// Copyright 2018 PingCAP, Inc.
//
// Licensed 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,
// See the License for the specific language governing permissions and
// limitations under the License.

package implementation

import (
	"math"

	plannercore "github.com/pingcap/tidb/planner/core"
	"github.com/pingcap/tidb/planner/memo"
)

// SortImpl implementation of PhysicalSort.
type SortImpl struct {
	baseImpl
}

// NewSortImpl creates a new sort Implementation.
func NewSortImpl(sort *plannercore.PhysicalSort) *SortImpl {
	return &SortImpl{baseImpl{plan: sort}}
}

// CalcCost calculates the cost of the sort Implementation.
func (impl *SortImpl) CalcCost(outCount float64, childCosts []float64, children ...*memo.Group) float64 {
	cnt := math.Min(children[0].Prop.Stats.RowCount, impl.plan.GetChildReqProps(0).ExpectedCnt)
	sort := impl.plan.(*plannercore.PhysicalSort)
	impl.cost = sort.GetCost(cnt) + childCosts[0]
	return impl.cost
}