Fetch artwork from MusicBrainz if not on FS

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 {