Update download script.

Author: CalebRas

Scripts/DowloadPortalItemData.swift

@@ -31,7 +31,7 @@ struct SampleDependency: Decodable {
 }
 
 /// A Portal Item and its data URL.
-struct PortalItem {
+struct PortalItem: Hashable {
     static let arcGISOnlinePortalURL = URL(string: "https://www.arcgis.com")!
 
     /// The identifier of the item.
@@ -125,61 +125,50 @@ func uncompressArchive(at sourceURL: URL, to destinationURL: URL) throws {
     process.waitUntilExit()
 }
 
-/// Downloads file from portal and write the file(s) to appropriate path(s).
+/// Downloads a file from a given portal and writes it to a given path.
 /// - Parameters:
 ///   - sourceURL: The portal URL to the resource.
-///   - downloadDirectory: The directory that stores downloaded data.
-///   - completion: A closure to handle the results.
-func downloadFile(at sourceURL: URL, to downloadDirectory: URL, completion: @escaping (Result<URL, Error>) -> Void) {
-    let downloadTaskCompleted = { (temporaryURL: URL?, response: URLResponse?, error: Error?) in
-        if let temporaryURL = temporaryURL,
-           let response = response,
-           let suggestedFilename = response.suggestedFilename {
-            do {
-                let downloadName: String
-                let isArchive = (suggestedFilename as NSString).pathExtension == "zip"
-                // If the downloaded file is an archive and contains
-                //   - 1 file, use the name of that file.
-                //   - multiple files, use the suggested filename (*.zip).
-                // If it is not an archive, use the server suggested filename.
-                if isArchive {
-                    let count = try count(ofFilesInArchiveAt: temporaryURL)
-                    if count == 1 {
-                        downloadName = try name(ofFileInArchiveAt: temporaryURL)
-                    } else {
-                        downloadName = suggestedFilename
-                    }
-                } else {
-                    downloadName = suggestedFilename
-                }
-                
-                let downloadURL = downloadDirectory.appendingPathComponent(downloadName, isDirectory: false)
-                
-                if FileManager.default.fileExists(atPath: downloadURL.path) {
-                    try FileManager.default.removeItem(at: downloadURL)
-                }
-                
-                if isArchive {
-                    let extractURL = downloadURL.pathExtension == "zip"
-                    // Uncompresses to directory named after archive.
-                    ? downloadURL.deletingPathExtension()
-                    // Uncompresses to appropriate subdirectory.
-                    : downloadURL.deletingLastPathComponent()
-                    try uncompressArchive(at: temporaryURL, to: extractURL)
-                } else {
-                    try FileManager.default.moveItem(at: temporaryURL, to: downloadURL)
-                }
-                
-                completion(.success(downloadURL))
-            } catch {
-                completion(.failure(error))
-            }
-        } else if let error = error {
-            completion(.failure(error))
+///   - downloadDirectory: The directory to store the downloaded data in.
+/// - Throws: Exceptions when downloading and moving the file.
+/// - Returns: The name of the downloaded file.
+func downloadFile(from sourceURL: URL, to downloadDirectory: URL) async throws -> String {
+    let portalURLRequest = URLRequest(url: sourceURL)
+    let (temporaryURL, response) = try await URLSession.shared.download(for: portalURLRequest)
+    
+    guard let suggestedFilename = response.suggestedFilename else { return "" }
+    let isArchive = NSString(string: suggestedFilename).pathExtension == "zip"
+    
+    let downloadName: String = try {
+        // If the downloaded file is an archive and contains
+        //   - 1 file, use the name of that file.
+        //   - multiple files, use the suggested filename (*.zip).
+        // If it is not an archive, use the server suggested filename.
+        if isArchive,
+           try count(ofFilesInArchiveAt: temporaryURL) == 1 {
+            return try name(ofFileInArchiveAt: temporaryURL)
+        } else {
+            return suggestedFilename
         }
+    }()
+    let downloadURL = downloadDirectory.appendingPathComponent(downloadName, isDirectory: false)
+    
+    if FileManager.default.fileExists(atPath: downloadURL.path) {
+        try FileManager.default.removeItem(at: downloadURL)
     }
-    let downloadTask = URLSession.shared.downloadTask(with: sourceURL, completionHandler: downloadTaskCompleted)
-    downloadTask.resume()
+    
+    if isArchive {
+        let extractURL = downloadURL.pathExtension == "zip"
+        // Uncompresses to directory named after archive.
+        ? downloadURL.deletingPathExtension()
+        // Uncompresses to appropriate subdirectory.
+        : downloadURL.deletingLastPathComponent()
+        
+        try uncompressArchive(at: temporaryURL, to: extractURL)
+    } else {
+        try FileManager.default.moveItem(at: temporaryURL, to: downloadURL)
+    }
+    
+    return downloadName
 }
 
 // MARK: Script Entry
@@ -207,7 +196,7 @@ if !FileManager.default.fileExists(atPath: downloadDirectoryURL.path) {
 }
 
 /// Portal Items created from iterating through all metadata's "offline\_data".
-let portalItems: [PortalItem] = {
+let portalItems: Set<PortalItem> = {
     do {
         // Finds all subdirectories under the root Samples directory.
         let sampleSubDirectories = try FileManager.default
@@ -218,7 +207,7 @@ let portalItems: [PortalItem] = {
         // Omit the decoding errors from samples that don't have dependencies.
         let sampleDependencies = sampleJSONs
             .compactMap { try? parseJSON(at: $0) }
-        return sampleDependencies.flatMap(\.offlineData)
+        return Set(sampleDependencies.flatMap(\.offlineData))
     } catch {
         print("error: Error decoding Samples dependencies: \(error.localizedDescription)")
         exit(1)
@@ -241,39 +230,56 @@ let previousDownloadedItems: DownloadedItems = {
 }()
 var downloadedItems = previousDownloadedItems
 
-// Asynchronously downloads portal items.
-let dispatchGroup = DispatchGroup()
-
-portalItems.forEach { portalItem in
-    let destinationURL = downloadDirectoryURL.appendingPathComponent(portalItem.identifier, isDirectory: true)
-    // Checks if a directory exists or not, to see if an item is already downloaded.
-    if FileManager.default.fileExists(atPath: destinationURL.path) {
-        print("info: Item \(portalItem.identifier) has already been downloaded.")
-    } else {
+await withTaskGroup(of: Void.self) { group in
+    for portalItem in portalItems {
+        // Checks to see if an item is already downloaded.
+        guard downloadedItems[portalItem.identifier] == nil else {
+            print("note: Item already downloaded: \(portalItem.identifier)")
+            continue
+        }
+        
+        let destinationURL = downloadDirectoryURL.appendingPathComponent(portalItem.identifier, isDirectory: true)
+        
+        // Deletes the directory if it already exists.
+        // This happens when the item is not in the plist and needs to be redownloaded.
+        if FileManager.default.fileExists(atPath: destinationURL.path) {
+            do {
+                print("note: Deleting directory: \(portalItem.identifier)")
+                try FileManager.default.removeItem(at: destinationURL)
+            } catch {
+                print("error: Error deleting downloaded directory: \(error.localizedDescription)")
+                exit(1)
+            }
+        }
+        
         do {
             // Creates an enclosing directory with portal item ID as its name.
             try FileManager.default.createDirectory(at: destinationURL, withIntermediateDirectories: false)
         } catch {
-            print("error: Error creating download directory: \(error.localizedDescription).")
+            print("error: Error creating download directory: \(error.localizedDescription)")
             exit(1)
         }
-        print("info: Downloading item \(portalItem.identifier)")
+        
+        print("note: Downloading item: \(portalItem.identifier)")
         fflush(stdout)
-        dispatchGroup.enter()
-        downloadFile(at: portalItem.dataURL, to: destinationURL) { result in
-            switch result {
-            case .success(let url):
-                downloadedItems[portalItem.identifier] = url.lastPathComponent
-                dispatchGroup.leave()
-            case .failure(let error):
+        
+        group.addTask {
+            do {
+                let downloadName = try await downloadFile(from: portalItem.dataURL, to: destinationURL)
+                print("note: Downloaded item: \(portalItem.identifier)")
+                fflush(stdout)
+                
+                await MainActor.run {
+                    downloadedItems[portalItem.identifier] = downloadName
+                }
+            } catch {
                 print("error: Error downloading item \(portalItem.identifier): \(error.localizedDescription)")
                 URLSession.shared.invalidateAndCancel()
                 exit(1)
             }
         }
     }
 }
-dispatchGroup.wait()
 
 // Updates the downloaded items property list record if needed.
 if downloadedItems != previousDownloadedItems {