from __future__ import annotations

try:
    from prometheus_client import Counter, Gauge  # type: ignore
except Exception:
    class _Metric:
        def __init__(self, *_, **__):
            self._values = {}
        def labels(self, **kwargs):
            key = tuple(sorted(kwargs.items()))
            class H:
                def __init__(self, parent, k):
                    self._p = parent; self._k = k
                def inc(self, v: float = 1.0):
                    self._p._values[self._k] = self._p._values.get(self._k, 0.0) + v
                def set(self, v: float):
                    self._p._values[self._k] = v
            return H(self, key)
    class Counter(_Metric):
        pass
    class Gauge(_Metric):
        pass


replication_under = Counter("dht_replication_under", "Times replication fell below target", ["content_id"])
replication_over = Counter("dht_replication_over", "Times replication exceeded target", ["content_id"])
leader_changes = Counter("dht_leader_changes_total", "Count of leader changes per content", ["content_id"])
merge_conflicts = Counter("dht_merge_conflicts_total", "Number of DHT merge conflicts", ["key"])
view_count_total = Gauge("dht_view_count_total", "Total content views per window", ["content_id", "window"])
unique_estimate = Gauge("dht_unique_view_estimate", "Estimated unique viewers per window", ["content_id", "window"])
watch_time_seconds = Gauge("dht_watch_time_seconds", "Aggregate watch time per window", ["content_id", "window"])
gossip_success = Counter("dht_gossip_success_total", "Successful gossip posts", ["peer"])
gossip_failure = Counter("dht_gossip_failure_total", "Failed gossip posts", ["peer"])
gossip_skipped = Counter("dht_gossip_skipped_total", "Skipped gossip posts due to backoff", ["peer", "reason"])
gossip_backoff = Gauge("dht_gossip_backoff_seconds", "Gossip backoff seconds remaining", ["peer"])


def record_replication_under(content_id: str, have: int) -> None:
    replication_under.labels(content_id=content_id).inc()


def record_replication_over(content_id: str, have: int) -> None:
    replication_over.labels(content_id=content_id).inc()


def record_leader_change(content_id: str) -> None:
    leader_changes.labels(content_id=content_id).inc()


def record_merge_conflict(key: str) -> None:
    merge_conflicts.labels(key=key).inc()


def update_view_metrics(content_id: str, window_id: str, views: int, unique: float, watch_time: int) -> None:
    view_count_total.labels(content_id=content_id, window=window_id).set(views)
    unique_estimate.labels(content_id=content_id, window=window_id).set(unique)
    watch_time_seconds.labels(content_id=content_id, window=window_id).set(watch_time)


def record_gossip_success(peer: str) -> None:
    gossip_success.labels(peer=peer).inc()
    gossip_backoff.labels(peer=peer).set(0)


def record_gossip_failure(peer: str, backoff_sec: float) -> None:
    gossip_failure.labels(peer=peer).inc()
    gossip_backoff.labels(peer=peer).set(backoff_sec)


def record_gossip_skipped(peer: str, reason: str) -> None:
    gossip_skipped.labels(peer=peer, reason=reason).inc()