/**
 * Copyright (C) 2019 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.Arrays;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Objects;
import java.util.Optional;
import java.util.Set;

/**
 * A class that can be used to specify names and a symbol for a unit.
 * 
 * @author Adrien Hopkins
 * @since 2019-10-21
 */
public final class NameSymbol {
	public static final NameSymbol EMPTY = new NameSymbol(Optional.empty(), Optional.empty(), new HashSet<>());

	/**
	 * Creates a {@code NameSymbol}, ensuring that if primaryName is null and
	 * otherNames is not empty, one name is moved from otherNames to primaryName
	 * 
	 * Ensure that otherNames is a copy of the inputted argument.
	 */
	private static final NameSymbol create(final String name, final String symbol, final Set<String> otherNames) {
		final Optional<String> primaryName;

		if (name == null && !otherNames.isEmpty()) {
			// get primary name and remove it from savedNames
			Iterator<String> it = otherNames.iterator();
			assert it.hasNext();
			primaryName = Optional.of(it.next());
			otherNames.remove(primaryName.get());
		} else {
			primaryName = Optional.ofNullable(name);
		}

		return new NameSymbol(primaryName, Optional.ofNullable(symbol), otherNames);
	}

	/**
	 * Gets a {@code NameSymbol} with a primary name, a symbol and no other names.
	 * 
	 * @param name   name to use
	 * @param symbol symbol to use
	 * @return NameSymbol instance
	 * @since 2019-10-21
	 * @throws NullPointerException if name or symbol is null
	 */
	public static final NameSymbol of(final String name, final String symbol) {
		return new NameSymbol(Optional.of(name), Optional.of(symbol), new HashSet<>());
	}

	/**
	 * Gets a {@code NameSymbol} with a primary name, a symbol and additional names.
	 * 
	 * @param name       name to use
	 * @param symbol     symbol to use
	 * @param otherNames other names to use
	 * @return NameSymbol instance
	 * @since 2019-10-21
	 * @throws NullPointerException if any argument is null
	 */
	public static final NameSymbol of(final String name, final String symbol, final Set<String> otherNames) {
		return new NameSymbol(Optional.of(name), Optional.of(symbol),
				new HashSet<>(Objects.requireNonNull(otherNames, "otherNames must not be null.")));
	}

	/**
	 * h * Gets a {@code NameSymbol} with a primary name, a symbol and additional
	 * names.
	 * 
	 * @param name       name to use
	 * @param symbol     symbol to use
	 * @param otherNames other names to use
	 * @return NameSymbol instance
	 * @since 2019-10-21
	 * @throws NullPointerException if any argument is null
	 */
	public static final NameSymbol of(final String name, final String symbol, final String... otherNames) {
		return new NameSymbol(Optional.of(name), Optional.of(symbol),
				new HashSet<>(Arrays.asList(Objects.requireNonNull(otherNames, "otherNames must not be null."))));
	}

	/**
	 * Gets a {@code NameSymbol} with a primary name, a symbol and an additional
	 * name.
	 * 
	 * @param name       name to use
	 * @param symbol     symbol to use
	 * @param otherNames other names to use
	 * @param name2      alternate name
	 * @return NameSymbol instance
	 * @since 2019-10-21
	 * @throws NullPointerException if any argument is null
	 */
	public static final NameSymbol of(final String name, final String symbol, final String name2) {
		final Set<String> otherNames = new HashSet<>();
		otherNames.add(Objects.requireNonNull(name2, "name2 must not be null."));
		return new NameSymbol(Optional.of(name), Optional.of(symbol), otherNames);
	}

	/**
	 * Gets a {@code NameSymbol} with a primary name, a symbol and additional names.
	 * 
	 * @param name       name to use
	 * @param symbol     symbol to use
	 * @param otherNames other names to use
	 * @param name2      alternate name
	 * @param name3      alternate name
	 * @return NameSymbol instance
	 * @since 2019-10-21
	 * @throws NullPointerException if any argument is null
	 */
	public static final NameSymbol of(final String name, final String symbol, final String name2, final String name3) {
		final Set<String> otherNames = new HashSet<>();
		otherNames.add(Objects.requireNonNull(name2, "name2 must not be null."));
		otherNames.add(Objects.requireNonNull(name3, "name3 must not be null."));
		return new NameSymbol(Optional.of(name), Optional.of(symbol), otherNames);
	}

	/**
	 * Gets a {@code NameSymbol} with a primary name, a symbol and additional names.
	 * 
	 * @param name       name to use
	 * @param symbol     symbol to use
	 * @param otherNames other names to use
	 * @param name2      alternate name
	 * @param name3      alternate name
	 * @param name4      alternate name
	 * @return NameSymbol instance
	 * @since 2019-10-21
	 * @throws NullPointerException if any argument is null
	 */
	public static final NameSymbol of(final String name, final String symbol, final String name2, final String name3,
			final String name4) {
		final Set<String> otherNames = new HashSet<>();
		otherNames.add(Objects.requireNonNull(name2, "name2 must not be null."));
		otherNames.add(Objects.requireNonNull(name3, "name3 must not be null."));
		otherNames.add(Objects.requireNonNull(name4, "name4 must not be null."));
		return new NameSymbol(Optional.of(name), Optional.of(symbol), otherNames);
	}

	/**
	 * Gets a {@code NameSymbol} with a primary name, no symbol, and no other names.
	 * 
	 * @param name name to use
	 * @return NameSymbol instance
	 * @since 2019-10-21
	 * @throws NullPointerException if name is null
	 */
	public static final NameSymbol ofName(final String name) {
		return new NameSymbol(Optional.of(name), Optional.empty(), new HashSet<>());
	}

	/**
	 * Gets a {@code NameSymbol} with a primary name, a symbol and additional names.
	 * <p>
	 * If any argument is null, this static factory replaces it with an empty
	 * Optional or empty Set.
	 * <p>
	 * If {@code name} is null and {@code otherNames} is not empty, a primary name
	 * will be picked from {@code otherNames}. This name will not appear in
	 * getOtherNames().
	 * 
	 * @param name       name to use
	 * @param symbol     symbol to use
	 * @param otherNames other names to use
	 * @return NameSymbol instance
	 * @since 2019-11-26
	 */
	public static final NameSymbol ofNullable(final String name, final String symbol, final Set<String> otherNames) {
		return NameSymbol.create(name, symbol, otherNames == null ? new HashSet<>() : new HashSet<>(otherNames));
	}

	/**
	 * h * Gets a {@code NameSymbol} with a primary name, a symbol and additional
	 * names.
	 * <p>
	 * If any argument is null, this static factory replaces it with an empty
	 * Optional or empty Set.
	 * <p>
	 * If {@code name} is null and {@code otherNames} is not empty, a primary name
	 * will be picked from {@code otherNames}. This name will not appear in
	 * getOtherNames().
	 * 
	 * @param name       name to use
	 * @param symbol     symbol to use
	 * @param otherNames other names to use
	 * @return NameSymbol instance
	 * @since 2019-11-26
	 */
	public static final NameSymbol ofNullable(final String name, final String symbol, final String... otherNames) {
		return create(name, symbol, otherNames == null ? new HashSet<>() : new HashSet<>(Arrays.asList(otherNames)));
	}

	/**
	 * Gets a {@code NameSymbol} with a symbol and no names.
	 * 
	 * @param symbol symbol to use
	 * @return NameSymbol instance
	 * @since 2019-10-21
	 * @throws NullPointerException if symbol is null
	 */
	public static final NameSymbol ofSymbol(final String symbol) {
		return new NameSymbol(Optional.empty(), Optional.of(symbol), new HashSet<>());
	}

	private final Optional<String> primaryName;
	private final Optional<String> symbol;

	private final Set<String> otherNames;

	/**
	 * Creates the {@code NameSymbol}.
	 * 
	 * @param primaryName primary name of unit
	 * @param symbol      symbol used to represent unit
	 * @param otherNames  other names and/or spellings, should be a mutable copy of
	 *                    the argument
	 * @since 2019-10-21
	 */
	private NameSymbol(final Optional<String> primaryName, final Optional<String> symbol,
			final Set<String> otherNames) {
		this.primaryName = primaryName;
		this.symbol = symbol;
		otherNames.remove(null);
		this.otherNames = Collections.unmodifiableSet(otherNames);
		
		if (this.primaryName.isEmpty())
			assert this.otherNames.isEmpty();
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (!(obj instanceof NameSymbol))
			return false;
		NameSymbol other = (NameSymbol) obj;
		if (otherNames == null) {
			if (other.otherNames != null)
				return false;
		} else if (!otherNames.equals(other.otherNames))
			return false;
		if (primaryName == null) {
			if (other.primaryName != null)
				return false;
		} else if (!primaryName.equals(other.primaryName))
			return false;
		if (symbol == null) {
			if (other.symbol != null)
				return false;
		} else if (!symbol.equals(other.symbol))
			return false;
		return true;
	}

	/**
	 * @return otherNames
	 * @since 2019-10-21
	 */
	public final Set<String> getOtherNames() {
		return this.otherNames;
	}

	/**
	 * @return primaryName
	 * @since 2019-10-21
	 */
	public final Optional<String> getPrimaryName() {
		return this.primaryName;
	}
	
	/**
	 * @return symbol
	 * @since 2019-10-21
	 */
	public final Optional<String> getSymbol() {
		return this.symbol;
	}

	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + ((otherNames == null) ? 0 : otherNames.hashCode());
		result = prime * result + ((primaryName == null) ? 0 : primaryName.hashCode());
		result = prime * result + ((symbol == null) ? 0 : symbol.hashCode());
		return result;
	}

	/**
	 * @return true iff this {@code NameSymbol} contains no names or symbols.
	 */
	public final boolean isEmpty() {
		// if primaryName is empty, otherNames must also be empty
		return this.primaryName.isEmpty() && this.symbol.isEmpty();
	}
}