/*
    * 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.RequiredArgsConstructor;
  import org.apache.shardingsphere.infra.binder.context.statement.SQLStatementContext;
  import org.apache.shardingsphere.infra.binder.engine.SQLBindEngine;
  import org.apache.shardingsphere.infra.database.core.type.DatabaseType;
  import org.apache.shardingsphere.infra.exception.mysql.exception.UnknownSystemVariableException;
  import org.apache.shardingsphere.infra.hint.HintValueContext;
  import org.apache.shardingsphere.infra.session.query.QueryContext;
  import org.apache.shardingsphere.infra.spi.type.typed.TypedSPILoader;
  import org.apache.shardingsphere.mode.metadata.MetaDataContexts;
  import org.apache.shardingsphere.parser.rule.SQLParserRule;
  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.DatabaseAdminExecutor;
  import org.apache.shardingsphere.proxy.backend.handler.admin.executor.variable.charset.CharsetSetExecutor;
  import org.apache.shardingsphere.proxy.backend.handler.admin.executor.variable.session.SessionVariableRecordExecutor;
  import org.apache.shardingsphere.proxy.backend.handler.data.DatabaseBackendHandler;
  import org.apache.shardingsphere.proxy.backend.mysql.handler.admin.executor.sysvar.MySQLSystemVariable;
  import org.apache.shardingsphere.proxy.backend.mysql.handler.admin.executor.sysvar.Scope;
  import org.apache.shardingsphere.proxy.backend.session.ConnectionSession;
  import org.apache.shardingsphere.sql.parser.sql.common.segment.dal.VariableAssignSegment;
  import org.apache.shardingsphere.sql.parser.sql.common.statement.SQLStatement;
  import org.apache.shardingsphere.sql.parser.sql.common.statement.dal.SetStatement;
  
  import java.sql.SQLException;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.LinkedHashMap;
  import java.util.Map;
  import java.util.stream.Collectors;
  
  /**
   * Set variable admin executor for MySQL.
   */
  @RequiredArgsConstructor
  public final class MySQLSetVariableAdminExecutor implements DatabaseAdminExecutor {
      
      private final DatabaseType databaseType = TypedSPILoader.getService(DatabaseType.class, "MySQL");
      
      private final SetStatement setStatement;
      
      @Override
      public void execute(final ConnectionSession connectionSession) throws SQLException {
          Map<String, String> sessionVariables = extractSessionVariables();
          validateSessionVariables(sessionVariables.keySet());
          new CharsetSetExecutor(databaseType, connectionSession).set(sessionVariables);
          new SessionVariableRecordExecutor(databaseType, connectionSession).recordVariable(sessionVariables);
          executeSetGlobalVariablesIfPresent(connectionSession);
      }
      
      private Map<String, String> extractSessionVariables() {
          return setStatement.getVariableAssigns().stream().filter(each -> !"global".equalsIgnoreCase(each.getVariable().getScope().orElse("")))
                  .collect(Collectors.toMap(each -> each.getVariable().getVariable(), VariableAssignSegment::getAssignValue));
      }
      
      private void validateSessionVariables(final Collection<String> sessionVariables) {
          for (String each : sessionVariables) {
              MySQLSystemVariable systemVariable = MySQLSystemVariable.findSystemVariable(each).orElseThrow(() -> new UnknownSystemVariableException(each));
              systemVariable.validateSetTargetScope(Scope.SESSION);
          }
      }
      
      private void executeSetGlobalVariablesIfPresent(final ConnectionSession connectionSession) throws SQLException {
          if (null == connectionSession.getDatabaseName()) {
              return;
          }
          String concatenatedGlobalVariables = extractGlobalVariables().entrySet().stream().map(entry -> String.format("@@GLOBAL.%s = %s", entry.getKey(), entry.getValue()))
                  .collect(Collectors.joining(", "));
          if (concatenatedGlobalVariables.isEmpty()) {
              return;
          }
          String sql = "SET " + concatenatedGlobalVariables;
          MetaDataContexts metaDataContexts = ProxyContext.getInstance().getContextManager().getMetaDataContexts();
          SQLParserRule sqlParserRule = metaDataContexts.getMetaData().getGlobalRuleMetaData().getSingleRule(SQLParserRule.class);
          SQLStatement sqlStatement = sqlParserRule.getSQLParserEngine(TypedSPILoader.getService(DatabaseType.class, "MySQL")).parse(sql, false);
          SQLStatementContext sqlStatementContext = new SQLBindEngine(ProxyContext.getInstance().getContextManager().getMetaDataContexts().getMetaData(),
                  connectionSession.getDefaultDatabaseName(), new HintValueContext()).bind(sqlStatement, Collections.emptyList());
          DatabaseBackendHandler databaseBackendHandler = DatabaseConnectorFactory.getInstance()
                  .newInstance(new QueryContext(sqlStatementContext, sql, Collections.emptyList(), new HintValueContext()), connectionSession.getDatabaseConnectionManager(), false);
          try {
              databaseBackendHandler.execute();
         } finally {
             databaseBackendHandler.close();
         }
     }
     
     private Map<String, String> extractGlobalVariables() {
         return setStatement.getVariableAssigns().stream().filter(each -> "global".equalsIgnoreCase(each.getVariable().getScope().orElse("")))
                 .collect(Collectors.toMap(each -> each.getVariable().getVariable(), VariableAssignSegment::getAssignValue, (oldValue, newValue) -> newValue, LinkedHashMap::new));
     }
 }