/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * 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
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.drill.exec.planner.sql.handlers;

import java.io.IOException;
import java.util.List;

import org.apache.calcite.schema.Schema;
import org.apache.calcite.schema.SchemaPlus;
import org.apache.calcite.schema.Table;
import org.apache.calcite.sql.SqlNode;
import org.apache.calcite.tools.RelConversionException;
import org.apache.calcite.tools.ValidationException;
import org.apache.drill.common.config.DrillConfig;
import org.apache.drill.common.exceptions.UserException;
import org.apache.drill.exec.physical.PhysicalPlan;
import org.apache.drill.exec.planner.sql.DirectPlan;
import org.apache.drill.exec.planner.sql.SchemaUtilites;
import org.apache.drill.exec.planner.sql.parser.SqlDropTable;
import org.apache.drill.exec.rpc.user.UserSession;
import org.apache.drill.exec.store.AbstractSchema;
import org.apache.drill.exec.store.dfs.FileSelection;

// SqlHandler for dropping a table.
public class DropTableHandler extends DefaultSqlHandler {

  private static org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(DropTableHandler.class);

  public DropTableHandler(SqlHandlerConfig config) {
    super(config);
  }

  /**
   * Function resolves the schema and invokes the drop method
   * (while IF EXISTS statement is used function invokes the drop method only if table exists).
   * Raises an exception if the schema is immutable.
   *
   * @param sqlNode - SqlDropTable (SQL parse tree of drop table [if exists] query)
   * @return - Single row indicating drop succeeded or table is not found while IF EXISTS statement is used,
   * raise exception otherwise
   */
  @Override
  public PhysicalPlan getPlan(SqlNode sqlNode) throws ValidationException, RelConversionException, IOException {
    SqlDropTable dropTableNode = ((SqlDropTable) sqlNode);
    String originalTableName = FileSelection.removeLeadingSlash(dropTableNode.getName());
    SchemaPlus defaultSchema = config.getConverter().getDefaultSchema();
    List<String> tableSchema = dropTableNode.getSchema();
    DrillConfig drillConfig = context.getConfig();
    UserSession session = context.getSession();

    AbstractSchema temporarySchema = resolveToTemporarySchema(tableSchema, defaultSchema, drillConfig);
    boolean isTemporaryTable = session.isTemporaryTable(temporarySchema, drillConfig, originalTableName);

    if (isTemporaryTable) {
      session.removeTemporaryTable(temporarySchema, originalTableName, drillConfig);
    } else {
      AbstractSchema drillSchema = SchemaUtilites.resolveToMutableDrillSchema(defaultSchema, tableSchema);
      Table tableToDrop = SqlHandlerUtil.getTableFromSchema(drillSchema, originalTableName);
      if (tableToDrop == null || tableToDrop.getJdbcTableType() != Schema.TableType.TABLE) {
        if (dropTableNode.checkTableExistence()) {
          return DirectPlan.createDirectPlan(context, false, String.format("Table [%s] not found", originalTableName));
        } else {
          throw UserException.validationError().message("Table [%s] not found", originalTableName).build(logger);
        }
      }
      SqlHandlerUtil.dropTableFromSchema(drillSchema, originalTableName);
    }

    String message = String.format("%s [%s] dropped", isTemporaryTable ? "Temporary table" : "Table", originalTableName);
    logger.info(message);
    return DirectPlan.createDirectPlan(context, true, message);
  }

  /**
   * If table schema is not indicated in sql call, returns temporary workspace.
   * If schema is indicated, resolves to mutable table schema.
   *
   * @param tableSchema table schema
   * @param defaultSchema default schema
   * @param config drill config
   * @return resolved schema
   */
  private AbstractSchema resolveToTemporarySchema(List<String> tableSchema, SchemaPlus defaultSchema, DrillConfig config) {
    if (tableSchema.size() == 0) {
      return SchemaUtilites.getTemporaryWorkspace(defaultSchema, config);
    } else {
      return SchemaUtilites.resolveToMutableDrillSchema(defaultSchema, tableSchema);
    }
  }

}
