from backend.events.bus import EventBus
from backend.metrics.node_state import NodeStateRegistry


class ObservabilityHub:
    """
    Single fusion layer for:
    - events (what happened)
    - metrics (what is happening)
    - state (what is true now)
    """

    def __init__(self, registry: NodeStateRegistry, bus: EventBus):
        self.registry = registry
        self.bus = bus
        self.subscribers = []

    # -----------------------------
    # STREAM OUT TO UI / PROMETHEUS / GRAFANA
    # -----------------------------
    def subscribe(self, fn):
        self.subscribers.append(fn)

    def emit(self, event: dict):

        # enrich event with live state snapshot
        if event.get("node"):
            node = self.registry.get(event["node"])
            if node:
                event["node_state"] = {
                    "cpu": node.cpu_load,
                    "temp": node.temp,
                    "instability": node.instability,
                    "active_jobs": node.active_jobs,
                }

        for sub in self.subscribers:
            sub(event)

    # -----------------------------
    # CONNECT EVENT BUS
    # -----------------------------
    def attach_bus(self):

        def forward(event):
            self.emit(event)

        self.bus.subscribe(forward)