Fetch artwork from MusicBrainz if not on FS

* 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>";
@@ -732,6 +735,7 @@
 				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
+  }
+}

Persephone/Models/Preferences.swift

@@ -62,6 +62,15 @@ struct Preferences {
     return NSString(string: mpdLibraryDirOrDefault).expandingTildeInPath
   }
 
+  var fetchMissingArtworkFromInternet: Bool {
+    get {
+      return preferences.bool(forKey: "fetchMissingArtworkFromInternet")
+    }
+    set {
+      preferences.set(newValue, forKey: "fetchMissingArtworkFromInternet")
+    }
+  }
+
   func addObserver(_ observer: NSObject, forKeyPath keyPath: String) {
     preferences.addObserver(observer, forKeyPath: keyPath, options: .new, context: nil)
   }

Persephone/Preferences/Controllers/AlbumArtPrefsController.swift

@@ -18,6 +18,12 @@ class AlbumArtPrefsController: NSViewController {
       mpdLibraryDirField.stringValue = mpdLibraryDir
     }
 
+    if preferences.fetchMissingArtworkFromInternet {
+      fetchMissingArtworkFromInternet.state = .on
+    } else {
+      fetchMissingArtworkFromInternet.state = .off
+    }
+
     preferredContentSize = NSMakeSize(view.frame.size.width, view.frame.size.height)
   }
 
@@ -34,4 +40,14 @@ class AlbumArtPrefsController: NSViewController {
   }
 
   @IBOutlet var mpdLibraryDirField: NSTextField!
+
+  @IBAction func updateFetchMissingArtworkFromInternet(_ sender: NSButton) {
+    if sender.state == .on {
+      preferences.fetchMissingArtworkFromInternet = true
+    } else {
+      preferences.fetchMissingArtworkFromInternet = false
+    }
+  }
+
+  @IBOutlet var fetchMissingArtworkFromInternet: NSButton!
 }

Persephone/Resources/Base.lproj/Main.storyboard

@@ -326,6 +326,9 @@
                                     <behavior key="behavior" changeContents="YES" doesNotDimImage="YES" lightByContents="YES"/>
                                     <font key="font" metaFont="system"/>
                                 </buttonCell>
+                                <connections>
+                                    <action selector="updateFetchMissingArtworkFromInternet:" target="3C9-vU-zjZ" id="I7x-9V-xJr"/>
+                                </connections>
                             </button>
                         </subviews>
                         <constraints>
@@ -339,6 +342,7 @@
                         </constraints>
                     </view>
                     <connections>
+                        <outlet property="fetchMissingArtworkFromInternet" destination="pRL-MG-1Be" id="Xcp-sb-iZm"/>
                         <outlet property="mpdLibraryDirField" destination="gDk-ca-eOa" id="myi-BQ-0NS"/>
                     </connections>
                 </viewController>

Persephone/Services/AlbumArtService.swift

@@ -9,11 +9,12 @@
 import Cocoa
 
 class AlbumArtService: NSObject {
+  var preferences = Preferences()
+  
   let cachedArtworkSize = 180
   let cachedArtworkQuality: CGFloat = 0.5
 
   static var shared = AlbumArtService()
-  var preferences = Preferences()
 
   var session = URLSession(configuration: .default)
   let cacheQueue = DispatchQueue(label: "albumArtCacheQueue", attributes: .concurrent)

Persephone/Services/Extensions/AlbumArtService+Filesystem.swift

@@ -12,7 +12,9 @@ extension AlbumArtService {
   func getArtworkFromFilesystem(
     for album: AlbumItem,
     callback: @escaping (_ image: NSImage) -> Void
-    ) {
+  ) {
+    var tryImage: NSImage?
+
     let coverArtFilenames = [
       "folder.jpg",
       "cover.jpg",
@@ -29,7 +31,9 @@ extension AlbumArtService {
       for coverArtFilename in coverArtFilenames {
         let coverArtURI = "\(fullAlbumURI)/\(coverArtFilename)"
 
-        if let image = self.tryImage(coverArtURI) {
+        tryImage = self.tryImage(coverArtURI)
+
+        if let image = tryImage {
           self.cacheArtwork(
             for: album,
             data: image.jpegData(compressionQuality: self.cachedArtworkQuality)
@@ -38,6 +42,10 @@ extension AlbumArtService {
           break
         }
       }
+
+      if tryImage == nil && self.preferences.fetchMissingArtworkFromInternet {
+        self.getRemoteArtwork(for: album, callback: callback)
+      }
     }
 
     AppDelegate.mpdClient.getAlbumURI(
@@ -47,17 +55,15 @@ extension AlbumArtService {
   }
 
   func tryImage(_ filePath: String) -> NSImage? {
-    if FileManager.default.fileExists(atPath: filePath),
+    guard FileManager.default.fileExists(atPath: filePath),
       let data = FileManager.default.contents(atPath: filePath),
-      let image = NSImage(data: data) {
+      let image = NSImage(data: data)
+      else { return nil }
 
-      let imageThumb = image.toFitBox(
-        size: NSSize(width: self.cachedArtworkSize, height: self.cachedArtworkSize)
-      )
+    let imageThumb = image.toFitBox(
+      size: NSSize(width: self.cachedArtworkSize, height: self.cachedArtworkSize)
+    )
 
-      return imageThumb
-    } else {
-      return nil
-    }
+    return imageThumb
   }
 }

Persephone/Services/Extensions/AlbumArtService+Remote.swift

@@ -40,8 +40,15 @@ extension AlbumArtService {
         let url = urlComponents!.url
         return URLSession.shared.dataTask(.promise, with: url!).validate()
       }.compactMap {
-        self.cacheArtwork(for: album, data: $0.data)
-        return NSImage(data: $0.data)
+        NSImage(data: $0.data)?.toFitBox(
+          size: NSSize(width: self.cachedArtworkSize, height: self.cachedArtworkSize)
+        )
+      }.compactMap {
+        self.cacheArtwork(
+          for: album,
+          data: $0.jpegData(compressionQuality: self.cachedArtworkQuality)
+        )
+        return $0
       }.done {
         callback($0)
       }.catch {