/*
 * Copyright 2002-2018 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.lang.Nullable;
import org.springframework.util.Assert;

A base CacheResolver implementation that requires the concrete implementation to provide the collection of cache name(s) based on the invocation context. 
Author:
Stephane Nicoll, Juergen Hoeller
Since:
4.1/**
 * 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
 * @author Juergen Hoeller
 * @since 4.1
 */
public abstract class AbstractCacheResolver implements CacheResolver, InitializingBean {

	@Nullable
	private CacheManager cacheManager;


	
Construct a new AbstractCacheResolver. 
See Also:
setCacheManager/**
	 * Construct a new {@code AbstractCacheResolver}.
	 * @see #setCacheManager
	 */
	protected AbstractCacheResolver() {
	}

	
Construct a new AbstractCacheResolver for the given CacheManager. 
Params:
cacheManager – the CacheManager to use/**
	 * Construct a new {@code AbstractCacheResolver} for the given {@link CacheManager}.
	 * @param cacheManager the CacheManager to use
	 */
	protected AbstractCacheResolver(CacheManager cacheManager) {
		this.cacheManager = cacheManager;
	}


	
Set the CacheManager that this instance should use. /**
	 * Set the {@link CacheManager} that this instance should use.
	 */
	public void setCacheManager(CacheManager cacheManager) {
		this.cacheManager = cacheManager;
	}

	
Return the CacheManager that this instance uses. /**
	 * Return the {@link CacheManager} that this instance uses.
	 */
	public CacheManager getCacheManager() {
		Assert.state(this.cacheManager != null, "No CacheManager set");
		return this.cacheManager;
	}

	@Override
	public void afterPropertiesSet()  {
		Assert.notNull(this.cacheManager, "CacheManager is required");
	}


	@Override
	public Collection<? extends Cache> resolveCaches(CacheOperationInvocationContext<?> context) {
		Collection<String> cacheNames = getCacheNames(context);
		if (cacheNames == null) {
			return Collections.emptyList();
		}
		Collection<Cache> result = new ArrayList<>(cacheNames.size());
		for (String cacheName : cacheNames) {
			Cache cache = getCacheManager().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.
It is acceptable to return null to indicate that no cache could be resolved for this invocation. 
Params:
context – the context of the particular invocation
Returns:
the cache name(s) to resolve, or null if no cache should be resolved/**
	 * 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
	 */
	@Nullable
	protected abstract Collection<String> getCacheNames(CacheOperationInvocationContext<?> context);

}