content: /*
   * 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.flink.streaming.connectors.redis.common.hanlder;
  
  import java.util.HashMap;
  import java.util.LinkedList;
  import java.util.List;
  import java.util.Map;
  import java.util.Optional;
  import java.util.ServiceConfigurationError;
  import java.util.ServiceLoader;
  import java.util.stream.Collectors;
  import org.apache.flink.table.api.TableException;
  import org.apache.flink.util.Preconditions;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Unified class to search for a {@link RedisHandler} of provided type and properties.
   * for find correct redis handler.
   * @param <T> redis handler type.
   */
  public class RedisHandlerServices<T> {
  
      private static final ServiceLoader<RedisHandler> defaultLoader = ServiceLoader.load(RedisHandler.class);
      private static final Logger LOG = LoggerFactory.getLogger(RedisHandlerServices.class);
  
      /**
       * use specified class and properties to find redis handler.
       * @param RedisHanlderClass specified redis handler class.
       * @param meta properties to search redis handler
       * @param <T>
       * @return
       */
      public static <T extends RedisHandler> T findRedisHandler(Class<T> RedisHanlderClass, Map<String, String> meta) {
          Preconditions.checkNotNull(meta);
          return findSingRedisHandler(RedisHanlderClass, meta, Optional.empty());
      }
  
  
      /**
       * use specified class and properties and class loader to find redis handler.
       * @param RedisHanlderClass specified redis handler class.
       * @param meta properties to search redis handler
       * @param classLoader class loader to load redis handler class
       * @param <T> redis handler
       * @return matched redis handler
       */
      private static <T extends RedisHandler> T findSingRedisHandler(
              Class<T> RedisHanlderClass,
              Map<String, String> meta,
              Optional<ClassLoader> classLoader) {
  
          List<RedisHandler> redisHandlers = discoverRedisHanlder(classLoader);
          List<T> filtered = filter(redisHandlers, RedisHanlderClass, meta);
  
          return filtered.get(0);
      }
  
  
      /**
       * Filters found redis by factory class and with matching context.
       */
      private static <T extends RedisHandler> List<T> filter(
              List<RedisHandler> redis,
              Class<T> redisClass,
              Map<String, String> meta) {
  
          Preconditions.checkNotNull(redisClass);
          Preconditions.checkNotNull(meta);
  
          List<T> redisFactories = filterByFactoryClass(
                  redisClass,
                  redis);
  
          List<T> contextFactories = filterByContext(
                  meta,
                  redisFactories);
          return contextFactories;
      }
  
      /**
       * Searches for redis using Java service providers.
       *
       * @return all redis in the classpath
       */
      private static List<RedisHandler> discoverRedisHanlder(Optional<ClassLoader> classLoader) {
          try {
              List<RedisHandler> result = new LinkedList<>();
              if (classLoader.isPresent()) {
                  ServiceLoader
                          .load(RedisHandler.class, classLoader.get())
                          .iterator()
                          .forEachRemaining(result::add);
              } else {
                  defaultLoader.iterator().forEachRemaining(result::add);
              }
              return result;
          } catch (ServiceConfigurationError e) {
              LOG.error("Could not load service provider for redis handler.", e);
              throw new TableException("Could not load service provider for redis handler.", e);
          }
  
      }
  
      /**
       * Filters factories with matching context by factory class.
       */
      @SuppressWarnings("unchecked")
      private static <T> List<T> filterByFactoryClass(
              Class<T> redisClass,
              List<RedisHandler> redis) {
  
          List<RedisHandler> redisList = redis.stream()
                  .filter(p -> redisClass.isAssignableFrom(p.getClass()))
                  .collect(Collectors.toList());
  
          if (redisList.isEmpty()) {
              throw new RuntimeException(
                      String.format("No redis hanlder implements '%s'.", redisClass.getCanonicalName()));
          }
  
          return (List<T>) redisList;
      }
  
      /**
       * Filters for factories with matching context.
       *
       * @return all matching factories
       */
      private static <T extends RedisHandler> List<T> filterByContext(
              Map<String, String> meta,
              List<T> redisList) {
  
          List<T> matchingredis = redisList.stream().filter(factory -> {
              Map<String, String> requestedContext = normalizeContext(factory);
  
              Map<String, String> plainContext = new HashMap<>(requestedContext);
  
              // check if required context is met
              return plainContext.keySet()
                      .stream()
                      .allMatch(e -> meta.containsKey(e) && meta.get(e).equals(plainContext.get(e)));
          }).collect(Collectors.toList());
  
          if (matchingredis.isEmpty()) {
              throw new RuntimeException("no match redis");
          }
  
          return matchingredis;
      }
  
      /**
       * Prepares the properties of a context to be used for match operations.
       */
      private static Map<String, String> normalizeContext(RedisHandler redis) {
          Map<String, String> requiredContext = redis.requiredContext();
          if (requiredContext == null) {
              throw new RuntimeException(
                      String.format("Required context of redis '%s' must not be null.", redis.getClass().getName()));
          }
          return requiredContext.keySet().stream()
                  .collect(Collectors.toMap(String::toLowerCase, requiredContext::get));
      }
  
  }
  