *                                  conversion with this unitlike form (as
	 *                                  tested by {@link Unit#canConvertTo}).
	 * @throws NullPointerException     if other is null
	 */
	public final double convertTo(Unit other, double... values) {
		final List<Double> valueList = new ArrayList<>(values.length);
		for (final double d : values) {
			valueList.add(d);
		}
		
		return this.convertTo(other, valueList);
	}
	
	@Override
	protected double convertToBase(List<Double> value) {
		if (value.size() != this.units.size())
			throw new IllegalArgumentException("Wrong number of values for "
					+ this.units.size() + "-unit MultiUnit.");
		
		double baseValue = 0;
		for (int i = 0; i < this.units.size(); i++) {
			baseValue += value.get(i) * this.units.get(i).getConversionFactor();
		}
		return baseValue;
	}
}