Add helper function for extracting attachment text.

Implements a somewhat arbitrary limit on how much text content is passed along for filtering, to avoid wasting compute time on large attachments that aren't intended to be read (such as CSVs)

1 files changed, 8 insertions, 1 deletions

diff --git a/bot/exts/filtering/filtering.py b/bot/exts/filtering/filtering.py
index a281aff79..f902ee9ec 100644
--- a/bot/exts/filtering/filtering.py
+++ b/bot/exts/filtering/filtering.py
@@ -67,6 +67,13 @@ OFFENSIVE_MSG_DELETE_TIME = datetime.timedelta(days=7)
 WEEKLY_REPORT_ISO_DAY = 3  # 1=Monday, 7=Sunday
 
 
+async def _extract_text_file_content(att: discord.Attachment) -> str:
+    """Extract up to the first 30 lines and first 2000 characters (whichever is shorter) of an attachment."""
+    file_lines: list[str] = (await att.read()).decode().splitlines()
+    first_n_lines = "\n".join(file_lines[:30])[:2_000]
+    return f"{att.filename}: {first_n_lines}"
+
+
 class Filtering(Cog):
     """Filtering and alerting for content posted on the server."""
 
@@ -226,7 +233,7 @@ class Filtering(Cog):
         ctx = FilterContext.from_message(Event.MESSAGE, msg, None, self.message_cache)
 
         text_contents = [
-            f"{a.filename}: " + (await a.read()).decode()
+            await _extract_text_file_content(a)
             for a in msg.attachments if a.content_type.startswith("text")
         ]
         if text_contents: