/*
 * 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 org.apache.servicecomb.config.kie.client;

import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.Executors;

import org.apache.servicecomb.config.common.ConfigConverter;
import org.apache.servicecomb.config.common.ConfigurationChangedEvent;
import org.apache.servicecomb.config.kie.client.model.ConfigurationsRequest;
import org.apache.servicecomb.config.kie.client.model.ConfigurationsRequestFactory;
import org.apache.servicecomb.config.kie.client.model.ConfigurationsResponse;
import org.apache.servicecomb.config.kie.client.model.KieConfiguration;
import org.apache.servicecomb.http.client.task.AbstractTask;
import org.apache.servicecomb.http.client.task.Task;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.eventbus.EventBus;

public class KieConfigManager extends AbstractTask {

  private static final Logger LOGGER = LoggerFactory.getLogger(KieConfigManager.class);

  private static long POLL_INTERVAL = 1000;

  private KieConfigOperation configKieClient;

  private final EventBus eventBus;

  private ConfigConverter configConverter;

  private List<ConfigurationsRequest> configurationsRequests;

  private KieConfiguration kieConfiguration;

  public KieConfigManager(KieConfigOperation configKieClient, EventBus eventBus,
      KieConfiguration kieConfiguration,
      ConfigConverter configConverter) {
    super("config-center-configuration-task");
    this.configurationsRequests = ConfigurationsRequestFactory.buildConfigurationRequests(kieConfiguration);
    this.configurationsRequests.sort(ConfigurationsRequest::compareTo);
    this.configKieClient = configKieClient;
    this.eventBus = eventBus;
    this.configConverter = configConverter;
    this.kieConfiguration = kieConfiguration;
  }

  public void firstPull() {
    try {
      Map<String, Object> data = new HashMap<>();
      this.configurationsRequests.forEach(r -> {
        r.setRevision(ConfigurationsRequest.INITIAL_REVISION);
        ConfigurationsResponse response = configKieClient.queryConfigurations(r);
        if (response.isChanged()) {
          r.setRevision(response.getRevision());
          r.setLastRawData(response.getConfigurations());
          data.putAll(response.getConfigurations());
        } else {
          throw new IllegalStateException("can not fetch config data.");
        }
      });
      this.configConverter.updateData(data);
    } catch (RuntimeException e) {
      if (this.kieConfiguration.isFirstPullRequired()) {
        throw e;
      } else {
        LOGGER.warn("first pull failed, and ignore {}", e.getMessage());
      }
    }
  }

  private void onDataChanged() {
    Map<String, Object> latestData = new HashMap<>();
    this.configurationsRequests.forEach(r -> latestData.putAll(r.getLastRawData()));

    Map<String, Object> lastData = configConverter.updateData(latestData);
    ConfigurationChangedEvent event = ConfigurationChangedEvent
        .createIncremental(configConverter.getCurrentData(), lastData);
    eventBus.post(event);
  }

  @Override
  protected void initTaskPool(String taskName) {
    this.taskPool = Executors.newFixedThreadPool(3, (task) ->
        new Thread(task, taskName));
  }

  public void startConfigKieManager() {
    this.configurationsRequests.forEach((t) ->
        this.startTask(new PollConfigurationTask(0, t)));
  }

  class PollConfigurationTask implements Task {
    final int failCount;

    ConfigurationsRequest configurationsRequest;

    public PollConfigurationTask(int failCount, ConfigurationsRequest configurationsRequest) {
      this.failCount = failCount;
      this.configurationsRequest = configurationsRequest;
    }

    @Override
    public void execute() {
      try {
        ConfigurationsResponse response = configKieClient.queryConfigurations(configurationsRequest);
        if (response.isChanged()) {
          configurationsRequest.setRevision(response.getRevision());
          configurationsRequest.setLastRawData(response.getConfigurations());
          onDataChanged();
        }
        if (KieConfigManager.this.kieConfiguration.isEnableLongPolling()) {
          startTask(new BackOffSleepTask(POLL_INTERVAL, new PollConfigurationTask(0, this.configurationsRequest)));
        } else {
          startTask(new PollConfigurationTask(0, this.configurationsRequest));
        }
      } catch (Exception e) {
        LOGGER.error("get configurations from KieConfigCenter failed, and will try again.", e);
        startTask(
            new BackOffSleepTask(failCount + 1, new PollConfigurationTask(failCount + 1, this.configurationsRequest)));
      }
    }
  }
}
