001/*
002 * Copyright (c) 2007-2015 Concurrent, Inc. All Rights Reserved.
003 *
004 * Project and contact information: http://www.cascading.org/
005 *
006 * This file is part of the Cascading project.
007 *
008 * Licensed under the Apache License, Version 2.0 (the "License");
009 * you may not use this file except in compliance with the License.
010 * You may obtain a copy of the License at
011 *
012 *     http://www.apache.org/licenses/LICENSE-2.0
013 *
014 * Unless required by applicable law or agreed to in writing, software
015 * distributed under the License is distributed on an "AS IS" BASIS,
016 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
017 * See the License for the specific language governing permissions and
018 * limitations under the License.
019 */
020
021package cascading.flow.planner.graph;
022
023import java.util.Set;
024
025import cascading.flow.FlowElement;
026import cascading.flow.planner.Scope;
027import cascading.property.ConfigDef;
028import cascading.tuple.Fields;
029
030/**
031 * Enum Extent provides simple markers for the head and tail of an {@link ElementGraph} {@link FlowElement} graph.
032 */
033public enum Extent implements FlowElement
034  {
035    head,
036    tail;
037
038  @Override
039  public Scope outgoingScopeFor( Set<Scope> scopes )
040    {
041    return new Scope();
042    }
043
044  @Override
045  public Fields resolveIncomingOperationArgumentFields( Scope incomingScope )
046    {
047    return null;
048    }
049
050  @Override
051  public Fields resolveIncomingOperationPassThroughFields( Scope incomingScope )
052    {
053    return null;
054    }
055
056  @Override
057  public boolean isEquivalentTo( FlowElement element )
058    {
059    return false;
060    }
061
062  @Override
063  public ConfigDef getStepConfigDef()
064    {
065    return null;
066    }
067
068  @Override
069  public boolean hasStepConfigDef()
070    {
071    return false;
072    }
073
074  @Override
075  public ConfigDef getNodeConfigDef()
076    {
077    return null;
078    }
079
080  @Override
081  public boolean hasNodeConfigDef()
082    {
083    return false;
084    }
085
086  @Override
087  public ConfigDef getConfigDef()
088    {
089    return null;
090    }
091
092  @Override
093  public boolean hasConfigDef()
094    {
095    return false;
096    }
097
098  @Override
099  public String toString()
100    {
101    return "[" + name() + "]";
102    }
103  }