package randao

import (
	"fmt"

	"github.com/gogo/protobuf/proto"
	v "github.com/prysmaticlabs/prysm/beacon-chain/core/validators"
	pb "github.com/prysmaticlabs/prysm/proto/beacon/p2p/v1"
)

// UpdateRandaoLayers increments the randao layer of the block proposer at the given slot.
func UpdateRandaoLayers(state *pb.BeaconState, slot uint64) (*pb.BeaconState, error) {
	newState := proto.Clone(state).(*pb.BeaconState)
	vreg := newState.GetValidatorRegistry()

	proposerIndex, err := v.BeaconProposerIndex(newState, slot)
	if err != nil {
		return nil, fmt.Errorf("unable to retrieve proposer index %v", err)
	}
	vreg[proposerIndex].RandaoLayers++
	state.ValidatorRegistry = vreg
	return newState, nil
}