/*
 * Copyright 1999-2015 dangdang.com.
 * <p>
 * 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.
 * </p>
 */

package io.elasticjob.lite.api.strategy;

import com.google.common.base.Strings;
import io.elasticjob.lite.api.strategy.impl.AverageAllocationJobShardingStrategy;
import io.elasticjob.lite.exception.JobConfigurationException;
import lombok.AccessLevel;
import lombok.NoArgsConstructor;

/**
 * 作业分片策略工厂.
 * 
 * @author zhangliang
 */
@NoArgsConstructor(access = AccessLevel.PRIVATE)
public final class JobShardingStrategyFactory {
    
    /**
     * 获取作业分片策略实例.
     * 
     * @param jobShardingStrategyClassName 作业分片策略类名
     * @return 作业分片策略实例
     */
    public static JobShardingStrategy getStrategy(final String jobShardingStrategyClassName) {
        if (Strings.isNullOrEmpty(jobShardingStrategyClassName)) {
            return new AverageAllocationJobShardingStrategy();
        }
        try {
            Class<?> jobShardingStrategyClass = Class.forName(jobShardingStrategyClassName);
            if (!JobShardingStrategy.class.isAssignableFrom(jobShardingStrategyClass)) {
                throw new JobConfigurationException("Class '%s' is not job strategy class", jobShardingStrategyClassName);
            }
            return (JobShardingStrategy) jobShardingStrategyClass.newInstance();
        } catch (final ClassNotFoundException | InstantiationException | IllegalAccessException ex) {
            throw new JobConfigurationException("Sharding strategy class '%s' config error, message details are '%s'", jobShardingStrategyClassName, ex.getMessage());
        }
    }
}
