package precompute

import (
	"github.com/prysmaticlabs/prysm/beacon-chain/core/helpers"
	pb "github.com/prysmaticlabs/prysm/proto/beacon/p2p/v1"
	"github.com/prysmaticlabs/prysm/shared/mathutil"
	"github.com/prysmaticlabs/prysm/shared/params"
)

// ProcessSlashingsPrecompute processes the slashed validators during epoch processing.
// This is an optimized version by passing in precomputed total epoch balances.
func ProcessSlashingsPrecompute(state *pb.BeaconState, p *Balance) *pb.BeaconState {
	currentEpoch := helpers.CurrentEpoch(state)
	exitLength := params.BeaconConfig().EpochsPerSlashingsVector

	// Compute the sum of state slashings
	totalSlashing := uint64(0)
	for _, slashing := range state.Slashings {
		totalSlashing += slashing
	}

	// Compute slashing for each validator.
	for index, validator := range state.Validators {
		correctEpoch := (currentEpoch + exitLength/2) == validator.WithdrawableEpoch
		if validator.Slashed && correctEpoch {
			minSlashing := mathutil.Min(totalSlashing*3, p.CurrentEpoch)
			increment := params.BeaconConfig().EffectiveBalanceIncrement
			penaltyNumerator := validator.EffectiveBalance / increment * minSlashing
			penalty := penaltyNumerator / p.CurrentEpoch * increment
			state = helpers.DecreaseBalance(state, uint64(index), penalty)
		}
	}
	return state
}