/*
    * 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.syncope.common.keymaster.client.zookeeper;
  
  import java.util.List;
  import java.util.Map;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.stream.Collectors;
  import org.apache.curator.framework.CuratorFramework;
  import org.apache.curator.x.discovery.ServiceDiscovery;
  import org.apache.curator.x.discovery.ServiceDiscoveryBuilder;
  import org.apache.curator.x.discovery.ServiceInstance;
  import org.apache.curator.x.discovery.ServiceProvider;
  import org.apache.syncope.common.keymaster.client.api.KeymasterException;
  import org.apache.syncope.common.keymaster.client.api.ServiceOps;
  import org.apache.syncope.common.keymaster.client.api.model.NetworkService;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  import org.springframework.beans.factory.InitializingBean;
  import org.springframework.beans.factory.annotation.Autowired;
  
  /**
   * Implements {@link ServiceOps} via Apache Curator / Zookeeper via Curator's {@link ServiceDiscovery}.
   */
  public class ZookeeperServiceDiscoveryOps implements ServiceOps, InitializingBean {
  
      private static final Logger LOG = LoggerFactory.getLogger(ServiceOps.class);
  
      private static final String SERVICE_PATH = "/services";
  
      private final Map<NetworkService.Type, ServiceProvider<Void>> providers = new ConcurrentHashMap<>();
  
      @Autowired
      private CuratorFramework client;
  
      private ServiceDiscovery<Void> discovery;
  
      @Override
      public void afterPropertiesSet() throws Exception {
          discovery = ServiceDiscoveryBuilder.builder(Void.class).
                  client(client).
                  basePath(SERVICE_PATH).
                  build();
          discovery.start();
      }
  
      private ServiceProvider<Void> getProvider(final NetworkService.Type type) {
          return providers.computeIfAbsent(type, t -> {
              try {
                  ServiceProvider<Void> provider = discovery.
                          serviceProviderBuilder().
                          serviceName(t.name()).build();
                  provider.start();
                  return provider;
              } catch (KeymasterException e) {
                  throw e;
              } catch (Exception e) {
                  throw new KeymasterException("While preparing ServiceProvider for " + type, e);
              }
          });
      }
  
      @Override
      public void register(final NetworkService service) {
          try {
              unregister(service);
  
              ServiceInstance<Void> instance = ServiceInstance.<Void>builder().
                      name(service.getType().name()).
                      address(service.getAddress()).
                      build();
              discovery.registerService(instance);
          } catch (KeymasterException e) {
              throw e;
          } catch (Exception e) {
              LOG.error("While registering {}", service, e);
              throw new KeymasterException(e);
          }
      }
  
      @Override
      public void unregister(final NetworkService service) {
          try {
             discovery.queryForInstances(service.getType().name()).stream().
                     filter(instance -> instance.getName().equals(service.getType().name())
                     && instance.getAddress().equals(service.getAddress())).findFirst().
                     ifPresent(instance -> {
                         try {
                             discovery.unregisterService(instance);
                         } catch (Exception e) {
                             LOG.error("While deregistering {}", service, e);
                             throw new KeymasterException(e);
                         }
                     });
         } catch (KeymasterException e) {
             throw e;
         } catch (Exception e) {
             LOG.error("While registering {}", service, e);
             throw new KeymasterException(e);
         }
     }
 
     private static NetworkService toNetworkService(
         final NetworkService.Type serviceType,
         final ServiceInstance<Void> serviceInstance) {
 
         NetworkService ns = new NetworkService();
         ns.setType(serviceType);
         ns.setAddress(serviceInstance.getAddress());
         return ns;
     }
 
     @Override
     public List<NetworkService> list(final NetworkService.Type serviceType) {
         try {
             return discovery.queryForInstances(serviceType.name()).stream().
                     map(serviceInstance -> toNetworkService(serviceType, serviceInstance)).
                     collect(Collectors.toList());
         } catch (KeymasterException e) {
             throw e;
         } catch (Exception e) {
             throw new KeymasterException(e);
         }
     }
 
     @Override
     public NetworkService get(final NetworkService.Type serviceType) {
         ServiceInstance<Void> serviceInstance = null;
         try {
             if (!discovery.queryForInstances(serviceType.name()).isEmpty()) {
                 serviceInstance = getProvider(serviceType).getInstance();
             }
         } catch (KeymasterException e) {
             throw e;
         } catch (Exception e) {
             throw new KeymasterException(e);
         }
 
         if (serviceInstance == null) {
             throw new KeymasterException("No services found for " + serviceType);
         }
         return toNetworkService(serviceType, serviceInstance);
     }
 }