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.cassandra.index.sai.analyzer.filter;
  
  import javax.annotation.concurrent.NotThreadSafe;
  
  import com.google.common.base.Preconditions;
  
  /**
   * A linked list of {@link Task} objects. Used to apply a sequence of filtering tasks
   * to provided textual input in a guaranteed order.
   */
  @NotThreadSafe
  public class FilterPipeline
  {
      private final Task head;
      private Task tail;
  
      public FilterPipeline(Task first)
      {
          this(first, first);
      }
  
      private FilterPipeline(Task first, Task tail)
      {
          this.head = first;
          this.tail = tail;
      }
  
      public FilterPipeline add(String name, Task task)
      {
          Preconditions.checkArgument(task != this.tail, "Provided last task [" + task.name + "] cannot be set to itself");
          
          this.tail.next = task;
          this.tail.name = name;
          
          this.tail = task;
          return this;
      }
  
      public Task head()
      {
          return this.head;
      }
  
      public abstract static class Task
      {
          public String name;
          public Task next;
  
          public abstract String process(String input);
      }
  }
  