DefaultExpirationPolicy.java

/*
 * Copyright (c) 2010, the Last.fm Java Project and Committers
 * All rights reserved.
 *
 * Redistribution and use of this software in source and binary forms, with or without modification, are
 * permitted provided that the following conditions are met:
 *
 * - Redistributions of source code must retain the above
 *   copyright notice, this list of conditions and the
 *   following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the
 *   following disclaimer in the documentation and/or other
 *   materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
 * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
 * TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package de.umass.lastfm.cache;

import java.util.HashSet;
import java.util.Map;
import java.util.Set;

/**
 * This Policy maintains a list of methods which should be cached one week. Everything else won't be cached if
 * using this policy.
 *
 * @author Janni Kovacs
 */
public class DefaultExpirationPolicy implements ExpirationPolicy {


	/**
	 * One day in milliseconds
	 */
	protected static final long ONE_DAY = 1000 * 60 * 60 * 24;

	/**
	 * One week in milliseconds
	 */
	protected static final long ONE_WEEK = ONE_DAY * 7;

	/**
	 * Contains method names for all requests that should be cached 1 week
	 */
	protected static final Set<String> ONE_WEEK_METHODS = new HashSet<String>();

	static {
		// similar data
		ONE_WEEK_METHODS.add("artist.getsimilar");
		ONE_WEEK_METHODS.add("tag.getsimilar");
		ONE_WEEK_METHODS.add("track.getsimilar");
		// top chart data
		ONE_WEEK_METHODS.add("artist.gettopalbums");
		ONE_WEEK_METHODS.add("artist.gettoptracks");
		ONE_WEEK_METHODS.add("geo.gettopartists");
		ONE_WEEK_METHODS.add("geo.gettoptracks");
		ONE_WEEK_METHODS.add("tag.gettopalbums");
		ONE_WEEK_METHODS.add("tag.gettopartists");
		ONE_WEEK_METHODS.add("tag.gettoptags");
		ONE_WEEK_METHODS.add("tag.gettoptracks");
		ONE_WEEK_METHODS.add("user.gettopalbums");
		ONE_WEEK_METHODS.add("user.gettopartists");
		ONE_WEEK_METHODS.add("user.gettoptracks");
		ONE_WEEK_METHODS.add("user.gettoptags");
	}

	/**
	 * Contains the expiration time for weekly chart data for the current week, which is
	 * one week by default; last.fm TOS says:
	 * "You agree to cache similar artist and any chart data (top tracks, top artists, top albums) for a minimum of one week."
	 * but they might be outdated the next day.
	 * For now we will cache them one week. If you always need the latest charts but don't want to disable
	 * caching use the {@link #setCacheRecentWeeklyCharts(long)} method to set this value.
	 * This variable also applies to the getWeeklyChartList method
	 */
	protected long cacheRecentWeeklyCharts = ONE_WEEK;

	public long getExpirationTime(String method, Map<String, String> params) {
		method = method.toLowerCase();
		if (method.contains("weekly")) {
			if (!method.contains("list"))
				return params.containsKey("to") && params
						.containsKey("from") ? Long.MAX_VALUE : cacheRecentWeeklyCharts;
			else
				return cacheRecentWeeklyCharts;
		}
		return ONE_WEEK_METHODS.contains(method) ? ONE_WEEK : -1;
	}

	public void setCacheRecentWeeklyCharts(long cacheRecentWeeklyCharts) {
		this.cacheRecentWeeklyCharts = cacheRecentWeeklyCharts;
	}
}