/*
    * 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.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.merge.result.MergedResult;
  import org.apache.shardingsphere.infra.merge.result.impl.local.LocalDataMergedResult;
  import org.apache.shardingsphere.infra.merge.result.impl.local.LocalDataQueryResultRow;
  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.common.segment.dml.item.ExpressionProjectionSegment;
  import org.apache.shardingsphere.sql.parser.sql.common.segment.dml.item.ProjectionSegment;
  import org.apache.shardingsphere.sql.parser.sql.common.statement.dml.SelectStatement;
  
  import java.sql.Types;
  import java.util.Collection;
  import java.util.Collections;
  
  /**
   * Show connection id executor.
   */
  @RequiredArgsConstructor
  @Getter
  public final class ShowConnectionIdExecutor implements DatabaseAdminQueryExecutor {
      
      public static final String FUNCTION_NAME = "connection_id()";
      
      private final SelectStatement sqlStatement;
      
      private MergedResult mergedResult;
      
      @Override
      public void execute(final ConnectionSession connectionSession) {
          mergedResult = new LocalDataMergedResult(Collections.singleton(new LocalDataQueryResultRow(connectionSession.getConnectionId())));
      }
      
      @Override
      public QueryResultMetaData getQueryResultMetaData() {
          return new RawQueryResultMetaData(Collections.singletonList(new RawQueryResultColumnMetaData("", FUNCTION_NAME, getLabel(), Types.VARCHAR, "VARCHAR", 100, 0)));
      }
      
      private String getLabel() {
          Collection<ProjectionSegment> projections = sqlStatement.getProjections().getProjections();
          for (ProjectionSegment each : projections) {
              if (each instanceof ExpressionProjectionSegment) {
                  return ((ExpressionProjectionSegment) each).getAliasName().orElse(FUNCTION_NAME);
              }
          }
          return FUNCTION_NAME;
      }
  }