/*
    * 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.statement.SQLStatementContext;
  import org.apache.shardingsphere.infra.binder.engine.SQLBindEngine;
  import org.apache.shardingsphere.infra.exception.core.ShardingSpherePreconditions;
  import org.apache.shardingsphere.infra.exception.dialect.exception.syntax.database.NoDatabaseSelectedException;
  import org.apache.shardingsphere.infra.exception.kernel.metadata.resource.storageunit.EmptyStorageUnitException;
  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.hint.HintValueContext;
  import org.apache.shardingsphere.infra.hint.SQLHintUtils;
  import org.apache.shardingsphere.infra.merge.result.MergedResult;
  import org.apache.shardingsphere.infra.merge.result.impl.transparent.TransparentMergedResult;
  import org.apache.shardingsphere.infra.session.query.QueryContext;
  import org.apache.shardingsphere.proxy.backend.connector.DatabaseConnector;
  import org.apache.shardingsphere.proxy.backend.connector.DatabaseConnectorFactory;
  import org.apache.shardingsphere.proxy.backend.context.ProxyContext;
  import org.apache.shardingsphere.proxy.backend.handler.admin.executor.DatabaseAdminQueryExecutor;
  import org.apache.shardingsphere.proxy.backend.response.header.ResponseHeader;
  import org.apache.shardingsphere.proxy.backend.response.header.query.QueryHeader;
  import org.apache.shardingsphere.proxy.backend.response.header.query.QueryResponseHeader;
  import org.apache.shardingsphere.proxy.backend.session.ConnectionSession;
  import org.apache.shardingsphere.sql.parser.sql.common.statement.dml.SelectStatement;
  
  import java.sql.SQLException;
  import java.sql.Types;
  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;
  
  /**
   * Unicast resource show executor.
   */
  @RequiredArgsConstructor
  @Getter
  public final class UnicastResourceShowExecutor implements DatabaseAdminQueryExecutor {
      
      private final DatabaseConnectorFactory databaseConnectorFactory = DatabaseConnectorFactory.getInstance();
      
      private final SelectStatement sqlStatement;
      
      private final String sql;
      
      private MergedResult mergedResult;
      
      private DatabaseConnector databaseConnector;
      
      private ResponseHeader responseHeader;
      
      @Override
      public void execute(final ConnectionSession connectionSession) throws SQLException {
          String originDatabase = connectionSession.getDatabaseName();
          String databaseName = null == originDatabase ? getFirstDatabaseName() : originDatabase;
          ShardingSpherePreconditions.checkState(ProxyContext.getInstance().getContextManager().getDatabase(databaseName).containsDataSource(), () -> new EmptyStorageUnitException(databaseName));
          HintValueContext hintValueContext = SQLHintUtils.extractHint(sql);
          try {
              connectionSession.setCurrentDatabase(databaseName);
              SQLStatementContext sqlStatementContext = new SQLBindEngine(ProxyContext.getInstance().getContextManager().getMetaDataContexts().getMetaData(),
                      connectionSession.getDefaultDatabaseName(), hintValueContext).bind(sqlStatement, Collections.emptyList());
              databaseConnector = databaseConnectorFactory.newInstance(new QueryContext(sqlStatementContext, sql, Collections.emptyList(), hintValueContext),
                      connectionSession.getDatabaseConnectionManager(), false);
              responseHeader = databaseConnector.execute();
              mergedResult = new TransparentMergedResult(createQueryResult());
          } finally {
              connectionSession.setCurrentDatabase(originDatabase);
              databaseConnector.close();
          }
      }
      
      private String getFirstDatabaseName() {
          Collection<String> databaseNames = ProxyContext.getInstance().getAllDatabaseNames();
          if (databaseNames.isEmpty()) {
              throw new NoDatabaseSelectedException();
         }
         Optional<String> result = databaseNames.stream().filter(each -> ProxyContext.getInstance().getContextManager().getDatabase(each).containsDataSource()).findFirst();
         ShardingSpherePreconditions.checkState(result.isPresent(), EmptyStorageUnitException::new);
         return result.get();
     }
     
     @Override
     public QueryResultMetaData getQueryResultMetaData() {
         List<RawQueryResultColumnMetaData> columns = ((QueryResponseHeader) responseHeader).getQueryHeaders().stream().map(QueryHeader::getColumnLabel)
                 .map(each -> new RawQueryResultColumnMetaData("", each, each, Types.VARCHAR, "VARCHAR", 100, 0))
                 .collect(Collectors.toList());
         return new RawQueryResultMetaData(columns);
     }
     
     private QueryResult createQueryResult() throws SQLException {
         List<MemoryQueryResultDataRow> rows = new LinkedList<>();
         while (databaseConnector.next()) {
             List<Object> data = databaseConnector.getRowData().getData();
             rows.add(new MemoryQueryResultDataRow(data));
         }
         return new RawMemoryQueryResult(getQueryResultMetaData(), rows);
     }
 }