Add BackgroundService For Link's Expiration Notificatioin

[mohammadKarimi]

[mohammadKarimi]

@MohamadReza-khani

[mohammadKarimi]

To implement a feature for notifying users about their link's expiration, you can follow these steps, leveraging the existing structure of the SwiftLink application:

1. Define a New Notification Type

First, define a new notification type for link expiration. This notification will be used to inform users when their links are nearing expiration or have expired.

public record LinkExpirationNotification : INotification
{
    public int LinkId { get; init; }
    public string SubscriberEmail { get; init; }
    public DateTime ExpirationDate { get; init; }
}

2. Create a Scheduled Task for Checking Link Expirations

Implement a scheduled task that runs periodically to check for links that are nearing expiration. This task will query the database for links that are set to expire within a certain threshold (e.g., within the next 24 hours) and have not yet been notified.

You can use a background service or a scheduled job (e.g., with Hangfire or Quartz.NET) for this purpose.

public class LinkExpirationChecker : IHostedService
{
    private readonly IApplicationDbContext _dbContext;
    private readonly IMediator _mediator;

    public LinkExpirationChecker(IApplicationDbContext dbContext, IMediator mediator)
    {
        _dbContext = dbContext;
        _mediator = mediator;
    }

    // Implement the logic to start the background task
    // and check for expiring links at scheduled intervals
}

3. Implement Notification Logic

In the scheduled task, for each link that is nearing expiration, publish a LinkExpirationNotification using the IMediator instance. This will be handled by a notification handler designed to send the actual notification to the user.

// Inside the scheduled task
var expiringLinks = // Query the database for links nearing expiration
foreach (var link in expiringLinks)
{
    await _mediator.Publish(new LinkExpirationNotification
    {
        LinkId = link.Id,
        SubscriberEmail = link.Subscriber.Email,
        ExpirationDate = link.ExpirationDate
    });
}

4. Handle the Expiration Notification

Create a handler for LinkExpirationNotification that sends an email or another form of notification to the user, informing them of the impending expiration of their link.

public class LinkExpirationNotificationHandler : INotificationHandler<LinkExpirationNotification>
{
    // Inject any services needed to send notifications (e.g., an email service)

    public async Task Handle(LinkExpirationNotification notification, CancellationToken cancellationToken)
    {
        // Implement the logic to notify the user, e.g., send an email
    }
}

5. Update the Link Entity (Optional)

If you want to track whether a notification has been sent for an expiring link, you might need to add a new property to the Link entity, such as ExpirationNotificationSent. Update the logic in your scheduled task to mark the link as notified after sending the notification.

public class Link
{
    // Existing properties

    public bool ExpirationNotificationSent { get; set; }
}

Conclusion

By following these steps, you can implement a feature to notify users about their links' expiration. This involves defining a new notification type, creating a scheduled task to check for expiring links, implementing the logic to send notifications, and optionally updating the Link entity to track notification status.

[MohamadReza-khani]

Hi @mohammadKarimi Thanks for the guidness🙌 Could you please clarify how we plan to send notifications for reminders? Are we considering options like email, SMS, or any other channels?

[mohammadKarimi]

Hi @mohammadKarimi Thanks for the guidness🙌 Could you please clarify how we plan to send notifications for reminders? Are we considering options like email, SMS, or any other channels?

for now, implement a decorator pattern to adapt your code with any type of channel. your code does not know who is responsible to send a notification, your decorator select one of available channel an a candidate. each strategies must be empty for now.