/**
 * Full-mesh topology — every peer connects to every other peer, up
 * to `maxPeers`. When capacity is reached, the lowest-scoring
 * existing peer is evicted to make room for the new arrival.
 */

import type { PeerInfo } from "../../types/peer.types.js";
import {
    type AdmitDecision,
    pickLowestScore,
    type TopologySelectOptions,
    type TopologyStrategy,
} from "./topology-strategy.js";

export class FullMeshStrategy implements TopologyStrategy {
    public readonly name = "full-mesh" as const;

    public selectConnections(
        currentPeers: readonly PeerInfo[],
        newPeer: PeerInfo,
        options: TopologySelectOptions
    ): readonly PeerInfo[] {
        if (newPeer.id === options.selfPeerId) return [];
        if (currentPeers.length >= options.maxPeers) return [];
        return [newPeer];
    }

    public admitOrEvict(
        currentPeers: readonly PeerInfo[],
        newPeer: PeerInfo,
        options: TopologySelectOptions
    ): AdmitDecision {
        if (currentPeers.some((p) => p.id === newPeer.id)) {
            return { admit: false };
        }
        if (currentPeers.length < options.maxPeers) {
            return { admit: true };
        }
        const newScore = options.metricsFor?.(newPeer.id)?.score ?? 1;
        const evictCandidate = pickLowestScore(
            currentPeers,
            options.metricsFor
        );
        if (evictCandidate === undefined) return { admit: false };
        const evictScore =
            options.metricsFor?.(evictCandidate.id)?.score ?? 0.5;
        if (newScore <= evictScore) return { admit: false };
        return { admit: true, evict: evictCandidate };
    }
}