package liquibase.change.core;

 import liquibase.change.AbstractChange;

 import liquibase.change.ChangeMetaData;

 import liquibase.change.ColumnConfig;

 import liquibase.database.Database;

 import liquibase.database.core.SQLiteDatabase;

 import liquibase.database.core.SQLiteDatabase.AlterTableVisitor;

 import liquibase.database.core.SybaseASADatabase;

 import liquibase.database.structure.Index;

 import liquibase.statement.SqlStatement;

 import liquibase.statement.core.DropUniqueConstraintStatement;

 import liquibase.util.StringUtils;

 import java.util.ArrayList;

 import java.util.List;

 /**

  * Removes an existing unique constraint.

  */

 public class DropUniqueConstraintChange extends AbstractChange {

     private String schemaName;

     private String tableName;

     private String constraintName;

     /**

      * Sybase ASA does drop unique constraint not by name, but using list of the columns in unique clause.

      */

     private String uniqueColumns;

     public DropUniqueConstraintChange() {

         super("dropUniqueConstraint", "Drop Unique Constraint", ChangeMetaData.PRIORITY_DEFAULT);

     }

     public String getSchemaName() {

         return schemaName;

     }

     public void setSchemaName(String schemaName) {

         this.schemaName = StringUtils.trimToNull(schemaName);

     }

     public String getTableName() {

         return tableName;

     }

     public void setTableName(String tableName) {

         this.tableName = tableName;

     }

     public String getConstraintName() {

         return constraintName;

     }

     public void setConstraintName(String constraintName) {

         this.constraintName = constraintName;

     }

     public String getUniqueColumns() {

         return uniqueColumns;

     }

     public void setUniqueColumns(String uniqueColumns) {

         this.uniqueColumns = uniqueColumns;

     }

     public SqlStatement[] generateStatements(Database database) {

         // todo if (database instanceof SQLiteDatabase) {

         // // return special statements for SQLite databases

         // return generateStatementsForSQLiteDatabase(database);

         // }

         DropUniqueConstraintStatement statement = new DropUniqueConstraintStatement(

                 getSchemaName() == null ? database.getDefaultSchemaName() : getSchemaName(), getTableName(),

                 getConstraintName());

         if (database instanceof SybaseASADatabase) {

             statement.setUniqueColumns(uniqueColumns);

         }

         return new SqlStatement[] { statement };

     }

     private SqlStatement[] generateStatementsForSQLiteDatabase(Database database) {

         // SQLite does not support this ALTER TABLE operation until now.

         // For more information see: http://www.sqlite.org/omitted.html.

         // This is a small work around...

         // Note: The attribute "constraintName" is used to pass the column

         // name instead of the constraint name.

         List<SqlStatement> statements = new ArrayList<SqlStatement>();

         // define alter table logic

         AlterTableVisitor rename_alter_visitor = new AlterTableVisitor() {

             public ColumnConfig[] getColumnsToAdd() {

                 return new ColumnConfig[0];

             }

             public boolean copyThisColumn(ColumnConfig column) {

                 return true;

             }

             public boolean createThisColumn(ColumnConfig column) {

                 if (column.getName().equals(getConstraintName())) {

                     column.getConstraints().setUnique(false);

                 }

                 return true;

             }

             public boolean createThisIndex(Index index) {

                 return true;

             }

         };

         try {

             // alter table

             statements.addAll(SQLiteDatabase.getAlterTableStatements(rename_alter_visitor, database, getSchemaName(),

                     getTableName()));

         } catch (Exception e) {

             e.printStackTrace();

         }

         return statements.toArray(new SqlStatement[statements.size()]);

     }

     public String getConfirmationMessage() {

         return "Unique constraint " + getConstraintName() + " dropped from " + getTableName();

     }

 }