add plugin that edits messages containing markdown tags

stdplugins/markdown.py

@@ -0,0 +1,93 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+import re
+from functools import partial
+
+from telethon import events
+from telethon.tl.functions.messages import EditMessageRequest
+from telethon.extensions.markdown import (
+    DEFAULT_URL_RE, _add_surrogate, _del_surrogate
+)
+from telethon.tl.types import (
+    MessageEntityBold, MessageEntityItalic, MessageEntityCode,
+    MessageEntityPre, MessageEntityTextUrl
+)
+
+
+def parse_url_match(m):
+    entity = MessageEntityTextUrl(
+        offset=m.start(),
+        length=len(m.group(1)),
+        url=_del_surrogate(m.group(2))
+    )
+    return m.group(1), entity
+
+
+def get_tag_parser(tag, entity):
+    # TODO unescape escaped tags?
+    def tag_parser(m):
+        return m.group(1), entity(offset=m.start(), length=len(m.group(1)))
+    tag = re.escape(tag)
+    return re.compile(tag + r'(.+?)' + tag, re.DOTALL), tag_parser
+
+
+MATCHERS = [
+    (DEFAULT_URL_RE, parse_url_match),
+    (get_tag_parser('**', MessageEntityBold)),
+    (get_tag_parser('__', MessageEntityItalic)),
+    (get_tag_parser('```', partial(MessageEntityPre, language=''))),
+    (get_tag_parser('`', MessageEntityCode))
+]
+
+
+def parse(message):
+    entities = []
+
+    i = 0
+    message = _add_surrogate(message)
+    while i < len(message):
+        # find the first pattern that matches
+        for pattern, parser in MATCHERS:
+            match = pattern.match(message, pos=i)
+            if match:
+                break
+
+        if match:
+            text, entity = parser(match)
+            # replace whole match with text from parser
+            message = ''.join((
+                message[:match.start()],
+                text,
+                message[match.end():]
+            ))
+
+            # append entity if we got one
+            if entity:
+                entities.append(entity)
+
+            # skip past the match
+            i += len(text)
+            continue
+
+        i += 1
+
+    return _del_surrogate(message), entities
+
+
+@borg.on(events.MessageEdited(outgoing=True))
+@borg.on(events.NewMessage(outgoing=True))
+async def reparse(event):
+    message, msg_entities = await borg._parse_message_text(event.text, parse)
+
+    if len(event.message.entities or []) == len(msg_entities) and event.raw_text == message:
+        return
+
+    await borg(EditMessageRequest(
+        peer=await event.input_chat,
+        id=event.message.id,
+        message=message,
+        no_webpage=not bool(event.message.media),
+        entities=msg_entities
+    ))
+    raise events.StopPropagation