Selected server and better settings

QueueCube/Backend/Server.swift

@@ -7,7 +7,7 @@
 
 import Foundation
 
-struct Server: Identifiable, Codable
+struct Server: Identifiable, Codable, Equatable
 {
     let serviceName: String?
     let baseURL: URL

QueueCube/Backend/Settings.swift

@@ -9,44 +9,106 @@ import Foundation
 
 struct Settings
 {
-    var configuredServers: [Server]
+    var selectedServer: Server?
+    
+    var configuredServers: [Server] {
+        willSet {
+            // Set selected server to whatever the first server is, if we're adding the first one.
+            if configuredServers.isEmpty && !newValue.isEmpty && selectedServer == nil {
+                selectedServer = newValue.first
+            }
+            
+            // If the selected server is being removed, set it to something else
+            if !newValue.contains(where: { $0 == selectedServer }) {
+                selectedServer = newValue.first // nil if empty
+            }
+        }
+    }
+    
+    var isConfigured: Bool { !configuredServers.isEmpty }
+    
+    static func fromDefaults() -> Settings {
+        let defaults = UserDefaults.standard
+        return Settings(
+            selectedServer: defaults[SelectedServerKey.self],
+            configuredServers: defaults[ConfiguredServersKey.self]
+        )
+    }
+    
+    func save() {
+        let defaults = UserDefaults.standard
+        defaults[ConfiguredServersKey.self] = configuredServers
+        defaults[SelectedServerKey.self] = selectedServer
+        
+        postSettingsChanged()
+    }
+    
+    func postSettingsChanged() {
+        NotificationCenter.default.post(name: .settingsChanged, object: nil)
+    }
+    
+    // MARK: - Modifiers
+    
+    func selectedServer(_ server: Server?) -> Self {
+        var copy = self
+        copy.selectedServer = server
+        return copy
+    }
     
     func configuredServers(_ servers: [Server]) -> Self {
         var copy = self
         copy.configuredServers = servers
-        return copy 
-    }
-    
-    var isConfigured: Bool {
-        !configuredServers.isEmpty
-    }
-    
-    static func fromDefaults() -> Settings {
-        let configuredServers: [Server] = {
-            guard let configuredServersData = UserDefaults.standard.data(forKey: Keys.configuredServers.rawValue)
-                else { return [] }
-            
-            guard let configuredServers = try? PropertyListDecoder().decode([Server].self, from: configuredServersData)
-                else { return [] }
-            
-            return configuredServers
-        }()
-        
-        return Settings(configuredServers: configuredServers)
-    }
-    
-    func save() {
-        let configuredServersData = try! PropertyListEncoder().encode(configuredServers)
-        UserDefaults.standard.set(configuredServersData, forKey: Keys.configuredServers.rawValue)
-        NotificationCenter.default.post(name: .settingsChanged, object: nil)
+        return copy
     }
     
     // MARK: - Types
     
     enum Keys: String
     {
+        case selectedServer
         case configuredServers
     }
+    
+    fileprivate protocol Key
+    {
+        associatedtype Value: Codable
+        
+        static var defaultValue: Value { get }
+        static var key: String { get }
+    }
+    
+    private struct ConfiguredServersKey: Key {
+        static var defaultValue: [Server] { [] }
+    }
+    
+    private struct SelectedServerKey: Key {
+        static var defaultValue: Server? { nil }
+    }
+}
+
+extension UserDefaults
+{
+    fileprivate subscript<T: Settings.Key>(_ type: T.Type) -> T.Value {
+        get {
+            guard let data = data(forKey: type.key)
+                else { return type.defaultValue }
+            
+            guard let value = try? PropertyListDecoder().decode(type.Value, from: data)
+                else { return type.defaultValue }
+            
+            return value
+        }
+        
+        set {
+            let data = try? PropertyListEncoder().encode(newValue)
+            set(data, forKey: type.key)
+        }
+    }
+}
+
+extension Settings.Key
+{
+    static var key: String { Mirror(reflecting: Self.self).description }
 }
 
 extension Notification.Name