/*
    * 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.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.ConnectionMode;
  import org.apache.shardingsphere.infra.executor.sql.execute.engine.SQLExecutorExceptionHandler;
  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.engine.driver.jdbc.JDBCExecutorCallback;
  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.resource.ResourceMetaData;
  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.UpdateResponseHeader;
  import org.apache.shardingsphere.proxy.backend.session.ConnectionSession;
  import org.apache.shardingsphere.sql.parser.sql.common.statement.SQLStatement;
  import org.apache.shardingsphere.sql.parser.sql.common.statement.dml.UpdateStatement;
  
  import java.sql.Connection;
  import java.sql.SQLException;
  import java.sql.Statement;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.LinkedList;
  import java.util.List;
  import java.util.Map;
  import java.util.Optional;
  import java.util.regex.Pattern;
  
  /**
   * Handler for MySQL multi statements.
   */
  public final class MySQLMultiStatementsHandler implements ProxyBackendHandler {
      
      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 KernelProcessor kernelProcessor = new KernelProcessor();
      
      private final JDBCExecutor jdbcExecutor;
      
      private final ConnectionSession connectionSession;
      
      private final SQLStatement sqlStatementSample;
      
      private final MetaDataContexts metaDataContexts = ProxyContext.getInstance().getContextManager().getMetaDataContexts();
      
      private final Collection<QueryContext> multiSQLQueryContexts = new LinkedList<>();
      
      public MySQLMultiStatementsHandler(final ConnectionSession connectionSession, final SQLStatement sqlStatementSample, final String sql) {
          jdbcExecutor = new JDBCExecutor(BackendExecutorContext.getInstance().getExecutorEngine(), connectionSession.getConnectionContext());
          connectionSession.getDatabaseConnectionManager().handleAutoCommit();
          this.connectionSession = connectionSession;
          this.sqlStatementSample = sqlStatementSample;
         Pattern pattern = sqlStatementSample instanceof UpdateStatement ? MULTI_UPDATE_STATEMENTS : MULTI_DELETE_STATEMENTS;
         SQLParserEngine sqlParserEngine = getSQLParserEngine();
         for (String each : extractMultiStatements(pattern, sql)) {
             SQLStatement eachSQLStatement = sqlParserEngine.parse(each, false);
             multiSQLQueryContexts.add(createQueryContext(each, eachSQLStatement));
         }
     }
     
     private SQLParserEngine getSQLParserEngine() {
         MetaDataContexts metaDataContexts = ProxyContext.getInstance().getContextManager().getMetaDataContexts();
         SQLParserRule sqlParserRule = metaDataContexts.getMetaData().getGlobalRuleMetaData().getSingleRule(SQLParserRule.class);
         return sqlParserRule.getSQLParserEngine(TypedSPILoader.getService(DatabaseType.class, "MySQL"));
     }
     
     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.getDatabaseName(), hintValueContext).bind(sqlStatement, Collections.emptyList());
         return new QueryContext(sqlStatementContext, sql, Collections.emptyList(), hintValueContext);
     }
     
     @Override
     public ResponseHeader execute() throws SQLException {
         Collection<ShardingSphereRule> rules = metaDataContexts.getMetaData().getDatabase(connectionSession.getDatabaseName()).getRuleMetaData().getRules();
         DriverExecutionPrepareEngine<JDBCExecutionUnit, Connection> prepareEngine = new DriverExecutionPrepareEngine<>(JDBCDriverType.STATEMENT, metaDataContexts.getMetaData().getProps()
                 .<Integer>getValue(ConfigurationPropertyKey.MAX_CONNECTIONS_SIZE_PER_QUERY), connectionSession.getDatabaseConnectionManager(),
                 (JDBCBackendStatement) connectionSession.getStatementManager(), new StatementOption(false), rules,
                 metaDataContexts.getMetaData().getDatabase(connectionSession.getDatabaseName()).getResourceMetaData().getStorageUnits());
         return executeMultiStatements(prepareEngine);
     }
     
     private UpdateResponseHeader executeMultiStatements(final DriverExecutionPrepareEngine<JDBCExecutionUnit, Connection> prepareEngine) throws SQLException {
         Collection<ExecutionContext> executionContexts = createExecutionContexts();
         Map<String, List<ExecutionUnit>> dataSourcesToExecutionUnits = buildDataSourcesToExecutionUnits(executionContexts);
         ExecutionGroupContext<JDBCExecutionUnit> executionGroupContext =
                 prepareEngine.prepare(executionContexts.iterator().next().getRouteContext(), samplingExecutionUnit(dataSourcesToExecutionUnits),
                         new ExecutionGroupReportContext(connectionSession.getProcessId(), connectionSession.getDatabaseName(), connectionSession.getGrantee()));
         for (ExecutionGroup<JDBCExecutionUnit> each : executionGroupContext.getInputGroups()) {
             for (JDBCExecutionUnit unit : each.getInputs()) {
                 prepareBatchedStatement(unit, dataSourcesToExecutionUnits);
             }
         }
         return executeBatchedStatements(executionGroupContext);
     }
     
     private Collection<ExecutionContext> createExecutionContexts() {
         Collection<ExecutionContext> result = new LinkedList<>();
         for (QueryContext each : multiSQLQueryContexts) {
             result.add(createExecutionContext(each));
         }
         return result;
     }
     
     private Map<String, List<ExecutionUnit>> buildDataSourcesToExecutionUnits(final Collection<ExecutionContext> executionContexts) {
         Map<String, List<ExecutionUnit>> result = new HashMap<>();
         for (ExecutionContext each : executionContexts) {
             for (ExecutionUnit executionUnit : each.getExecutionUnits()) {
                 result.computeIfAbsent(executionUnit.getDataSourceName(), unused -> new LinkedList<>()).add(executionUnit);
             }
         }
         return result;
     }
     
     private ExecutionContext createExecutionContext(final QueryContext queryContext) {
         RuleMetaData globalRuleMetaData = metaDataContexts.getMetaData().getGlobalRuleMetaData();
         ShardingSphereDatabase currentDatabase = metaDataContexts.getMetaData().getDatabase(connectionSession.getDatabaseName());
         SQLAuditEngine.audit(queryContext.getSqlStatementContext(), queryContext.getParameters(), globalRuleMetaData, currentDatabase, null, queryContext.getHintValueContext());
         return kernelProcessor.generateExecutionContext(queryContext, currentDatabase, globalRuleMetaData, metaDataContexts.getMetaData().getProps(), connectionSession.getConnectionContext());
     }
     
     private Collection<ExecutionUnit> samplingExecutionUnit(final Map<String, List<ExecutionUnit>> dataSourcesToExecutionUnits) {
         Collection<ExecutionUnit> result = new LinkedList<>();
         for (List<ExecutionUnit> each : dataSourcesToExecutionUnits.values()) {
             result.add(each.get(0));
         }
         return result;
     }
     
     private void prepareBatchedStatement(final JDBCExecutionUnit executionUnit, final Map<String, List<ExecutionUnit>> dataSourcesToExecutionUnits) throws SQLException {
         Statement statement = executionUnit.getStorageResource();
         for (ExecutionUnit each : dataSourcesToExecutionUnits.get(executionUnit.getExecutionUnit().getDataSourceName())) {
             statement.addBatch(each.getSqlUnit().getSql());
         }
     }
     
     private UpdateResponseHeader executeBatchedStatements(final ExecutionGroupContext<JDBCExecutionUnit> executionGroupContext) throws SQLException {
         boolean isExceptionThrown = SQLExecutorExceptionHandler.isExceptionThrown();
         ResourceMetaData resourceMetaData = metaDataContexts.getMetaData().getDatabase(connectionSession.getDatabaseName()).getResourceMetaData();
         JDBCExecutorCallback<int[]> callback = new BatchedJDBCExecutorCallback(resourceMetaData, sqlStatementSample, isExceptionThrown);
         List<int[]> executeResults = jdbcExecutor.execute(executionGroupContext, callback);
         int updated = 0;
         for (int[] eachResult : executeResults) {
             for (int each : eachResult) {
                 updated += each;
             }
         }
         // TODO Each logic SQL should correspond to an OK Packet.
         return new UpdateResponseHeader(sqlStatementSample, Collections.singletonList(new UpdateResult(updated, 0L)));
     }
     
     private static final class BatchedJDBCExecutorCallback extends JDBCExecutorCallback<int[]> {
         
         private BatchedJDBCExecutorCallback(final ResourceMetaData resourceMetaData, final SQLStatement sqlStatement, final boolean isExceptionThrown) {
             super(TypedSPILoader.getService(DatabaseType.class, "MySQL"), resourceMetaData, sqlStatement, isExceptionThrown);
         }
         
         @Override
         protected int[] executeSQL(final String sql, final Statement statement, final ConnectionMode connectionMode, final DatabaseType storageType) throws SQLException {
             try {
                 return statement.executeBatch();
             } finally {
                 statement.close();
             }
         }
         
         @SuppressWarnings("OptionalContainsCollection")
         @Override
         protected Optional<int[]> getSaneResult(final SQLStatement sqlStatement, final SQLException ex) {
             return Optional.empty();
         }
     }
 }