package liquibase.sqlgenerator.core;

 import liquibase.database.Database;

 import liquibase.database.core.FirebirdDatabase;

 import liquibase.database.core.InformixDatabase;

 import liquibase.database.core.MSSQLDatabase;

 import liquibase.database.core.OracleDatabase;

 import liquibase.database.core.PostgresDatabase;

 import liquibase.database.core.SQLiteDatabase;

 import liquibase.exception.ValidationErrors;

 import liquibase.sql.Sql;

 import liquibase.sql.UnparsedSql;

 import liquibase.sqlgenerator.SqlGeneratorChain;

 import liquibase.statement.core.DropPrimaryKeyStatement;

 public class DropPrimaryKeyGenerator extends AbstractSqlGenerator<DropPrimaryKeyStatement> {

     @Override

     public boolean supports(DropPrimaryKeyStatement statement, Database database) {

         return (!(database instanceof SQLiteDatabase));

     }

     @Override

     public ValidationErrors validate(DropPrimaryKeyStatement dropPrimaryKeyStatement, Database database,

             SqlGeneratorChain sqlGeneratorChain) {

         ValidationErrors validationErrors = new ValidationErrors();

         validationErrors.checkRequiredField("tableName", dropPrimaryKeyStatement.getTableName());

         if (database instanceof FirebirdDatabase || database instanceof InformixDatabase) {

             validationErrors.checkRequiredField("constraintName", dropPrimaryKeyStatement.getConstraintName());

         }

         return validationErrors;

     }

     @Override

     public Sql[] generateSql(DropPrimaryKeyStatement statement, Database database, SqlGeneratorChain sqlGeneratorChain) {

         String sql;

         if (database instanceof MSSQLDatabase) {

             if (statement.getConstraintName() == null) {

                 StringBuilder query = new StringBuilder();

                 query.append("DECLARE @pkname nvarchar(255)");

                 query.append("\n");

                 query.append("DECLARE @sql nvarchar(2048)");

                 query.append("\n");

                 query.append("select @pkname=i.name from sysindexes i");

                 query.append(" join sysobjects o ON i.id = o.id");

                 query.append(" join sysobjects pk ON i.name = pk.name AND pk.parent_obj = i.id AND pk.xtype = 'PK'");

                 query.append(" join sysindexkeys ik on i.id = ik.id AND i.indid = ik.indid");

                 query.append(" join syscolumns c ON ik.id = c.id AND ik.colid = c.colid");

                 query.append(" where o.name = '").append(statement.getTableName()).append("'");

                 query.append("\n");

                 query.append("set @sql='alter table ")

                         .append(database.escapeTableName(statement.getSchemaName(), statement.getTableName()))

                         .append(" drop constraint ' + @pkname");

                 query.append("\n");

                 query.append("exec(@sql)");

                 query.append("\n");

                 sql = query.toString();

             } else {

                 sql = "ALTER TABLE " + database.escapeTableName(statement.getSchemaName(), statement.getTableName())

                         + " DROP CONSTRAINT " + database.escapeConstraintName(statement.getConstraintName());

             }

         } else if (database instanceof PostgresDatabase) {

             if (statement.getConstraintName() == null) {

                 StringBuilder query = new StringBuilder();

                 query.append("create or replace function __liquibase_drop_pk(tableName text) returns void as $$");

                 query.append(" declare");

                 query.append(" pkname text;");

                 query.append(" sql text;");

                 query.append(" begin");

                 query.append(" pkname = c.conname");

                 query.append(" from pg_class r, pg_constraint c");

                 query.append(" where r.oid = c.conrelid");

                 query.append(" and contype = 'p'");

                 query.append(" and relname ilike tableName;");

                 query.append(" sql = 'alter table ' || tableName || ' drop constraint ' || pkname;");

                 query.append(" execute sql;");

                 query.append(" end;");

                 query.append(" $$ language plpgsql;");

                 query.append(" select __liquibase_drop_pk('").append(statement.getTableName()).append("');");

                 query.append(" drop function __liquibase_drop_pk(tableName text);");

                 sql = query.toString();

             } else {

                 sql = "ALTER TABLE " + database.escapeTableName(statement.getSchemaName(), statement.getTableName())

                         + " DROP CONSTRAINT " + database.escapeConstraintName(statement.getConstraintName());

             }

         } else if (database instanceof FirebirdDatabase) {

             sql = "ALTER TABLE " + database.escapeTableName(statement.getSchemaName(), statement.getTableName())

                     + " DROP CONSTRAINT " + database.escapeConstraintName(statement.getConstraintName());

         } else if (database instanceof OracleDatabase) {

             sql = "ALTER TABLE " + database.escapeTableName(statement.getSchemaName(), statement.getTableName())

                     + " DROP PRIMARY KEY DROP INDEX";

         } else if (database instanceof InformixDatabase) {

             sql = "ALTER TABLE " + database.escapeTableName(statement.getSchemaName(), statement.getTableName())

                     + " DROP CONSTRAINT " + database.escapeConstraintName(statement.getConstraintName());

         } else {

             sql = "ALTER TABLE " + database.escapeTableName(statement.getSchemaName(), statement.getTableName())

                     + " DROP PRIMARY KEY";

         }

         return new Sql[] { new UnparsedSql(sql) };

     }

 }