/**
 * 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 com.twitter.distributedlog.service.config;

import com.google.common.base.Optional;
import com.twitter.distributedlog.config.DynamicConfigurationFactory;
import com.twitter.distributedlog.config.DynamicDistributedLogConfiguration;
import com.twitter.distributedlog.service.streamset.StreamPartitionConverter;
import java.io.File;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import org.apache.commons.configuration.ConfigurationException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Provide per stream configuration to DistributedLog service layer.
 */
public class ServiceStreamConfigProvider implements StreamConfigProvider {

    private static final Logger LOG = LoggerFactory.getLogger(ServiceStreamConfigProvider.class);

    private static final String CONFIG_EXTENSION = "conf";

    private final File configBaseDir;
    private final File defaultConfigFile;
    private final StreamPartitionConverter partitionConverter;
    private final DynamicConfigurationFactory configFactory;
    private final DynamicDistributedLogConfiguration defaultDynConf;

    public ServiceStreamConfigProvider(String configPath,
                                       String defaultConfigPath,
                                       StreamPartitionConverter partitionConverter,
                                       ScheduledExecutorService executorService,
                                       int reloadPeriod,
                                       TimeUnit reloadUnit)
                                       throws ConfigurationException {
        this.configBaseDir = new File(configPath);
        if (!configBaseDir.exists()) {
            throw new ConfigurationException("Stream configuration base directory "
                + configPath + " does not exist");
        }
        this.defaultConfigFile = new File(configPath);
        if (!defaultConfigFile.exists()) {
            throw new ConfigurationException("Stream configuration default config "
                + defaultConfigPath + " does not exist");
        }

        // Construct reloading default configuration
        this.partitionConverter = partitionConverter;
        this.configFactory = new DynamicConfigurationFactory(executorService, reloadPeriod, reloadUnit);
        // We know it exists from the check above.
        this.defaultDynConf = configFactory.getDynamicConfiguration(defaultConfigPath).get();
    }

    @Override
    public Optional<DynamicDistributedLogConfiguration> getDynamicStreamConfig(String streamName) {
        String configName = partitionConverter.convert(streamName).getStream();
        String configPath = getConfigPath(configName);
        Optional<DynamicDistributedLogConfiguration> dynConf = Optional.<DynamicDistributedLogConfiguration>absent();
        try {
            dynConf = configFactory.getDynamicConfiguration(configPath, defaultDynConf);
        } catch (ConfigurationException ex) {
            LOG.warn("Configuration exception for stream {} ({}) at {}",
                    new Object[] {streamName, configName, configPath, ex});
        }
        return dynConf;
    }

    private String getConfigPath(String configName) {
        return new File(configBaseDir, String.format("%s.%s", configName, CONFIG_EXTENSION)).getPath();
    }
}