class ClusterState:

    def __init__(self):

        self.nodes = {}

    def register_node(self, node_id, node_state):

        self.nodes[node_id] = node_state

    # -----------------------------
    # GLOBAL AGGREGATION (VERY CHEAP)
    # -----------------------------
    def snapshot(self):

        hot_nodes = 0
        total_temp = 0
        total_cpu = 0
        instability_sum = 0
        n = len(self.nodes)

        if n == 0:
            return {}

        for node in self.nodes.values():

            s = node.snapshot()

            total_temp += s["avg_temp"]
            total_cpu += s["avg_cpu"]
            instability_sum += s["instability"]

            if s["avg_temp"] > 80:
                hot_nodes += 1

        return {
            "avg_cluster_temp": total_temp / n,
            "avg_cluster_cpu": total_cpu / n,
            "instability": instability_sum / n,
            "hot_nodes": hot_nodes
        }