From a254819cc7d3a88bf115c55635e2b4335136d0ff Mon Sep 17 00:00:00 2001
From: Max Radermacher <max@signal.org>
Date: Thu, 23 Mar 2023 16:49:14 -0700
Subject: [PATCH] Improve performance of link fetcher unit tests

---
 SignalServiceKit/src/Util/LinkValidator.swift       |  9 +++++++--
 SignalServiceKit/tests/Util/LinkValidatorTest.swift | 12 +++++++-----
 SignalUI/Utils/LinkPreviewFetcher.swift             |  5 -----
 3 files changed, 14 insertions(+), 12 deletions(-)

diff --git a/SignalServiceKit/src/Util/LinkValidator.swift b/SignalServiceKit/src/Util/LinkValidator.swift
index 6ac3f0afcc..1859c97ec7 100644
--- a/SignalServiceKit/src/Util/LinkValidator.swift
+++ b/SignalServiceKit/src/Util/LinkValidator.swift
@@ -27,8 +27,8 @@ public enum LinkValidator {
     }
 
     public static func firstLinkPreviewURL(in entireMessage: String) -> URL? {
-        guard let detector = try? NSDataDetector(types: NSTextCheckingResult.CheckingType.link.rawValue) else {
-            owsFailDebug("Could not create NSDataDetector")
+        // Don't include link previews for oversize text messages.
+        guard entireMessage.utf8.dropFirst(Int(kOversizeTextMessageSizeThreshold) - 1).isEmpty else {
             return nil
         }
 
@@ -36,6 +36,11 @@ public enum LinkValidator {
             return nil
         }
 
+        guard let detector = try? NSDataDetector(types: NSTextCheckingResult.CheckingType.link.rawValue) else {
+            owsFailDebug("Could not create NSDataDetector")
+            return nil
+        }
+
         var result: URL?
         detector.enumerateMatches(in: entireMessage, range: entireMessage.entireRange) { match, _, stop in
             guard let match = match else { return }
diff --git a/SignalServiceKit/tests/Util/LinkValidatorTest.swift b/SignalServiceKit/tests/Util/LinkValidatorTest.swift
index 86df60f556..df1603c3b6 100644
--- a/SignalServiceKit/tests/Util/LinkValidatorTest.swift
+++ b/SignalServiceKit/tests/Util/LinkValidatorTest.swift
@@ -77,8 +77,11 @@ class LinkValidatorTest: XCTestCase {
 
             ("alice bob https://www.youtube.com/watch?v=tP-Ipsat90c jim", "https://www.youtube.com/watch?v=tP-Ipsat90c"),
 
-            // If there are more than one, take the first.
-            ("alice bob https://signal.org/url_1 jim https://signal.org/url_2 carol", "https://signal.org/url_1")
+            // If there is more than one, take the first.
+            ("alice bob https://signal.org/url_1 jim https://signal.org/url_2 carol", "https://signal.org/url_1"),
+
+            // If there's too much text, we can't parse any URLs.
+            ("https://signal.org " + String(repeating: "A", count: 4096), nil)
         ]
         for (entireMessage, expectedValue) in testCases {
             let actualValue = LinkValidator.firstLinkPreviewURL(in: entireMessage)
@@ -86,12 +89,11 @@ class LinkValidatorTest: XCTestCase {
         }
     }
 
-    func testFindFirstValidUrlPerformance() throws {
+    func testFirstLinkPreviewURLPerformance() throws {
         let entireMessage = String(repeating: "https://example.com ", count: 1_000_000)
-        let expectedValue = try XCTUnwrap(URL(string: "https://example.com"))
         measure {
             let actualValue = LinkValidator.firstLinkPreviewURL(in: entireMessage)
-            XCTAssertEqual(actualValue, expectedValue)
+            XCTAssertNil(actualValue)
         }
     }
 }
diff --git a/SignalUI/Utils/LinkPreviewFetcher.swift b/SignalUI/Utils/LinkPreviewFetcher.swift
index 3074f583ca..33cbf0918f 100644
--- a/SignalUI/Utils/LinkPreviewFetcher.swift
+++ b/SignalUI/Utils/LinkPreviewFetcher.swift
@@ -149,11 +149,6 @@ public class LinkPreviewFetcher {
             self.prependSchemeIfNeeded(to: &filteredText)
         }
 
-        // Don't include link previews for oversize text messages.
-        guard filteredText.lengthOfBytes(using: .utf8) < kOversizeTextMessageSizeThreshold else {
-            return nil
-        }
-
         return LinkValidator.firstLinkPreviewURL(in: filteredText)
     }