content: /*
   * Copyright 1999-2012 Alibaba Group.
   *  
   * 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.
   */
  /**
   * (created at 2011-2-9)
   */
  package com.alibaba.cobar.parser.ast.fragment.tableref;
  
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  
  import com.alibaba.cobar.parser.ast.expression.Expression;
  import com.alibaba.cobar.parser.visitor.SQLASTVisitor;
  
  /**
   * @author <a href="mailto:shuo.qius@alibaba-inc.com">QIU Shuo</a>
   */
  public class InnerJoin implements TableReference {
      private static List<String> ensureListType(List<String> list) {
          if (list == null)
              return null;
          if (list.isEmpty())
              return Collections.emptyList();
          if (list instanceof ArrayList)
              return list;
          return new ArrayList<String>(list);
      }
  
      private final TableReference leftTableRef;
      private final TableReference rightTableRef;
      private Expression onCond;
      private List<String> using;
  
      private InnerJoin(TableReference leftTableRef, TableReference rightTableRef, Expression onCond, List<String> using) {
          super();
          this.leftTableRef = leftTableRef;
          this.rightTableRef = rightTableRef;
          this.onCond = onCond;
          this.using = ensureListType(using);
      }
  
      public InnerJoin(TableReference leftTableRef, TableReference rightTableRef) {
          this(leftTableRef, rightTableRef, null, null);
      }
  
      public InnerJoin(TableReference leftTableRef, TableReference rightTableRef, Expression onCond) {
          this(leftTableRef, rightTableRef, onCond, null);
      }
  
      public InnerJoin(TableReference leftTableRef, TableReference rightTableRef, List<String> using) {
          this(leftTableRef, rightTableRef, null, using);
      }
  
      public TableReference getLeftTableRef() {
          return leftTableRef;
      }
  
      public TableReference getRightTableRef() {
          return rightTableRef;
      }
  
      public Expression getOnCond() {
          return onCond;
      }
  
      public List<String> getUsing() {
          return using;
      }
  
      @Override
      public Object removeLastConditionElement() {
          Object obj;
          if (onCond != null) {
              obj = onCond;
              onCond = null;
          } else if (using != null) {
              obj = using;
              using = null;
          } else {
              return null;
          }
          return obj;
      }
  
      @Override
      public boolean isSingleTable() {
          return false;
      }
  
      @Override
      public int getPrecedence() {
          return TableReference.PRECEDENCE_JOIN;
      }
  
      @Override
      public void accept(SQLASTVisitor visitor) {
          visitor.visit(this);
      }
  
  }
  