/*
 * This file is part of ELKI:
 * Environment for Developing KDD-Applications Supported by Index-Structures
 *
 * Copyright (C) 2017
 * ELKI Development Team
 *
 * 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 <http://www.gnu.org/licenses/>.
 */
package de.lmu.ifi.dbs.elki.index;

import java.io.Externalizable;

import de.lmu.ifi.dbs.elki.persistent.MemoryPageFileFactory;
import de.lmu.ifi.dbs.elki.persistent.Page;
import de.lmu.ifi.dbs.elki.persistent.PageFile;
import de.lmu.ifi.dbs.elki.persistent.PageFileFactory;
import de.lmu.ifi.dbs.elki.utilities.optionhandling.AbstractParameterizer;
import de.lmu.ifi.dbs.elki.utilities.optionhandling.OptionID;
import de.lmu.ifi.dbs.elki.utilities.optionhandling.parameterization.Parameterization;
import de.lmu.ifi.dbs.elki.utilities.optionhandling.parameters.ObjectParameter;

/**
 * Abstract base class for tree-based indexes.
 * 
 * @author Erich Schubert
 * @since 0.4.0
 * 
 * @apiviz.stereotype factory,interface
 * @apiviz.excludeSubtypes
 * @apiviz.composedOf PageFileFactory
 * 
 * @param <O>
 *            Object type
 * @param <I>
 *            Index type
 */
public abstract class PagedIndexFactory<O, I extends Index> implements IndexFactory<O, I> {
	/**
	 * Page file factory.
	 */
	private PageFileFactory<?> pageFileFactory;

	/**
	 * Constructor.
	 * 
	 * @param pageFileFactory
	 *            Page file factory
	 */
	public PagedIndexFactory(PageFileFactory<?> pageFileFactory) {
		super();
		this.pageFileFactory = pageFileFactory;
	}

	/**
	 * Make the page file for this index.
	 * 
	 * @param <N>
	 *            page type
	 * @param cls
	 *            Class information
	 * @return Page file
	 */
	protected <N extends Page & Externalizable> PageFile<N> makePageFile(Class<N> cls) {
		@SuppressWarnings("unchecked")
		final PageFileFactory<N> castFactory = (PageFileFactory<N>) pageFileFactory;
		return castFactory.newPageFile(cls);
	}

	/**
	 * Parameterization class.
	 * 
	 * @author Erich Schubert
	 * 
	 * @apiviz.exclude
	 */
	public abstract static class Parameterizer<O> extends AbstractParameterizer {
		/**
		 * Optional parameter that specifies the factory type of pagefile to use
		 * for the index.
		 * <p>
		 * Key: {@code -index.pagefile}
		 * </p>
		 */
		public static final OptionID PAGEFILE_ID = new OptionID("index.pagefile",
				"The pagefile factory for storing the index.");

		/**
		 * Page file factory.
		 */
		protected PageFileFactory<?> pageFileFactory;

		@Override
		protected void makeOptions(Parameterization config) {
			super.makeOptions(config);
			ObjectParameter<PageFileFactory<?>> pffP = new ObjectParameter<>(PAGEFILE_ID, PageFileFactory.class,
					MemoryPageFileFactory.class);
			if (config.grab(pffP)) {
				pageFileFactory = pffP.instantiateClass(config);
			}
		}

		@Override
		protected abstract PagedIndexFactory<O, ?> makeInstance();
	}
}