/*
    * 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.shardingsphere.proxy.backend.mysql.handler.admin.executor;
  
  import lombok.Getter;
  import lombok.RequiredArgsConstructor;
  import org.apache.shardingsphere.infra.exception.dialect.exception.syntax.database.UnknownDatabaseException;
  import org.apache.shardingsphere.infra.executor.sql.execute.result.query.QueryResult;
  import org.apache.shardingsphere.infra.executor.sql.execute.result.query.QueryResultMetaData;
  import org.apache.shardingsphere.infra.executor.sql.execute.result.query.impl.raw.metadata.RawQueryResultColumnMetaData;
  import org.apache.shardingsphere.infra.executor.sql.execute.result.query.impl.raw.metadata.RawQueryResultMetaData;
  import org.apache.shardingsphere.infra.executor.sql.execute.result.query.impl.raw.type.RawMemoryQueryResult;
  import org.apache.shardingsphere.infra.executor.sql.execute.result.query.type.memory.row.MemoryQueryResultDataRow;
  import org.apache.shardingsphere.infra.merge.result.MergedResult;
  import org.apache.shardingsphere.infra.merge.result.impl.transparent.TransparentMergedResult;
  import org.apache.shardingsphere.proxy.backend.context.ProxyContext;
  import org.apache.shardingsphere.proxy.backend.handler.admin.executor.DatabaseAdminQueryExecutor;
  import org.apache.shardingsphere.proxy.backend.session.ConnectionSession;
  import org.apache.shardingsphere.sql.parser.sql.dialect.statement.mysql.dal.MySQLShowCreateDatabaseStatement;
  
  import java.sql.Types;
  import java.util.Arrays;
  import java.util.LinkedList;
  import java.util.List;
  
  /**
   * Show create database executor.
   */
  @RequiredArgsConstructor
  @Getter
  public final class ShowCreateDatabaseExecutor implements DatabaseAdminQueryExecutor {
      
      private static final String CREATE_DATABASE_PATTERN = "CREATE DATABASE `%s`;";
      
      private static final String DATABASE = "Database";
      
      private static final String CREATE_DATABASE = "CREATE DATABASE ";
      
      private final MySQLShowCreateDatabaseStatement showCreateDatabaseStatement;
      
      private QueryResultMetaData queryResultMetaData;
      
      private MergedResult mergedResult;
      
      @Override
      public void execute(final ConnectionSession connectionSession) {
          queryResultMetaData = createQueryResultMetaData();
          mergedResult = new TransparentMergedResult(getQueryResult(showCreateDatabaseStatement.getDatabaseName()));
      }
      
      private QueryResult getQueryResult(final String databaseName) {
          if (!ProxyContext.getInstance().databaseExists(databaseName)) {
              throw new UnknownDatabaseException(databaseName);
          }
          List<MemoryQueryResultDataRow> rows = new LinkedList<>();
          rows.add(new MemoryQueryResultDataRow(Arrays.asList(databaseName, String.format(CREATE_DATABASE_PATTERN, databaseName))));
          return new RawMemoryQueryResult(queryResultMetaData, rows);
      }
      
      private QueryResultMetaData createQueryResultMetaData() {
          List<RawQueryResultColumnMetaData> columnMetaData = Arrays.asList(new RawQueryResultColumnMetaData("", DATABASE, DATABASE, Types.VARCHAR, "VARCHAR", 255, 0),
                  new RawQueryResultColumnMetaData("", CREATE_DATABASE, CREATE_DATABASE, Types.VARCHAR, "VARCHAR", 255, 0));
          return new RawQueryResultMetaData(columnMetaData);
      }
  }