WebSub Subscriber implementation written in Swift

Below are the list of implemeneted features of WebSub Subscriber protocol. The list are copied from implementation report template.

• 100: HTTP header discovery - discovers the hub and self URLs from HTTP headers
• 101: HTML tag discovery - discovers the hub and self URLs from the HTML <link> tags
• 102: Atom feed discovery - discovers the hub and self URLs from the XML <link> tags
• 103: RSS feed discovery - discovers the hub and self URLs from the XML <atom:link> tags
• 104: Discovery priority - prioritizes the hub and self in HTTP headers over the links in the body

• 1xx: Successfully creates a subscription
• 200: Subscribing to a URL that reports a different rel=self
• 201: Subscribing to a topic URL that sends an HTTP 302 temporary redirect
• 202: Subscribing to a topic URL that sends an HTTP 301 permanent redirect
• 203: Subscribing to a hub that sends a 302 temporary redirect
• 204: Subscribing to a hub that sends a 301 permanent redirect
• 205: Rejects a verification request with an invalid topic URL
• 1xx: Requests a subscription using a secret (optional)
  • Please select the signature method(s) that the subscriber recognizes. All methods listed below are currently acceptable for the hub to choose:
  • sha1
  • sha256
  • sha384
  • sha512
• 1xx: Requests a subscription with a specific lease_seconds (optional, hub may ignore)
• Callback URL is unique per subscription (should)
• Callback URL is an unguessable URL (should)
• 1xx: Sends an unsubscription request

• 300: Returns HTTP 2xx when the notification payload is delivered
• 1xx: Verifies a valid signature for authenticated distribution
• 301: Rejects a distribution request with an invalid signature
• 302: Rejects a distribution request with no signature when the subscription was made with a secret

(1xx denotes that you can can use any of the 100-104 tests to confirm this feature)

SubscriberKit isn't designed for building complete end-user solutions. Its primary function is to provide an abstract implementation of the WebSub Subscriber protocol. SubscriberKit doesn't include server-side components. To create a full end-user solution, consider using SubscriberVapor, which leverages Vapor for its server-side implementation.

In the future, we plan to support SubscriberKit integration with other Swift server-side solutions like Kitura and Hummingbird in the future.