common/model/product/model.go

package productv1

import (
	"fmt"
	"math"
	"strings"
	"time"

	"github.com/expr-lang/expr"
	"gorm.io/gorm"
)

const (
	defaultExchangeRate float64 = 7.3
	defaultFreight      float64 = 100
)

type Website int

const (
	WebSite_US_Coach_Outlet Website = iota + 1
	WebSite_CN_Coach_Outlet
	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"`

	OriginalPrice float64     `json:"originalPrice"`
	Website       Website     `json:"website"`
	DiscPercent   int         `json:"discPercent" gorm:"index"` //折扣力度
	CNYPrice      float64     `json:"cnyPrice"`                 // 最终的价格
	CalMark       string      `json:"calMark"`                  //计算价格的过程
	DWPrice       float64     `json:"dwPrice"`
	DWSkuId       int         `json:"dwSkuId"`               // 得物sku_id
	DWSpuId       int         `json:"dwSpuId"`               //得物spu_id
	Freight       float64     `json:"freight"`               //运费
	ExchangeRate  float64     `json:"exchangeRate" gorm:"-"` //汇率
	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"`
	CalculateProcess []CalculateProcess `gorm:"foreignKey:Pid;references:Pid" json:"calculateProcess"`
}

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

func (p *Product) Env() map[string]any {
	return map[string]any{
		"originalPrice": p.OriginalPrice,
		"freight":       p.Freight,
		"exchangeRate":  p.ExchangeRate,
	}
}

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

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

func (p *Product) CalCNY(calculateProcess []CalculateProcess) {
	env := p.Env()
	var calculateStrings = make([]string, 0, len(calculateProcess))
	p.CNYPrice = 0
	for _, c := range calculateProcess {
		process, price := c.Calculate(env)
		if process != "" {
			calculateStrings = append(calculateStrings, process)
			if p.CNYPrice == 0 {
				p.CNYPrice = price
			}
			p.CNYPrice = min(p.CNYPrice, price)
		}
	}
	p.CalMark = strings.Join(calculateStrings, "\n")
}

// CalRate 计算收益率
func (p *Product) CalRate() {
	if p.DWPrice > 0 && p.CNYPrice > 0 {
		// 如果有得物价格，就计算收益率
		p.Rate = Decimal((p.DWPrice - p.CNYPrice) / p.CNYPrice * 100)
	} else if p.Rate > 0 {
		// 如果得物价格为0, 收益率应该设置为0
		p.Rate = 0
	}

	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"`
	OriginalPrice float64 `json:"originalPrice"`
}

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"`
}

// CalculateProcess 计算过程
type CalculateProcess struct {
	ID        uint           `gorm:"primary_key" json:"id"`
	CreatedAt time.Time      `json:"createdAt"`
	UpdatedAt time.Time      `json:"updatedAt"`
	DeletedAt gorm.DeletedAt `gorm:"index"`

	Pid       string
	Website   Website
	Condition string
	Process   string
	Name      string
}

func (c *CalculateProcess) Calculate(env map[string]any) (string, float64) {
	if c.Condition != "" {
		condition, err := expr.Compile(c.Condition, expr.AsBool())
		if err != nil {
			return fmt.Sprintf("【%s】 condition compile error: %v", c.Name, err), 0
		}
		if ok, err := expr.Run(condition, env); err != nil {
			return fmt.Sprintf("【%s】 condition run error: %v", c.Name, err), 0
		} else if !ok.(bool) {
			return "", 0
		}
	}
	program, err := expr.Compile(c.Process, expr.AsFloat64())
	if err != nil {
		return fmt.Sprintf("【%s】 process compile error: %v", c.Name, err), 0
	}

	output, err := expr.Run(program, env)
	if err != nil {
		return fmt.Sprintf("【%s】 process run error: %v", c.Name, err), 0
	}
	var replaceList = make([]string, 0, 2*len(env))
	for k, v := range env {
		replaceList = append(replaceList, k, fmt.Sprintf("%v", v))
	}
	replacer := strings.NewReplacer(replaceList...)
	return replacer.Replace(fmt.Sprintf("【%s】 %s = %.2f", c.Name, c.Process, output.(float64))), output.(float64)
}