Trigger an HTMLMetadata download not more than once an hour (per URL).

Modules/FoundationExtras/Sources/FoundationExtras/Date+Extensions.swift

@@ -16,6 +16,10 @@ public extension Date {
 		return addingTimeInterval(0.0 - TimeInterval(days: days))
 	}
 
+	func bySubtracting(hours: Int) -> Date {
+		return addingTimeInterval(0.0 - TimeInterval(hours: hours))
+	}
+
 	func byAdding(days: Int) -> Date {
 		return addingTimeInterval(TimeInterval(days: days))
 	}
@@ -26,4 +30,8 @@ public extension TimeInterval {
 	init(days: Int) {
 		self.init(days * 24 * 60 * 60)
 	}
+
+	init(hours: Int) {
+		self.init(hours * 60 * 60)
+	}
 }

Modules/Images/Sources/Images/Favicons/FaviconURLFinder.swift

@@ -30,7 +30,7 @@ import UniformTypeIdentifiers
 		print("findFaviconURLs \(homePageURL)")
 
 		// If the favicon has an explicit type, check that for an ignored type; otherwise, check the file extension.
-		let htmlMetadata = HTMLMetadataDownloader.cachedMetadata(for: homePageURL)
+		let htmlMetadata = HTMLMetadataDownloader.shared.cachedMetadata(for: homePageURL)
 
 		let faviconURLs = htmlMetadata?.favicons?.compactMap { favicon -> String? in
 			shouldAllowFavicon(favicon) ? favicon.urlString : nil

Modules/Images/Sources/Images/FeedIconDownloader.swift

@@ -156,7 +156,7 @@ private extension FeedIconDownloader {
 			return nil
 		}
 
-		guard let metadata = HTMLMetadataDownloader.cachedMetadata(for: homePageURL) else {
+		guard let metadata = HTMLMetadataDownloader.shared.cachedMetadata(for: homePageURL) else {
 			return nil
 		}
 

Modules/Images/Sources/Images/HTMLMetadataDownloader.swift

@@ -11,74 +11,90 @@ import os
 import Web
 import Parser
 
-public struct HTMLMetadataDownloader {
+public final class HTMLMetadataDownloader: Sendable {
+
+	static let shared = HTMLMetadataDownloader()
 
 	nonisolated(unsafe) private static let logger = Logger(subsystem: Bundle.main.bundleIdentifier!, category: "HTMLMetadataDownloader")
-	private static let debugLoggingEnabled = false
-	private static let cache = HTMLMetadataCache()
+	private let debugLoggingEnabled = false
+	private let cache = HTMLMetadataCache()
+	private let attemptDatesLock = OSAllocatedUnfairLock(initialState: [String: Date]())
 
-	public static func cachedMetadata(for url: String) -> HTMLMetadata? {
+	public func cachedMetadata(for url: String) -> HTMLMetadata? {
 
 		if debugLoggingEnabled {
-			logger.debug("HTMLMetadataDownloader requested cached metadata for \(url)")
+			Self.logger.debug("HTMLMetadataDownloader requested cached metadata for \(url)")
 		}
 
 		guard let htmlMetadata = cache[url] else {
+			downloadMetadataIfNeeded(url)
 			return nil
 		}
 
 		if debugLoggingEnabled {
-			logger.debug("HTMLMetadataDownloader returning cached metadata for \(url)")
+			Self.logger.debug("HTMLMetadataDownloader returning cached metadata for \(url)")
 		}
 		return htmlMetadata
 	}
+}
 
-	public static func downloadMetadata(for url: String) async -> HTMLMetadata? {
+private extension HTMLMetadataDownloader {
 
-		if let htmlMetadata = cachedMetadata(for: url) {
-			return htmlMetadata
+	private func downloadMetadataIfNeeded(_ url: String) {
+
+		// We try a download once an hour at most.
+		let shouldDownload = attemptDatesLock.withLock { attemptDates in
+
+			let currentDate = Date()
+
+			if let attemptDate = attemptDates[url], attemptDate > currentDate.bySubtracting(hours: 1) {
+				if debugLoggingEnabled {
+					Self.logger.debug("HTMLMetadataDownloader skipping download for \(url) because an attempt was made less than an hour ago.")
+				}
+				return false
+			}
+
+			attemptDates[url] = currentDate
+			return true
 		}
 
+		if shouldDownload {
+			downloadMetadata(url)
+		}
+	}
+
+	private func downloadMetadata(_ url: String) {
+
 		guard let actualURL = URL(string: url) else {
-			return nil
+			if debugLoggingEnabled {
+				Self.logger.debug("HTMLMetadataDownloader skipping download for \(url) because it couldn’t construct a URL.")
+			}
+			return
 		}
 		
 		if debugLoggingEnabled {
-			logger.debug("HTMLMetadataDownloader downloading for \(url)")
+			Self.logger.debug("HTMLMetadataDownloader downloading for \(url)")
 		}
 
-		let downloadRecord = try? await DownloadWithCacheManager.shared.download(actualURL)
-		let data = downloadRecord?.data
-		let response = downloadRecord?.response
+		Task {
+			let downloadRecord = try? await DownloadWithCacheManager.shared.download(actualURL)
+			let data = downloadRecord?.data
+			let response = downloadRecord?.response
 
-		if let data, !data.isEmpty, let response, response.statusIsOK {
-			let urlToUse = response.url ?? actualURL
-			let parserData = ParserData(url: urlToUse.absoluteString, data: data)
-
-			if let htmlMetadata = await parseMetadata(with: parserData) {
+			if let data, !data.isEmpty, let response, response.statusIsOK {
+				let urlToUse = response.url ?? actualURL
+				let parserData = ParserData(url: urlToUse.absoluteString, data: data)
+				let htmlMetadata = HTMLMetadataParser.metadata(with: parserData)
 				if debugLoggingEnabled {
-					logger.debug("HTMLMetadataDownloader caching parsed metadata for \(url)")
+					Self.logger.debug("HTMLMetadataDownloader caching parsed metadata for \(url)")
 				}
-			cache[url] = htmlMetadata
-				return htmlMetadata
+				cache[url] = htmlMetadata
+				return
 			}
 
 			if debugLoggingEnabled {
-				logger.debug("HTMLMetadataDownloader parser returned nil for \(url)")
+				Self.logger.debug("HTMLMetadataDownloader failed download for \(url)")
 			}
-
-			return nil
 		}
-
-		if debugLoggingEnabled {
-			logger.debug("HTMLMetadataDownloader failed download for \(url)")
-		}
-
-		return nil
-	}
-
-	private static func parseMetadata(with parserData: ParserData) async -> HTMLMetadata? {
-
-		return HTMLMetadataParser.metadata(with: parserData)
 	}
 }