/*
    * 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.handler.distsql.rul;
  
  import com.google.common.base.Preconditions;
  import lombok.Setter;
  import org.apache.shardingsphere.database.connector.core.type.DatabaseType;
  import org.apache.shardingsphere.database.connector.core.type.DatabaseTypeRegistry;
  import org.apache.shardingsphere.distsql.handler.aware.DistSQLExecutorConnectionContextAware;
  import org.apache.shardingsphere.distsql.handler.aware.DistSQLExecutorDatabaseAware;
  import org.apache.shardingsphere.distsql.handler.engine.DistSQLConnectionContext;
  import org.apache.shardingsphere.distsql.handler.engine.query.DistSQLQueryExecutor;
  import org.apache.shardingsphere.distsql.statement.type.rul.sql.PreviewStatement;
  import org.apache.shardingsphere.infra.binder.context.statement.SQLStatementContext;
  import org.apache.shardingsphere.infra.binder.context.statement.type.ddl.CursorHeldSQLStatementContext;
  import org.apache.shardingsphere.infra.binder.context.statement.type.ddl.CursorStatementContext;
  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.exception.ShardingSpherePreconditions;
  import org.apache.shardingsphere.infra.exception.kernel.metadata.rule.EmptyRuleException;
  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.ExecuteResult;
  import org.apache.shardingsphere.infra.executor.sql.execute.result.query.impl.driver.jdbc.type.stream.JDBCStreamQueryResult;
  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.merge.result.impl.local.LocalDataQueryResultRow;
  import org.apache.shardingsphere.infra.metadata.ShardingSphereMetaData;
  import org.apache.shardingsphere.infra.metadata.database.ShardingSphereDatabase;
  import org.apache.shardingsphere.infra.session.query.QueryContext;
  import org.apache.shardingsphere.mode.manager.ContextManager;
  import org.apache.shardingsphere.parser.rule.SQLParserRule;
  import org.apache.shardingsphere.proxy.backend.connector.ProxyDatabaseConnectionManager;
  import org.apache.shardingsphere.proxy.backend.context.BackendExecutorContext;
  import org.apache.shardingsphere.sql.parser.statement.core.segment.ddl.cursor.CursorNameSegment;
  import org.apache.shardingsphere.sql.parser.statement.core.statement.SQLStatement;
  import org.apache.shardingsphere.sql.parser.statement.core.statement.attribute.type.CursorSQLStatementAttribute;
  import org.apache.shardingsphere.sqlfederation.context.SQLFederationContext;
  import org.apache.shardingsphere.sqlfederation.engine.SQLFederationEngine;
  
  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.Optional;
  import java.util.stream.Collectors;
  
  /**
   * Preview executor.
   */
  @Setter
  public final class PreviewExecutor implements DistSQLQueryExecutor<PreviewStatement>, DistSQLExecutorDatabaseAware, DistSQLExecutorConnectionContextAware {
      
      private ShardingSphereDatabase database;
      
      private DistSQLConnectionContext connectionContext;
      
      @Override
      public Collection<String> getColumnNames(final PreviewStatement sqlStatement) {
          return Arrays.asList("data_source_name", "actual_sql");
      }
      
      @Override
      public Collection<LocalDataQueryResultRow> getRows(final PreviewStatement sqlStatement, final ContextManager contextManager) {
          ShardingSphereMetaData metaData = contextManager.getMetaDataContexts().getMetaData();
          String toBePreviewedSQL = sqlStatement.getSql();
          SQLStatement toBePreviewedStatement = metaData.getGlobalRuleMetaData().getSingleRule(SQLParserRule.class).getSQLParserEngine(database.getProtocolType()).parse(toBePreviewedSQL, false);
          HintValueContext hintValueContext = connectionContext.getQueryContext().getHintValueContext();
          hintValueContext.setSkipMetadataValidate(true);
          String currentDatabaseName = connectionContext.getQueryContext().getConnectionContext().getCurrentDatabaseName().orElse(null);
          SQLStatementContext toBePreviewedStatementContext = new SQLBindEngine(metaData, currentDatabaseName, hintValueContext).bind(toBePreviewedStatement);
          QueryContext queryContext = new QueryContext(
                  toBePreviewedStatementContext, toBePreviewedSQL, Collections.emptyList(), hintValueContext, connectionContext.getQueryContext().getConnectionContext(), metaData);
          if (toBePreviewedStatementContext.getSqlStatement().getAttributes().findAttribute(CursorSQLStatementAttribute.class).isPresent()
                  && toBePreviewedStatementContext instanceof CursorHeldSQLStatementContext) {
             setUpCursorDefinition((CursorHeldSQLStatementContext) toBePreviewedStatementContext);
         }
         ShardingSpherePreconditions.checkState(database.isComplete(), () -> new EmptyRuleException(database.getName()));
         String schemaName = getSchemaName(queryContext.getSqlStatementContext(), database);
         Collection<ExecutionUnit> executionUnits = getExecutionUnits(contextManager, schemaName, metaData, queryContext);
         return executionUnits.stream().map(each -> new LocalDataQueryResultRow(each.getDataSourceName(), each.getSqlUnit().getSql())).collect(Collectors.toList());
     }
     
     private String getSchemaName(final SQLStatementContext sqlStatementContext, final ShardingSphereDatabase database) {
         String defaultSchemaName = new DatabaseTypeRegistry(sqlStatementContext.getSqlStatement().getDatabaseType()).getDefaultSchemaName(database.getName());
         return sqlStatementContext.getTablesContext().getSchemaName().orElse(defaultSchemaName);
     }
     
     private Collection<ExecutionUnit> getExecutionUnits(final ContextManager contextManager, final String schemaName, final ShardingSphereMetaData metaData, final QueryContext queryContext) {
         JDBCExecutor jdbcExecutor = new JDBCExecutor(BackendExecutorContext.getInstance().getExecutorEngine(), connectionContext.getQueryContext().getConnectionContext());
         SQLFederationEngine federationEngine = new SQLFederationEngine(database.getName(), schemaName, metaData, contextManager.getMetaDataContexts().getStatistics(), jdbcExecutor);
         if (federationEngine.decide(queryContext, metaData.getGlobalRuleMetaData())) {
             return getFederationExecutionUnits(queryContext, metaData, federationEngine);
         }
         return new KernelProcessor().generateExecutionContext(queryContext, metaData.getGlobalRuleMetaData(), metaData.getProps()).getExecutionUnits();
     }
     
     private void setUpCursorDefinition(final CursorHeldSQLStatementContext toBePreviewedStatementContext) {
         Optional<CursorNameSegment> cursorNameSegment = toBePreviewedStatementContext.getSqlStatement().getAttributes().getAttribute(CursorSQLStatementAttribute.class).getCursorName();
         if (!cursorNameSegment.isPresent()) {
             return;
         }
         String cursorName = cursorNameSegment.get().getIdentifier().getValue().toLowerCase();
         CursorStatementContext cursorStatementContext = connectionContext.getQueryContext().getConnectionContext().getCursorContext().getCursorStatementContexts().get(cursorName);
         Preconditions.checkNotNull(cursorStatementContext, "Cursor %s does not exist.", cursorName);
         toBePreviewedStatementContext.setCursorStatementContext(cursorStatementContext);
     }
     
     private Collection<ExecutionUnit> getFederationExecutionUnits(final QueryContext queryContext, final ShardingSphereMetaData metaData, final SQLFederationEngine federationEngine) {
         SQLStatement sqlStatement = queryContext.getSqlStatementContext().getSqlStatement();
         DriverExecutionPrepareEngine<JDBCExecutionUnit, Connection> prepareEngine = createDriverExecutionPrepareEngine(metaData);
         SQLFederationContext context = new SQLFederationContext(true, queryContext, metaData,
                 ((ProxyDatabaseConnectionManager) connectionContext.getDatabaseConnectionManager()).getConnectionSession().getProcessId());
         federationEngine.executeQuery(prepareEngine, createPreviewCallback(sqlStatement), context);
         return context.getPreviewExecutionUnits();
     }
     
     private JDBCExecutorCallback<ExecuteResult> createPreviewCallback(final SQLStatement sqlStatement) {
         return new JDBCExecutorCallback<ExecuteResult>(database.getProtocolType(), database.getResourceMetaData(), sqlStatement, SQLExecutorExceptionHandler.isExceptionThrown()) {
             
             @Override
             protected ExecuteResult executeSQL(final String sql, final Statement statement, final ConnectionMode connectionMode, final DatabaseType storageType) throws SQLException {
                 return new JDBCStreamQueryResult(statement.executeQuery(sql));
             }
             
             @Override
             protected Optional<ExecuteResult> getSaneResult(final SQLStatement sqlStatement, final SQLException ex) {
                 return Optional.empty();
             }
         };
     }
     
     @SuppressWarnings({"unchecked", "rawtypes"})
     private DriverExecutionPrepareEngine<JDBCExecutionUnit, Connection> createDriverExecutionPrepareEngine(final ShardingSphereMetaData metaData) {
         int maxConnectionsSizePerQuery = metaData.getProps().<Integer>getValue(ConfigurationPropertyKey.MAX_CONNECTIONS_SIZE_PER_QUERY);
         return new DriverExecutionPrepareEngine<>(JDBCDriverType.STATEMENT, maxConnectionsSizePerQuery, connectionContext.getDatabaseConnectionManager(),
                 connectionContext.getExecutorStatementManager(), new StatementOption(false), database.getRuleMetaData().getRules(), metaData);
     }
     
     @Override
     public Class<PreviewStatement> getType() {
         return PreviewStatement.class;
     }
 }