From db1db7b701288f4c5ca4545f524370f2c7b47e4e Mon Sep 17 00:00:00 2001
From: Brent Simmons <brent@ranchero.com>
Date: Wed, 13 Dec 2017 19:46:03 -0800
Subject: [PATCH] =?UTF-8?q?Cache=20parsed=20metadata=20when=20finding=20a?=
 =?UTF-8?q?=20home=20page=E2=80=99s=20favicon=20URL.=20Also:=20do=20the=20?=
 =?UTF-8?q?parsing=20in=20the=20background,=20for=20performance=20reasons.?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 Evergreen/Favicons/FaviconURLFinder.swift | 33 ++++++++++++++++++-----
 1 file changed, 27 insertions(+), 6 deletions(-)

diff --git a/Evergreen/Favicons/FaviconURLFinder.swift b/Evergreen/Favicons/FaviconURLFinder.swift
index 07cae4c8a..fe0324e89 100644
--- a/Evergreen/Favicons/FaviconURLFinder.swift
+++ b/Evergreen/Favicons/FaviconURLFinder.swift
@@ -9,11 +9,15 @@
 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 {
@@ -36,16 +40,33 @@ struct FaviconURLFinder {
 			// will be made absolute correctly.
 
 			let urlToUse = response.url?.absoluteString ?? homePageURL
-			let link = faviconURL(urlToUse, data)
-			callback(link)
+			faviconURL(urlToUse, data, callback)
 		}
 	}
 
-	static private func faviconURL(_ url: String, _ webPageData: Data) -> String? {
+	static private func faviconURL(_ url: String, _ webPageData: Data, _ callback: @escaping (String?) -> Void) {
 
-		let parserData = ParserData(url: url, data: webPageData)
-		let htmlMetadata = RSHTMLMetadataParser.htmlMetadata(with: parserData)
-		return htmlMetadata.faviconLink
+		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)
+			}
+		}
 	}
 }