inventary.go

package db

import (
	"time"

	"gorm.io/gorm"
	"gorm.io/gorm/clause"
)

type Supplier struct {
	gorm.Model
	Name string `json:"name" gorm:"unique;index"`
}

type Inventary struct {
	gorm.Model
	MemberNum  int                `json:"-" gorm:"column:member"`
	Member     *Member            `json:"member,omitempty" gorm:"foreignKey:MemberNum;references:Num"`
	Date       time.Time          `json:"date"`
	SupplierID *uint              `json:"supplier_id"`
	Supplier   *Supplier          `json:"supplier"`
	Comment    string             `json:"comment"`
	Products   []InventaryProduct `json:"products"`
}

type InventaryProduct struct {
	gorm.Model
	InventaryID uint     `json:"-"`
	ProductCode int      `json:"code" gorm:"column:product"`
	Product     *Product `json:"product" gorm:"foreignKey:ProductCode;references:Code"`
	StockUpdate *int     `json:"stock"`
	Price       *int     `json:"price"`
}

func (d *DB) AddSupplier(supplier *Supplier) error {
	return d.db.Create(supplier).Error
}

func (d *DB) ListSuppliers() (suppliers []Supplier, err error) {
	err = d.db.Find(&suppliers).Error
	return
}

func (d *DB) AddInventary(num int, inventary *Inventary) error {
	inventary.Date = time.Now()
	inventary.MemberNum = num
	return d.db.Transaction(func(tx *gorm.DB) error {
		for _, product := range inventary.Products {
			query := tx.Model(&Product{}).
				Where("code = ?", product.ProductCode)
			if product.StockUpdate != nil {
				query = query.Update("stock", gorm.Expr("stock + ?", *product.StockUpdate))
			}
			if product.Price != nil {
				price, err := d.inventaryNewPrice(product)
				if err != nil {
					return err
				}
				query = query.Update("price", price)
			}
			err := query.Error
			if err != nil {
				return err
			}
		}

		return tx.Create(inventary).Error
	})
}

func (d *DB) inventaryNewPrice(product InventaryProduct) (int, error) {
	if product.StockUpdate == nil || *product.StockUpdate == 0 {
		return *product.Price, nil
	}

	existingProduct, err := d.GetProduct(product.ProductCode)
	if err != nil {
		return 0, err
	}
	price := ((existingProduct.Price * existingProduct.Stock) + (*product.Price * *product.StockUpdate)) / (existingProduct.Stock + *product.StockUpdate)
	return price, nil
}

func (d *DB) GetInventary(id int) (inventary Inventary, err error) {
	err = d.db.Preload("Products.Product").
		Preload(clause.Associations).
		First(&inventary, id).
		Error
	return
}

func (d *DB) ListInventary() (inventaries []Inventary, err error) {
	err = d.db.Preload("Products.Product").
		Preload(clause.Associations).
		Order("date desc").
		Find(&inventaries).
		Error
	return
}