Replace Starscream with URLSessionWebSocketTask

Changelog-Fixed: Fix slow reconnection issues

damus/Nostr/WebSocket.swift

@@ -0,0 +1,87 @@
+//
+//  WebSocket.swift
+//  damus
+//
+//  Created by Bryan Montz on 4/13/23.
+//
+
+import Combine
+import Foundation
+
+enum WebSocketEvent {
+    case connected
+    case message(URLSessionWebSocketTask.Message)
+    case disconnected(URLSessionWebSocketTask.CloseCode, String?)
+    case error(Error)
+}
+
+final class WebSocket: NSObject, URLSessionWebSocketDelegate {
+    
+    private let url: URL
+    private let session: URLSession
+    private lazy var webSocketTask: URLSessionWebSocketTask = {
+        let task = session.webSocketTask(with: url)
+        task.delegate = self
+        return task
+    }()
+    
+    let subject = PassthroughSubject<WebSocketEvent, Never>()
+    
+    init(_ url: URL, session: URLSession = .shared) {
+        self.url = url
+        self.session = session
+    }
+    
+    func connect() {
+        resume()
+    }
+    
+    func disconnect(closeCode: URLSessionWebSocketTask.CloseCode = .normalClosure, reason: Data? = nil) {
+        webSocketTask.cancel(with: closeCode, reason: reason)
+        
+        // reset after disconnecting to be ready for reconnecting
+        let task = session.webSocketTask(with: url)
+        task.delegate = self
+        webSocketTask = task
+        
+        let reason_str: String?
+        if let reason {
+            reason_str = String(data: reason, encoding: .utf8)
+        } else {
+            reason_str = nil
+        }
+        subject.send(.disconnected(closeCode, reason_str))
+    }
+    
+    func send(_ message: URLSessionWebSocketTask.Message) {
+        webSocketTask.send(message) { [weak self] error in
+            if let error {
+                self?.subject.send(.error(error))
+            }
+        }
+    }
+    
+    private func resume() {
+        webSocketTask.receive { [weak self] result in
+            switch result {
+            case .success(let message):
+                self?.subject.send(.message(message))
+                self?.resume()
+            case .failure(let error):
+                self?.subject.send(.error(error))
+            }
+        }
+        
+        webSocketTask.resume()
+    }
+    
+    // MARK: - URLSessionWebSocketDelegate
+    
+    func urlSession(_ session: URLSession, webSocketTask: URLSessionWebSocketTask, didOpenWithProtocol theProtocol: String?) {
+        subject.send(.connected)
+    }
+    
+    func urlSession(_ session: URLSession, webSocketTask: URLSessionWebSocketTask, didCloseWith closeCode: URLSessionWebSocketTask.CloseCode, reason: Data?) {
+        disconnect(closeCode: closeCode, reason: reason)
+    }
+}