/*
    * 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.pagination;
  
  import lombok.Getter;
  import org.apache.shardingsphere.infra.binder.context.statement.type.dml.SelectStatementContext;
  import org.apache.shardingsphere.sql.parser.statement.core.segment.dml.pagination.NumberLiteralPaginationValueSegment;
  import org.apache.shardingsphere.sql.parser.statement.core.segment.dml.pagination.PaginationValueSegment;
  import org.apache.shardingsphere.sql.parser.statement.core.segment.dml.pagination.ParameterMarkerPaginationValueSegment;
  import org.apache.shardingsphere.sql.parser.statement.core.segment.dml.pagination.limit.LimitValueSegment;
  import org.apache.shardingsphere.sql.parser.statement.core.segment.dml.pagination.rownum.ExpressionRowNumberValueSegment;
  
  import java.util.List;
  import java.util.Optional;
  
  /**
   * Pagination context.
   */
  public final class PaginationContext {
      
      @Getter
      private final boolean hasPagination;
      
      private final PaginationValueSegment offsetSegment;
      
      private final PaginationValueSegment rowCountSegment;
      
      private final Long actualOffset;
      
      private final Long actualRowCount;
      
      public PaginationContext(final PaginationValueSegment offsetSegment, final PaginationValueSegment rowCountSegment, final List<Object> params) {
          hasPagination = null != offsetSegment || null != rowCountSegment;
          this.offsetSegment = offsetSegment;
          this.rowCountSegment = rowCountSegment;
          actualOffset = null == offsetSegment ? Long.valueOf(0L) : getValue(offsetSegment, params);
          actualRowCount = null == rowCountSegment ? null : getValue(rowCountSegment, params);
      }
      
      private Long getValue(final PaginationValueSegment paginationValueSegment, final List<Object> params) {
          if (paginationValueSegment instanceof ParameterMarkerPaginationValueSegment) {
              Object obj = null == params || params.isEmpty() ? 0L : params.get(((ParameterMarkerPaginationValueSegment) paginationValueSegment).getParameterIndex());
              if (null == obj) {
                  return null;
              }
              return obj instanceof Long ? (long) obj : (int) obj;
          }
          if (paginationValueSegment instanceof ExpressionRowNumberValueSegment) {
              return ((ExpressionRowNumberValueSegment) paginationValueSegment).getValue(params);
          }
          return ((NumberLiteralPaginationValueSegment) paginationValueSegment).getValue();
      }
      
      /**
       * Get offset segment.
       *
       * @return offset segment
       */
      public Optional<PaginationValueSegment> getOffsetSegment() {
          return Optional.ofNullable(offsetSegment);
      }
      
      /**
       * Get row count segment.
       *
       * @return row count segment
       */
      public Optional<PaginationValueSegment> getRowCountSegment() {
          return Optional.ofNullable(rowCountSegment);
      }
      
      /**
       * Get actual offset.
       *
       * @return actual offset
       */
      public long getActualOffset() {
          if (null == offsetSegment) {
              return 0L;
          }
          return offsetSegment.isBoundOpened() ? actualOffset - 1 : actualOffset;
      }
      
      /**
      * Get actual row count.
      *
      * @return actual row count
      */
     public Optional<Long> getActualRowCount() {
         if (null == rowCountSegment) {
             return Optional.empty();
         }
         return Optional.of(rowCountSegment.isBoundOpened() ? actualRowCount + 1L : actualRowCount);
     }
     
     /**
      * Get offset parameter index.
      *
      * @return offset parameter index
      */
     public Optional<Integer> getOffsetParameterIndex() {
         // TODO handle offsetSegment instance of ExpressionRowNumberValueSegment
         return offsetSegment instanceof ParameterMarkerPaginationValueSegment ? Optional.of(((ParameterMarkerPaginationValueSegment) offsetSegment).getParameterIndex()) : Optional.empty();
     }
     
     /**
      * Get row count parameter index.
      *
      * @return row count parameter index
      */
     public Optional<Integer> getRowCountParameterIndex() {
         // TODO handle offsetSegment instance of ExpressionRowNumberValueSegment
         return rowCountSegment instanceof ParameterMarkerPaginationValueSegment
                 ? Optional.of(((ParameterMarkerPaginationValueSegment) rowCountSegment).getParameterIndex())
                 : Optional.empty();
     }
     
     /**
      * Get revised offset.
      *
      * @return revised offset
      */
     public long getRevisedOffset() {
         return 0L;
     }
     
     /**
      * Get revised row count.
      *
      * @param selectStatementContext select statement context
      * @return revised row count
      */
     public long getRevisedRowCount(final SelectStatementContext selectStatementContext) {
         if (isMaxRowCount(selectStatementContext)) {
             return Integer.MAX_VALUE;
         }
         return rowCountSegment instanceof LimitValueSegment ? actualOffset + actualRowCount : actualRowCount;
     }
     
     private boolean isMaxRowCount(final SelectStatementContext selectStatementContext) {
         return (!selectStatementContext.getGroupByContext().getItems().isEmpty()
                 || !selectStatementContext.getProjectionsContext().getAggregationProjections().isEmpty()) && !selectStatementContext.isSameGroupByAndOrderByItems();
     }
 }