Add AppConfig to Core.

Core/Sources/Core/AppConfig.swift

@@ -0,0 +1,67 @@
+//
+//  AppConfig.swift
+//  NetNewsWire
+//
+//  Created by Brent Simmons on 6/26/24.
+//  Copyright © 2024 Ranchero Software. All rights reserved.
+//
+
+import Foundation
+
+public final class AppConfig {
+
+	public static let appName: String = (Bundle.main.infoDictionary!["CFBundleExecutable"]! as! String)
+
+	public static let cacheFolder: URL = {
+
+		let folderURL: URL
+
+		if let userCacheFolder = try? FileManager.default.url(for: .cachesDirectory, in: .userDomainMask, appropriateFor: nil, create: true) {
+			folderURL = userCacheFolder
+		} else {
+			let bundleIdentifier = (Bundle.main.infoDictionary!["CFBundleIdentifier"]! as! String)
+			let tempFolder = (NSTemporaryDirectory() as NSString).appendingPathComponent(bundleIdentifier)
+			folderURL = URL(fileURLWithPath: tempFolder, isDirectory: true)
+			createFolderIfNecessary(folderURL)
+		}
+
+		return folderURL
+	}()
+
+	/// Returns URL to subfolder in cache folder (creating the folder if it doesn’t exist)
+	public static func cacheSubfolder(named name: String) -> URL {
+		ensureSubfolder(named: name, folderURL: cacheFolder)
+	}
+
+	public static let dataFolder: URL = {
+
+#if os(macOS)
+		var dataFolder = try! FileManager.default.url(for: .applicationSupportDirectory, in: .userDomainMask, appropriateFor: nil, create: true)
+		dataFolder = dataFolder.appendingPathComponent(appName)
+#elseif os(iOS)
+		var dataFolder = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
+#endif
+
+		createFolderIfNecessary(dataFolder)
+		return dataFolder
+	}()
+
+	/// Returns URL to subfolder in data folder (creating the folder if it doesn’t exist)
+	public static func dataSubfolder(named name: String) -> URL {
+		ensureSubfolder(named: name, folderURL: dataFolder)
+	}
+
+	public static func ensureSubfolder(named name: String, folderURL: URL) -> URL {
+
+		let folder = folderURL.appendingPathComponent(name, isDirectory: true)
+		createFolderIfNecessary(folder)
+		return folder
+	}
+}
+
+private extension AppConfig {
+
+	static func createFolderIfNecessary(_ folderURL: URL) {
+		try! FileManager.default.createDirectory(at: folderURL, withIntermediateDirectories: true, attributes: nil)
+	}
+}