/*
    * 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.sqlfederation.optimizer.statement;
  
  import lombok.RequiredArgsConstructor;
  import org.apache.calcite.adapter.enumerable.EnumerableConvention;
  import org.apache.calcite.plan.RelOptPlanner;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.metadata.JaninoRelMetadataProvider;
  import org.apache.calcite.rel.metadata.RelMetadataQueryBase;
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.sql.SqlNode;
  import org.apache.calcite.sql2rel.SqlToRelConverter;
  import org.apache.shardingsphere.sql.parser.sql.common.statement.SQLStatement;
  import org.apache.shardingsphere.sqlfederation.optimizer.SQLFederationExecutionPlan;
  import org.apache.shardingsphere.sqlfederation.optimizer.converter.SQLNodeConverterEngine;
  import org.apache.shardingsphere.sqlfederation.optimizer.operator.util.LogicalScanRelShuttle;
  import org.apache.shardingsphere.sqlfederation.optimizer.planner.util.SQLFederationPlannerUtils;
  
  import java.util.Objects;
  
  /**
   * SQL statement compiler.
   */
  @RequiredArgsConstructor
  public final class SQLStatementCompiler {
      
      private final SqlToRelConverter converter;
      
      /**
       * Compile sql statement to execution plan.
       *
       * @param sqlStatement SQL statement
       * @param databaseType database type
       * @return sql federation execution plan
       */
      public SQLFederationExecutionPlan compile(final SQLStatement sqlStatement, final String databaseType) {
          RelMetadataQueryBase.THREAD_PROVIDERS.set(JaninoRelMetadataProvider.DEFAULT);
          SqlNode sqlNode = SQLNodeConverterEngine.convert(sqlStatement);
          RelNode logicalPlan = converter.convertQuery(sqlNode, true, true).rel;
          RelDataType resultColumnType = Objects.requireNonNull(converter.validator).getValidatedNodeType(sqlNode);
          RelNode replacePlan = LogicalScanRelShuttle.replace(logicalPlan, databaseType);
          RelNode rewritePlan = rewrite(replacePlan, SQLFederationPlannerUtils.createHepPlanner());
          RelNode physicalPlan = optimize(rewritePlan, converter);
          RelMetadataQueryBase.THREAD_PROVIDERS.remove();
          return new SQLFederationExecutionPlan(physicalPlan, resultColumnType);
      }
      
      private RelNode rewrite(final RelNode logicalPlan, final RelOptPlanner hepPlanner) {
          hepPlanner.setRoot(logicalPlan);
          return hepPlanner.findBestExp();
      }
      
      private RelNode optimize(final RelNode rewritePlan, final SqlToRelConverter converter) {
          RelOptPlanner planner = converter.getCluster().getPlanner();
          if (rewritePlan.getTraitSet().equals(converter.getCluster().traitSet().replace(EnumerableConvention.INSTANCE))) {
              planner.setRoot(rewritePlan);
          } else {
              planner.setRoot(planner.changeTraits(rewritePlan, converter.getCluster().traitSet().replace(EnumerableConvention.INSTANCE)));
          }
          return planner.findBestExp();
      }
  }