Fixes issue where connectivity issues can lead to persistent "Offline" status in UI

This fixes the problem where either internet connectivity issues on the device or intermittant
server issues can cause a persistent "OFFLINE" indicator even though that is not the case.

This requires the server protocol to be more granular about what their connection status is,
and adds a new signal from the multiplexer to the MainViewController allowing it to notify the
delegate that an acknowledgement was heard from one of the servers, allowing the main view
controller to update its UI according to whatever status best represents the group of servers
as a whole.

Testing
- This can be tested by using the network link conditioner to simulate connection issues
  *after* the control panel has connected to all servers in the multiplex.
- Tested losing internet connection and regaining internet connection
- Tested starting off with no connection and regaining connection later

XIONControlPanel/Controllers/MainViewController.swift

@@ -206,11 +206,6 @@ class MainViewController: UIViewController, SwitchesViewControllerDelegate, Serv
     {
         _switchesController.devices = Array(multiplex.devices)
         _updateVisualization(false)
-        
-        // Update connection status too, if applicable
-        if _serverMultiplex.numServers == _serverMultiplex.numberOfConnectedServers() {
-            _updateConnectivityStatus(.connected)
-        }
     }
     
     func serverMultiplex(_ multiplex: ServerMultiplex, devicesStateChanged devices: [AnyDevice])
@@ -218,6 +213,13 @@ class MainViewController: UIViewController, SwitchesViewControllerDelegate, Serv
         _switchesController.devicesStateChanged(devices)
     }
     
+    func serverMultiplex(_ multiplex: ServerMultiplex, didReceiveAcknowledgementFromServer server: Server)
+    {
+        // Update connection status too, if applicable
+        let groupConnectionStatus = multiplex.groupConnectionStatus()
+        _updateConnectivityStatus(groupConnectionStatus)
+    }
+    
     func serverMultiplex(_ multiplex: ServerMultiplex, didEncounterError error: Error)
     {
         _updateConnectivityStatus(.error)

XIONControlPanel/Servers/HubitatServer.swift

@@ -16,7 +16,7 @@ public enum HubitatServerError : Error
 
 public class HubitatServer : Server
 {
-    var connected: Bool = false
+    var connectionStatus: ConnectionStatus = .disconnected
     
     public fileprivate(set) var devices: [HubitatDevice] = []
     
@@ -33,13 +33,13 @@ public class HubitatServer : Server
     func connect(_ completion: @escaping (Error?) -> Void)
     {
         // RESTful, assume we're connected unless we get an error
-        self.connected = true
+        connectionStatus = .connected
         completion(nil)
     }
     
     func disconnect(_ completion: (Error?) -> Void)
     {
-        self.connected = false
+        connectionStatus = .disconnected
     }
     
     func fetchDevices(_ fetchCompletion: @escaping (Result<[AnyDevice], Error>) -> Void)
@@ -52,10 +52,10 @@ public class HubitatServer : Server
             .decode(type: [HubitatDevice].self, decoder: JSONDecoder())
             .sink(receiveCompletion: { completion in
                 if case let Subscribers.Completion.failure(error) = completion {
-                    self.connected = false
+                    self.connectionStatus = .error
                     fetchCompletion(.failure(error))
                 } else {
-                    self.connected = true
+                    self.connectionStatus = .connected
                 }
             }) { (devices: [HubitatDevice]) in
                 self.devices = devices

XIONControlPanel/Servers/ServerMultiplex.swift

@@ -12,6 +12,7 @@ protocol ServerMultiplexDelegate
 {
     func serverMultiplex(_ multiplex: ServerMultiplex, didAddDevices devices: [AnyDevice])
     func serverMultiplex(_ multiplex: ServerMultiplex, devicesStateChanged devices: [AnyDevice])
+    func serverMultiplex(_ multiplex: ServerMultiplex, didReceiveAcknowledgementFromServer server: Server)
     func serverMultiplex(_ multiplex: ServerMultiplex, didEncounterError error: Error)
 }
 
@@ -33,9 +34,26 @@ class ServerMultiplex
         servers.append(server)
     }
     
-    public func numberOfConnectedServers() -> Int
+    /// Returns a status that best represents the status of the whole group, as if it were one device
+    public func groupConnectionStatus() -> ConnectionStatus
     {
-        return servers.filter { $0.connected == true }.count
+        let relevancyRank: (ConnectionStatus) -> Int = { status in
+            switch status {
+            case .disconnected: return 0
+            case .connected:    return 1
+            case .connecting:   return 2
+            case .error:        return 3
+            }
+        }
+        
+        var groupStatus = ConnectionStatus.connected
+        servers.forEach { server in
+            if relevancyRank(server.connectionStatus) > relevancyRank(groupStatus) {
+                groupStatus = server.connectionStatus
+            }
+        }
+        
+        return groupStatus
     }
     
     public func toggleDeviceState(_ device: AnyDevice, state: DeviceState, completion: @escaping (Error?) -> Void)
@@ -56,7 +74,7 @@ class ServerMultiplex
     {
         self.servers.forEach { (server: Server) in
             server.fetchDevices { (result: Result<[AnyDevice], Error>) in
-                self.handleServerFetchResult(result)
+                self.handleServerFetchResult(forServer: server, result: result)
             }
         }
     }
@@ -64,18 +82,22 @@ class ServerMultiplex
 
 extension ServerMultiplex
 {
-    private func handleServerFetchResult(_ result: Result<[AnyDevice], Error>)
+    private func handleServerFetchResult(forServer server: Server, result: Result<[AnyDevice], Error>)
     {
         switch result {
         case .success(let devices):
-            handleDevicesChanged(devices)
+            handleDevicesChanged(forServer: server, devicesChanged: devices)
         case .failure(let error):
-            handleError(error)
+            handleError(forServer: server, error: error)
         }
     }
     
-    private func handleDevicesChanged(_ devicesChanged: [AnyDevice])
+    private func handleDevicesChanged(forServer server: Server, devicesChanged: [AnyDevice])
     {
+        // First send server acknowledgement
+        self.delegate?.serverMultiplex(self, didReceiveAcknowledgementFromServer: server)
+        
+        // Then, optionally notify about new devices or device state changes
         let newDevicesSet = Set<AnyDevice>(devicesChanged)
         let additions = newDevicesSet.subtracting(self.devices)
         let changed = newDevicesSet.filter { (device: AnyDevice) in
@@ -101,7 +123,7 @@ extension ServerMultiplex
         }
     }
     
-    private func handleError(_ error: Error)
+    private func handleError(forServer server: Server, error: Error)
     {
         DispatchQueue.main.async {
             self.delegate?.serverMultiplex(self, didEncounterError: error)

XIONControlPanel/Servers/ServerProtocol.swift

@@ -8,9 +8,17 @@
 
 import Foundation
 
+enum ConnectionStatus
+{
+    case disconnected
+    case connecting
+    case connected
+    case error
+}
+
 protocol Server
 {
-    var connected: Bool { get }
+    var connectionStatus: ConnectionStatus { get }
     
     /// Designated initializer. Takes an API endpoint URL
     init(_ url: URL)

XIONControlPanel/Servers/WemoServer.swift

@@ -8,14 +8,6 @@
 
 import Foundation
 
-enum ConnectionStatus
-{
-    case disconnected
-    case connecting
-    case connected
-    case error
-}
-
 enum ConnectionError : Error
 {
     case unknown
@@ -25,11 +17,9 @@ enum ConnectionError : Error
 class WemoServer : Server
 {
     private var devices: [WemoDevice] = []
-    
-    public var connected: Bool { get { return self.connectionStatus == .connected } }
+    public var connectionStatus: ConnectionStatus = .disconnected
     
     fileprivate(set) var baseURL:    URL
-    fileprivate(set) var connectionStatus: ConnectionStatus = .disconnected
     
     fileprivate var _urlSession:     URLSession
     fileprivate var _errorStream:    StandardErrorOutputStream = StandardErrorOutputStream()
@@ -48,6 +38,8 @@ class WemoServer : Server
     func connect(_ completion: @escaping (Error?) -> Void)
     {
         if (self.connectionStatus == .disconnected) {
+            self.connectionStatus = .connecting
+            
             let op = ConnectOperation(baseURL: self.baseURL, session: _urlSession)
             weak var weakOp = op
             op.completionBlock = {
@@ -103,7 +95,7 @@ class WemoServer : Server
     
     func toggleDevice(_ device: AnyDevice, state: DeviceState, completion: @escaping (Error?) -> Void)
     {
-        if self.connected, let device = findDevice(device) {
+        if connectionStatus == .connected, let device = findDevice(device) {
             let op = ToggleDeviceOperation(baseURL: self.baseURL, session: _urlSession, device: device, state: state)
             weak var weakOp = op
             op.completionBlock = {