/*
 * Copyright 2011-2013 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.data.redis.support.collections;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.List;

import org.springframework.dao.DataAccessException;
import org.springframework.data.redis.core.RedisOperations;
import org.springframework.data.redis.core.SessionCallback;

/**
 * Utility class used mainly for type conversion by the default collection implementations. Meant for internal use.
 * 
 * @author Costin Leau
 */
abstract class CollectionUtils {

	@SuppressWarnings("unchecked")
	static <E> Collection<E> reverse(Collection<? extends E> c) {
		Object[] reverse = new Object[c.size()];
		int index = c.size();
		for (E e : c) {
			reverse[--index] = e;
		}

		return (List<E>) Arrays.asList(reverse);
	}

	static Collection<String> extractKeys(Collection<? extends RedisStore> stores) {
		Collection<String> keys = new ArrayList<String>(stores.size());

		for (RedisStore store : stores) {
			keys.add(store.getKey());
		}

		return keys;
	}

	static <K> void rename(final K key, final K newKey, RedisOperations<K, ?> operations) {
		operations.execute(new SessionCallback<Object>() {
			@SuppressWarnings("unchecked")
			public Object execute(RedisOperations operations) throws DataAccessException {
				do {
					operations.watch(key);

					if (operations.hasKey(key)) {
						operations.multi();
						operations.rename(key, newKey);
					} else {
						operations.multi();
					}
				} while (operations.exec() == null);
				return null;
			}
		});
	}

	static <K> Boolean renameIfAbsent(final K key, final K newKey, RedisOperations<K, ?> operations) {
		return operations.execute(new SessionCallback<Boolean>() {
			@SuppressWarnings("unchecked")
			public Boolean execute(RedisOperations operations) throws DataAccessException {
				List<Object> exec = null;
				do {
					operations.watch(key);

					if (operations.hasKey(key)) {
						operations.multi();
						operations.renameIfAbsent(key, newKey);
					} else {
						operations.watch(newKey);
						operations.multi();
						operations.hasKey(newKey);
						operations.hasKey(newKey);
					}
					exec = operations.exec();
				} while (exec == null);

				boolean result = ((Long) exec.get(0) == 1);
				if (exec.size() > 1) {
					result = !result;
				}
				return result;
			}
		});
	}
}