Ping relays on resume, if there's an error then try to reconnect

This is an attempt to fix the fail-to-reconnect issues. Let's see if it works.

damus/Nostr/RelayConnection.swift

@@ -42,6 +42,7 @@ final class RelayConnection {
     private(set) var isConnecting = false
     
     private(set) var last_connection_attempt: TimeInterval = 0
+    private(set) var last_pong: Date? = nil
     private(set) var backoff: TimeInterval = 1.0
     private lazy var socket = WebSocket(url.url)
     private var subscriptionToken: AnyCancellable?
@@ -54,6 +55,18 @@ final class RelayConnection {
         self.handleEvent = handleEvent
     }
     
+    func ping() {
+        socket.ping { err in
+            if let err {
+                self.isConnecting = false
+                self.isConnected = false
+                self.reconnect_with_backoff()
+            } else {
+                self.last_pong = .now
+            }
+        }
+    }
+    
     func connect(force: Bool = false) {
         if !force && (isConnected || isConnecting) {
             return
@@ -111,15 +124,14 @@ final class RelayConnection {
             DispatchQueue.main.async {
                 self.isConnected = false
                 self.isConnecting = false
-                self.reconnect()
+                self.reconnect_with_backoff()
             }
         case .error(let error):
             print("⚠️ Warning: RelayConnection (\(self.url)) error: \(error)")
             DispatchQueue.main.async {
                 self.isConnected = false
                 self.isConnecting = false
-                self.backoff *= 1.5
-                self.reconnect_in(after: self.backoff)
+                self.reconnect_with_backoff()
             }
         }
         DispatchQueue.main.async {
@@ -127,6 +139,11 @@ final class RelayConnection {
         }
     }
     
+    func reconnect_with_backoff() {
+        self.backoff *= 1.5
+        self.reconnect_in(after: self.backoff)
+    }
+    
     func reconnect() {
         guard !isConnecting else {
             return  // we're already trying to connect

damus/Nostr/RelayPool.swift

@@ -79,7 +79,13 @@ class RelayPool {
         self.handlers = handlers.filter { $0.sub_id != sub_id }
         print("removing \(sub_id) handler, current: \(handlers.count)")
     }
-
+    
+    func ping() {
+        for relay in relays {
+            relay.connection.ping()
+        }
+    }
+    
     func register_handler(sub_id: String, handler: @escaping (String, NostrConnectionEvent) -> ()) {
         for handler in handlers {
             // don't add duplicate handlers

damus/Nostr/WebSocket.swift

@@ -32,6 +32,10 @@ final class WebSocket: NSObject, URLSessionWebSocketDelegate {
         self.session = session
     }
     
+    func ping(receiveHandler: @escaping (Error?) -> Void) {
+        self.webSocketTask.sendPing(pongReceiveHandler: receiveHandler)
+    }
+    
     func connect() {
         resume()
     }