perf: load comics async

ImageViewer/ViewController.swift

@@ -249,27 +249,27 @@ final class ViewController: UIViewController, UIGestureRecognizerDelegate {
             preferredStyle: .alert
         )
         alert.addAction(UIAlertAction(title: "OK", style: .default, handler: nil))
-        do {
-            var directories: [URL] = []
+        var directories: [URL] = []
 
-            guard let contents = try? fileManager.contentsOfDirectory(
-                at: documentsURL,
-                includingPropertiesForKeys: [.isDirectoryKey],
-                options: [.skipsHiddenFiles]
-            )
-            else {
-                alert.message = String(format: "Failed to read contents of directory: \(documentsURL)")
-                pendingAlert = alert
-                return
-            }
+        guard let contents = try? fileManager.contentsOfDirectory(
+            at: documentsURL,
+            includingPropertiesForKeys: [.isDirectoryKey],
+            options: [.skipsHiddenFiles]
+        )
+        else {
+            alert.message = String(format: "Failed to read contents of directory: \(documentsURL)")
+            pendingAlert = alert
+            return
+        }
 
-            directories = contents.filter { url in
-                var isDirectory: ObjCBool = false
-                return fileManager.fileExists(atPath: url.path, isDirectory: &isDirectory)
-                    && isDirectory.boolValue
-            }.sorted { $0.path < $1.path }
+        directories = contents.filter { url in
+            var isDirectory: ObjCBool = false
+            return fileManager.fileExists(atPath: url.path, isDirectory: &isDirectory)
+                && isDirectory.boolValue
+        }.sorted { $0.path < $1.path }
 
-            for dir in directories {
+        for dir in directories {
+            queue.async { [self] in
                 if !fileManager.fileExists(atPath: dir.appendingPathComponent(metadataFilename).path) {
                     getMetadataFromFilename(path: dir)
                     if pendingAlert != nil {
@@ -298,7 +298,15 @@ final class ViewController: UIViewController, UIGestureRecognizerDelegate {
                 loadLocalState()
                 let volCovP = ProgressIndices(v: state[currentPath.lastPathComponent]!.progress.v, c: 0, i: 0)
                 let archivePath = getArchiveURL(volCovP.v)
-                let archive = try Archive(url: archivePath, accessMode: .read)
+                let archive: Archive!
+                do {
+                    let a = try Archive(url: archivePath, accessMode: .read)
+                    archive = a
+                } catch {
+                    alert.message = String(format: "Could not open Archive: \(archivePath)")
+                    pendingAlert = alert
+                    return
+                }
                 let filename = metadata.volumes[volCovP.v].chapters[volCovP.c].images[volCovP.i].filename!
                 guard let targetEntry = archive[filename] else {
                     alert.message = String(format: "Archive entry does not exist: \(filename)")
@@ -327,11 +335,10 @@ final class ViewController: UIViewController, UIGestureRecognizerDelegate {
                         path: dir
                     )
                 )
+                DispatchQueue.main.async {
+                    self.comicCollectionView.reloadData()
+                }
             }
-        } catch {
-            pendingAlert = alert
-            alert.message = String(format: "Generic failure.")
-            print("Failed to read directories")
         }
     }