Add ActiveApplicationMonitor

So we don't have to worry about failures in searching for an active Xcode

Author: intitni

Core/Package.swift

@@ -51,8 +51,14 @@ let package = Package(
         ),
         .target(
             name: "Service",
-            dependencies: ["CopilotModel", "CopilotService", "XPCShared", "CGEventObserver",
-                           "DisplayLink"]
+            dependencies: [
+                "CopilotModel",
+                "CopilotService",
+                "XPCShared",
+                "CGEventObserver",
+                "DisplayLink",
+                "ActiveApplicationMonitor",
+            ]
         ),
         .target(
             name: "XPCShared",
@@ -65,5 +71,6 @@ let package = Package(
         .target(name: "FileChangeChecker"),
         .target(name: "LaunchAgentManager"),
         .target(name: "DisplayLink"),
+        .target(name: "ActiveApplicationMonitor"),
     ]
 )

Core/Sources/ActiveApplicationMonitor/ActiveApplicationMonitor.swift

@@ -0,0 +1,56 @@
+import AppKit
+
+public final class ActiveApplicationMonitor {
+    static let shared = ActiveApplicationMonitor()
+    var activeApplication = NSWorkspace.shared.runningApplications.first(where: \.isActive)
+    private var continuations: [UUID: AsyncStream<NSRunningApplication?>.Continuation] = [:]
+
+    private init() {
+        Task {
+            let sequence = NSWorkspace.shared.notificationCenter
+                .notifications(named: NSWorkspace.didActivateApplicationNotification)
+            for await notification in sequence {
+                guard let app = notification
+                    .userInfo?[NSWorkspace.applicationUserInfoKey] as? NSRunningApplication
+                else { continue }
+                activeApplication = app
+                notifyContinuations()
+            }
+        }
+    }
+
+    deinit {
+        for continuation in continuations {
+            continuation.value.finish()
+        }
+    }
+
+    public static var activeApplication: NSRunningApplication? { shared.activeApplication }
+
+    public static func createStream() -> AsyncStream<NSRunningApplication?> {
+        .init { continuation in
+            let id = UUID()
+            ActiveApplicationMonitor.shared.addContinuation(continuation, id: id)
+            continuation.onTermination = { _ in
+                ActiveApplicationMonitor.shared.removeContinuation(id: id)
+            }
+        }
+    }
+
+    func addContinuation(
+        _ continuation: AsyncStream<NSRunningApplication?>.Continuation,
+        id: UUID
+    ) {
+        continuations[id] = continuation
+    }
+
+    func removeContinuation(id: UUID) {
+        continuations[id] = nil
+    }
+
+    private func notifyContinuations() {
+        for continuation in continuations {
+            continuation.value.yield(activeApplication)
+        }
+    }
+}

Core/Sources/Service/GUI/SuggestionPanelController.swift

@@ -1,3 +1,4 @@
+import ActiveApplicationMonitor
 import AppKit
 import DisplayLink
 import SwiftUI
@@ -25,7 +26,11 @@ final class SuggestionPanelController {
     }()
 
     private var displayLinkTask: Task<Void, Never>?
+    private var activeApplicationMonitorTask: Task<Void, Never>?
     private let viewModel = SuggestionPanelViewModel()
+    private var activeApplication: NSRunningApplication? {
+        ActiveApplicationMonitor.activeApplication
+    }
 
     nonisolated init() {
         Task { @MainActor in
@@ -34,23 +39,29 @@ final class SuggestionPanelController {
                     self.updateWindowLocation()
                 }
             }
+
+            activeApplicationMonitorTask = Task {
+                for await _ in ActiveApplicationMonitor.createStream() {
+                    self.updateWindowLocation()
+                }
+            }
         }
     }
 
     /// Update the window location
     ///
     /// - note:
     private func updateWindowLocation() {
-        if let activeXcode = NSRunningApplication
-            .runningApplications(withBundleIdentifier: "com.apple.dt.Xcode")
-            .first(where: \.isActive)
+        if let activeXcode = activeApplication,
+           activeXcode.bundleIdentifier == "com.apple.dt.Xcode"
         {
             let application = AXUIElementCreateApplication(activeXcode.processIdentifier)
             if let focusElement: AXUIElement = try? application
                 .copyValue(key: kAXFocusedUIElementAttribute),
-               let focusElementType: String = try? focusElement.copyValue(key: kAXDescriptionAttribute),
-               focusElementType == "Source Editor",
-               let parent: AXUIElement = try? focusElement.copyValue(key: kAXParentAttribute),
+                let focusElementType: String = try? focusElement
+                .copyValue(key: kAXDescriptionAttribute),
+                focusElementType == "Source Editor",
+                let parent: AXUIElement = try? focusElement.copyValue(key: kAXParentAttribute),
                 let positionValue: AXValue = try? parent
                 .copyValue(key: kAXPositionAttribute),
                 let sizeValue: AXValue = try? parent