implement a fix for tags being found in code blocks

still needs polish, consider this a rough draft

src/Discord.Net.Rest/Entities/Messages/MessageHelper.cs

@@ -98,14 +98,56 @@ namespace Discord.Rest
         public static ImmutableArray<ITag> ParseTags(string text, IMessageChannel channel, IGuild guild, IReadOnlyCollection<IUser> userMentions)
         {
             var tags = ImmutableArray.CreateBuilder<ITag>();
+
+            // gets the next index of a codeblock stop/start
+            int IndexOfCode(int startIndex)
+            {
+                // code block has precedence over inline code
+                var codeIndex = text.IndexOf("```", startIndex);
+                if (codeIndex != -1)
+                    return codeIndex + 3;
+                codeIndex = text.IndexOf('`', startIndex);
+                if (codeIndex != -1)
+                    return codeIndex + 1;
+                return -1;
+            }
             
             int index = 0;
+            int codeBlockIndex = 0;
             while (true)
             {
                 index = text.IndexOf('<', index);
                 if (index == -1) break;
                 int endIndex = text.IndexOf('>', index + 1);
                 if (endIndex == -1) break;
+
+                int closeIndex = 0;
+                bool CheckCloseIndex()
+                    => closeIndex != -1 && closeIndex < index;
+
+                // check for code blocks before the start index, of either type
+                codeBlockIndex = IndexOfCode(codeBlockIndex);
+                while (codeBlockIndex != -1)
+                {
+                    // code block opens before this tag
+                    closeIndex = IndexOfCode(codeBlockIndex);
+                    // not closed at all
+                    if (closeIndex == -1)
+                        break;
+                    // closed somewhere after the start index
+                    if (closeIndex > index)
+                        break;
+                    // advance codeblock start index
+                    codeBlockIndex = IndexOfCode(closeIndex);
+                }
+                // unclosed code block
+                if (closeIndex == -1)
+                    break;
+                // closed somewhere after the start index
+                if (closeIndex > index)
+                    break;
+
+
                 string content = text.Substring(index, endIndex - index + 1);
 
                 if (MentionUtils.TryParseUser(content, out ulong id))
@@ -148,8 +190,35 @@ namespace Discord.Rest
             }
 
             index = 0;
+            codeBlockIndex = 0;
             while (true)
             {
+                int closeIndex = 0;
+                bool CheckCloseIndex()
+                    => closeIndex != -1 && closeIndex < index;
+
+                // check for code blocks before the start index, of either type
+                codeBlockIndex = IndexOfCode(codeBlockIndex);
+                while (codeBlockIndex != -1)
+                {
+                    // code block opens before this tag
+                    closeIndex = IndexOfCode(codeBlockIndex);
+                    // not closed at all
+                    if (closeIndex == -1)
+                        break;
+                    // closed somewhere after the start index
+                    if (closeIndex > index)
+                        break;
+                    // advance codeblock start index
+                    codeBlockIndex = IndexOfCode(closeIndex);
+                }
+                // unclosed code block
+                if (closeIndex == -1)
+                    break;
+                // closed somewhere after the start index
+                if (closeIndex > index)
+                    break;
+
                 index = text.IndexOf("@everyone", index);
                 if (index == -1) break;
                 var tagIndex = FindIndex(tags, index);

test/Discord.Net.Tests/MessageHelperTests.cs

@@ -0,0 +1,44 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using Xunit;
+
+namespace Discord
+{
+    /// <summary>
+    ///     Tests for <see cref="Discord.Rest.MessageHelper"/> parsing.
+    /// </summary>
+    public class MessageHelperTests
+    {
+        /// <summary>
+        ///     Tests that no tags work while they are in code blocks.
+        /// </summary>
+        [Theory]
+        [InlineData("`@everyone`")]
+        [InlineData("`<@&163184946742034432>`")]
+        [InlineData("```@everyone```")]
+        [InlineData("```cs \n @everyone```")]
+        [InlineData("```cs <@&163184946742034432> ```")]
+        [InlineData("``` test ``` ```cs <@&163184946742034432> ```")]
+        public void NoTagsInCodeBlocks(string testData)
+        {
+            // don't care that I'm passing in null channels/guilds/users
+            // as they shouldn't be required
+            var result = Rest.MessageHelper.ParseTags(testData, null, null, null);
+            Assert.Empty(result);
+        }
+
+        [Theory]
+        [InlineData("`` <@&163184946742034432>")]
+        [InlineData("``` test ``` ``` test ``` <@&163184946742034432>")]
+        public void TagsWork(string testData) // todo better names
+        {
+            // don't care that I'm passing in null channels/guilds/users
+            // as they shouldn't be required
+            var result = Rest.MessageHelper.ParseTags(testData, null, null, null);
+            Assert.NotEmpty(result);
+        }
+
+    }
+}
+