Add basic support for bridging custom emojis from Telegram

mautrix_telegram/formatter/from_telegram.py

@@ -20,7 +20,7 @@ import logging
 import re
 
 from telethon.errors import RPCError
-from telethon.helpers import add_surrogate, del_surrogate, within_surrogate
+from telethon.helpers import add_surrogate, del_surrogate
 from telethon.tl.custom import Message
 from telethon.tl.types import (
     MessageEntityBlockquote,
@@ -52,8 +52,9 @@ from telethon.tl.types import (
 from mautrix.types import Format, MessageType, TextMessageEventContent
 
 from .. import abstract_user as au, portal as po, puppet as pu, user as u
-from ..db import Message as DBMessage
+from ..db import Message as DBMessage, TelegramFile as DBTelegramFile
 from ..types import TelegramID
+from ..util.file_transfer import transfer_custom_emojis_to_matrix
 
 log: logging.Logger = logging.getLogger("mau.fmt.tg")
 
@@ -125,6 +126,27 @@ async def _add_forward_header(
     )
 
 
+class ReuploadedCustomEmoji(MessageEntityCustomEmoji):
+    file: DBTelegramFile
+
+    def __init__(self, parent: MessageEntityCustomEmoji, file: DBTelegramFile) -> None:
+        super().__init__(parent.offset, parent.length, parent.document_id)
+        self.file = file
+
+
+async def _convert_custom_emoji(
+    source: au.AbstractUser, entities: list[TypeMessageEntity]
+) -> None:
+    emoji_ids = [
+        entity.document_id for entity in entities if isinstance(entity, MessageEntityCustomEmoji)
+    ]
+    custom_emojis = await transfer_custom_emojis_to_matrix(source, emoji_ids)
+    if len(custom_emojis) > 0:
+        for i, entity in enumerate(entities):
+            if isinstance(entity, MessageEntityCustomEmoji):
+                entities[i] = ReuploadedCustomEmoji(entity, custom_emojis[entity.document_id])
+
+
 async def telegram_to_matrix(
     evt: Message | SponsoredMessage,
     source: au.AbstractUser,
@@ -138,6 +160,7 @@ async def telegram_to_matrix(
     )
     entities = override_entities or evt.entities
     if entities:
+        await _convert_custom_emoji(source, entities)
         content.format = Format.HTML
         html = await _telegram_entities_to_matrix_catch(add_surrogate(content.body), entities)
         content.formatted_body = del_surrogate(html)
@@ -166,9 +189,20 @@ async def _telegram_entities_to_matrix_catch(text: str, entities: list[TypeMessa
     return "[failed conversion in _telegram_entities_to_matrix]"
 
 
+def within_surrogate(text, index):
+    """
+    `True` if ``index`` is within a surrogate (before and after it, not at!).
+    """
+    return (
+        1 < index < len(text)  # in bounds
+        and "\ud800" <= text[index - 1] <= "\udbff"  # current is low surrogate
+        and "\udc00" <= text[index] <= "\udfff"  # previous is high surrogate
+    )
+
+
 async def _telegram_entities_to_matrix(
     text: str,
-    entities: list[TypeMessageEntity],
+    entities: list[TypeMessageEntity | ReuploadedCustomEmoji],
     offset: int = 0,
     length: int = None,
     in_codeblock: bool = False,
@@ -197,10 +231,9 @@ async def _telegram_entities_to_matrix(
         elif relative_offset < last_offset:
             continue
 
-        # TODO this breaks when there are lots of emojis in a row (e.g. custom emojis)
-        # while within_surrogate(text, relative_offset, length=length):
-        #     relative_offset += 1
-        while within_surrogate(text, relative_offset + entity.length, length=length):
+        while within_surrogate(text, relative_offset):
+            relative_offset += 1
+        while within_surrogate(text, relative_offset + entity.length):
             entity.length += 1
 
         skip_entity = False
@@ -244,8 +277,12 @@ async def _telegram_entities_to_matrix(
                 html, entity_text, entity.url if entity_type == MessageEntityTextUrl else None
             )
         elif entity_type == MessageEntityCustomEmoji:
-            # TODO support properly
             html.append(entity_text)
+        elif entity_type == ReuploadedCustomEmoji:
+            html.append(
+                f'<img data-mx-emoticon src="{escape(entity.file.mxc)}" height="32" '
+                f'alt="{entity_text}" title="{entity_text}"/>'
+            )
         elif entity_type in (
             MessageEntityBotCommand,
             MessageEntityHashtag,