/*
    * Copyright 2002-2014 the original author or authors.
    *
    * 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 org.springframework.cache.interceptor;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  
  import org.springframework.beans.factory.InitializingBean;
  import org.springframework.cache.Cache;
  import org.springframework.cache.CacheManager;
  import org.springframework.util.Assert;
  
  /**
   * A base {@link CacheResolver} implementation that requires the concrete
   * implementation to provide the collection of cache name(s) based on the
   * invocation context.
   *
   * @author Stephane Nicoll
   * @since 4.1
   */
  public abstract class AbstractCacheResolver implements CacheResolver, InitializingBean {
  
  	private CacheManager cacheManager;
  
  
  	protected AbstractCacheResolver() {
  	}
  
  	protected AbstractCacheResolver(CacheManager cacheManager) {
  		this.cacheManager = cacheManager;
  	}
  
  
  	/**
  	 * Set the {@link CacheManager} that this instance should use.
  	 */
  	public void setCacheManager(CacheManager cacheManager) {
  		this.cacheManager = cacheManager;
  	}
  
  	/**
  	 * Return the {@link CacheManager} that this instance use.
  	 */
  	public CacheManager getCacheManager() {
  		return this.cacheManager;
  	}
  
  	@Override
  	public void afterPropertiesSet()  {
  		Assert.notNull(this.cacheManager, "CacheManager must not be null");
  	}
  
  
  	@Override
  	public Collection<? extends Cache> resolveCaches(CacheOperationInvocationContext<?> context) {
  		Collection<String> cacheNames = getCacheNames(context);
  		if (cacheNames == null) {
  			return Collections.emptyList();
  		}
  		else {
  			Collection<Cache> result = new ArrayList<Cache>();
  			for (String cacheName : cacheNames) {
  				Cache cache = this.cacheManager.getCache(cacheName);
  				if (cache == null) {
  					throw new IllegalArgumentException("Cannot find cache named '" +
  							cacheName + "' for " + context.getOperation());
  				}
  				result.add(cache);
  			}
  			return result;
  		}
  	}
  
  	/**
  	 * Provide the name of the cache(s) to resolve against the current cache manager.
  	 * <p>It is acceptable to return {@code null} to indicate that no cache could
  	 * be resolved for this invocation.
  	 * @param context the context of the particular invocation
  	 * @return the cache name(s) to resolve or {@code null} if no cache should be resolved
  	 */
  	protected abstract Collection<String> getCacheNames(CacheOperationInvocationContext<?> context);
  
  }