Add strikethrough/underline <-> unicode converter to formatter

mautrix_telegram/formatter/util.py

@@ -1,3 +1,4 @@
+from html import escape
 import struct
 import re
 
@@ -31,3 +32,33 @@ HTML_REPLY_FALLBACK_REGEX = re.compile(r"^<blockquote data-mx-reply>[\s\S]+?</bl
 
 def trim_reply_fallback_html(html):
     return HTML_REPLY_FALLBACK_REGEX.sub("", html)
+
+
+def unicode_to_html(text, html, ctrl, tag):
+    if "\u0336" not in text and "\u0332" not in text:
+        return html
+    if not html:
+        html = escape(text)
+    tag_start = f"<{tag}>"
+    tag_end = f"</{tag}>"
+    characters = html.split(ctrl)
+    html = ""
+    in_del = False
+    for char in characters:
+        if not in_del:
+            if len(char) > 1:
+                html += char[0:-1]
+                char = char[-1]
+            html += tag_start
+            in_del = True
+            html += char
+        else:
+            if len(char) > 1:
+                html += tag_end
+                in_del = False
+            html += char
+    return html
+
+
+def html_to_unicode(text, ctrl):
+    return ctrl.join(text) + ctrl