Make FeedMetadataFile use DataFile.

Account/Sources/Account/FeedMetadataFile.swift

@@ -12,71 +12,69 @@ import Core
 
 @MainActor final class FeedMetadataFile {
 	
-	private let log = OSLog(subsystem: Bundle.main.bundleIdentifier!, category: "feedMetadataFile")
-
 	private let fileURL: URL
 	private let account: Account
-
-	private var isDirty = false {
-		didSet {
-			queueSaveToDiskIfNeeded()
-		}
-	}
-	private let saveQueue = CoalescingQueue(name: "Save Queue", interval: 0.5)
+	private let dataFile: DataFile
+	private let logger = Logger(subsystem: Bundle.main.bundleIdentifier!, category: "FeedMetadataFile")
 
 	init(filename: String, account: Account) {
+
 		self.fileURL = URL(fileURLWithPath: filename)
 		self.account = account
+		self.dataFile = DataFile(fileURL: self.fileURL)
+
+		self.dataFile.delegate = self
 	}
 	
 	func markAsDirty() {
-		isDirty = true
+		
+		dataFile.markAsDirty()
 	}
 	
 	func load() {
+
 		if let fileData = try? Data(contentsOf: fileURL) {
 			let decoder = PropertyListDecoder()
 			account.feedMetadata = (try? decoder.decode(Account.FeedMetadataDictionary.self, from: fileData)) ?? Account.FeedMetadataDictionary()
 		}
 		account.feedMetadata.values.forEach { $0.delegate = account }
 	}
-	
+
+	// Save immediately
 	func save() {
-		guard !account.isDeleted else { return }
 		
+		dataFile.save()
+	}
+}
+
+extension FeedMetadataFile: DataFileDelegate {
+
+	func data(for dataFile: DataFile) -> Data? {
+
+		guard !account.isDeleted else {
+			return nil
+		}
+
 		let feedMetadata = metadataForOnlySubscribedToFeeds()
 
 		let encoder = PropertyListEncoder()
 		encoder.outputFormat = .binary
-
-		do {
-			let data = try encoder.encode(feedMetadata)
-			try data.write(to: fileURL)
-		} catch let error as NSError {
-			os_log(.error, log: log, "Save to disk failed: %@.", error.localizedDescription)
-		}
+		return try? encoder.encode(feedMetadata)
+	}
+
+	func dataFileWriteToDiskDidFail(for dataFile: DataFile, error: Error) {
+
+		logger.error("FeedMetadataFile save to disk failed for \(self.fileURL): \(error.localizedDescription)")
 	}
-		
 }
 
 private extension FeedMetadataFile {
 
-	func queueSaveToDiskIfNeeded() {
-		saveQueue.add(self, #selector(saveToDiskIfNeeded))
-	}
-
-	@objc func saveToDiskIfNeeded() {
-		if isDirty {
-			isDirty = false
-			save()
-		}
-	}
-
 	private func metadataForOnlySubscribedToFeeds() -> Account.FeedMetadataDictionary {
+
 		let feedIDs = account.idToFeedDictionary.keys
 		return account.feedMetadata.filter { (feedID: String, metadata: FeedMetadata) -> Bool in
 			return feedIDs.contains(metadata.feedID)
 		}
 	}
-
 }