extract dm ack tracker service

app/services/dm_ack_tracker.py

@@ -0,0 +1,43 @@
+"""Shared pending ACK tracking for outgoing direct messages."""
+
+import logging
+import time
+
+logger = logging.getLogger(__name__)
+
+PendingAck = tuple[int, float, int]
+
+_pending_acks: dict[str, PendingAck] = {}
+
+
+def track_pending_ack(expected_ack: str, message_id: int, timeout_ms: int) -> None:
+    """Track an expected ACK code for an outgoing direct message."""
+    _pending_acks[expected_ack] = (message_id, time.time(), timeout_ms)
+    logger.debug(
+        "Tracking pending ACK %s for message %d (timeout %dms)",
+        expected_ack,
+        message_id,
+        timeout_ms,
+    )
+
+
+def cleanup_expired_acks() -> None:
+    """Remove stale pending ACK entries."""
+    now = time.time()
+    expired_codes = [
+        code
+        for code, (_message_id, created_at, timeout_ms) in _pending_acks.items()
+        if now - created_at > (timeout_ms / 1000) * 2
+    ]
+    for code in expired_codes:
+        del _pending_acks[code]
+        logger.debug("Expired pending ACK %s", code)
+
+
+def pop_pending_ack(ack_code: str) -> int | None:
+    """Claim the tracked message ID for an ACK code if present."""
+    pending = _pending_acks.pop(ack_code, None)
+    if pending is None:
+        return None
+    message_id, _, _ = pending
+    return message_id