backend-service/internal/models/notification.go

package models

import (
	"errors"
	"time"

	"gorm.io/gorm"
)

// NotificationType represents the different types of notifications
type NotificationType string

const (
	NotificationTypeWelcome        NotificationType = "welcome"
	NotificationTypePaymentSuccess NotificationType = "payment_success"
	NotificationTypePaymentFailed  NotificationType = "payment_failed"
	NotificationTypeMeetingInfo    NotificationType = "meeting_info"
	NotificationTypeReminder       NotificationType = "reminder"
	NotificationTypeCancellation   NotificationType = "cancellation"
	NotificationTypeReschedule     NotificationType = "reschedule"
)

// NotificationStatus represents the status of a notification
type NotificationStatus string

const (
	NotificationStatusPending NotificationStatus = "pending"
	NotificationStatusSent    NotificationStatus = "sent"
	NotificationStatusFailed  NotificationStatus = "failed"
	NotificationStatusSkipped NotificationStatus = "skipped"
)

// Notification represents email notifications
type Notification struct {
	gorm.Model
	UserID      uint               `json:"user_id" gorm:"index" validate:"required"`
	User        User               `json:"user" gorm:"foreignKey:UserID;constraint:OnUpdate:CASCADE,OnDelete:CASCADE"`
	BookingID   *uint              `json:"booking_id" gorm:"index"`
	Booking     *Booking           `json:"booking" gorm:"foreignKey:BookingID;constraint:OnUpdate:CASCADE,OnDelete:SET NULL"`
	Type        NotificationType   `json:"type" gorm:"not null;size:50;index" validate:"required,oneof=welcome payment_success payment_failed meeting_info reminder cancellation reschedule"`
	Subject     string             `json:"subject" gorm:"not null;size:255" validate:"required,max=255"`
	Body        string             `json:"body" gorm:"type:text" validate:"required"`
	SentAt      *time.Time         `json:"sent_at" gorm:"index"`
	Status      NotificationStatus `json:"status" gorm:"default:'pending';size:20;index" validate:"required,oneof=pending sent failed skipped"`
	ScheduledAt *time.Time         `json:"scheduled_at" gorm:"index"`
	RetryCount  int                `json:"retry_count" gorm:"default:0;check:retry_count >= 0"`
	ErrorMsg    string             `json:"error_msg" gorm:"size:500"`
}

// BeforeCreate is a GORM hook that runs before creating a notification record
func (n *Notification) BeforeCreate(tx *gorm.DB) error {
	// Set default status if not provided
	if n.Status == "" {
		n.Status = NotificationStatusPending
	}

	// Validate required fields
	if n.Subject == "" {
		return errors.New("notification subject is required")
	}

	if n.Body == "" {
		return errors.New("notification body is required")
	}

	// If scheduled at is not set, schedule for immediate sending
	if n.ScheduledAt == nil {
		now := time.Now()
		n.ScheduledAt = &now
	}

	return nil
}

// BeforeUpdate is a GORM hook that runs before updating a notification record
func (n *Notification) BeforeUpdate(tx *gorm.DB) error {
	// If status is being set to sent, set SentAt timestamp
	if n.Status == NotificationStatusSent && n.SentAt == nil {
		now := time.Now()
		n.SentAt = &now
	}

	return nil
}

// IsReadyToSend checks if the notification is ready to be sent
func (n *Notification) IsReadyToSend() bool {
	if n.Status != NotificationStatusPending {
		return false
	}

	if n.ScheduledAt == nil {
		return true
	}

	return n.ScheduledAt.Before(time.Now()) || n.ScheduledAt.Equal(time.Now())
}

// CanRetry checks if the notification can be retried (max 3 retries)
func (n *Notification) CanRetry() bool {
	return n.Status == NotificationStatusFailed && n.RetryCount < 3
}

// MarkAsSent marks the notification as successfully sent
func (n *Notification) MarkAsSent() {
	n.Status = NotificationStatusSent
	now := time.Now()
	n.SentAt = &now
	n.ErrorMsg = ""
}

// MarkAsFailed marks the notification as failed with an error message
func (n *Notification) MarkAsFailed(errorMsg string) {
	n.Status = NotificationStatusFailed
	n.RetryCount++
	n.ErrorMsg = errorMsg
}