Add config options for saving artwork to filesystem

Still to be done: if an image does not exist on the filesystem it will
keep fetching it remotely. We probably shouldn't do this.

Persephone.xcodeproj/project.pbxproj

@@ -298,23 +298,23 @@
 		E407861A2110CE6E006887B1 /* Persephone */ = {
 			isa = PBXGroup;
 			children = (
-				E450AD9E2229B9BC0091BED3 /* PersephoneBridgingHeader.h */,
+				E407861B2110CE6E006887B1 /* AppDelegate.swift */,
-				E450AD8922262B420091BED3 /* Operations */,
+				E407861F2110CE70006887B1 /* Assets.xcassets */,
-				E4A83BF2222207BE0098FED6 /* Services */,
+				E4D1B597220BA3A20026F233 /* Controllers */,
-				E4A83BEC2221F5DD0098FED6 /* Preferences */,
+				E4F6B45E221E117600ACF42A /* DataSources */,
+				E408D3B7220DE8CC0006D9BE /* Extensions */,
+				E41B22C721FB966C00D544F6 /* include */,
+				E40786242110CE70006887B1 /* Info.plist */,
 				E47E2FE32220AA0700F747E6 /* Layouts */,
 				E4F6B461221E124700ACF42A /* Models */,
-				E4F6B45E221E117600ACF42A /* DataSources */,
-				E407861F2110CE70006887B1 /* Assets.xcassets */,
-				E408D3B7220DE8CC0006D9BE /* Extensions */,
-				E4D1B598220BA3C90026F233 /* Resources */,
-				E4D1B597220BA3A20026F233 /* Controllers */,
-				E408D3C3220E138B0006D9BE /* Views */,
-				E41B22C721FB966C00D544F6 /* include */,
-				E407861B2110CE6E006887B1 /* AppDelegate.swift */,
-				E40786242110CE70006887B1 /* Info.plist */,
-				E40786252110CE70006887B1 /* Persephone.entitlements */,
 				E4A642DB220912FA00067D21 /* MPDClient */,
+				E450AD8922262B420091BED3 /* Operations */,
+				E40786252110CE70006887B1 /* Persephone.entitlements */,
+				E450AD9E2229B9BC0091BED3 /* PersephoneBridgingHeader.h */,
+				E4A83BEC2221F5DD0098FED6 /* Preferences */,
+				E4D1B598220BA3C90026F233 /* Resources */,
+				E4A83BF2222207BE0098FED6 /* Services */,
+				E408D3C3220E138B0006D9BE /* Views */,
 			);
 			path = Persephone;
 			sourceTree = "<group>";
@@ -342,10 +342,10 @@
 			children = (
 				E4928E0A2218D62A001D4BEA /* CGColor.swift */,
 				E408D3B5220DD8970006D9BE /* Notification.swift */,
-				E408D3B8220DE98F0006D9BE /* NSUserInterfaceItemIdentifier.swift */,
 				E40FE71A221B904300A4223F /* NSEvent.swift */,
 				E435E3E1221CD4E200184CFC /* NSFont.swift */,
 				E435E3E3221CD75D00184CFC /* NSImage.swift */,
+				E408D3B8220DE98F0006D9BE /* NSUserInterfaceItemIdentifier.swift */,
 				E450AD9C2229B9050091BED3 /* String.swift */,
 			);
 			path = Extensions;
@@ -354,15 +354,15 @@
 		E408D3BC220E03D20006D9BE /* Extensions */ = {
 			isa = PBXGroup;
 			children = (
+				E41E530A223C033700173814 /* MPDClient+Album.swift */,
+				E41E5308223C020400173814 /* MPDClient+Command.swift */,
 				E41E52FC223BF87300173814 /* MPDClient+Connection.swift */,
 				E42410B52241B956005ED6DF /* MPDClient+Database.swift */,
-				E41E52FE223BF95E00173814 /* MPDClient+Transport.swift */,
-				E41E5300223BF99300173814 /* MPDClient+Queue.swift */,
-				E41E5302223BF9C300173814 /* MPDClient+Idle.swift */,
 				E41E5304223BFB0700173814 /* MPDClient+Error.swift */,
+				E41E5302223BF9C300173814 /* MPDClient+Idle.swift */,
+				E41E5300223BF99300173814 /* MPDClient+Queue.swift */,
 				E41E5306223C019100173814 /* MPDClient+Status.swift */,
-				E41E5308223C020400173814 /* MPDClient+Command.swift */,
+				E41E52FE223BF95E00173814 /* MPDClient+Transport.swift */,
-				E41E530A223C033700173814 /* MPDClient+Album.swift */,
 				E408D3BD220E03EE0006D9BE /* RawRepresentable.swift */,
 			);
 			path = Extensions;
@@ -450,8 +450,8 @@
 			isa = PBXGroup;
 			children = (
 				E41E530D223EF4CF00173814 /* AlbumArtService+Caching.swift */,
-				E41E530F223EF6CE00173814 /* AlbumArtService+Remote.swift */,
 				E41E5311223EF74A00173814 /* AlbumArtService+Filesystem.swift */,
+				E41E530F223EF6CE00173814 /* AlbumArtService+Remote.swift */,
 			);
 			path = Extensions;
 			sourceTree = "<group>";
@@ -475,10 +475,10 @@
 		E4A642DB220912FA00067D21 /* MPDClient */ = {
 			isa = PBXGroup;
 			children = (
-				E41B22C521FB932700D544F6 /* MPDClient.swift */,
 				E408D3BC220E03D20006D9BE /* Extensions */,
-				E4D1B595220BA27C0026F233 /* Protocols */,
 				E4D1B594220BA2490026F233 /* Models */,
+				E41B22C521FB932700D544F6 /* MPDClient.swift */,
+				E4D1B595220BA27C0026F233 /* Protocols */,
 			);
 			path = MPDClient;
 			sourceTree = "<group>";
@@ -494,8 +494,8 @@
 		E4A83BED2221F5E60098FED6 /* Controllers */ = {
 			isa = PBXGroup;
 			children = (
-				E41EA46B221636AF0068EF46 /* GeneralPrefsViewController.swift */,
 				E4A83BEE2221F8CF0098FED6 /* AlbumArtPrefsController.swift */,
+				E41EA46B221636AF0068EF46 /* GeneralPrefsViewController.swift */,
 				E4A83BF02221FAA00098FED6 /* PreferencesViewController.swift */,
 				E4C8B53B22342005009A20F3 /* PreferencesWindowController.swift */,
 			);
@@ -505,8 +505,8 @@
 		E4A83BF2222207BE0098FED6 /* Services */ = {
 			isa = PBXGroup;
 			children = (
-				E41E530C223EF4BA00173814 /* Extensions */,
 				E4A83BF3222207D50098FED6 /* AlbumArtService.swift */,
+				E41E530C223EF4BA00173814 /* Extensions */,
 			);
 			path = Services;
 			sourceTree = "<group>";
@@ -514,12 +514,12 @@
 		E4D1B594220BA2490026F233 /* Models */ = {
 			isa = PBXGroup;
 			children = (
+				E4EB237A220F7CF1008C70C0 /* MPDAlbum.swift */,
+				E45962C52241A78500FC1A1E /* MPDCommand.swift */,
+				E4C8B53D22349002009A20F3 /* MPDIdle.swift */,
+				E4EB2378220F10B8008C70C0 /* MPDPair.swift */,
 				E4E8CC9922075D370024217A /* MPDSong.swift */,
 				E4A642D922090CBE00067D21 /* MPDStatus.swift */,
-				E4EB2378220F10B8008C70C0 /* MPDPair.swift */,
-				E4EB237A220F7CF1008C70C0 /* MPDAlbum.swift */,
-				E4C8B53D22349002009A20F3 /* MPDIdle.swift */,
-				E45962C52241A78500FC1A1E /* MPDCommand.swift */,
 			);
 			path = Models;
 			sourceTree = "<group>";
@@ -535,12 +535,12 @@
 		E4D1B597220BA3A20026F233 /* Controllers */ = {
 			isa = PBXGroup;
 			children = (
-				E47E2FD4222071FD00F747E6 /* AlbumViewItem.swift */,
 				E408D3C1220E134F0006D9BE /* AlbumViewController.swift */,
+				E47E2FD4222071FD00F747E6 /* AlbumViewItem.swift */,
+				E47E2FD022205C4600F747E6 /* MainSplitViewController.swift */,
 				E4E8CC932206097F0024217A /* NotificationsController.swift */,
 				E4E8CC912204F4B80024217A /* QueueViewController.swift */,
 				E465049921E94DF500A70F4C /* WindowController.swift */,
-				E47E2FD022205C4600F747E6 /* MainSplitViewController.swift */,
 			);
 			path = Controllers;
 			sourceTree = "<group>";
@@ -557,8 +557,8 @@
 		E4F6B45E221E117600ACF42A /* DataSources */ = {
 			isa = PBXGroup;
 			children = (
-				E4F6B45F221E119B00ACF42A /* QueueDataSource.swift */,
 				E4F6B466221E233200ACF42A /* AlbumDataSource.swift */,
+				E4F6B45F221E119B00ACF42A /* QueueDataSource.swift */,
 			);
 			path = DataSources;
 			sourceTree = "<group>";

Persephone/Controllers/QueueViewController.swift

@@ -7,6 +7,7 @@
 //
 
 import Cocoa
+import PromiseKit
 
 class QueueViewController: NSViewController,
                            NSOutlineViewDelegate {
@@ -66,8 +67,18 @@ class QueueViewController: NSViewController,
   }
 
   func updateAlbumArt() {
-    if let playingSong = dataSource.queue.first(where: { $0.isPlaying }) {
+    if let playingQueueItem = dataSource.queue.first(where: { $0.isPlaying }) {
+      let albumArtService = AlbumArtService(song: playingQueueItem.song)
 
+      albumArtService.fetchBigAlbumArt()
+        .done() {
+          guard let image = $0 else { return }
+
+          self.queueAlbumArtImage.image = image.toFitBox(
+            size: NSSize(width: 500, height: 500)
+          )
+        }
+        .cauterize()
     } else {
       queueAlbumArtImage.image = NSImage.defaultCoverArt
     }

Persephone/DataSources/AlbumDataSource.swift

@@ -7,6 +7,7 @@
 //
 
 import Cocoa
+import PromiseKit
 
 class AlbumDataSource: NSObject, NSCollectionViewDataSource {
   var albums: [Album] = []
@@ -26,7 +27,9 @@ class AlbumDataSource: NSObject, NSCollectionViewDataSource {
       AppDelegate.mpdClient.getAlbumFirstSong(for: albums[indexPath.item].mpdAlbum) {
         guard let song = $0 else { return }
         
-        AlbumArtService(song: Song(mpdSong: song)).fetchAlbumArt { image in
+        AlbumArtService(song: Song(mpdSong: song))
+          .fetchAlbumArt()
+          .done { image in
             self.albums[indexPath.item].coverArt = image
 
             DispatchQueue.main.async {

Persephone/Resources/Base.lproj/Main.storyboard

@@ -1,8 +1,8 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<document type="com.apple.InterfaceBuilder3.Cocoa.Storyboard.XIB" version="3.0" toolsVersion="14460.31" targetRuntime="MacOSX.Cocoa" propertyAccessControl="none" useAutolayout="YES" initialViewController="B8D-0N-5wS">
+<document type="com.apple.InterfaceBuilder3.Cocoa.Storyboard.XIB" version="3.0" toolsVersion="14490.70" targetRuntime="MacOSX.Cocoa" propertyAccessControl="none" useAutolayout="YES" initialViewController="B8D-0N-5wS">
     <dependencies>
         <deployment identifier="macosx"/>
-        <plugIn identifier="com.apple.InterfaceBuilder.CocoaPlugin" version="14460.31"/>
+        <plugIn identifier="com.apple.InterfaceBuilder.CocoaPlugin" version="14490.70"/>
         <capability name="System colors introduced in macOS 10.14" minToolsVersion="10.0"/>
         <capability name="documents saved in the Xcode 8 format" minToolsVersion="8.0"/>
     </dependencies>
@@ -315,11 +315,11 @@
             <objects>
                 <viewController title="Album Art" id="3C9-vU-zjZ" customClass="AlbumArtPrefsController" customModule="Persephone" customModuleProvider="target" sceneMemberID="viewController">
                     <view key="view" id="PyK-v2-kus">
-                        <rect key="frame" x="0.0" y="0.0" width="524" height="100"/>
+                        <rect key="frame" x="0.0" y="0.0" width="524" height="168"/>
                         <autoresizingMask key="autoresizingMask"/>
                         <subviews>
                             <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" translatesAutoresizingMaskIntoConstraints="NO" id="zZn-Rm-e1f">
-                                <rect key="frame" x="53" y="62" width="104" height="17"/>
+                                <rect key="frame" x="53" y="130" width="104" height="17"/>
                                 <textFieldCell key="cell" lineBreakMode="clipping" title="Music Directory:" id="sPn-V6-CfK">
                                     <font key="font" usesAppearanceFont="YES"/>
                                     <color key="textColor" name="labelColor" catalog="System" colorSpace="catalog"/>
@@ -327,7 +327,7 @@
                                 </textFieldCell>
                             </textField>
                             <textField verticalHuggingPriority="750" translatesAutoresizingMaskIntoConstraints="NO" id="gDk-ca-eOa">
-                                <rect key="frame" x="162" y="58" width="288" height="22"/>
+                                <rect key="frame" x="162" y="126" width="288" height="22"/>
                                 <textFieldCell key="cell" scrollable="YES" lineBreakMode="clipping" selectable="YES" editable="YES" sendsActionOnEndEditing="YES" borderStyle="bezel" placeholderString="~/Music" drawsBackground="YES" id="7WZ-b7-GUs">
                                     <font key="font" metaFont="system"/>
                                     <color key="textColor" name="controlTextColor" catalog="System" colorSpace="catalog"/>
@@ -338,7 +338,7 @@
                                 </connections>
                             </textField>
                             <button verticalHuggingPriority="750" translatesAutoresizingMaskIntoConstraints="NO" id="pRL-MG-1Be">
-                                <rect key="frame" x="160" y="27" width="265" height="18"/>
+                                <rect key="frame" x="160" y="95" width="264" height="18"/>
                                 <buttonCell key="cell" type="check" title="Fetch missing artwork from MusicBrainz" bezelStyle="regularSquare" imagePosition="left" inset="2" id="LpD-Ew-HMd">
                                     <behavior key="behavior" changeContents="YES" doesNotDimImage="YES" lightByContents="YES"/>
                                     <font key="font" metaFont="system"/>
@@ -347,15 +347,51 @@
                                     <action selector="updateFetchMissingArtworkFromInternet:" target="3C9-vU-zjZ" id="I7x-9V-xJr"/>
                                 </connections>
                             </button>
+                            <button verticalHuggingPriority="750" translatesAutoresizingMaskIntoConstraints="NO" id="z1g-nP-ksw">
+                                <rect key="frame" x="160" y="64" width="264" height="18"/>
+                                <constraints>
+                                    <constraint firstAttribute="width" constant="260" id="gK0-aW-CJy"/>
+                                </constraints>
+                                <buttonCell key="cell" type="check" title="Save fetched artwork to music directory" bezelStyle="regularSquare" imagePosition="left" inset="2" id="ZeZ-O4-vjS">
+                                    <behavior key="behavior" changeContents="YES" doesNotDimImage="YES" lightByContents="YES"/>
+                                    <font key="font" metaFont="system"/>
+                                </buttonCell>
+                            </button>
+                            <textField verticalHuggingPriority="750" translatesAutoresizingMaskIntoConstraints="NO" id="xgS-Kg-8KR">
+                                <rect key="frame" x="162" y="26" width="144" height="22"/>
+                                <constraints>
+                                    <constraint firstAttribute="width" constant="144" id="DSX-th-Wn1"/>
+                                </constraints>
+                                <textFieldCell key="cell" scrollable="YES" lineBreakMode="clipping" selectable="YES" editable="YES" sendsActionOnEndEditing="YES" borderStyle="bezel" placeholderString="folder.jpg" drawsBackground="YES" id="nKF-YI-xBL">
+                                    <font key="font" metaFont="system"/>
+                                    <color key="textColor" name="controlTextColor" catalog="System" colorSpace="catalog"/>
+                                    <color key="backgroundColor" name="textBackgroundColor" catalog="System" colorSpace="catalog"/>
+                                </textFieldCell>
+                            </textField>
+                            <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" translatesAutoresizingMaskIntoConstraints="NO" id="SmH-w6-5QI">
+                                <rect key="frame" x="37" y="30" width="119" height="17"/>
+                                <textFieldCell key="cell" lineBreakMode="clipping" alignment="right" title="Cover art filename:" id="b4u-u7-iWD">
+                                    <font key="font" metaFont="system"/>
+                                    <color key="textColor" name="labelColor" catalog="System" colorSpace="catalog"/>
+                                    <color key="backgroundColor" name="textBackgroundColor" catalog="System" colorSpace="catalog"/>
+                                </textFieldCell>
+                            </textField>
                         </subviews>
                         <constraints>
+                            <constraint firstItem="pRL-MG-1Be" firstAttribute="centerX" secondItem="z1g-nP-ksw" secondAttribute="centerX" id="0Ev-Ia-XBO"/>
                             <constraint firstItem="gDk-ca-eOa" firstAttribute="leading" secondItem="pRL-MG-1Be" secondAttribute="leading" id="1jd-wZ-a4Q"/>
+                            <constraint firstItem="pRL-MG-1Be" firstAttribute="leading" secondItem="z1g-nP-ksw" secondAttribute="leading" id="3tZ-Ub-RaT"/>
                             <constraint firstItem="gDk-ca-eOa" firstAttribute="leading" secondItem="zZn-Rm-e1f" secondAttribute="trailing" constant="7" id="C0m-yx-gXh"/>
-                            <constraint firstItem="gDk-ca-eOa" firstAttribute="top" secondItem="PyK-v2-kus" secondAttribute="top" constant="20" symbolic="YES" id="HZD-uf-Mhl"/>
+                            <constraint firstItem="z1g-nP-ksw" firstAttribute="leading" secondItem="xgS-Kg-8KR" secondAttribute="leading" id="Dkv-ai-X2G"/>
+                            <constraint firstItem="xgS-Kg-8KR" firstAttribute="leading" secondItem="SmH-w6-5QI" secondAttribute="trailing" constant="8" symbolic="YES" id="KQk-nr-H8y"/>
                             <constraint firstItem="zZn-Rm-e1f" firstAttribute="leading" secondItem="PyK-v2-kus" secondAttribute="leading" constant="55" id="OzK-MR-zuB"/>
-                            <constraint firstItem="zZn-Rm-e1f" firstAttribute="top" secondItem="PyK-v2-kus" secondAttribute="top" constant="21" id="RpF-wL-4nE"/>
+                            <constraint firstAttribute="bottom" secondItem="SmH-w6-5QI" secondAttribute="bottom" constant="30" id="aBY-Ny-jPe"/>
                             <constraint firstItem="pRL-MG-1Be" firstAttribute="top" secondItem="gDk-ca-eOa" secondAttribute="bottom" constant="15" id="dKy-uC-r43"/>
+                            <constraint firstItem="xgS-Kg-8KR" firstAttribute="top" secondItem="z1g-nP-ksw" secondAttribute="bottom" constant="18" id="lfR-Im-bd4"/>
                             <constraint firstAttribute="trailing" secondItem="gDk-ca-eOa" secondAttribute="trailing" constant="74" id="n8X-T2-tXA"/>
+                            <constraint firstAttribute="bottom" secondItem="xgS-Kg-8KR" secondAttribute="bottom" constant="26" id="oXZ-qo-HwX"/>
+                            <constraint firstItem="SmH-w6-5QI" firstAttribute="top" secondItem="zZn-Rm-e1f" secondAttribute="bottom" constant="83" id="qhC-mD-Bvw"/>
+                            <constraint firstItem="z1g-nP-ksw" firstAttribute="top" secondItem="pRL-MG-1Be" secondAttribute="bottom" constant="17" id="sTP-hk-zfU"/>
                         </constraints>
                     </view>
                     <connections>
@@ -365,7 +401,7 @@
                 </viewController>
                 <customObject id="KzD-E3-lpA" userLabel="First Responder" customClass="NSResponder" sceneMemberID="firstResponder"/>
             </objects>
-            <point key="canvasLocation" x="1626" y="339"/>
+            <point key="canvasLocation" x="1626" y="373"/>
         </scene>
         <!--General-->
         <scene sceneID="xTC-Y5-Agk">
@@ -427,13 +463,13 @@
                         <constraints>
                             <constraint firstItem="kvB-99-zwY" firstAttribute="centerX" secondItem="AU9-wN-kbU" secondAttribute="centerX" id="6bm-yZ-rJu"/>
                             <constraint firstItem="AU9-wN-kbU" firstAttribute="top" secondItem="kvB-99-zwY" secondAttribute="bottom" constant="15" id="6qh-zn-2xt"/>
-                            <constraint firstItem="kvB-99-zwY" firstAttribute="top" secondItem="Uwt-Lw-ILP" secondAttribute="top" constant="21" id="AyL-F9-VTD"/>
                             <constraint firstAttribute="trailing" secondItem="wPm-sJ-e9E" secondAttribute="trailing" constant="74" id="B0v-nc-2aA"/>
-                            <constraint firstItem="wPm-sJ-e9E" firstAttribute="top" secondItem="Uwt-Lw-ILP" secondAttribute="top" constant="20" symbolic="YES" id="F0N-Yn-jbd"/>
                             <constraint firstItem="kvB-99-zwY" firstAttribute="leading" secondItem="Uwt-Lw-ILP" secondAttribute="leading" constant="78" id="Hvc-Wt-Uha"/>
                             <constraint firstItem="wPm-sJ-e9E" firstAttribute="leading" secondItem="kvB-99-zwY" secondAttribute="trailing" constant="8" symbolic="YES" id="NAc-1j-JEH"/>
-                            <constraint firstItem="IbX-oV-soD" firstAttribute="top" secondItem="wPm-sJ-e9E" secondAttribute="bottom" constant="10" symbolic="YES" id="gT9-JL-dW0"/>
+                            <constraint firstAttribute="bottom" secondItem="IbX-oV-soD" secondAttribute="bottom" constant="26" id="QHJ-ID-D3L"/>
+                            <constraint firstAttribute="bottom" secondItem="AU9-wN-kbU" secondAttribute="bottom" constant="30" id="j5r-By-kiE"/>
                             <constraint firstItem="wPm-sJ-e9E" firstAttribute="leading" secondItem="IbX-oV-soD" secondAttribute="leading" id="lz4-7S-QQb"/>
+                            <constraint firstItem="IbX-oV-soD" firstAttribute="top" secondItem="wPm-sJ-e9E" secondAttribute="bottom" constant="10" id="sZA-01-JAS"/>
                         </constraints>
                     </view>
                     <connections>
@@ -599,7 +635,7 @@
                                 <rect key="frame" x="0.0" y="220" width="328" height="328"/>
                                 <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMaxY="YES"/>
                                 <subviews>
-                                    <imageView horizontalHuggingPriority="251" verticalHuggingPriority="251" translatesAutoresizingMaskIntoConstraints="NO" id="Dw3-M5-tWY">
+                                    <imageView horizontalHuggingPriority="251" verticalHuggingPriority="251" horizontalCompressionResistancePriority="250" verticalCompressionResistancePriority="250" translatesAutoresizingMaskIntoConstraints="NO" id="Dw3-M5-tWY">
                                         <rect key="frame" x="0.0" y="0.0" width="328" height="328"/>
                                         <imageCell key="cell" refusesFirstResponder="YES" alignment="left" imageScaling="proportionallyUpOrDown" image="blankAlbum" id="IoN-3N-TCb"/>
                                     </imageView>

Persephone/Services/AlbumArtService.swift

@@ -17,39 +17,68 @@ class AlbumArtService {
   let cachedArtworkSize = 180
   let cachedArtworkQuality: CGFloat = 0.5
 
+  let bigArtworkSize = 600
+
   var session = URLSession(configuration: .default)
-  let cacheQueue = DispatchQueue(label: "albumArtCacheQueue")
+  let artworkQueue = DispatchQueue(label: "albumArtQueue", qos: .background)
 
   init(song: Song) {
     self.song = song
     self.album = song.album
   }
 
-  func fetchAlbumArt(callback: @escaping (_ image: NSImage?) -> Void) {
+  func fetchBigAlbumArt() -> Promise<NSImage?> {
-    cacheQueue.async {
+    return firstly {
-      firstly {
+      self.getArtworkFromFilesystem()
+    }.then { (image: NSImage?) -> Promise<NSImage?> in
+      image.map(Promise.value) ?? self.getRemoteArtwork()
+    }.compactMap(on :artworkQueue) { image in
+      if self.fileSystemArtworkFilePath() != nil {
+        let sizedImage = image?.toFitBox(
+          size: NSSize(width: self.bigArtworkSize, height: self.bigArtworkSize)
+        )
+        self.saveArtworkToFilesystem(data: sizedImage?.jpegData(compressionQuality: self.cachedArtworkQuality))
+        return sizedImage
+      } else {
+        return image
+      }
+    }
+  }
+
+  func fetchAlbumArt() -> Guarantee<NSImage?> {
+    return firstly {
       self.getCachedArtwork()
-      }.then { artwork -> Promise<NSImage?> in
+    }.then { (artwork: NSImage?) -> Promise<NSImage?> in
-        artwork.map { Promise.value($0 as NSImage?) } ?? self.cacheIfNecessary(self.getArtworkFromFilesystem())
+      artwork.map(Promise.value) ?? self.getArtworkFromFilesystem()
-      }.then { artwork -> Promise<NSImage?> in
+    }.then { (artwork: NSImage?) -> Promise<NSImage?> in
-        artwork.map { Promise.value($0 as NSImage?) } ?? self.cacheIfNecessary(self.getArtworkFromMusicBrainz().map(Optional.some))
+      artwork.map(Promise.value) ?? self.getRemoteArtwork()
-      }.tap { result in
+    }.compactMap(on: artworkQueue) {
-        switch result {
+      return self.sizeAndCacheImage($0).map(Optional.some)
-        case .fulfilled(nil), .rejected(MusicBrainzError.noArtworkAvailable):
+    }.recover { error in
+      switch error {
+      case RemoteArtworkError.noArtworkAvailable:
         self.cacheArtwork(data: Data())
       default:
         break
       }
-      }.recover { error in
+      return .value(nil)
-        .value(nil)
-      }.done(callback)
     }
   }
 
-  func cacheIfNecessary(_ promise: Promise<NSImage?>) -> Promise<NSImage?> {
+  func sizeAndCacheImage(_ image: NSImage?) -> NSImage? {
-    return promise.get { image in
+    switch image {
-      if let data = image?.jpegData(compressionQuality: self.cachedArtworkQuality) {
+    case nil:
-        self.cacheArtwork(data: data)
+      self.cacheArtwork(data: Data())
+      return image
+    case let image:
+      if self.isArtworkCached() {
+        return image
+      } else {
+        let sizedImage = image?.toFitBox(
+          size: NSSize(width: self.cachedArtworkSize, height: self.cachedArtworkSize)
+        )
+        self.cacheArtwork(data: sizedImage?.jpegData(compressionQuality: self.cachedArtworkQuality))
+        return sizedImage
       }
     }
   }

Persephone/Services/Extensions/AlbumArtService+Caching.swift

@@ -14,24 +14,38 @@ extension AlbumArtService {
 
   func getCachedArtwork() -> Promise<NSImage?> {
     return Promise { seal in
-      let cacheFilePath = AlbumArtService.cacheDir.appendingPathComponent(album.hash).path
+      artworkQueue.async {
+        if self.isArtworkCached() {
+          let cacheFilePath = AlbumArtService.cacheDir.appendingPathComponent(self.album.hash).path
           let data = FileManager.default.contents(atPath: cacheFilePath)
-      let image = data.flatMap(NSImage.init(data:))
+          let image = NSImage(data: data ?? Data()) ?? NSImage.defaultCoverArt
 
           seal.fulfill(image)
+        } else {
+          seal.fulfill(nil)
+        }
+      }
     }
   }
 
   func cacheArtwork(data: Data?) {
+    artworkQueue.async {
       guard let bundleIdentifier = Bundle.main.bundleIdentifier,
         let cacheDir = try? FileManager.default.url(for: .cachesDirectory, in: .userDomainMask, appropriateFor: nil, create: true)
           .appendingPathComponent(bundleIdentifier)
         else { return }
 
-    let cacheFilePath = cacheDir.appendingPathComponent(album.hash).path
+      let cacheFilePath = cacheDir.appendingPathComponent(self.album.hash).path
 
-    if !FileManager.default.fileExists(atPath: cacheFilePath) {
+      if !self.isArtworkCached() {
         FileManager.default.createFile(atPath: cacheFilePath, contents: data, attributes: nil)
       }
     }
   }
+
+  func isArtworkCached() -> Bool {
+    let cacheFilePath = AlbumArtService.cacheDir.appendingPathComponent(album.hash).path
+
+    return FileManager.default.fileExists(atPath: cacheFilePath)
+  }
+}

Persephone/Services/Extensions/AlbumArtService+Filesystem.swift

@@ -10,29 +10,57 @@ import Cocoa
 import PromiseKit
 
 extension AlbumArtService {
-  func getArtworkFromFilesystem() -> Promise<NSImage?> {
+  var coverArtFilenames: [String] {
-    let coverArtFilenames = [
+    return [
       "folder.jpg",
       "cover.jpg",
       "\(album.artist) - \(album.title).jpg"
     ]
+  }
 
-    let musicDir = self.preferences.expandedMpdLibraryDir
+  var musicDir: String {
-    let songPath = self.songPath()
+    return self.preferences.expandedMpdLibraryDir
+  }
 
+  func getArtworkFromFilesystem() -> Promise<NSImage?> {
     return Promise { seal in
-      let image = coverArtFilenames
+      artworkQueue.async {
-        .lazy
+        guard let artworkPath = self.fileSystemArtworkFilePath()
-        .map { "\(musicDir)/\(songPath)/\($0)" }
+          else { seal.fulfill(nil); return }
-        .compactMap(self.tryImage)
+
-        .first
+        let image = self.tryImage(artworkPath)
 
         seal.fulfill(image)
       }
     }
+  }
 
-  func songPath() -> String {
+  func saveArtworkToFilesystem(data: Data?) {
-    return song.mpdSong
+    let artworkFileName = coverArtFilenames.first!
+
+    if self.fileSystemArtworkFilePath() == nil {
+      FileManager.default.createFile(
+        atPath: "\(self.musicDir)/\(self.songPath)/\(artworkFileName)",
+        contents: data,
+        attributes: nil
+      )
+    }
+  }
+
+  func fileSystemArtworkFilePath() -> String? {
+    let musicDir = self.preferences.expandedMpdLibraryDir
+
+    return self.coverArtFilenames
+      .lazy
+      .map { "\(musicDir)/\(self.songPath)/\($0)" }
+      .first {
+        FileManager.default.fileExists(atPath: $0)
+      }
+  }
+
+  var songPath: String {
+    return song
+      .mpdSong
       .uriString
       .split(separator: "/")
       .dropLast()

Persephone/Services/Extensions/AlbumArtService+Remote.swift

@@ -12,26 +12,34 @@ import PromiseKit
 import PMKFoundation
 
 extension AlbumArtService {
-  enum MusicBrainzError: Error {
+  enum RemoteArtworkError: Error {
     case noArtworkAvailable
+    case notConfigured
   }
 
-  func getRemoteArtwork() -> Promise<NSImage> {
+  func getRemoteArtwork() -> Promise<NSImage?> {
     return Promise { seal in
+      if preferences.fetchMissingArtworkFromInternet {
+        artworkQueue.async {
           let albumArtWorkItem = DispatchWorkItem {
-        self.getArtworkFromMusicBrainz().pipe(to: seal.resolve)
+            self.getArtworkFromMusicBrainz().map(Optional.some).pipe(to: seal.resolve)
           }
 
           AlbumArtQueue.shared.addToQueue(workItem: albumArtWorkItem)
         }
+      } else {
+        throw RemoteArtworkError.notConfigured
+      }
+    }
   }
 
   func getArtworkFromMusicBrainz() -> Promise<NSImage> {
     var search = URLComponents(string: "https://musicbrainz.org/ws/2/release/")!
     search.query = "query=artist:\(album.artist) AND release:\(album.title) AND country:US&limit=1&fmt=json"
 
-    return URLSession.shared.dataTask(.promise, with: search.url!).validate()
+    return firstly {
-      .compactMap {
+      URLSession.shared.dataTask(.promise, with: search.url!).validate()
+    }.compactMap {
       JSON($0.data)
     }.compactMap {
       $0["releases"][0]["id"].string
@@ -45,7 +53,7 @@ extension AlbumArtService {
       )
     }.recover { error -> Promise<NSImage> in
       if case PMKHTTPError.badStatusCode(404, _, _) = error {
-          throw MusicBrainzError.noArtworkAvailable
+        throw RemoteArtworkError.noArtworkAvailable
       } else {
         throw error
       }