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 2011-1-25)
   */
  package com.alibaba.cobar.parser.ast.fragment.tableref;
  
  import java.sql.SQLSyntaxErrorException;
  import java.util.ArrayList;
  import java.util.List;
  
  import com.alibaba.cobar.parser.visitor.SQLASTVisitor;
  
  /**
   * used in <code>FROM</code> fragment
   * 
   * @author <a href="mailto:shuo.qius@alibaba-inc.com">QIU Shuo</a>
   */
  public class TableReferences implements TableReference {
      protected static List<TableReference> ensureListType(List<TableReference> list) {
          if (list instanceof ArrayList)
              return list;
          return new ArrayList<TableReference>(list);
      }
  
      private final List<TableReference> list;
  
      /**
       * @return never null
       */
      public List<TableReference> getTableReferenceList() {
          return list;
      }
  
      public TableReferences(List<TableReference> list) throws SQLSyntaxErrorException {
          if (list == null || list.isEmpty()) {
              throw new SQLSyntaxErrorException("at least one table reference");
          }
          this.list = ensureListType(list);
      }
  
      @Override
      public Object removeLastConditionElement() {
          if (list != null && !list.isEmpty()) {
              return list.get(list.size() - 1).removeLastConditionElement();
          }
          return null;
      }
  
      @Override
      public boolean isSingleTable() {
          if (list == null) {
              return false;
          }
          int count = 0;
          TableReference first = null;
          for (TableReference ref : list) {
              if (ref != null && 1 == ++count) {
                  first = ref;
              }
          }
          return count == 1 && first.isSingleTable();
      }
  
      @Override
      public int getPrecedence() {
          return TableReference.PRECEDENCE_REFS;
      }
  
      @Override
      public void accept(SQLASTVisitor visitor) {
          visitor.visit(this);
      }
  
  }
  