/*
    * 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.frontend.mysql.command.query.text.query;
  
  import org.apache.shardingsphere.driver.executor.engine.batch.preparedstatement.BatchExecutionUnit;
  import org.apache.shardingsphere.driver.executor.engine.batch.preparedstatement.BatchPreparedStatementExecutor;
  import org.apache.shardingsphere.infra.binder.context.statement.SQLStatementContext;
  import org.apache.shardingsphere.infra.binder.engine.SQLBindEngine;
  import org.apache.shardingsphere.infra.config.props.ConfigurationPropertyKey;
  import org.apache.shardingsphere.infra.connection.kernel.KernelProcessor;
  import org.apache.shardingsphere.infra.database.core.type.DatabaseType;
  import org.apache.shardingsphere.infra.executor.audit.SQLAuditEngine;
  import org.apache.shardingsphere.infra.executor.kernel.model.ExecutionGroup;
  import org.apache.shardingsphere.infra.executor.kernel.model.ExecutionGroupContext;
  import org.apache.shardingsphere.infra.executor.kernel.model.ExecutionGroupReportContext;
  import org.apache.shardingsphere.infra.executor.sql.context.ExecutionContext;
  import org.apache.shardingsphere.infra.executor.sql.context.ExecutionUnit;
  import org.apache.shardingsphere.infra.executor.sql.execute.engine.driver.jdbc.JDBCExecutionUnit;
  import org.apache.shardingsphere.infra.executor.sql.execute.engine.driver.jdbc.JDBCExecutor;
  import org.apache.shardingsphere.infra.executor.sql.execute.result.update.UpdateResult;
  import org.apache.shardingsphere.infra.executor.sql.prepare.driver.DriverExecutionPrepareEngine;
  import org.apache.shardingsphere.infra.executor.sql.prepare.driver.jdbc.JDBCDriverType;
  import org.apache.shardingsphere.infra.executor.sql.prepare.driver.jdbc.StatementOption;
  import org.apache.shardingsphere.infra.hint.HintValueContext;
  import org.apache.shardingsphere.infra.hint.SQLHintUtils;
  import org.apache.shardingsphere.infra.metadata.database.ShardingSphereDatabase;
  import org.apache.shardingsphere.infra.metadata.database.rule.RuleMetaData;
  import org.apache.shardingsphere.infra.parser.SQLParserEngine;
  import org.apache.shardingsphere.infra.rule.ShardingSphereRule;
  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.jdbc.statement.JDBCBackendStatement;
  import org.apache.shardingsphere.proxy.backend.context.BackendExecutorContext;
  import org.apache.shardingsphere.proxy.backend.context.ProxyContext;
  import org.apache.shardingsphere.proxy.backend.handler.ProxyBackendHandler;
  import org.apache.shardingsphere.proxy.backend.response.header.ResponseHeader;
  import org.apache.shardingsphere.proxy.backend.response.header.update.MultiStatementsUpdateResponseHeader;
  import org.apache.shardingsphere.proxy.backend.response.header.update.UpdateResponseHeader;
  import org.apache.shardingsphere.proxy.backend.session.ConnectionSession;
  import org.apache.shardingsphere.sql.parser.statement.core.statement.SQLStatement;
  import org.apache.shardingsphere.sql.parser.statement.core.statement.type.dml.InsertStatement;
  import org.apache.shardingsphere.sql.parser.statement.core.statement.type.dml.UpdateStatement;
  
  import java.sql.Connection;
  import java.sql.SQLException;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.LinkedList;
  import java.util.List;
  import java.util.regex.Pattern;
  
  /**
   * Handler for MySQL multi statements.
   */
  public final class MySQLMultiStatementsHandler implements ProxyBackendHandler {
      
      private static final Pattern MULTI_INSERT_STATEMENTS = Pattern.compile(";(?=\\s*insert)", Pattern.CASE_INSENSITIVE);
      
      private static final Pattern MULTI_UPDATE_STATEMENTS = Pattern.compile(";(?=\\s*update)", Pattern.CASE_INSENSITIVE);
      
      private static final Pattern MULTI_DELETE_STATEMENTS = Pattern.compile(";(?=\\s*delete)", Pattern.CASE_INSENSITIVE);
      
      private final DatabaseType databaseType = TypedSPILoader.getService(DatabaseType.class, "MySQL");
      
      private final MetaDataContexts metaDataContexts = ProxyContext.getInstance().getContextManager().getMetaDataContexts();
      
      private final Collection<QueryContext> multiSQLQueryContexts = new LinkedList<>();
      
      private final ConnectionSession connectionSession;
      
      private final SQLStatement sqlStatementSample;
      
      private final BatchPreparedStatementExecutor batchExecutor;
      
      public MySQLMultiStatementsHandler(final ConnectionSession connectionSession, final SQLStatement sqlStatementSample, final String sql) {
          connectionSession.getDatabaseConnectionManager().handleAutoCommit();
          this.connectionSession = connectionSession;
          this.sqlStatementSample = sqlStatementSample;
          JDBCExecutor jdbcExecutor = new JDBCExecutor(BackendExecutorContext.getInstance().getExecutorEngine(), connectionSession.getConnectionContext());
          batchExecutor = new BatchPreparedStatementExecutor(metaDataContexts.getMetaData().getDatabase(connectionSession.getUsedDatabaseName()), jdbcExecutor, connectionSession.getProcessId());
         Pattern pattern = getPattern(sqlStatementSample);
         SQLParserEngine sqlParserEngine = getSQLParserEngine();
         for (String each : extractMultiStatements(pattern, sql)) {
             SQLStatement eachSQLStatement = sqlParserEngine.parse(each, false);
             multiSQLQueryContexts.add(createQueryContext(each, eachSQLStatement));
         }
     }
     
     private Pattern getPattern(final SQLStatement sqlStatementSample) {
         if (sqlStatementSample instanceof InsertStatement) {
             return MULTI_INSERT_STATEMENTS;
         }
         return sqlStatementSample instanceof UpdateStatement ? MULTI_UPDATE_STATEMENTS : MULTI_DELETE_STATEMENTS;
     }
     
     private SQLParserEngine getSQLParserEngine() {
         MetaDataContexts metaDataContexts = ProxyContext.getInstance().getContextManager().getMetaDataContexts();
         SQLParserRule sqlParserRule = metaDataContexts.getMetaData().getGlobalRuleMetaData().getSingleRule(SQLParserRule.class);
         return sqlParserRule.getSQLParserEngine(databaseType);
     }
     
     private List<String> extractMultiStatements(final Pattern pattern, final String sql) {
         // TODO Multi statements should be split by SQL Parser instead of simple regexp.
         return Arrays.asList(pattern.split(sql));
     }
     
     private QueryContext createQueryContext(final String sql, final SQLStatement sqlStatement) {
         HintValueContext hintValueContext = SQLHintUtils.extractHint(sql);
         SQLStatementContext sqlStatementContext = new SQLBindEngine(
                 metaDataContexts.getMetaData(), connectionSession.getCurrentDatabaseName(), hintValueContext).bind(databaseType, sqlStatement, Collections.emptyList());
         return new QueryContext(sqlStatementContext, sql, Collections.emptyList(), hintValueContext, connectionSession.getConnectionContext(), metaDataContexts.getMetaData());
     }
     
     @Override
     public ResponseHeader execute() throws SQLException {
         Collection<ShardingSphereRule> rules = metaDataContexts.getMetaData().getDatabase(connectionSession.getUsedDatabaseName()).getRuleMetaData().getRules();
         int maxConnectionsSizePerQuery = metaDataContexts.getMetaData().getProps().<Integer>getValue(ConfigurationPropertyKey.MAX_CONNECTIONS_SIZE_PER_QUERY);
         DriverExecutionPrepareEngine<JDBCExecutionUnit, Connection> prepareEngine =
                 new DriverExecutionPrepareEngine<>(JDBCDriverType.STATEMENT, maxConnectionsSizePerQuery, connectionSession.getDatabaseConnectionManager(),
                         (JDBCBackendStatement) connectionSession.getStatementManager(), new StatementOption(false), rules, metaDataContexts.getMetaData());
         return executeMultiStatements(prepareEngine);
     }
     
     private ResponseHeader executeMultiStatements(final DriverExecutionPrepareEngine<JDBCExecutionUnit, Connection> prepareEngine) throws SQLException {
         Collection<ExecutionContext> executionContexts = createExecutionContexts();
         ExecutionGroupContext<JDBCExecutionUnit> executionGroupContext =
                 prepareEngine.prepare(connectionSession.getUsedDatabaseName(), executionContexts.iterator().next().getRouteContext(), createExecutionUnits(),
                         new ExecutionGroupReportContext(connectionSession.getProcessId(), connectionSession.getUsedDatabaseName(), connectionSession.getConnectionContext().getGrantee()));
         batchExecutor.init(executionGroupContext);
         executeAddBatch(executionGroupContext);
         return new MultiStatementsUpdateResponseHeader(buildUpdateResponseHeaders(batchExecutor.executeBatch(multiSQLQueryContexts.iterator().next().getSqlStatementContext())));
     }
     
     private List<ExecutionUnit> createExecutionUnits() {
         List<ExecutionUnit> result = new ArrayList<>(batchExecutor.getBatchExecutionUnits().size());
         for (BatchExecutionUnit each : batchExecutor.getBatchExecutionUnits()) {
             ExecutionUnit executionUnit = each.getExecutionUnit();
             result.add(executionUnit);
         }
         return result;
     }
     
     private Collection<ExecutionContext> createExecutionContexts() {
         Collection<ExecutionContext> result = new LinkedList<>();
         for (QueryContext each : multiSQLQueryContexts) {
             ExecutionContext executionContext = createExecutionContext(each);
             batchExecutor.addBatchForExecutionUnits(executionContext.getExecutionUnits());
             result.add(executionContext);
         }
         return result;
     }
     
     private ExecutionContext createExecutionContext(final QueryContext queryContext) {
         RuleMetaData globalRuleMetaData = metaDataContexts.getMetaData().getGlobalRuleMetaData();
         ShardingSphereDatabase currentDatabase = metaDataContexts.getMetaData().getDatabase(connectionSession.getCurrentDatabaseName());
         SQLAuditEngine.audit(queryContext, globalRuleMetaData, currentDatabase);
         return new KernelProcessor().generateExecutionContext(queryContext, globalRuleMetaData, metaDataContexts.getMetaData().getProps());
     }
     
     private void executeAddBatch(final ExecutionGroupContext<JDBCExecutionUnit> executionGroupContext) throws SQLException {
         for (ExecutionGroup<JDBCExecutionUnit> each : executionGroupContext.getInputGroups()) {
             for (JDBCExecutionUnit unit : each.getInputs()) {
                 unit.getStorageResource().addBatch(unit.getExecutionUnit().getSqlUnit().getSql());
             }
         }
     }
     
     private Collection<UpdateResponseHeader> buildUpdateResponseHeaders(final int[] updateCounts) {
         Collection<UpdateResponseHeader> result = new LinkedList<>();
         for (int each : updateCounts) {
             result.add(new UpdateResponseHeader(sqlStatementSample, Collections.singletonList(new UpdateResult(each, 0L))));
         }
         return result;
     }
 }