From cd88559ede26d7f5f1cb1f50dfba551b3463f586 Mon Sep 17 00:00:00 2001
From: Alan Mantoux <alan.mantoux@gmail.com>
Date: Sat, 25 Nov 2023 06:35:50 +0100
Subject: [PATCH] Add strike through to Markdown codec (#177)

Support strike through in markdown codec
---
 .../parchment/lib/src/codecs/markdown.dart    | 15 ++++++++++++
 .../parchment/test/codecs/markdown_test.dart  | 23 ++++++++++++++++---
 2 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/packages/parchment/lib/src/codecs/markdown.dart b/packages/parchment/lib/src/codecs/markdown.dart
index f15e534e..e651295e 100644
--- a/packages/parchment/lib/src/codecs/markdown.dart
+++ b/packages/parchment/lib/src/codecs/markdown.dart
@@ -33,6 +33,8 @@ class _ParchmentMarkdownDecoder extends Converter<String, ParchmentDocument> {
     r'((\*{2}|_{2})([*_])(?<bold_italic_text>.*?[^ \7\6])\7\6)|'
     // italic or bold
     r'(((\*{1,2})|(_{1,2}))(?<bold_or_italic_text>.*?[^ \10])\10)|'
+    // strike through
+    r'(~~(?<strike_through_text>.+?)~~)|'
     // inline code
     r'(`(?<inline_code_text>.+?)`)',
   );
@@ -247,6 +249,9 @@ class _ParchmentMarkdownDecoder extends Converter<String, ParchmentDocument> {
       } else if (match.namedGroup('bold_or_italic_text') != null) {
         text = match.namedGroup('bold_or_italic_text')!;
         styleTag = match.group(10)!;
+      } else if (match.namedGroup('strike_through_text') != null) {
+        text = match.namedGroup('strike_through_text')!;
+        styleTag = '~~';
       } else {
         assert(match.namedGroup('inline_code_text') != null);
         text = match.namedGroup('inline_code_text')!;
@@ -268,6 +273,7 @@ class _ParchmentMarkdownDecoder extends Converter<String, ParchmentDocument> {
   ParchmentStyle _fromStyleTag(String styleTag) {
     assert(
         (styleTag == '`') |
+            (styleTag == '~~') |
             (styleTag == '_') |
             (styleTag == '*') |
             (styleTag == '__') |
@@ -283,6 +289,9 @@ class _ParchmentMarkdownDecoder extends Converter<String, ParchmentDocument> {
     if (styleTag == '`') {
       return ParchmentStyle().put(ParchmentAttribute.inlineCode);
     }
+    if (styleTag == '~~') {
+      return ParchmentStyle().put(ParchmentAttribute.strikethrough);
+    }
     if (styleTag.length == 3) {
       return ParchmentStyle()
           .putAll([ParchmentAttribute.bold, ParchmentAttribute.italic]);
@@ -439,6 +448,8 @@ class _ParchmentMarkdownEncoder extends Converter<ParchmentDocument, String> {
       _writeItalicTag(buffer);
     } else if (attribute == ParchmentAttribute.inlineCode) {
       _writeInlineCodeTag(buffer);
+    } else if (attribute == ParchmentAttribute.strikethrough) {
+      _writeStrikeThoughTag(buffer);
     } else if (attribute?.key == ParchmentAttribute.link.key) {
       _writeLinkTag(buffer, attribute as ParchmentAttribute<String>,
           close: close);
@@ -464,6 +475,10 @@ class _ParchmentMarkdownEncoder extends Converter<ParchmentDocument, String> {
     buffer.write('`');
   }
 
+  void _writeStrikeThoughTag(StringBuffer buffer) {
+    buffer.write('~~');
+  }
+
   void _writeLinkTag(StringBuffer buffer, ParchmentAttribute<String> link,
       {bool close = false}) {
     if (close) {
diff --git a/packages/parchment/test/codecs/markdown_test.dart b/packages/parchment/test/codecs/markdown_test.dart
index fa6015de..60a23555 100644
--- a/packages/parchment/test/codecs/markdown_test.dart
+++ b/packages/parchment/test/codecs/markdown_test.dart
@@ -9,7 +9,7 @@ import 'package:quill_delta/quill_delta.dart';
 import 'package:test/test.dart';
 
 void main() {
-  group('$ParchmentMarkdownCodec.decode', () {
+  group('ParchmentMarkdownCodec.decode', () {
     test('should convert empty markdown to valid empty document', () {
       final markdown = '';
       final newParchment = ParchmentDocument();
@@ -133,6 +133,21 @@ void main() {
           false);
     });
 
+    test('strike through', () {
+      void runFor(String markdown, bool testEncode) {
+        final document = parchmentMarkdown.decode(markdown);
+        final delta = document.toDelta();
+        expect(delta.elementAt(0).data, 'strike through');
+        expect(delta.elementAt(0).attributes?['s'], true);
+        if (testEncode) {
+          final andBack = parchmentMarkdown.encode(document);
+          expect(andBack, markdown);
+        }
+      }
+
+      runFor('~~strike through~~\n\n', true);
+    });
+
     test('intersecting inline styles', () {
       final markdown = 'This **house _is a_ circus**\n\n';
       final document = parchmentMarkdown.decode(markdown);
@@ -390,7 +405,7 @@ void main() {
     });
   });
 
-  group('$ParchmentMarkdownCodec.encode', () {
+  group('ParchmentMarkdownCodec.encode', () {
     test('split adjacent paragraphs', () {
       final delta = Delta()..insert('First line\nSecond line\n');
       final result =
@@ -398,7 +413,7 @@ void main() {
       expect(result, 'First line\n\nSecond line\n\n');
     });
 
-    test('bold italic', () {
+    test('bold italic strike though', () {
       void runFor(ParchmentAttribute<bool> attribute, String expected) {
         final delta = Delta()
           ..insert('This ')
@@ -414,6 +429,8 @@ void main() {
 
       runFor(ParchmentAttribute.bold, 'This **house** is a **circus**\n\n');
       runFor(ParchmentAttribute.italic, 'This _house_ is a _circus_\n\n');
+      runFor(ParchmentAttribute.strikethrough,
+          'This ~~house~~ is a ~~circus~~\n\n');
     });
 
     test('intersecting inline styles', () {