Add implementation for db.UserIdentifiable for Income

db/income.go

@@ -1,6 +1,7 @@
 package db
 
 import (
+	"errors"
 	"time"
 
 	"gorm.io/gorm"
@@ -16,3 +17,93 @@ type Income struct {
 	UserID  uint
 	User    *User
 }
+
+// Implements db.UserIdentifiable:1
+func (e Income) GetID() uint {
+	return e.ID
+}
+
+// Implements db.UserIdentifiable:2
+func (e Income) GetUserID() uint {
+	return e.UserID
+}
+
+// Implements db.UserIdentifiable:3
+func (e *Income) SetUserID(id uint) {
+	e.UserID = id
+}
+
+var (
+	ERROR_INCOME_INVALID_USERID            = errors.New("Income's `UserID` and Card's `UserID` are not equal")
+	ERROR_INCOME_CARD_INSUFFICIENT_BALANCE = errors.New("Card's `Balance` is lower than Income's Value")
+	ERROR_INCOME_INVALID_TYPE_USERID       = errors.New("Income's `UserID` and Type's `UserID` are not equal")
+)
+
+func (i *Income) BeforeCreate(tx *gorm.DB) error {
+	card := &Card{}
+	if err := tx.Find(card, i.CardID).Error; err != nil {
+		return err
+	}
+	if card.UserID != i.UserID {
+		return ERROR_INCOME_INVALID_USERID
+	}
+	card.Balance += i.Value
+	if err := tx.Save(card).Error; err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (i *Income) BeforeUpdate(tx *gorm.DB) (err error) {
+	var original Income
+	if err := tx.Model(&Income{}).Select("card_id", "value").Where("id = ?", i.ID).First(&original).Error; err != nil {
+		return err
+	}
+	if original.CardID != 0 {
+		oldCard := &Card{}
+		if err := tx.Find(oldCard, original.CardID).Error; err != nil {
+			return err
+		}
+		if oldCard.UserID != i.UserID {
+			return ERROR_INCOME_INVALID_USERID
+		}
+		if oldCard.Balance < original.Value {
+			return ERROR_INCOME_CARD_INSUFFICIENT_BALANCE
+		}
+		oldCard.Balance -= original.Value
+		if err := tx.Save(oldCard).Error; err != nil {
+			return err
+		}
+	}
+
+	if i.CardID != 0 {
+		newCard := &Card{}
+		if err := tx.Find(newCard, i.CardID).Error; err != nil {
+			return err
+		}
+		if newCard.UserID != i.UserID {
+			return ERROR_INCOME_INVALID_USERID
+		}
+		newCard.Balance += i.Value
+		if err := tx.Save(newCard).Error; err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (e *Income) AfterDelete(tx *gorm.DB) (err error) {
+	card := &Card{}
+	if err := tx.Find(card, e.CardID).Error; err != nil {
+		return err
+	}
+	if card.UserID != e.UserID {
+		return ERROR_INCOME_INVALID_USERID
+	}
+	card.Balance -= e.Value
+	if err := tx.Save(card).Error; err != nil {
+		return err
+	}
+	return nil
+}