Add duplicate checks for the "pull" command

This checks the received JSON against following columns:
* now
* time
* md5
* com
* sub
* board
and will add them to the database if they don't exist.

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

chanbans/pull.py

@@ -1,4 +1,5 @@
 import asyncio
+from collections import defaultdict
 import json
 import logging
 from pathlib import Path
@@ -74,8 +75,7 @@ async def pull():
             for key, value in zip(labels, [c for c in row if c != "\n"])
             if key != "time"
         }
-        post = posts[cols["post"]["data-pid"]]
-        cols["post"] = post
+        post = defaultdict(lambda: None, posts[cols["post"]["data-pid"]])
 
         if "thumb" in post:
             thumb_path = Path(THUMBS_DIR, f"{post['thumb']}s.jpg")
@@ -86,7 +86,32 @@ async def pull():
         # Try to create post in database
         try:
             with db:
-                post = cols["post"]
+
+                # Check the last N bans for the given board. If the following columns are equal:
+                # * now
+                # * time
+                # * md5
+                # * com
+                # * sub
+                # * board
+                # Then we consider it to be a duplicate.
+                result = db.execute(
+                    """
+                    select id, now, time, md5, com, sub, board
+                    from bans
+                    where
+                        now = :now
+                    and time = :time
+                    and md5 = :md5
+                    and com = :com
+                    and sub = :sub
+                    and board = :board
+                    """,
+                    post,
+                )
+                if _row := result.fetchone():
+                    log.debug("duplicate found, skipping - %s", _row["id"])
+                    continue
 
                 post["action"] = cols["action"]
                 # post['board'] = cols['board']
@@ -167,6 +192,6 @@ async def pull():
             msg = str(ex)
             if "UNIQUE" not in msg:
                 log.exception("error inserting data")
-                raise SystemExit()
+                log.info("Continuing")
     # Finish off thumbnail jobs
     await asyncio.gather(*download_jobs)