content: /*
   * Copyright 1999-2018 Alibaba Group Holding Ltd.
   *
   * Licensed 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.alibaba.csp.sentinel.command;
  
  import java.util.*;
  
  import com.alibaba.csp.sentinel.command.annotation.CommandMapping;
  import com.alibaba.csp.sentinel.command.handler.InterceptingCommandHandler;
  import com.alibaba.csp.sentinel.spi.SpiLoader;
  import com.alibaba.csp.sentinel.util.StringUtil;
  
  /**
   * Provides and filters command handlers registered via SPI.
   *
   * @author Eric Zhao
   */
  public class CommandHandlerProvider implements Iterable<CommandHandler> {
  
      private final SpiLoader<CommandHandler> spiLoader = SpiLoader.of(CommandHandler.class);
  
      /**
       * Get all command handlers annotated with {@link CommandMapping} with command name.
       *
       * @return list of all named command handlers
       */
      public Map<String, CommandHandler> namedHandlers() {
          Map<String, CommandHandler> map = new HashMap<String, CommandHandler>();
          List<CommandHandler> handlers = spiLoader.loadInstanceList();
          List<CommandHandlerInterceptor> commandHandlerInterceptors = SpiLoader.of(CommandHandlerInterceptor.class).loadInstanceListSorted();
          for (CommandHandler handler : handlers) {
              String name = parseCommandName(handler);
              if (StringUtil.isEmpty(name)) {
                  continue;
              }
              if (!commandHandlerInterceptors.isEmpty()) {
                  List<CommandHandlerInterceptor> interceptors = new ArrayList<>();
                  for (CommandHandlerInterceptor commandHandlerInterceptor : commandHandlerInterceptors) {
                      if (commandHandlerInterceptor.shouldIntercept(name)) {
                          interceptors.add(commandHandlerInterceptor);
                      }
                  }
                  if (!interceptors.isEmpty()) {
                      handler = new InterceptingCommandHandler(handler, interceptors);
                  }
              }
              map.put(name, handler);
          }
          return map;
      }
  
      private String parseCommandName(CommandHandler handler) {
          CommandMapping commandMapping = handler.getClass().getAnnotation(CommandMapping.class);
          if (commandMapping != null) {
              return commandMapping.name();
          } else {
              return null;
          }
      }
  
      @Override
      public Iterator<CommandHandler> iterator() {
          return spiLoader.loadInstanceList().iterator();
      }
  
      private static final CommandHandlerProvider INSTANCE = new CommandHandlerProvider();
  
      public static CommandHandlerProvider getInstance() {
          return INSTANCE;
      }
  }
  