/*
    * 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.infra.binder.context.segment.select.projection.impl;
  
  import lombok.EqualsAndHashCode;
  import lombok.Getter;
  import lombok.RequiredArgsConstructor;
  import lombok.ToString;
  import org.apache.shardingsphere.infra.binder.context.segment.select.projection.Projection;
  import org.apache.shardingsphere.infra.binder.context.segment.select.projection.util.ProjectionUtils;
  import org.apache.shardingsphere.infra.database.core.type.DatabaseType;
  import org.apache.shardingsphere.sql.parser.sql.common.segment.dml.item.ExpressionProjectionSegment;
  import org.apache.shardingsphere.sql.parser.sql.common.value.identifier.IdentifierValue;
  
  import java.util.Optional;
  
  /**
   * Expression projection.
   */
  @RequiredArgsConstructor
  @Getter
  @EqualsAndHashCode
  @ToString
  public final class ExpressionProjection implements Projection {
      
      private final ExpressionProjectionSegment expressionSegment;
      
      private final IdentifierValue alias;
      
      private final DatabaseType databaseType;
      
      @Override
      public String getColumnName() {
          return getColumnLabel();
      }
      
      @Override
      public String getColumnLabel() {
          return getAlias().isPresent() ? ProjectionUtils.getColumnLabelFromAlias(getAlias().get(), databaseType)
                  : ProjectionUtils.getColumnNameFromExpression(expressionSegment.getText(), databaseType);
      }
      
      @Override
      public String getExpression() {
          return expressionSegment.getText();
      }
      
      @Override
      public Optional<IdentifierValue> getAlias() {
          return Optional.ofNullable(alias);
      }
  }