/*
 * 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.knox.gateway.services.factory;

import java.util.Collection;
import java.util.Map;

import org.apache.commons.lang3.StringUtils;
import org.apache.knox.gateway.GatewayMessages;
import org.apache.knox.gateway.config.GatewayConfig;
import org.apache.knox.gateway.i18n.messages.MessagesFactory;
import org.apache.knox.gateway.services.GatewayServices;
import org.apache.knox.gateway.services.Service;
import org.apache.knox.gateway.services.ServiceFactory;
import org.apache.knox.gateway.services.ServiceLifecycleException;
import org.apache.knox.gateway.services.ServiceType;
import org.apache.knox.gateway.services.security.AliasService;
import org.apache.knox.gateway.services.security.KeystoreService;
import org.apache.knox.gateway.services.security.MasterService;

public abstract class AbstractServiceFactory implements ServiceFactory {

  private static final GatewayMessages LOG = MessagesFactory.get(GatewayMessages.class);
  private static final String IMPLEMENTATION_PARAM_NAME = "impl";
  private static final String EMPTY_DEFAULT_IMPLEMENTATION = "";

  @Override
  public Service create(GatewayServices gatewayServices, ServiceType serviceType, GatewayConfig gatewayConfig, Map<String, String> options) throws ServiceLifecycleException {
    return create(gatewayServices, serviceType, gatewayConfig, options, getImplementation(gatewayConfig));
  }

  @Override
  public Service create(GatewayServices gatewayServices, ServiceType serviceType, GatewayConfig gatewayConfig, Map<String, String> options, String implementation)
      throws ServiceLifecycleException {
    Service service = null;
    if (getServiceType() == serviceType) {
      service = createService(gatewayServices, serviceType, gatewayConfig, options, implementation);
      if (service == null && StringUtils.isNotBlank(implementation)) {
        // no known service implementation created, try to create the custom one
        try {
          service = Service.class.cast(Class.forName(implementation).newInstance());
          logServiceUsage(implementation, serviceType);
        } catch (InstantiationException | IllegalAccessException | ClassNotFoundException e) {
          throw new ServiceLifecycleException("Errror while instantiating " + serviceType.getShortName() + " service implementation " + implementation, e);
        }
      }
    }
    return service;
  }

  protected String getImplementation(GatewayConfig gatewayConfig) {
    return gatewayConfig.getServiceParameter(getServiceType().getShortName(), IMPLEMENTATION_PARAM_NAME);
  }

  protected boolean matchesImplementation(String implementation, Class<? extends Object> clazz) {
    return matchesImplementation(implementation, clazz, false);
  }

  protected boolean matchesImplementation(String implementation, Class<? extends Object> clazz, boolean acceptEmptyImplementation) {
    boolean match = clazz.getName().equals(implementation);
    if (!match && acceptEmptyImplementation) {
      match = isEmptyDefaultImplementation(implementation);
    }
    return match;
  }

  private boolean isEmptyDefaultImplementation(String implementation) {
    return EMPTY_DEFAULT_IMPLEMENTATION.equals(implementation);
  }

  protected boolean shouldCreateService(String implementation) {
    return implementation == null || isEmptyDefaultImplementation(implementation) || getKnownImplementations().contains(implementation);
  }

  protected MasterService getMasterService(GatewayServices gatewayServices) {
    return gatewayServices.getService(ServiceType.MASTER_SERVICE);
  }

  protected KeystoreService getKeystoreService(GatewayServices gatewayServices) {
    return gatewayServices.getService(ServiceType.KEYSTORE_SERVICE);
  }

  protected AliasService getAliasService(GatewayServices gatewayServices) {
    return gatewayServices.getService(ServiceType.ALIAS_SERVICE);
  }

  protected void logServiceUsage(String implementation, ServiceType serviceType) {
    LOG.usingServiceImplementation("".equals(implementation) ? "default" : implementation, serviceType.getServiceTypeName());
  }

  // abstract methods

  protected abstract Service createService(GatewayServices gatewayServices, ServiceType serviceType, GatewayConfig gatewayConfig, Map<String, String> options,
      String implementation) throws ServiceLifecycleException;

  protected abstract ServiceType getServiceType();

  protected abstract Collection<String> getKnownImplementations();
}