/*
    * 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.converter.segment.projection;
  
  import lombok.AccessLevel;
  import lombok.NoArgsConstructor;
  import org.apache.calcite.sql.SqlNode;
  import org.apache.calcite.sql.SqlNodeList;
  import org.apache.calcite.sql.parser.SqlParserPos;
  import org.apache.shardingsphere.sql.parser.sql.common.segment.dml.expr.simple.ParameterMarkerExpressionSegment;
  import org.apache.shardingsphere.sql.parser.sql.common.segment.dml.item.AggregationProjectionSegment;
  import org.apache.shardingsphere.sql.parser.sql.common.segment.dml.item.ColumnProjectionSegment;
  import org.apache.shardingsphere.sql.parser.sql.common.segment.dml.item.ExpressionProjectionSegment;
  import org.apache.shardingsphere.sql.parser.sql.common.segment.dml.item.ProjectionSegment;
  import org.apache.shardingsphere.sql.parser.sql.common.segment.dml.item.ProjectionsSegment;
  import org.apache.shardingsphere.sql.parser.sql.common.segment.dml.item.ShorthandProjectionSegment;
  import org.apache.shardingsphere.sql.parser.sql.common.segment.dml.item.SubqueryProjectionSegment;
  import org.apache.shardingsphere.sqlfederation.optimizer.converter.segment.expression.impl.ParameterMarkerExpressionConverter;
  import org.apache.shardingsphere.sqlfederation.optimizer.converter.segment.projection.impl.AggregationProjectionConverter;
  import org.apache.shardingsphere.sqlfederation.optimizer.converter.segment.projection.impl.ColumnProjectionConverter;
  import org.apache.shardingsphere.sqlfederation.optimizer.converter.segment.projection.impl.ExpressionProjectionConverter;
  import org.apache.shardingsphere.sqlfederation.optimizer.converter.segment.projection.impl.ShorthandProjectionConverter;
  import org.apache.shardingsphere.sqlfederation.optimizer.converter.segment.projection.impl.SubqueryProjectionConverter;
  
  import java.util.Collection;
  import java.util.LinkedList;
  import java.util.Optional;
  
  /**
   * Projection converter.
   */
  @NoArgsConstructor(access = AccessLevel.PRIVATE)
  public final class ProjectionsConverter {
      
      /**
       * Convert projections segment to sql node list.
       * 
       * @param segment projections segment
       * @return sql node list
       */
      public static Optional<SqlNodeList> convert(final ProjectionsSegment segment) {
          Collection<SqlNode> projectionSQLNodes = new LinkedList<>();
          for (ProjectionSegment each : segment.getProjections()) {
              getProjectionSQLNode(each).ifPresent(projectionSQLNodes::add);
          }
          return Optional.of(new SqlNodeList(projectionSQLNodes, SqlParserPos.ZERO));
      }
      
      private static Optional<SqlNode> getProjectionSQLNode(final ProjectionSegment segment) {
          if (segment instanceof ColumnProjectionSegment) {
              return ColumnProjectionConverter.convert((ColumnProjectionSegment) segment);
          }
          if (segment instanceof ExpressionProjectionSegment) {
              return ExpressionProjectionConverter.convert((ExpressionProjectionSegment) segment);
          }
          if (segment instanceof ShorthandProjectionSegment) {
              return ShorthandProjectionConverter.convert((ShorthandProjectionSegment) segment);
          }
          if (segment instanceof SubqueryProjectionSegment) {
              return SubqueryProjectionConverter.convert((SubqueryProjectionSegment) segment);
          }
          if (segment instanceof AggregationProjectionSegment) {
              return AggregationProjectionConverter.convert((AggregationProjectionSegment) segment);
          }
          if (segment instanceof ParameterMarkerExpressionSegment) {
              return ParameterMarkerExpressionConverter.convert((ParameterMarkerExpressionSegment) segment);
          }
          // TODO process other projection
          return Optional.empty();
      }
  }