Handle xpc connection interruptions

kordophone2/XPC/XPCClient.swift

@@ -11,10 +11,12 @@ import XPC
 
 private let serviceName = "net.buzzert.kordophonecd"
 
-
 final class XPCClient
 {
-    private let connection: xpc_connection_t
+    private var connection: xpc_connection_t?
+    private let connectionQueue = DispatchQueue(label: "net.buzzert.kordophone.xpc.connection")
+    private var isReconnecting: Bool = false
+    private var reconnectAttempt: Int = 0
     private let signalLock = NSLock()
     private var signalSinks: [UUID: (Signal) -> Void] = [:]
     private var didSubscribeSignals: Bool = false
@@ -28,21 +30,14 @@ final class XPCClient
             
             return service
         } catch {
-            fatalError("Unable to register agent: \(error)")
+            print("Unable to register agent: \(error)")
+            fatalError()
         }
     }()
 
     init() {
         _ = Self.appService
-        
-        self.connection = xpc_connection_create_mach_service(serviceName, nil, 0)
-
-        let handler: xpc_handler_t = { [weak self] event in
-            self?.handleIncomingXPCEvent(event)
-        }
-        
-        xpc_connection_set_event_handler(connection, handler)
-        xpc_connection_resume(connection)
+        connect()
     }
     
     public func eventStream() -> AsyncStream<Signal> {
@@ -197,6 +192,7 @@ final class XPCClient
         case typeError
         case encodingError
         case badFileHandle
+        case connectionError
     }
     
     enum Signal
@@ -211,6 +207,49 @@ final class XPCClient
 
 extension XPCClient
 {
+    private func connect() {
+        connectionQueue.async { [weak self] in
+            guard let self else { return }
+            
+            if let existing = connection {
+                xpc_connection_cancel(existing)
+                connection = nil
+            }
+
+            let newConn = xpc_connection_create_mach_service(serviceName, nil, 0)
+            let handler: xpc_handler_t = { [weak self] event in
+                self?.handleIncomingXPCEvent(event)
+            }
+            xpc_connection_set_event_handler(newConn, handler)
+            xpc_connection_resume(newConn)
+
+            self.connection = newConn
+            self.isReconnecting = false
+            self.reconnectAttempt = 0
+        }
+
+        if didSubscribeSignals {
+            Task { try? await subscribeToSignals() }
+        }
+    }
+
+    private func scheduleReconnect() {
+        connectionQueue.async { [weak self] in
+            guard let self else { return }
+            
+            if self.isReconnecting { return }
+            self.isReconnecting = true
+
+            let attempt = self.reconnectAttempt
+            self.reconnectAttempt += 1
+            
+            let delaySeconds = min(pow(2.0, Double(attempt)), 30.0)
+            self.connectionQueue.asyncAfter(deadline: .now() + delaySeconds) { [weak self] in
+                self?.connect()
+            }
+        }
+    }
+
     private func subscribeToSignals() async throws {
         let req = makeRequest(method: "SubscribeSignals")
         _ = try await sendSync(req)
@@ -237,15 +276,22 @@ extension XPCClient
 
     private func sendSync(_ request: xpc_object_t) async throws -> xpc_object_t? {
         try await withCheckedThrowingContinuation { continuation in
-            xpc_connection_send_message_with_reply(connection, request, DispatchQueue.global(qos: .userInitiated)) { r in
+            let conn: xpc_connection_t? = self.connectionQueue.sync { self.connection }
+            guard let conn else {
+                self.scheduleReconnect()
+                continuation.resume(throwing: Error.connectionError)
+                return
+            }
+
+            xpc_connection_send_message_with_reply(conn, request, DispatchQueue.global(qos: .userInitiated)) { r in
                 switch xpc_get_type(r) {
                     case XPC_TYPE_ERROR:
-                        let error = xpc_dictionary_get_value(r, "error")
-                        if let error = error, let errorString = xpc_string_get_string_ptr(error) {
-                            print("XPC error: \(String(cString: errorString))")
+                        if r.isInterruptionError {
+                            self.scheduleReconnect()
+                            continuation.resume(throwing: Error.connectionError)
+                        } else {
+                            continuation.resume(throwing: Error.typeError)
                         }
-                        
-                        continuation.resume(throwing: Error.typeError)
 
                     case XPC_TYPE_DICTIONARY:
                         continuation.resume(returning: r)
@@ -295,8 +341,8 @@ extension XPCClient
             }
 
         case XPC_TYPE_ERROR:
-            if let errStr = xpc_string_get_string_ptr(event) {
-                print("XPC event error: \(String(cString: errStr))")
+            if event.isInterruptionError {
+                scheduleReconnect()
             }
         default:
             break
@@ -304,4 +350,14 @@ extension XPCClient
     }
 }
 
+extension xpc_object_t
+{
+    var isInterruptionError: Bool {
+        return (
+            xpc_equal(self, XPC_ERROR_CONNECTION_INTERRUPTED) ||
+            xpc_equal(self, XPC_ERROR_CONNECTION_INVALID) ||
+            xpc_equal(self, XPC_ERROR_TERMINATION_IMMINENT)
+         )
+    }
+}