/*
 * VectorGraphics2D: Vector export for Java(R) Graphics2D
 *
 * (C) Copyright 2010-2017 Erich Seifert <dev[at]erichseifert.de>,
 * Michael Seifert <mseifert[at]error-reports.org>
 *
 * This file is part of VectorGraphics2D.
 *
 * VectorGraphics2D is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * VectorGraphics2D 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with VectorGraphics2D.  If not, see <http://www.gnu.org/licenses/>.
 */
package de.erichseifert.vectorgraphics2d.intermediate.filters;

import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;

import de.erichseifert.vectorgraphics2d.intermediate.CommandSequence;
import de.erichseifert.vectorgraphics2d.intermediate.commands.Command;

public abstract class StreamingFilter implements Iterator<Command<?>>, Filter {
	private final Queue<Command<?>> buffer;
	private final Iterator<Command<?>> iterator;

	public StreamingFilter(CommandSequence stream) {
		buffer = new LinkedList<>();
		iterator = stream.iterator();
	}

	public Iterator<Command<?>> iterator() {
		return this;
	}

	public boolean hasNext() {
		findNextCommand();
		return !buffer.isEmpty();
	}

	private void findNextCommand() {
		while (buffer.isEmpty() && iterator.hasNext()) {
			Command<?> command = iterator.next();
			List<Command<?>> commands = filter(command);
			if (commands != null) {
				buffer.addAll(commands);
			}
		}
	}

	public Command<?> next() {
		findNextCommand();
		return buffer.poll();
	}

	public void remove() {
	}

	protected abstract List<Command<?>> filter(Command<?> command);
}

