From cfaedb29756be3f9271c0d2d3dd9b47a917281e1 Mon Sep 17 00:00:00 2001
From: Nathan Perkins <lnp@bu.edu>
Date: Wed, 11 Nov 2015 09:21:08 -0500
Subject: [PATCH] Listen for device changes. Refresh menu on device change.
 Terminate when closing menu and no active processors.

---
 SyllableDetector/AudioInterface.swift     | 78 +++++++++++++++++++++++
 SyllableDetector/ViewControllerMenu.swift | 24 +++++--
 2 files changed, 98 insertions(+), 4 deletions(-)

diff --git a/SyllableDetector/AudioInterface.swift b/SyllableDetector/AudioInterface.swift
index bdd4264..87a6ce0 100644
--- a/SyllableDetector/AudioInterface.swift
+++ b/SyllableDetector/AudioInterface.swift
@@ -91,6 +91,9 @@ private func checkError(status: OSStatus, type: AudioInterfaceError? = nil, func
 
 class AudioInterface
 {
+    // event listeners
+    static var listeners = [AudioObjectPropertySelector: Array<(Int, (() -> Void))>]()
+    
     struct AudioDevice {
         let deviceID: AudioDeviceID
         let deviceUID: String
@@ -247,6 +250,81 @@ class AudioInterface
             return AudioDevice(deviceID: $0)
         }
     }
+    
+    static func createListenerForDeviceChange<T: Hashable>(cb: (Void) -> Void, withIdentifier unique: T) throws {
+        let selector = kAudioHardwarePropertyDevices
+        
+        // alread has listener
+        if var cur = listeners[selector] {
+            // add callback
+            cur.append((unique.hashValue, cb))
+            
+            // update listeners
+            listeners[selector] = cur
+            
+            return
+        }
+        
+        // property address
+        var propertyAddress = AudioObjectPropertyAddress(mSelector: selector, mScope: kAudioObjectPropertyScopeGlobal, mElement: kAudioObjectPropertyElementMaster)
+        let onAudioObject = AudioObjectID(bitPattern: kAudioObjectSystemObject)
+        
+        // create listener
+        try checkError(AudioObjectAddPropertyListenerBlock(onAudioObject, &propertyAddress, nil, dispatchEvent))
+        
+        // create callbacks array
+        let cbs: Array<(Int, (() -> Void))> = [(unique.hashValue, cb)]
+        listeners[selector] = cbs
+    }
+    
+    static func destroyListenerForDeviceChange<T: Hashable>(withIdentifier unique: T) {
+        let selector = kAudioHardwarePropertyDevices
+        
+        guard var cur = listeners[selector] else {
+            // nothing to remove
+            return
+        }
+        
+        // hash to remove
+        let hashToRemove = unique.hashValue
+        
+        // remove from listeners
+        cur = cur.filter() {
+            return $0.0 != hashToRemove
+        }
+        
+        // if empty
+        if cur.isEmpty {
+            // remove listener
+            listeners.removeValueForKey(selector)
+            
+            // property address
+            var propertyAddress = AudioObjectPropertyAddress(mSelector: selector, mScope: kAudioObjectPropertyScopeGlobal, mElement: kAudioObjectPropertyElementMaster)
+            let onAudioObject = AudioObjectID(bitPattern: kAudioObjectSystemObject)
+            
+            do {
+                try checkError(AudioObjectRemovePropertyListenerBlock(onAudioObject, &propertyAddress, nil, dispatchEvent))
+            }
+            catch {
+                DLog("unable to remove listener")
+            }
+        }
+        else {
+            // update listeners
+            listeners[selector] = cur
+        }
+    }
+    
+    static func dispatchEvent(numAddresses: UInt32, addresses: UnsafePointer<AudioObjectPropertyAddress>) {
+        for var i: UInt32 = 0; i < numAddresses; ++i {
+            let selector = addresses[Int(i)].mSelector
+            if let listenersForSelector = listeners[selector] {
+                for entry in listenersForSelector {
+                    dispatch_async(dispatch_get_main_queue(), entry.1)
+                }
+            }
+        }
+    }
 }
 
 class AudioOutputInterface: AudioInterface
diff --git a/SyllableDetector/ViewControllerMenu.swift b/SyllableDetector/ViewControllerMenu.swift
index 27d56dd..0c8c38f 100644
--- a/SyllableDetector/ViewControllerMenu.swift
+++ b/SyllableDetector/ViewControllerMenu.swift
@@ -22,12 +22,28 @@ class ViewControllerMenu: NSViewController, WindowControllerProcessorDelegate {
         // reload devices
         buttonLaunch.enabled = false
         reloadDevices()
+        
+        // listen
+        do {
+            try AudioInterface.createListenerForDeviceChange({
+                DLog("refreshing device")
+                self.reloadDevices()
+                }, withIdentifier: self)
+        }
+        catch {
+            DLog("Unable to add device change listener: \(error)")
+        }
     }
     
-//    override func viewDidDisappear() {
-//        // terminate
-//        NSApp.terminate(nil)
-//    }
+    override func viewDidDisappear() {
+        // remove listener
+        AudioInterface.destroyListenerForDeviceChange(withIdentifier: self)
+        
+        // terminate
+        if 0 == openProcessors.count {
+            NSApp.terminate(nil)
+        }
+    }
     
     func reloadDevices() {
         // fetch list of devices