Initial commit

hashing.py

@@ -0,0 +1,71 @@
+"""
+Media-hash helpers.
+
+Strategy
+--------
+We never download files just to hash them. Instead we use Telegram's
+file_unique_id as a stable, server-side content identifier – two files
+that are byte-for-byte identical always share the same file_unique_id,
+regardless of who uploaded them or when.
+
+The cache (backup_ids.json) stores:
+{ "<file_unique_id>": "<sha256_hex>" }
+"""
+
+import hashlib
+import logging
+
+from aiogram import Bot
+
+import bot_state as state
+from persistence import save_backup_ids
+
+logger = logging.getLogger(__name__)
+
+
+def _hash(file_unique_id: str) -> str:
+    return hashlib.sha256(file_unique_id.encode()).hexdigest()
+
+
+def register_file(file_unique_id: str) -> bool:
+    """Add a file to the in-memory cache and persist it.
+
+    Returns True if the file was new, False if it was already known.
+    """
+    if file_unique_id in state.backup_hashes:
+        return False
+    state.backup_hashes[file_unique_id] = _hash(file_unique_id)
+    save_backup_ids()
+    return True
+
+
+def is_duplicate(file_unique_id: str) -> bool:
+    return file_unique_id in state.backup_hashes
+
+
+def check_media_list(media: list[dict]) -> tuple[list[dict], list[dict]]:
+    """Split a media list into (unique, duplicates)."""
+    unique, dupes = [], []
+    for item in media:
+        if is_duplicate(item.get("file_unique_id", "")):
+            dupes.append(item)
+        else:
+            unique.append(item)
+    return unique, dupes
+
+
+async def preload_backup_hashes(bot: Bot, chat_id: int) -> None:
+    """
+    Since the standard Bot API does not expose a bulk message history
+    endpoint for groups, we:
+    1. Load whatever is already in backup_ids.json (done by load_backup_ids).
+    2. On each new message in the backup group, register via register_file.
+
+    To do a full historical reindex, admins forward all older media back
+    into the backup group — the bot registers each file automatically.
+    """
+    logger.info(
+        "Backup hash cache loaded from disk: %d known files. "
+        "New files arriving in the backup group will be indexed automatically.",
+        len(state.backup_hashes),
+    )