/*
    * 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.binder.context.segment.select.projection.engine.ProjectionEngine;
  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.handler.admin.executor.DatabaseAdminQueryExecutor;
  import org.apache.shardingsphere.proxy.backend.session.ConnectionSession;
  import org.apache.shardingsphere.sql.parser.sql.common.segment.dml.item.ShorthandProjectionSegment;
  import org.apache.shardingsphere.sql.parser.sql.common.statement.dml.SelectStatement;
  
  import java.sql.Types;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.LinkedList;
  import java.util.List;
  import java.util.Optional;
  import java.util.stream.Collectors;
  
  /**
   * No resource show executor.
   */
  @Getter
  @RequiredArgsConstructor
  public final class NoResourceShowExecutor implements DatabaseAdminQueryExecutor {
      
      private MergedResult mergedResult;
      
      private final SelectStatement sqlStatement;
      
      private Collection<Object> expressions = Collections.emptyList();
      
      @Override
      public void execute(final ConnectionSession connectionSession) {
          expressions = sqlStatement.getProjections().getProjections().stream().filter(each -> !(each instanceof ShorthandProjectionSegment))
                  .map(each -> new ProjectionEngine(null).createProjection(each))
                  .filter(Optional::isPresent).map(each -> each.get().getAlias().isPresent() ? each.get().getAlias().get() : each.get().getExpression()).collect(Collectors.toList());
          mergedResult = new TransparentMergedResult(getQueryResult());
      }
      
      private QueryResult getQueryResult() {
          List<MemoryQueryResultDataRow> rows = new LinkedList<>();
          if (expressions.isEmpty()) {
              rows.add(new MemoryQueryResultDataRow(Collections.singletonList("")));
              return new RawMemoryQueryResult(getQueryResultMetaData(), rows);
          }
          List<Object> row = new ArrayList<>(expressions);
          Collections.fill(row, "");
          rows.add(new MemoryQueryResultDataRow(row));
          return new RawMemoryQueryResult(getQueryResultMetaData(), rows);
      }
      
      @Override
      public QueryResultMetaData getQueryResultMetaData() {
          if (expressions.isEmpty()) {
              RawQueryResultColumnMetaData defaultColumnMetaData = new RawQueryResultColumnMetaData("", "", "", Types.VARCHAR, "VARCHAR", 100, 0);
              return new RawQueryResultMetaData(Collections.singletonList(defaultColumnMetaData));
          }
          List<RawQueryResultColumnMetaData> columns = expressions.stream().map(each -> new RawQueryResultColumnMetaData("", each.toString(), each.toString(), Types.VARCHAR, "VARCHAR", 100, 0))
                  .collect(Collectors.toList());
          return new RawQueryResultMetaData(columns);
      }
  }