feat: clock + place games

polylan_submitter/clock/tasks.py

@@ -0,0 +1,79 @@
+"""Self-rescheduling heartbeat, replacing pplace's standalone `watch_timer`
+management command with the project's existing self-rescheduling django-tasks
+pattern (see submissions.tasks.sync_event_game_scopes_task).
+
+Resets any event's timer once it expires - even if nobody presses or
+reconnects to notice - and gives already-connected clients a periodic tick.
+Note this is a safety net, not the only way the timer gets reset: every press
+and every new connection (see consumers.py) also calls reset_if_expired(), so
+the game works correctly even if this chain is never started or dies -
+connected-but-idle clients just won't see the countdown restart until someone
+acts.
+"""
+
+from datetime import timedelta
+
+from asgiref.sync import async_to_sync
+from channels.layers import get_channel_layer
+from django.core.cache import cache
+from django.db import transaction
+from django.tasks import task
+from django.utils import timezone
+
+from games.models import EventGame
+
+from .broadcast import clock_group
+from .models import ClockTimer
+from .wire import to_epoch_ms
+
+HEARTBEAT_INTERVAL_SECONDS = 1
+# One chain ticks every event with the game enabled - this lock keeps a
+# second chain from starting underneath an already-running one (e.g. two
+# EventGame saves close together). Refreshed every tick, wide enough that a
+# single slow tick doesn't let a second chain slip in.
+HEARTBEAT_LOCK_KEY = "clock:heartbeat:lock"
+HEARTBEAT_LOCK_TIMEOUT_SECONDS = HEARTBEAT_INTERVAL_SECONDS * 5
+
+
+@task
+def clock_heartbeat_task():
+    event_games = list(
+        EventGame.objects.filter(game__path="clock", enabled=True).select_related(
+            "event"
+        )
+    )
+
+    if not event_games:
+        # Nothing left to tick - let the chain die. start_clock_heartbeat()
+        # starts a fresh one next time an event enables the game.
+        cache.delete(HEARTBEAT_LOCK_KEY)
+        return
+
+    channel_layer = get_channel_layer()
+    for event_game in event_games:
+        event = event_game.event
+        ClockTimer.current(event)
+        with transaction.atomic():
+            timer = ClockTimer.objects.select_for_update().get(event=event)
+            timer.reset_if_expired()
+
+        async_to_sync(channel_layer.group_send)(
+            clock_group(event.path),
+            {
+                "type": "tick",
+                "end": to_epoch_ms(timer.end_time),
+                "now": to_epoch_ms(timezone.now()),
+                "pressed": False,
+            },
+        )
+
+    cache.set(HEARTBEAT_LOCK_KEY, 1, timeout=HEARTBEAT_LOCK_TIMEOUT_SECONDS)
+    clock_heartbeat_task.using(
+        run_after=timezone.now() + timedelta(seconds=HEARTBEAT_INTERVAL_SECONDS)
+    ).enqueue()
+
+
+def start_clock_heartbeat():
+    """Enqueues the heartbeat chain, unless one is already running."""
+    if cache.add(HEARTBEAT_LOCK_KEY, 1, timeout=HEARTBEAT_LOCK_TIMEOUT_SECONDS):
+        clock_heartbeat_task.enqueue()