Fix GH-356

Author: mysticmind

src/ReverseMarkdown.Test/ConverterTests.When_Strikethrough_And_Nested_Strikethrough.verified.md

@@ -0,0 +1 @@
+This is the 1~~st~~ sentence to t~~est the strikethrough tag conversion~~

src/ReverseMarkdown.Test/ConverterTests.cs

@@ -1327,5 +1327,12 @@ public Task When_Anchor_Text_with_Underscore_Do_Not_Escape()
             var html = $"This a sample <strong>paragraph</strong> from <a href=\"https://www.w3schools.com/html/mov_bbb.mp4\">https://www.w3schools.com/html/mov_bbb.mp4</a>";
             return CheckConversion(html);
         }
+
+        [Fact]
+        public Task When_Strikethrough_And_Nested_Strikethrough()
+        {
+            var html = $"This is the 1<s>st</s> sentence to t<del>e<strike>s</strike></strike>t the strikethrough tag conversion";
+            return CheckConversion(html);
+        }
     }
 }

src/ReverseMarkdown.Test/ReverseMarkdown.Test.csproj

@@ -42,5 +42,8 @@
     <None Update="ConverterTests.When_Anchor_Text_with_Underscore_Do_Not_Escape.verified.md">
       <DependentUpon>ConverterTests.WhenThereIsSingleAsteriskInText_ThenConvertToMarkdownEscapedAsterisk.verified.md</DependentUpon>
     </None>
+    <None Update="ConverterTests.When_Strikethrough_And_Nested_Strikethrough.verified.md">
+      <DependentUpon>ConverterTests.WhenThereIsUnorderedListAndBulletIsAsterisk_ThenConvertToMarkdownList.verified.md</DependentUpon>
+    </None>
   </ItemGroup>
 </Project>

src/ReverseMarkdown/Converters/S.cs

@@ -0,0 +1,33 @@
+using System.Linq;
+using HtmlAgilityPack;
+
+namespace ReverseMarkdown.Converters
+{
+    public class S : ConverterBase
+    {
+        public S(Converter converter) : base(converter)
+        {
+            Converter.Register("s", this);
+            Converter.Register("del", this);
+            Converter.Register("strike", this);
+        }
+
+        public override string Convert(HtmlNode node)
+        {
+            var content = TreatChildren(node);
+            if (string.IsNullOrEmpty(content) || AlreadyStrikethrough(node))
+            {
+                return content;
+            }
+            else
+            {
+                return $"~~{content.Trim().Chomp(all:true)}~~";
+            }
+        }
+
+        private static bool AlreadyStrikethrough(HtmlNode node)
+        {
+            return node.Ancestors("s").Any() || node.Ancestors("del").Any() || node.Ancestors("strike").Any();
+        }
+    }
+}