sequenceDiagram
    actor User
    box Purple App Frontend
    participant A as Client Window
    participant B as Client Worker
    end
    box brown Not our software
    participant C as Browser
    participant OS
    participant D as Push Server
    end
    participant E as App Backend
    User->>A: Turn on notifications
    A->>C: Notifications permissions?
    A->>B: Register a worker
    A->>C: Subscribe my worker to push messages. Here's the public signing key. What's the endpoint?
    activate A
    C->>D: Make an endpoint for this worker. Here's the public signing key.
    D-->>C: Here's your endpoint
    C->>C: Generate encryption keys
    C-->>A: Here's your endpoint and public encryption key
    A->>E: Here's the endpoint and public encryption key
    E->>E: Store sensitive endpoint and encryption key
    destroy A
    User-xA: Close
    C--xB: Done with you
    Note right of E: Notification to send?
    E->>E: Encrypt and sign data
    E->>D: Signed and encrypted notification
    D->>D: Verify it's signed by expected server
    Note right of D: Can't decrypt
    D--)C: New notification
    C->>C: Decrypt
    C->>B: Wake up and deal with this
    B->>C: Notify
    C->>OS: Notify
    OS->>User: Ding!