common/model/product/model.go

package productv1

import (
	"fmt"
	"gorm.io/gorm"
	"math"
	"strings"
	"time"
)

const (
	defaultExchangeRate float64 = 7.3
	defaultFreight      float64 = 100
)

type Website int

const (
	WebSite_US_Coach_Outlet Website = iota + 1
	WebSite_CN_Coach
)

type PriceStatus int

const (
	PriceStatus_NoChange PriceStatus = iota
	PriceStatus_UP
	PriceStatus_DOWN //降价
)

type Product struct {
	ID        uint           `gorm:"primary_key" json:"id"`
	CreatedAt time.Time      `json:"createdAt"`
	UpdatedAt time.Time      `json:"updatedAt"`
	DeletedAt gorm.DeletedAt `gorm:"index"`

	Name      string `gorm:"index" json:"name"`
	Pid       string `gorm:"unique;not null" json:"pid"`
	Color     string `json:"color"`
	Link      string `json:"link"`
	Image     string `json:"image"`
	Orderable bool   `json:"orderable"`

	USPrice      float64     `json:"usPrice"`
	Website      Website     `json:"website" gorm:"index"`
	DiscPercent  int         `json:"discPercent" gorm:"index"` //折扣力度
	CNYPrice     float64     `json:"cnyPrice"`
	CalMark      string      `json:"calMark"` //计算价格的过程
	DWPrice      float64     `json:"dwPrice"`
	Freight      float64     `json:"freight"`               //运费
	ExchangeRate float64     `json:"exchangeRate" gorm:"-"` //汇率
	Discount     int         `json:"discount" gorm:"-"`     //折扣
	Rate         float64     `json:"rate" gorm:"index"`     //利润率
	PriceStatus  PriceStatus `json:"priceStatus"`           //价格状态
	Remark       string      `json:"remark"`                //备注

	HistoryPrices   []HistoryPrice   `gorm:"foreignKey:Pid;references:Pid" json:"historyPrices"`
	DWHistoryPrices []DWHistoryPrice `gorm:"foreignKey:Pid;references:Pid" json:"dwHistoryPrices"`
}

func (p *Product) TableName() string {
	return "products"
}

func (p *Product) BeforeSave(tx *gorm.DB) (err error) {
	p.CalRate()
	p.fillPriceStatus(tx)
	return
}

func (p *Product) fillPriceStatus(tx *gorm.DB) {
	switch p.Website {
	case WebSite_US_Coach_Outlet:
		p.fillUSCoachPriceStatus(tx)
	case WebSite_CN_Coach:
		p.fillCNCoachPriceStatus(tx)
	}
}

func (p *Product) fillUSCoachPriceStatus(tx *gorm.DB) {
	var lastPrice float64
	tx.Model(&HistoryPrice{}).Where("pid = ?", p.Pid).Order("created_at desc").Limit(1).Pluck("us_price", &lastPrice)
	if p.USPrice != lastPrice {
		p.HistoryPrices = append(p.HistoryPrices, HistoryPrice{
			USPrice: p.USPrice,
		})
		if p.USPrice > lastPrice {
			p.PriceStatus = PriceStatus_UP
		} else {
			p.PriceStatus = PriceStatus_DOWN
		}
	}
}

func (p *Product) fillCNCoachPriceStatus(tx *gorm.DB) {
	var lastPrice float64
	tx.Model(&HistoryPrice{}).Where("pid = ?", p.Pid).Order("created_at desc").Limit(1).Pluck("us_price", &lastPrice)
	if p.CNYPrice != lastPrice {
		p.HistoryPrices = append(p.HistoryPrices, HistoryPrice{
			USPrice: p.CNYPrice,
		})
		if p.CNYPrice > lastPrice {
			p.PriceStatus = PriceStatus_UP
		} else {
			p.PriceStatus = PriceStatus_DOWN
		}
	}
}

func (p *Product) CalRate() {
	switch p.Website {
	case WebSite_US_Coach_Outlet:
		p.CalRateUSCoach()
	case WebSite_CN_Coach:
		p.CalRateCNCoach()
	}
}

func (p *Product) CalRateUSCoach() {
	calculationProcess := make([]string, 0, 2) //存放计算过程
	if p.ExchangeRate == 0 {
		p.ExchangeRate = defaultExchangeRate
	}
	if p.Freight == 0 {
		p.Freight = defaultFreight
	}
	if p.Discount == 0 {
		p.Discount = 100
	}

	//先计算打九折的价格
	tmpPrice := p.USPrice * 0.9 // 这是打九折的价格
	p.CNYPrice = tmpPrice*p.ExchangeRate + p.Freight
	calculationProcess = append(calculationProcess, fmt.Sprintf("【九折】%.2f * 0.9 * %.2f + %.2f = %.2f", p.USPrice, p.ExchangeRate, p.Freight, p.CNYPrice))
	var discountPrice = p.USPrice
	if 0 < p.Discount && p.Discount < 100 {
		discountPrice = p.USPrice * float64(p.Discount) / 100
	}
	if discountPrice >= 150 {
		calculationProcess = append(calculationProcess, fmt.Sprintf("【150 -20】(%.2f * %d%% - 20) * %.2f + %.2f = %.2f", p.USPrice, p.Discount, p.ExchangeRate, p.Freight, (discountPrice-20)*p.ExchangeRate+p.Freight))
		if discountPrice-20 < tmpPrice {
			// 符合满150-20,而且比九折便宜
			tmpPrice = discountPrice - 20
			p.CNYPrice = tmpPrice*p.ExchangeRate + p.Freight
		}
	} else if discountPrice >= 100 {
		calculationProcess = append(calculationProcess, fmt.Sprintf("【100 -10】(%.2f * %d%%  - 10) * %.2f + %.2f = %.2f", p.USPrice, p.Discount, p.ExchangeRate, p.Freight, (discountPrice-10)*p.ExchangeRate+p.Freight))
		if discountPrice-10 < tmpPrice {
			// 符合满100 -10,而且比九折便宜
			tmpPrice = discountPrice - 10
			p.CNYPrice = tmpPrice*p.ExchangeRate + p.Freight
		}
	} else if p.Discount < 90 {
		calculationProcess = append(calculationProcess, fmt.Sprintf("【打折扣】%.2f * %d%% * %.2f + %.2f = %.2f", p.USPrice, p.Discount, p.ExchangeRate, p.Freight, p.USPrice*float64(p.Discount)/100*p.ExchangeRate+p.Freight))
		p.CNYPrice = p.USPrice*float64(p.Discount)/100*p.ExchangeRate + p.Freight
	}
	p.CalMark = strings.Join(calculationProcess, "\n")
	if p.DWPrice > 0 {
		// 如果有得物价格，就计算收益率
		p.Rate = Decimal((p.DWPrice - p.CNYPrice) / p.CNYPrice * 100)
	}

	p.CNYPrice = Decimal(p.CNYPrice)
}

func (p *Product) CalRateCNCoach() {
	if p.DWPrice > 0 {
		// 如果有得物价格，就计算收益率
		p.Rate = Decimal((p.DWPrice - p.CNYPrice) / p.CNYPrice * 100)
	}

	p.CNYPrice = Decimal(p.CNYPrice)
}

// Decimal 保留两位小数
func Decimal(value float64) float64 {
	return math.Trunc(value*1e2+0.5) * 1e-2
}

type HistoryPrice struct {
	ID        uint      `gorm:"primary_key" json:"id"`
	CreatedAt time.Time `json:"createdAt"`

	Pid     string  `gorm:"index" json:"pid"`
	USPrice float64 `json:"usPrice"`
}

type DWHistoryPrice struct {
	ID        uint      `gorm:"primary_key" json:"id"`
	CreatedAt time.Time `json:"createdAt"`

	Pid     string  `gorm:"index" json:"pid"`
	DWPrice float64 `json:"dwPrice"`
}