Add a cache to HTMLMetadataDownloader; do all parsing off the main thread, for better UI performance. Also: make FaviconURLFinder use HTMLMetadataDownloader, as it should have in the first place.

Evergreen/Favicons/FaviconURLFinder.swift

@@ -8,64 +8,20 @@
 
 import Foundation
 import RSParser
-import RSWeb
-import RSCore
 
 // The favicon URL may be specified in the head section of the home page.
 
 struct FaviconURLFinder {
 
-	static var metadataCache = [String: RSHTMLMetadata]()
-	static let serialDispatchQueue = DispatchQueue(label: "FaviconURLFinder")
-
 	static func findFaviconURL(_ homePageURL: String, _ callback: @escaping (String?) -> Void) {
 
-		guard let url = URL(string: homePageURL) else {
+		guard let _ = URL(string: homePageURL) else {
 			callback(nil)
 			return
 		}
 
-		downloadUsingCache(url) { (data, response, error) in
+		HTMLMetadataDownloader.downloadMetadata(for: homePageURL) { (htmlMetadata) in
-
+			callback(htmlMetadata?.faviconLink)
-			guard let data = data, let response = response, response.statusIsOK else {
-				callback(nil)
-				return
-			}
-
-			// Use the absoluteString of the response’s URL instead of the homePageURL,
-			// since the homePageURL might actually have been redirected.
-			// Example: Dr. Drang’s feed reports the homePageURL as http://www.leancrew.com/all-this —
-			// but it gets redirected to http://www.leancrew.com/all-this/ — which is correct.
-			// This way any relative link to a favicon in the page’s metadata
-			// will be made absolute correctly.
-
-			let urlToUse = response.url?.absoluteString ?? homePageURL
-			faviconURL(urlToUse, data, callback)
-		}
-	}
-
-	static private func faviconURL(_ url: String, _ webPageData: Data, _ callback: @escaping (String?) -> Void) {
-
-		serialDispatchQueue.async {
-
-			let md5String = (webPageData as NSData).rs_md5HashString()
-			if let md5String = md5String, let cachedMetadata = metadataCache[md5String] {
-				let cachedURL = cachedMetadata.faviconLink
-				DispatchQueue.main.async {
-					callback(cachedURL)
-				}
-				return
-			}
-
-			let parserData = ParserData(url: url, data: webPageData)
-			let htmlMetadata = RSHTMLMetadataParser.htmlMetadata(with: parserData)
-			if let md5String = md5String {
-				metadataCache[md5String] = htmlMetadata
-			}
-			let url = htmlMetadata.faviconLink
-			DispatchQueue.main.async {
-				callback(url)
-			}
 		}
 	}
 }

Evergreen/HTMLMetadata/HTMLMetadataDownloader.swift

@@ -12,6 +12,9 @@ import RSParser
 
 struct HTMLMetadataDownloader {
 
+	static var metadataCache = [String: RSHTMLMetadata]()
+	static let serialDispatchQueue = DispatchQueue(label: "HTMLMetadataDownloader")
+
 	static func downloadMetadata(for url: String, _ callback: @escaping (RSHTMLMetadata?) -> Void) {
 
 		guard let actualURL = URL(string: url) else {
@@ -25,8 +28,7 @@ struct HTMLMetadataDownloader {
 
 				let urlToUse = response.url ?? actualURL
 				let parserData = ParserData(url: urlToUse.absoluteString, data: data)
-				let metadata = RSHTMLMetadataParser.htmlMetadata(with: parserData)
+				parseMetadata(with: parserData, callback)
-				callback(metadata)
 				return
 			}
 
@@ -37,4 +39,27 @@ struct HTMLMetadataDownloader {
 			callback(nil)
 		}
 	}
+
+	private static func parseMetadata(with parserData: ParserData, _ callback: @escaping (RSHTMLMetadata?) -> Void) {
+
+		serialDispatchQueue.async {
+
+			let md5String = (parserData.data as NSData).rs_md5HashString()
+			if let md5String = md5String, let cachedMetadata = metadataCache[md5String] {
+				DispatchQueue.main.async {
+					callback(cachedMetadata)
+				}
+				return
+			}
+
+			let htmlMetadata = RSHTMLMetadataParser.htmlMetadata(with: parserData)
+			if let md5String = md5String {
+				metadataCache[md5String] = htmlMetadata
+			}
+
+			DispatchQueue.main.async {
+				callback(htmlMetadata)
+			}
+		}
+	}
 }