fleetd/bridged/src/main/java/dev/ltms/bridged/placement/RoundRobinPlacementPolicy.java

package dev.ltms.bridged.placement;

import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * Deterministic round-robin over the profiles that still have capacity and are not known to be
 * unreachable. The index advances only on successful selections so the distribution stays even
 * across spawns.
 */
final class RoundRobinPlacementPolicy implements PlacementPolicy {

    private final AtomicInteger index = new AtomicInteger(0);

    @Override
    public synchronized PlacementCandidate select(PlacementContext ctx) {
        List<PlacementCandidate> available = PlacementPolicyUtil.available(ctx);
        if (available.isEmpty()) {
            throw PlacementPolicyUtil.emptyException(ctx);
        }
        return available.get(index.getAndIncrement() % available.size());
    }
}