package liquibase.change.core;

 import liquibase.change.AbstractChange;

 import liquibase.change.ChangeMetaData;

 import liquibase.change.ColumnConfig;

 import liquibase.database.Database;

 import liquibase.database.core.DB2Database;

 import liquibase.database.core.SQLiteDatabase;

 import liquibase.database.core.SQLiteDatabase.AlterTableVisitor;

 import liquibase.database.structure.Index;

 import liquibase.statement.SqlStatement;

 import liquibase.statement.core.DropColumnStatement;

 import liquibase.statement.core.ReorganizeTableStatement;

 import liquibase.util.StringUtils;

 import java.util.ArrayList;

 import java.util.List;

 /**

  * Drops an existing column from a table.

  */

 public class DropColumnChange extends AbstractChange {

     private String schemaName;

     private String tableName;

     private String columnName;

     public DropColumnChange() {

         super("dropColumn", "Drop Column", ChangeMetaData.PRIORITY_DEFAULT);

     }

     public String getColumnName() {

         return columnName;

     }

     public void setColumnName(String columnName) {

         this.columnName = columnName;

     }

     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 SqlStatement[] generateStatements(Database database) {

         // todo if (database instanceof SQLiteDatabase) {

         // // return special statements for SQLite databases

         // return generateStatementsForSQLiteDatabase(database);

         // }

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

         String schemaName = getSchemaName() == null ? database.getDefaultSchemaName() : getSchemaName();

         statements.add(new DropColumnStatement(schemaName, getTableName(), getColumnName()));

         if (database instanceof DB2Database) {

             statements.add(new ReorganizeTableStatement(schemaName, getTableName()));

         }

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

     }

     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...

         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 createThisColumn(ColumnConfig column) {

                 return !column.getName().equals(getColumnName());

             }

             public boolean copyThisColumn(ColumnConfig column) {

                 return !column.getName().equals(getColumnName());

             }

             public boolean createThisIndex(Index index) {

                 return !index.getColumns().contains(getColumnName());

             }

         };

         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 "Column " + getTableName() + "." + getColumnName() + " dropped";

     }

 }