feat(userbot): after a restart the userbot catches up on what it missed while down, from a saved cursor and within bounds

backend/src/userbot/modules/catchup/repository.py

@@ -0,0 +1,41 @@
+from dataclasses import dataclass
+
+import asyncpg
+
+_LOAD = """
+SELECT catchup_pts, catchup_qts, catchup_date FROM accounts WHERE account_id = $1
+"""
+
+_SAVE = """
+UPDATE accounts SET catchup_pts = $2, catchup_qts = $3, catchup_date = $4
+WHERE account_id = $1
+"""
+
+_CLEAR = """
+UPDATE accounts SET catchup_pts = NULL, catchup_qts = NULL, catchup_date = NULL
+WHERE account_id = $1
+"""
+
+
+@dataclass(frozen=True)
+class UpdateCursor:
+    pts: int
+    qts: int
+    date: int
+
+
+async def load_cursor(pool: asyncpg.Pool, account_id: int) -> UpdateCursor | None:
+    row = await pool.fetchrow(_LOAD, account_id)
+    if row is None or row["catchup_pts"] is None:
+        return None
+    return UpdateCursor(row["catchup_pts"], row["catchup_qts"], row["catchup_date"])
+
+
+async def save_cursor(
+    pool: asyncpg.Pool, account_id: int, cursor: UpdateCursor
+) -> None:
+    await pool.execute(_SAVE, account_id, cursor.pts, cursor.qts, cursor.date)
+
+
+async def clear_cursor(pool: asyncpg.Pool, account_id: int) -> None:
+    await pool.execute(_CLEAR, account_id)