Address PR feedback

* Use the OperationQueue's `operationCount` function instead of keeping
count ourselves. This is reliable now each command is entirely self
contained.

* Rename `queueCommand` to `enqueueCommand`

* Move the command Enum into its own model file

* Move the `enqueueCommand` function into MPDClient+Command

Persephone.xcodeproj/project.pbxproj

@@ -53,6 +53,7 @@
 		E450ADA12229E7C90091BED3 /* PMKFoundation.framework.dSYM in Resources */ = {isa = PBXBuildFile; fileRef = E450AD9F2229E7C90091BED3 /* PMKFoundation.framework.dSYM */; };
 		E450ADA32229E7E00091BED3 /* PMKFoundation.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = E450ADA02229E7C90091BED3 /* PMKFoundation.framework */; };
 		E450ADA42229E7E00091BED3 /* PMKFoundation.framework in Embed Libraries */ = {isa = PBXBuildFile; fileRef = E450ADA02229E7C90091BED3 /* PMKFoundation.framework */; settings = {ATTRIBUTES = (CodeSignOnCopy, RemoveHeadersOnCopy, ); }; };
+		E45962C62241A78500FC1A1E /* Command.swift in Sources */ = {isa = PBXBuildFile; fileRef = E45962C52241A78500FC1A1E /* Command.swift */; };
 		E465049A21E94DF500A70F4C /* WindowController.swift in Sources */ = {isa = PBXBuildFile; fileRef = E465049921E94DF500A70F4C /* WindowController.swift */; };
 		E47E2FCC2220573500F747E6 /* MediaKeyTap.framework.dSYM in Resources */ = {isa = PBXBuildFile; fileRef = E47E2FCB2220573500F747E6 /* MediaKeyTap.framework.dSYM */; };
 		E47E2FD122205C4600F747E6 /* MainSplitViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = E47E2FD022205C4600F747E6 /* MainSplitViewController.swift */; };
@@ -210,6 +211,7 @@
 		E450AD9E2229B9BC0091BED3 /* PersephoneBridgingHeader.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = PersephoneBridgingHeader.h; sourceTree = "<group>"; };
 		E450AD9F2229E7C90091BED3 /* PMKFoundation.framework.dSYM */ = {isa = PBXFileReference; lastKnownFileType = wrapper.dsym; name = PMKFoundation.framework.dSYM; path = Carthage/Build/Mac/PMKFoundation.framework.dSYM; sourceTree = "<group>"; };
 		E450ADA02229E7C90091BED3 /* PMKFoundation.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = PMKFoundation.framework; path = Carthage/Build/Mac/PMKFoundation.framework; sourceTree = "<group>"; };
+		E45962C52241A78500FC1A1E /* Command.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Command.swift; sourceTree = "<group>"; };
 		E465049921E94DF500A70F4C /* WindowController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = WindowController.swift; sourceTree = "<group>"; };
 		E47E2FCB2220573500F747E6 /* MediaKeyTap.framework.dSYM */ = {isa = PBXFileReference; lastKnownFileType = wrapper.dsym; name = MediaKeyTap.framework.dSYM; path = Carthage/Build/Mac/MediaKeyTap.framework.dSYM; sourceTree = "<group>"; };
 		E47E2FD022205C4600F747E6 /* MainSplitViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MainSplitViewController.swift; sourceTree = "<group>"; };
@@ -512,6 +514,7 @@
 				E4EB2378220F10B8008C70C0 /* Pair.swift */,
 				E4EB237A220F7CF1008C70C0 /* Album.swift */,
 				E4C8B53D22349002009A20F3 /* Idle.swift */,
+				E45962C52241A78500FC1A1E /* Command.swift */,
 			);
 			path = Models;
 			sourceTree = "<group>";
@@ -753,6 +756,7 @@
 				E450AD7E222620A10091BED3 /* AlbumItem.swift in Sources */,
 				E4E8CC942206097F0024217A /* NotificationsController.swift in Sources */,
 				E408D3B6220DD8970006D9BE /* Notification.swift in Sources */,
+				E45962C62241A78500FC1A1E /* Command.swift in Sources */,
 				E408D3B9220DE98F0006D9BE /* NSUserInterfaceItemIdentifier.swift in Sources */,
 				E4EB2379220F10B8008C70C0 /* Pair.swift in Sources */,
 				E4F6B463221E125900ACF42A /* SongItem.swift in Sources */,

Persephone/MPDClient/Extensions/MPDClient+Album.swift

@@ -11,15 +11,15 @@ import mpdclient
 
 extension MPDClient {
   func fetchAllAlbums() {
-    queueCommand(command: .fetchAllAlbums)
+    enqueueCommand(command: .fetchAllAlbums)
   }
 
   func playAlbum(_ album: Album) {
-    queueCommand(command: .playAlbum, userData: ["album": album])
+    enqueueCommand(command: .playAlbum, userData: ["album": album])
   }
 
   func getAlbumURI(for album: Album, callback: @escaping (String?) -> Void) {
-    queueCommand(
+    enqueueCommand(
       command: .getAlbumURI,
       priority: .low,
       userData: ["album": album, "callback": callback]

Persephone/MPDClient/Extensions/MPDClient+Command.swift

@@ -54,4 +54,22 @@ extension MPDClient {
       albumURI(for: album, callback: callback)
     }
   }
+
+  func enqueueCommand(
+    command: Command,
+    priority: BlockOperation.QueuePriority = .normal,
+    userData: Dictionary<String, Any> = [:]
+  ) {
+    guard isConnected else { return }
+
+    noIdle()
+
+    let commandOperation = BlockOperation() { [unowned self] in
+      self.sendCommand(command: command, userData: userData)
+
+      self.idle()
+    }
+    commandOperation.queuePriority = priority
+    commandQueue.addOperation(commandOperation)
+  }
 }

Persephone/MPDClient/Extensions/MPDClient+Idle.swift

@@ -18,7 +18,7 @@ extension MPDClient {
   }
 
   func idle() {
-    if !self.isIdle && self.commandsQueued == 0 {
+    if !self.isIdle && self.commandQueue.operationCount == 1 {
       mpd_send_idle(self.connection)
       self.isIdle = true
 

Persephone/MPDClient/Extensions/MPDClient+Queue.swift

@@ -15,7 +15,7 @@ extension MPDClient {
   }
 
   func playTrack(at queuePos: Int) {
-    queueCommand(command: .playTrack, userData: ["queuePos": queuePos])
+    enqueueCommand(command: .playTrack, userData: ["queuePos": queuePos])
   }
 
   func sendPlayTrack(at queuePos: Int) {

Persephone/MPDClient/Extensions/MPDClient+Transport.swift

@@ -11,23 +11,23 @@ import mpdclient
 
 extension MPDClient {
   func playPause() {
-    queueCommand(command: .playPause)
+    enqueueCommand(command: .playPause)
   }
 
   func stop() {
-    queueCommand(command: .stop)
+    enqueueCommand(command: .stop)
   }
 
   func prevTrack() {
-    queueCommand(command: .prevTrack)
+    enqueueCommand(command: .prevTrack)
   }
 
   func nextTrack() {
-    queueCommand(command: .nextTrack)
+    enqueueCommand(command: .nextTrack)
   }
 
   func seekCurrentSong(timeInSeconds: Float) {
-    queueCommand(
+    enqueueCommand(
       command: .seekCurrentSong,
       userData: ["timeInSeconds": timeInSeconds]
     )

Persephone/MPDClient/MPDClient.swift

@@ -19,36 +19,9 @@ class MPDClient {
   var queue: [Song] = []
 
   let commandQueue = OperationQueue()
-  var commandsQueued: UInt = 0
-
-  enum Command {
-    case prevTrack, nextTrack, playPause, stop, seekCurrentSong,
-      fetchStatus, fetchQueue, playTrack, fetchAllAlbums,
-      playAlbum, getAlbumURI
-  }
 
   init(withDelegate delegate: MPDClientDelegate?) {
     commandQueue.maxConcurrentOperationCount = 1
     self.delegate = delegate
   }
-
-  func queueCommand(
-    command: Command,
-    priority: BlockOperation.QueuePriority = .normal,
-    userData: Dictionary<String, Any> = [:]
-  ) {
-    guard isConnected else { return }
-
-    noIdle()
-
-    let commandOperation = BlockOperation() { [unowned self] in
-      self.commandsQueued -= 1
-      self.sendCommand(command: command, userData: userData)
-
-      self.idle()
-    }
-    commandOperation.queuePriority = priority
-    commandsQueued += 1
-    commandQueue.addOperation(commandOperation)
-  }
 }

Persephone/MPDClient/Models/Command.swift

@@ -0,0 +1,32 @@
+//
+//  Command.swift
+//  Persephone
+//
+//  Created by Daniel Barber on 2019/3/19.
+//  Copyright © 2019 Dan Barber. All rights reserved.
+//
+
+import Foundation
+
+extension MPDClient {
+  enum Command {
+    // Transport commands
+    case prevTrack
+    case nextTrack
+    case playPause
+    case stop
+    case seekCurrentSong
+
+    // Status commands
+    case fetchStatus
+
+    // Queue commands
+    case fetchQueue
+    case playTrack
+
+    // Album commands
+    case fetchAllAlbums
+    case playAlbum
+    case getAlbumURI
+  }
+}