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   *  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
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  package org.apache.cayenne.dbsync.merge.token.db;
  
  import java.util.Collections;
  import java.util.List;
  
  import org.apache.cayenne.dba.DbAdapter;
  import org.apache.cayenne.dba.QuotingStrategy;
  import org.apache.cayenne.dbsync.merge.factory.MergerTokenFactory;
  import org.apache.cayenne.dbsync.merge.token.MergerToken;
  import org.apache.cayenne.map.DbAttribute;
  import org.apache.cayenne.map.DbEntity;
  
  /**
   * @since 4.0
   */
  public class SetGeneratedFlagToDb extends AbstractToDbToken.EntityAndColumn {
  
      private final boolean isGenerated;
  
      public SetGeneratedFlagToDb(DbEntity entity, DbAttribute column, boolean isGenerated) {
          // drop generated attribute must go first
          super("Set Is Generated", isGenerated ? 111 : 109, entity, column);
          this.isGenerated = isGenerated;
      }
  
      @Override
      public MergerToken createReverse(MergerTokenFactory factory) {
          return factory.createSetGeneratedFlagToModel(getEntity(), getColumn(), !isGenerated);
      }
  
      @Override
      public boolean isEmpty() {
          return true;
      }
  
      protected void appendAutoIncrement(DbAdapter adapter, StringBuffer builder) {
          throw new UnsupportedOperationException("Not supported on generic DB");
      }
  
      protected void appendDropAutoIncrement(DbAdapter adapter, StringBuffer builder) {
          throw new UnsupportedOperationException("Not supported on generic DB");
      }
  
      protected void appendAlterColumnClause(DbAdapter adapter, StringBuffer builder) {
          QuotingStrategy context = adapter.getQuotingStrategy();
          builder.append(" ALTER COLUMN ").append(context.quotedName(getColumn())).append(" ");
      }
  
      @SuppressWarnings("unchecked")
      @Override
      public List<String> createSql(DbAdapter adapter) {
          if(!adapter.supportsGeneratedKeys()) {
              return (List<String>)Collections.EMPTY_LIST;
          }
  
          QuotingStrategy context = adapter.getQuotingStrategy();
  
          StringBuffer builder = new StringBuffer();
          builder.append("ALTER TABLE ").append(context.quotedFullyQualifiedName(getEntity()));
          appendAlterColumnClause(adapter, builder);
          if(isGenerated) {
              appendAutoIncrement(adapter, builder);
          } else {
              appendDropAutoIncrement(adapter, builder);
          }
  
          return Collections.singletonList(builder.toString());
      }
  }
  