/**
 * 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 org.unitConverter.unit;

import java.util.Objects;

import org.unitConverter.dimension.UnitDimension;

/**
 * A unit that is the base for its dimension. It does not have to be for a base dimension, so units like the Newton and
 * Joule are still base units.
 * 
 * @author Adrien Hopkins
 * @since 2018-12-23
 * @since v0.1.0
 */
public final class BaseUnit extends AbstractUnit implements OperatableUnit {
	/**
	 * Is this unit a full base (i.e. m, s, ... but not N, J, ...)
	 * 
	 * @since 2019-01-15
	 * @since v0.1.0
	 */
	private final boolean isFullBase;

	/**
	 * Creates the {@code BaseUnit}.
	 * 
	 * @param dimension
	 *            dimension measured by unit
	 * @param system
	 *            system that unit is a part of
	 * @param name
	 *            name of unit
	 * @param symbol
	 *            symbol of unit
	 * @since 2018-12-23
	 * @since v0.1.0
	 */
	BaseUnit(final UnitDimension dimension, final UnitSystem system) {
		super(dimension, system);
		this.isFullBase = dimension.isBase();
	}

	/**
	 * @return this unit as a {@code LinearUnit}
	 * @since 2019-01-25
	 * @since v0.1.0
	 */
	public LinearUnit asLinearUnit() {
		return this.times(1);
	}

	@Override
	public double convertFromBase(final double value) {
		return value;
	}

	@Override
	public double convertToBase(final double value) {
		return value;
	}

	/**
	 * Divides this unit by another unit.
	 * 
	 * @param other
	 *            unit to divide by
	 * @return quotient of two units
	 * @throws IllegalArgumentException
	 *             if this unit's system is not other's system
	 * @throws NullPointerException
	 *             if other is null
	 * @since 2018-12-22
	 * @since v0.1.0
	 */
	public BaseUnit dividedBy(final BaseUnit other) {
		Objects.requireNonNull(other, "other must not be null.");
		if (!this.getSystem().equals(other.getSystem()))
			throw new IllegalArgumentException("Incompatible base units for division.");
		return new BaseUnit(this.getDimension().dividedBy(other.getDimension()), this.getSystem());
	}

	/**
	 * Divides this unit by a divisor
	 * 
	 * @param divisor
	 *            amount to divide by
	 * @return quotient
	 * @since 2018-12-23
	 * @since v0.1.0
	 */
	public LinearUnit dividedBy(final double divisor) {
		return new LinearUnit(this, 1 / divisor);
	}

	@Override
	public boolean equals(final Object obj) {
		if (!(obj instanceof BaseUnit))
			return false;
		final BaseUnit other = (BaseUnit) obj;
		return Objects.equals(this.getSystem(), other.getSystem())
				&& Objects.equals(this.getDimension(), other.getDimension());
	}

	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = result * prime + this.getSystem().hashCode();
		result = result * prime + this.getDimension().hashCode();
		return result;
	}

	@Override
	public LinearUnit negated() {
		return this.times(-1);
	}

	@Override
	public OperatableUnit plus(final OperatableUnit addend) {
		Objects.requireNonNull(addend, "addend must not be null.");

		// reject addends that cannot be added to this unit
		if (!this.getSystem().equals(addend.getSystem()))
			throw new IllegalArgumentException(
					String.format("Incompatible units for addition or subtraction \"%s\" and \"%s\".", this, addend));
		if (!this.getDimension().equals(addend.getDimension()))
			throw new IllegalArgumentException(
					String.format("Incompatible units for addition or subtraction \"%s\" and \"%s\".", this, addend));

		// add them together
		if (addend instanceof BaseUnit)
			return this.times(2);
		else
			return addend.plus(this);
	}

	@Override
	public BaseUnit reciprocal() {
		return this.toExponent(-1);
	}

	/**
	 * Multiplies this unit by another unit.
	 * 
	 * @param other
	 *            unit to multiply by
	 * @return product of two units
	 * @throws IllegalArgumentException
	 *             if this unit's system is not other's system
	 * @throws NullPointerException
	 *             if other is null
	 * @since 2018-12-22
	 * @since v0.1.0
	 */
	public BaseUnit times(final BaseUnit other) {
		Objects.requireNonNull(other, "other must not be null.");
		if (!this.getSystem().equals(other.getSystem()))
			throw new IllegalArgumentException("Incompatible base units for multiplication.");
		return new BaseUnit(this.getDimension().times(other.getDimension()), this.getSystem());
	}

	/**
	 * Multiplies this unit by a multiplier.
	 * 
	 * @param multiplier
	 *            amount to multiply by
	 * @return product
	 * @since 2018-12-23
	 * @since v0.1.0
	 */
	public LinearUnit times(final double multiplier) {
		return new LinearUnit(this, multiplier);
	}

	@Override
	public OperatableUnit times(final OperatableUnit multiplier) {
		Objects.requireNonNull(multiplier, "multiplier must not be null.");

		// reject multipliers that cannot be muliplied by this unit
		if (!this.getSystem().equals(multiplier.getSystem()))
			throw new IllegalArgumentException(String
					.format("Incompatible units for multiplication or division \"%s\" and \"%s\".", this, multiplier));

		// multiply the units
		if (multiplier instanceof BaseUnit)
			return new BaseUnit(this.getDimension().times(multiplier.getDimension()), this.getSystem());
		else
			return multiplier.times(this);
	}

	/**
	 * Returns this unit, but to an exponent.
	 * 
	 * @param exponent
	 *            exponent
	 * @return result of exponentiation
	 * @since 2019-01-15
	 * @since v0.1.0
	 */
	@Override
	public BaseUnit toExponent(final int exponent) {
		return this.getSystem().getBaseUnit(this.getDimension().toExponent(exponent));
	}

	@Override
	public String toString() {
		return String.format("%s base unit of%s dimension %s", this.getSystem(), this.isFullBase ? " base" : "",
				this.getDimension());
	}
}