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PlantUML is a component that allows to quickly write diagrams from text.
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// THIS FILE HAS BEEN GENERATED BY A PREPROCESSOR.
/* +=======================================================================
 * |
 * |      PlantUML : a free UML diagram generator
 * |
 * +=======================================================================
 *
 * (C) Copyright 2009-2024, Arnaud Roques
 *
 * Project Info:  https://plantuml.com
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 * PlantUML is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License V2.
 *
 * THE ACCOMPANYING PROGRAM IS PROVIDED UNDER THE TERMS OF THIS ECLIPSE PUBLIC
 * LICENSE ("AGREEMENT"). [GNU General Public License V2]
 *
 * ANY USE, REPRODUCTION OR DISTRIBUTION OF THE PROGRAM CONSTITUTES
 * RECIPIENT'S ACCEPTANCE OF THIS AGREEMENT.
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 * You may obtain a copy of the License at
 *
 * https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
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 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * PlantUML can occasionally display sponsored or advertising messages. Those
 * messages are usually generated on welcome or error images and never on
 * functional diagrams.
 * See https://plantuml.com/professional if you want to remove them
 *
 * Images (whatever their format : PNG, SVG, EPS...) generated by running PlantUML
 * are owned by the author of their corresponding sources code (that is, their
 * textual description in PlantUML language). Those images are not covered by
 * this GPL v2 license.
 *
 * The generated images can then be used without any reference to the GPL v2 license.
 * It is not even necessary to stipulate that they have been generated with PlantUML,
 * although this will be appreciated by the PlantUML team.
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 * There is an exception : if the textual description in PlantUML language is also covered
 * by any license, then the generated images are logically covered
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 * This is the IGY distribution (Install GraphViz by Yourself).
 * You have to install GraphViz and to setup the GRAPHVIZ_DOT environment variable
 * (see https://plantuml.com/graphviz-dot )
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 * Icons provided by OpenIconic :  https://useiconic.com/open
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 * ASCIIMathML (c) Peter Jipsen http://www.chapman.edu/~jipsen
 * ASCIIMathML (c) David Lippman http://www.pierce.ctc.edu/dlippman
 * CafeUndZopfli ported by Eugene Klyuchnikov https://github.com/eustas/CafeUndZopfli
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 *
 */
package net.sourceforge.plantuml.quantization;

import java.util.AbstractCollection;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;

public final class HashMultiset extends AbstractCollection implements Multiset {
	private final Map elementCounts = new HashMap<>();
	private int size;

	public HashMultiset() {
	}

	public HashMultiset(Collection source) {
		addAll(source);
	}

	@Override
	public void add(E element, int n) {
		Count count = elementCounts.get(element);
		if (count != null)
			count.value += n;
		else
			elementCounts.put(element, new Count(n));

		size += n;
	}

	@Override
	public boolean add(E element) {
		add(element, 1);
		return true;
	}

	@Override
	public int remove(Object element, int n) {
		Count count = elementCounts.get(element);
		if (count == null)
			return 0;

		if (n < count.value) {
			count.value -= n;
			size -= n;
			return n;
		}

		elementCounts.remove(element);
		size -= count.value;
		return count.value;
	}

	@Override
	public boolean remove(Object element) {
		return remove(element, 1) > 0;
	}

	@Override
	public Iterator iterator() {
		return new HashMultisetIterator();
	}

	@Override
	public int size() {
		return size;
	}

	@Override
	public int count(Object element) {
		Count countOrNull = elementCounts.get(element);
		return countOrNull != null ? countOrNull.value : 0;
	}

	@Override
	public Set getDistinctElements() {
		return elementCounts.keySet();
	}

	private final class HashMultisetIterator implements Iterator {
		final private Iterator> distinctElementIterator;
		private E currentElement;
		private int currentCount;
		private boolean currentElementRemoved;

		HashMultisetIterator() {
			this.distinctElementIterator = elementCounts.entrySet().iterator();
			this.currentCount = 0;
		}

		@Override
		public boolean hasNext() {
			return currentCount > 0 || distinctElementIterator.hasNext();
		}

		@Override
		public E next() {
			if (hasNext() == false)
				throw new NoSuchElementException("iterator has been exhausted");

			if (currentCount == 0) {
				Map.Entry next = distinctElementIterator.next();
				currentElement = next.getKey();
				currentCount = next.getValue().value;
			}

			currentCount--;
			currentElementRemoved = false;
			return currentElement;
		}

		@Override
		public void remove() {
			if (currentElement == null)
				throw new IllegalStateException("next() has not been called");

			if (currentElementRemoved)
				throw new IllegalStateException("remove() already called for current element");

			HashMultiset.this.remove(currentElement);
		}
	}

	private static final class Count {
		private int value;

		Count(int value) {
			this.value = value;
		}
	}
}