Switch to gRPC client in Swift app

Apple/UI/TunnelButton.swift

@@ -0,0 +1,73 @@
+import SwiftUI
+
+struct TunnelButton: View {
+    @Environment(\.tunnel)
+    var tunnel: any Tunnel
+
+    private var action: Action? { tunnel.action }
+
+    var body: some View {
+        Button {
+            if let action {
+                tunnel.perform(action)
+            }
+        } label: {
+            Text(action.description)
+        }
+        .disabled(action.isDisabled)
+        .padding(.horizontal)
+        .buttonStyle(.floating)
+    }
+}
+
+extension Tunnel {
+    @MainActor fileprivate var action: TunnelButton.Action? {
+        switch status {
+        case .permissionRequired, .invalid:
+            .enable
+        case .disabled, .disconnecting, .disconnected:
+            .start
+        case .connecting, .connected, .reasserting:
+            .stop
+        case .unknown, .configurationReadWriteFailed:
+            nil
+        }
+    }
+}
+
+extension TunnelButton {
+    fileprivate enum Action {
+        case enable
+        case start
+        case stop
+    }
+}
+
+extension TunnelButton.Action? {
+    var description: LocalizedStringKey {
+        switch self {
+        case .enable: "Enable"
+        case .start: "Start"
+        case .stop: "Stop"
+        case .none: "Start"
+        }
+    }
+
+    var isDisabled: Bool {
+        if case .none = self {
+            true
+        } else {
+            false
+        }
+    }
+}
+
+extension Tunnel {
+    fileprivate func perform(_ action: TunnelButton.Action) {
+        switch action {
+        case .enable: enable()
+        case .start: start()
+        case .stop: stop()
+        }
+    }
+}