use a single high-quality, well-tested unfurlable url regex for both places Izzy needs this check

Izzy-Moonbot/Helpers/DiscordHelper.cs

@@ -355,4 +355,11 @@ public static string DisplayName(IIzzyUser user, IIzzyGuild? guild)
         var member = guild?.GetUser(user.Id);
         return member != null ? member.DisplayName : user.GlobalName ?? user.Username;
     }
+
+    // In Discord, <> angle brackets around a url prevent it from being automatically unfurled.
+    // Izzy often wants to identify urls in a message that *will* unfurl, so we need a reliable way
+    // to identify urls that aren't enclosed by <>.
+    // This is essentially https://stackoverflow.com/a/3809435 with added lookaround for <>s.
+    public static Regex UnfurlableUrl =
+        new(@"(?<!<)(https?://(www\.)?[-a-zA-Z0-9@:%._+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b([-a-zA-Z0-9()@:%_+.~#?&//=]*))(?!>)");
 }

Izzy-Moonbot/Modules/QuotesModule.cs

@@ -63,7 +63,7 @@ private static string SanitizeQuote(string quote)
     {
         // Find all unfurling urls in the given string and surround them with <>. If any are already non-unfurling then ignore them
         // Regex taken from https://stackoverflow.com/a/3809435
-        return Regex.Replace(quote, @"(?<!<)(https?:\/\/(www\.)?[-a-zA-Z0-9@:%._\+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b([-a-zA-Z0-9()@:%_\+.~#?&//=]*))(?!>)", "<$&>");
+        return DiscordHelper.UnfurlableUrl.Replace(quote, "<$&>");
     }
 
     [Command("quote")]

Izzy-Moonbot/Service/SpamService.cs

@@ -25,8 +25,6 @@ public class SpamService
     private readonly TransientState _state;
 
     private readonly Regex _mention = new("<@&?[0-9]+>");
-    private readonly Regex _url = new("https?://(.+\\.)*(.+)\\.([A-z]+)(/?.+)*", RegexOptions.IgnoreCase);
-    private readonly Regex _noUnfurlUrl = new("<{1}https?://(.+\\.)*(.+)\\.([A-z]+)(/?.+)*>{1}", RegexOptions.IgnoreCase);
     /*
      * The test string is a way to test the spam filter without actually spamming
      * The test string is programmed to immediately set pressure to Config.SpamMaxPressure.
@@ -109,30 +107,9 @@ private void calculateMessagePressureWithoutDecay(RecentMessage message, RecentM
         }
 
         // Check if there's at least one url in the message (and there's no embeds)
-        if (_url.IsMatch(message.Content) && message.EmbedsCount == 0)
+        if (DiscordHelper.UnfurlableUrl.IsMatch(message.Content) && message.EmbedsCount == 0)
         {
-            // Because url pressure can occur multiple times, we store the pressure to add here
-            var totalMatches = 0;
-
-            // Go through each "word" because the URL regex is funky
-            foreach (var content in message.Content.Split(" "))
-            {
-                // Filter out matches 
-                var matches = _url.Matches(content).ToList();
-                foreach (Match match in _noUnfurlUrl.Matches(content))
-                {
-                    // Check if url is in fact set to not unfurl
-                    var matchToRemove = matches.Find(urlMatch => match.Value.Contains(urlMatch.Value));
-                    // If not, just continue
-                    if (matchToRemove == null) continue;
-
-                    // If it is, remove the match.
-                    matches.Remove(matchToRemove);
-                }
-
-                totalMatches += matches.Count;
-            }
-
+            var totalMatches = DiscordHelper.UnfurlableUrl.Count(message.Content);
             var embedPressure = Math.Round(_config.SpamImagePressure * totalMatches, 2);
             if (embedPressure > 0.0)
             {

Izzy-MoonbotTests/Tests/DiscordHelperTests.cs

@@ -220,4 +220,33 @@ public void LevenshteinDistance_Tests()
         Assert.IsTrue(WithinLevenshteinDistanceOf("SpamMaxPressure", "SpamPressureMax", 6));
         Assert.IsTrue(WithinLevenshteinDistanceOf("SpamMaxPressure", "SpamPressureMax", 7));
     }
+
+    [TestMethod()]
+    public void UnfurlableUrlRegex_Tests()
+    {
+        Assert.AreEqual(UnfurlableUrl.Count(""), 0);
+        Assert.AreEqual(UnfurlableUrl.Count("this is normal text"), 0);
+
+        Assert.AreEqual(UnfurlableUrl.Count("http://stackoverflow.com/a/3809435"), 1);
+        Assert.AreEqual(UnfurlableUrl.Count("https://stackoverflow.com/a/3809435"), 1);
+        Assert.AreEqual(UnfurlableUrl.Count("<https://stackoverflow.com/a/3809435>"), 0);
+        Assert.AreEqual(UnfurlableUrl.Count("https://stackoverflow.com/a/3809435 https://stackoverflow.com/a/3809435 https://stackoverflow.com/a/3809435"), 3);
+        Assert.AreEqual(UnfurlableUrl.Count("<https://stackoverflow.com/a/3809435> https://stackoverflow.com/a/3809435 <https://stackoverflow.com/a/3809435>"), 1);
+        Assert.AreEqual(UnfurlableUrl.Count("<https://stackoverflow.com/a/3809435> <https://stackoverflow.com/a/3809435> <https://stackoverflow.com/a/3809435>"), 0);
+
+        Assert.AreEqual(UnfurlableUrl.Count("htt://stackoverflow.com/a/3809435"), 0);
+        Assert.AreEqual(UnfurlableUrl.Count("httpss://stackoverflow.com/a/3809435"), 0);
+        Assert.AreEqual(UnfurlableUrl.Count("https:/stackoverflow.com/a/3809435"), 0);
+        Assert.AreEqual(UnfurlableUrl.Count("http//stackoverflow.com/a/3809435"), 0);
+
+        Assert.AreEqual(UnfurlableUrl.Count("http://www.stackoverflow.com/a/3809435"), 1);
+        Assert.AreEqual(UnfurlableUrl.Count("http://w.stackoverflow.com/a/3809435"), 1);
+        Assert.AreEqual(UnfurlableUrl.Count("http://abc.stackoverflow.com/a/3809435"), 1);
+        Assert.AreEqual(UnfurlableUrl.Count("http://stackoverflow.com/"), 1);
+        Assert.AreEqual(UnfurlableUrl.Count("http://stackoverflow.com"), 1);
+        Assert.AreEqual(UnfurlableUrl.Count("http://stackoverflow.c"), 1);
+
+        Assert.AreEqual(UnfurlableUrl.Count("http://stackoverflow."), 0);
+        Assert.AreEqual(UnfurlableUrl.Count("http://stackoverflow"), 0);
+    }
 }