package comm

import "math/rand"

type WeightItem struct {
	Id     interface{}
	Weight int
}

// 权重项目
type WeightedRandom struct {
	items       []*WeightItem
	totalWeight int
}

func NewWeightedRandom(items []*WeightItem) *WeightedRandom {
	wr := &WeightedRandom{items: items}
	for _, item := range wr.items {
		wr.totalWeight += int(item.Weight)
	}
	return wr
}

func (wr *WeightedRandom) Pick() *WeightItem {
	if wr.totalWeight <= 0 {
		return nil
	}
	randomNumber := rand.Intn(wr.totalWeight)
	for _, item := range wr.items {
		if randomNumber < int(item.Weight) {
			return item
		}
		randomNumber -= int(item.Weight)
	}
	return nil
}