apskel-pos-backend/internal/entities/order_item.go

package entities

import (
	"database/sql/driver"
	"encoding/json"
	"errors"
	"math"
	"time"

	"github.com/google/uuid"
	"gorm.io/gorm"
)

type Modifiers []map[string]interface{}

func (m Modifiers) Value() (driver.Value, error) {
	return json.Marshal(m)
}

func (m *Modifiers) Scan(value interface{}) error {
	if value == nil {
		*m = make(Modifiers, 0)
		return nil
	}

	bytes, ok := value.([]byte)
	if !ok {
		return errors.New("type assertion to []byte failed")
	}

	return json.Unmarshal(bytes, m)
}

type OrderItemStatus string

const (
	OrderItemStatusPending   OrderItemStatus = "pending"
	OrderItemStatusPreparing OrderItemStatus = "preparing"
	OrderItemStatusReady     OrderItemStatus = "ready"
	OrderItemStatusServed    OrderItemStatus = "served"
	OrderItemStatusCancelled OrderItemStatus = "cancelled"
	OrderItemStatusPaid      OrderItemStatus = "paid"
)

type OrderItem struct {
	ID                  uuid.UUID       `gorm:"type:uuid;primary_key;default:gen_random_uuid()" json:"id"`
	OrderID             uuid.UUID       `gorm:"type:uuid;not null;index" json:"order_id" validate:"required"`
	ProductID           uuid.UUID       `gorm:"type:uuid;not null;index" json:"product_id" validate:"required"`
	ProductVariantID    *uuid.UUID      `gorm:"type:uuid;index" json:"product_variant_id"`
	Quantity            int             `gorm:"not null" json:"quantity" validate:"required,min=1"`
	Weight              *float64        `gorm:"type:decimal(12,3)" json:"weight,omitempty"`
	UnitID              *uuid.UUID      `gorm:"type:uuid;index" json:"unit_id,omitempty"`
	UnitPrice           float64         `gorm:"type:decimal(10,2);not null" json:"unit_price" validate:"required,min=0"`
	TotalPrice          float64         `gorm:"type:decimal(10,2);not null" json:"total_price" validate:"required,min=0"`
	UnitCost            float64         `gorm:"type:decimal(10,2);default:0.00" json:"unit_cost"`
	TotalCost           float64         `gorm:"type:decimal(10,2);default:0.00" json:"total_cost"`
	RefundAmount        float64         `gorm:"type:decimal(10,2);default:0.00" json:"refund_amount"`
	RefundQuantity      int             `gorm:"default:0" json:"refund_quantity"`
	IsPartiallyRefunded bool            `gorm:"default:false" json:"is_partially_refunded"`
	IsFullyRefunded     bool            `gorm:"default:false" json:"is_fully_refunded"`
	RefundReason        *string         `gorm:"size:255" json:"refund_reason,omitempty"`
	RefundedAt          *time.Time      `gorm:"" json:"refunded_at,omitempty"`
	RefundedBy          *uuid.UUID      `gorm:"type:uuid" json:"refunded_by,omitempty"`
	Modifiers           Modifiers       `gorm:"type:jsonb;default:'[]'" json:"modifiers"`
	Notes               *string         `gorm:"size:500" json:"notes,omitempty"`
	Metadata            Metadata        `gorm:"type:jsonb;default:'{}'" json:"metadata"`
	Status              OrderItemStatus `gorm:"default:'pending';size:50" json:"status"`
	CreatedAt           time.Time       `gorm:"autoCreateTime" json:"created_at"`
	UpdatedAt           time.Time       `gorm:"autoUpdateTime" json:"updated_at"`

	Order          Order           `gorm:"foreignKey:OrderID" json:"order,omitempty"`
	Product        Product         `gorm:"foreignKey:ProductID" json:"product,omitempty"`
	ProductVariant *ProductVariant `gorm:"foreignKey:ProductVariantID" json:"product_variant,omitempty"`
	Unit           *Unit           `gorm:"foreignKey:UnitID" json:"unit,omitempty"`
}

func (oi *OrderItem) BeforeCreate(tx *gorm.DB) error {
	if oi.ID == uuid.Nil {
		oi.ID = uuid.New()
	}
	return nil
}

func (OrderItem) TableName() string {
	return "order_items"
}

// IsWeighed reports whether this line was sold by weight rather than by count.
func (oi *OrderItem) IsWeighed() bool {
	return oi.Weight != nil
}

// BillableQuantity is the multiplier for unit price and unit cost on this line:
// the weighed amount for weight-based products, the item count otherwise.
//
// This is the ONLY place that decides between the two. Every price or cost
// calculation must go through it — multiplying by Quantity directly would bill a
// 4.2 ons fish as a single ons.
//
// Weighed lines are pinned to quantity = 1 by chk_order_items_weight_single_line,
// so there is no ambiguity between counting and weighing.
func (oi *OrderItem) BillableQuantity() float64 {
	if oi.Weight != nil {
		return *oi.Weight
	}
	return float64(oi.Quantity)
}

// BillableQuantityFor is BillableQuantity for a partial action on this line, such as
// voiding or refunding `units` of it.
//
// Weighed lines are always acted on in full — quantity is 1, so any void or refund
// covers the whole weighing — hence the full weight is returned regardless of units.
func (oi *OrderItem) BillableQuantityFor(units int) float64 {
	if oi.Weight != nil {
		return *oi.Weight
	}
	return float64(units)
}

// RoundMoney rounds to the 2 decimals that every monetary column stores, so the
// value written back always matches what the database keeps.
func RoundMoney(amount float64) float64 {
	return math.Round(amount*100) / 100
}

// RoundWeight rounds to the 3 decimals of order_items.weight, so a validated value
// is identical to the stored one.
func RoundWeight(weight float64) float64 {
	return math.Round(weight*1000) / 1000
}

func (oi *OrderItem) CalculateTotalPrice() {
	oi.TotalPrice = RoundMoney(oi.BillableQuantity() * oi.UnitPrice)
}

func (oi *OrderItem) CalculateTotalCost() {
	oi.TotalCost = RoundMoney(oi.BillableQuantity() * oi.UnitCost)
}

func (oi *OrderItem) CanBeModified() bool {
	return oi.Status == OrderItemStatusPending
}