DiskCache.java

/*
 *  Copyright 2012 Eric F. Savage, code@efsavage.com
 *
 *   Licensed under the Apache License, Version 2.0 (the "License");
 *   you may not use this file except in compliance with the License.
 *   You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 *   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.
 */
package com.ajah.http.cache;

import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.Date;
import java.util.logging.Level;

import lombok.extern.java.Log;

import com.ajah.crypto.SHA;
import com.ajah.http.Http;
import com.ajah.http.err.HttpException;
import com.ajah.http.err.InternalServerError;
import com.ajah.http.err.NotFoundException;
import com.ajah.http.err.UnexpectedResponseCode;
import com.ajah.util.config.Config;
import com.ajah.util.date.DateUtils;
import com.ajah.util.io.file.FileHashUtils;
import com.ajah.util.io.file.FileUtils;

/**
 * Disk-based implementation of HttpCache.
 * 
 * @author <a href="http://efsavage.com">Eric F. Savage</a>, <a
 *         href="mailto:code@efsavage.com">code@efsavage.com</a>.
 * @author <a href="http://whirlycott.com">Philip Jacob</a>, <a
 *         href="mailto:phil@whirlycott.com">phil@whirlycott.com</a>.
 */
@Log
public class DiskCache implements HttpCache {

	/**
	 * Fetches a URI as a string, with a cache expiration time.
	 * 
	 * @param uri
	 *            The URI to fetch
	 * @param maxAge
	 *            The maximum age of the cached copy to use.
	 * @return The fetched string.
	 * @throws IOException
	 *             If the URI could not be fetched.
	 * @throws NotFoundException
	 *             If the URI is 404
	 * @throws NotFoundException
	 *             If the resource was not found.
	 * @throws UnexpectedResponseCode
	 *             If the URI returns a response code that {@link Http} cannot
	 *             not handle.
	 * @throws InternalServerError
	 */
	public static String get(final URI uri, final long maxAge) throws IOException, HttpException {
		return new String(getBytes(uri, maxAge), "UTF-8");
	}

	/**
	 * Returns the content from cache if possible, and if not, will fetch and
	 * cache it.
	 * 
	 * @param uri
	 *            The URI to fetch.
	 * @param maxAge
	 *            The maximum age in milliseconds of the cached copy to return.
	 *            Use -1 to force a fresh fetch.
	 * @return The content from cache or as fetched.
	 * @throws IOException
	 *             If the URI could not be fetched.
	 * @throws NotFoundException
	 *             If the URI is 404
	 * @throws UnexpectedResponseCode
	 *             If the URI returns a response code that {@link Http} cannot
	 *             not handle.
	 * @throws InternalServerError
	 */
	public static byte[] getBytes(final URI uri, final long maxAge) throws IOException, HttpException {
		// TODO Add max-age
		// IDEA Store expires header, check last-modified
		final String path = FileHashUtils.getHashedFileName(SHA.sha1Hex(uri.toString()), 3, 2);
		final File cacheDir = new File(Config.i.get("ajah.http.cache.dir", "/tmp/ajah-http-cache"));
		final File f = new File(cacheDir, path);
		log.finest("Cache location: " + f.getAbsolutePath());

		byte[] data = null;
		if (f.exists()) {
			if (maxAge == Long.MAX_VALUE) {
				log.finest("Indefinite caching enabled; getting " + uri);
				return FileUtils.readFileAsBytes(f);
			} else if (maxAge > 0) {
				final long mod = f.lastModified();
				if (log.isLoggable(Level.FINEST)) {
					log.finest("File modified " + new Date(mod));
					log.finest("Expiration is " + new Date(System.currentTimeMillis() - maxAge));
				}
				if (mod + maxAge > System.currentTimeMillis()) {
					log.finest("Cache hit for " + uri + " (expires in " + DateUtils.formatInterval(maxAge - (System.currentTimeMillis() - mod)) + ")");
					return FileUtils.readFileAsBytes(f);
				}
				log.fine("Cache expired; getting " + uri);
			}

		} else {
			log.fine("Cache miss; getting " + uri);
		}

		data = Http.getBytes(uri);
		FileUtils.write(f, data);
		return data;
	}

	/**
	 * Returns an input stream of the contents of the URL. Note that this does
	 * not stream live off of the server.
	 * 
	 * @param uri
	 *            The URI to fetch.
	 * @param maxAge
	 *            The maximum age in milliseconds of the cached copy to use.
	 * @return The fetched content.
	 * @throws NotFoundException
	 *             If the URI is 404
	 * @throws NotFoundException
	 *             If the resource was not found.
	 * @throws UnexpectedResponseCode
	 *             If the URI returns a response code that {@link Http} cannot
	 *             not handle.
	 * @throws IOException
	 *             If the URI could not be fetched.
	 * @throws InternalServerError
	 */
	public static InputStream getStream(final URI uri, final int maxAge) throws IOException, HttpException {
		return new ByteArrayInputStream(getBytes(uri, maxAge));
	}

	/**
	 * {@inheritDoc}
	 * 
	 * @throws InternalServerError
	 */
	@Override
	public String get(final URI uri) throws IOException, HttpException {
		return new String(getBytes(uri, Long.MAX_VALUE));
	}

	/**
	 * {@inheritDoc}
	 * 
	 * @throws InternalServerError
	 */
	@Override
	public byte[] getBytes(final String uri) throws IOException, URISyntaxException, HttpException {
		return getBytes(new URI(uri), Long.MAX_VALUE);
	}

	/**
	 * Calls {@link #getBytes(URI, long)} with {@link Long#MAX_VALUE} for a
	 * maxAge.
	 * 
	 * @throws InternalServerError
	 * 
	 * @see com.ajah.http.cache.HttpCache#getBytes(java.net.URI)
	 */
	@Override
	public byte[] getBytes(final URI uri) throws IOException, HttpException {
		return getBytes(uri, Long.MAX_VALUE);
	}

}