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  package org.apache.cayenne.dbsync.merge.token.db;
  
  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.DbEntity;
  import org.apache.cayenne.map.DbRelationship;
  import org.apache.cayenne.dbsync.reverse.dbload.DbRelationshipDetected;
  
  import java.util.Collections;
  import java.util.List;
  
  public class DropRelationshipToDb extends AbstractToDbToken.Entity {
  
      private DbRelationship relationship;
  
      public DropRelationshipToDb(DbEntity entity, DbRelationship relationship) {
          super("Drop foreign key", 10, entity);
          this.relationship = relationship;
      }
      
      public String getFkName() {
          if (relationship instanceof DbRelationshipDetected) {
              return ((DbRelationshipDetected) relationship).getFkName();
          }
          return null;
      }
  
      @Override
      public List<String> createSql(DbAdapter adapter) {
          if (isEmpty()) {
              return Collections.emptyList();
          }
  
          QuotingStrategy context = adapter.getQuotingStrategy();
          return Collections.singletonList(
                  "ALTER TABLE " + context.quotedFullyQualifiedName(getEntity()) + " DROP CONSTRAINT " + getFkName());
      }
  
      public MergerToken createReverse(MergerTokenFactory factory) {
          return factory.createAddRelationshipToModel(getEntity(), relationship);
      }
  
      @Override
      public boolean isEmpty() {
          return getFkName() == null || relationship.isToMany();
      }
  
      @Override
      public String getTokenValue() {
          if(relationship.isToMany()) {
              return "Skip. No sql representation.";
          }
          return relationship.getSourceEntity().getName() + "->" + relationship.getTargetEntityName();
      }
  }
  