/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.shiro.cache.ehcache;

import org.apache.shiro.cache.Cache;
import org.apache.shiro.cache.CacheException;
import org.apache.shiro.cache.CacheManager;
import org.apache.shiro.config.ConfigurationException;
import org.apache.shiro.io.ResourceUtils;
import org.apache.shiro.util.Destroyable;
import org.apache.shiro.util.Initializable;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.io.InputStream;

/**
 * Shiro {@code CacheManager} implementation utilizing the Ehcache framework for all cache functionality.
 * <p/>
 * This class can {@link #setCacheManager(net.sf.ehcache.CacheManager) accept} a manually configured
 * {@link net.sf.ehcache.CacheManager net.sf.ehcache.CacheManager} instance,
 * or an {@code ehcache.xml} path location can be specified instead and one will be constructed. If neither are
 * specified, Shiro's failsafe <code><a href="./ehcache.xml">ehcache.xml</a>} file will be used by default.
 * <p/>
 * This implementation requires EhCache 1.2 and above. Make sure EhCache 1.1 or earlier
 * is not in the classpath or it will not work.
 * <p/>
 * Please see the <a href="http://ehcache.sf.net" target="_top">Ehcache website</a> for their documentation.
 *
 * @see <a href="http://ehcache.sf.net" target="_top">The Ehcache website</a>
 * @since 0.2
 */
public class EhCacheManager implements CacheManager, Initializable, Destroyable {

    /**
     * This class's private log instance.
     */
    private static final Logger log = LoggerFactory.getLogger(EhCacheManager.class);

    /**
     * The EhCache cache manager used by this implementation to create caches.
     */
    protected net.sf.ehcache.CacheManager manager;

    /**
     * Indicates if the CacheManager instance was implicitly/automatically created by this instance, indicating that
     * it should be automatically cleaned up as well on shutdown.
     */
    private boolean cacheManagerImplicitlyCreated = false;

    /**
     * Classpath file location of the ehcache CacheManager config file.
     */
    private String cacheManagerConfigFile = "classpath:org/apache/shiro/cache/ehcache/ehcache.xml";

    /**
     * Default no argument constructor
     */
    public EhCacheManager() {
    }

    /**
     * Returns the wrapped Ehcache {@link net.sf.ehcache.CacheManager CacheManager} instance.
     *
     * @return the wrapped Ehcache {@link net.sf.ehcache.CacheManager CacheManager} instance.
     */
    public net.sf.ehcache.CacheManager getCacheManager() {
        return manager;
    }

    /**
     * Sets the wrapped Ehcache {@link net.sf.ehcache.CacheManager CacheManager} instance.
     *
     * @param manager the wrapped Ehcache {@link net.sf.ehcache.CacheManager CacheManager} instance.
     */
    public void setCacheManager(net.sf.ehcache.CacheManager manager) {
        this.manager = manager;
    }

    /**
     * Returns the resource location of the config file used to initialize a new
     * EhCache CacheManager instance.  The string can be any resource path supported by the
     * {@link org.apache.shiro.io.ResourceUtils#getInputStreamForPath(String)} call.
     * <p/>
     * This property is ignored if the CacheManager instance is injected directly - that is, it is only used to
     * lazily create a CacheManager if one is not already provided.
     *
     * @return the resource location of the config file used to initialize the wrapped
     *         EhCache CacheManager instance.
     */
    public String getCacheManagerConfigFile() {
        return this.cacheManagerConfigFile;
    }

    /**
     * Sets the resource location of the config file used to initialize the wrapped
     * EhCache CacheManager instance.  The string can be any resource path supported by the
     * {@link org.apache.shiro.io.ResourceUtils#getInputStreamForPath(String)} call.
     * <p/>
     * This property is ignored if the CacheManager instance is injected directly - that is, it is only used to
     * lazily create a CacheManager if one is not already provided.
     *
     * @param classpathLocation resource location of the config file used to create the wrapped
     *                          EhCache CacheManager instance.
     */
    public void setCacheManagerConfigFile(String classpathLocation) {
        this.cacheManagerConfigFile = classpathLocation;
    }

    /**
     * Acquires the InputStream for the ehcache configuration file using
     * {@link ResourceUtils#getInputStreamForPath(String) ResourceUtils.getInputStreamForPath} with the
     * path returned from {@link #getCacheManagerConfigFile() getCacheManagerConfigFile()}.
     *
     * @return the InputStream for the ehcache configuration file.
     */
    protected InputStream getCacheManagerConfigFileInputStream() {
        String configFile = getCacheManagerConfigFile();
        try {
            return ResourceUtils.getInputStreamForPath(configFile);
        } catch (IOException e) {
            throw new ConfigurationException("Unable to obtain input stream for cacheManagerConfigFile [" +
                    configFile + "]", e);
        }
    }

    /**
     * Loads an existing EhCache from the cache manager, or starts a new cache if one is not found.
     *
     * @param name the name of the cache to load/create.
     */
    public final <K, V> Cache<K, V> getCache(String name) throws CacheException {

        if (log.isTraceEnabled()) {
            log.trace("Acquiring EhCache instance named [" + name + "]");
        }

        try {
            net.sf.ehcache.Ehcache cache = ensureCacheManager().getEhcache(name);
            if (cache == null) {
                if (log.isInfoEnabled()) {
                    log.info("Cache with name '{}' does not yet exist.  Creating now.", name);
                }
                this.manager.addCache(name);

                cache = manager.getCache(name);

                if (log.isInfoEnabled()) {
                    log.info("Added EhCache named [" + name + "]");
                }
            } else {
                if (log.isInfoEnabled()) {
                    log.info("Using existing EHCache named [" + cache.getName() + "]");
                }
            }
            return new EhCache<K, V>(cache);
        } catch (net.sf.ehcache.CacheException e) {
            throw new CacheException(e);
        }
    }

    /**
     * Initializes this instance.
     * <p/>
     * If a {@link #setCacheManager CacheManager} has been
     * explicitly set (e.g. via Dependency Injection or programatically) prior to calling this
     * method, this method does nothing.
     * <p/>
     * However, if no {@code CacheManager} has been set, the default Ehcache singleton will be initialized, where
     * Ehcache will look for an {@code ehcache.xml} file at the root of the classpath.  If one is not found,
     * Ehcache will use its own failsafe configuration file.
     * <p/>
     * Because Shiro cannot use the failsafe defaults (fail-safe expunges cached objects after 2 minutes,
     * something not desirable for Shiro sessions), this class manages an internal default configuration for
     * this case.
     *
     * @throws org.apache.shiro.cache.CacheException
     *          if there are any CacheExceptions thrown by EhCache.
     * @see net.sf.ehcache.CacheManager#create
     */
    public final void init() throws CacheException {
        ensureCacheManager();
    }

    private net.sf.ehcache.CacheManager ensureCacheManager() {
        try {
            if (this.manager == null) {
                if (log.isDebugEnabled()) {
                    log.debug("cacheManager property not set.  Constructing CacheManager instance... ");
                }
                //using the CacheManager constructor, the resulting instance is _not_ a VM singleton
                //(as would be the case by calling CacheManager.getInstance().  We do not use the getInstance here
                //because we need to know if we need to destroy the CacheManager instance - using the static call,
                //we don't know which component is responsible for shutting it down.  By using a single EhCacheManager,
                //it will always know to shut down the instance if it was responsible for creating it.
                this.manager = new net.sf.ehcache.CacheManager(getCacheManagerConfigFileInputStream());
                if (log.isTraceEnabled()) {
                    log.trace("instantiated Ehcache CacheManager instance.");
                }
                cacheManagerImplicitlyCreated = true;
                if (log.isDebugEnabled()) {
                    log.debug("implicit cacheManager created successfully.");
                }
            }
            return this.manager;
        } catch (Exception e) {
            throw new CacheException(e);
        }
    }

    /**
     * Shuts-down the wrapped Ehcache CacheManager <b>only if implicitly created</b>.
     * <p/>
     * If another component injected
     * a non-null CacheManager into this instace before calling {@link #init() init}, this instance expects that same
     * component to also destroy the CacheManager instance, and it will not attempt to do so.
     */
    public void destroy() {
        if (cacheManagerImplicitlyCreated) {
            try {
                net.sf.ehcache.CacheManager cacheMgr = getCacheManager();
                cacheMgr.shutdown();
            } catch (Exception e) {
                if (log.isWarnEnabled()) {
                    log.warn("Unable to cleanly shutdown implicitly created CacheManager instance.  " +
                            "Ignoring (shutting down)...");
                }
            }
            cacheManagerImplicitlyCreated = false;
        }
    }
}
