lotus/chain/actors/actor_miner.go

package actors

import (
	"context"
	"encoding/binary"
	"fmt"

	"github.com/filecoin-project/lotus/build"
	"github.com/filecoin-project/lotus/chain/actors/aerrors"
	"github.com/filecoin-project/lotus/chain/address"
	"github.com/filecoin-project/lotus/chain/types"
	"github.com/filecoin-project/lotus/lib/sectorbuilder"

	"github.com/filecoin-project/go-amt-ipld"
	"github.com/ipfs/go-cid"
	cbor "github.com/ipfs/go-ipld-cbor"
	"github.com/libp2p/go-libp2p-core/peer"
	cbg "github.com/whyrusleeping/cbor-gen"
	"go.opencensus.io/trace"
	"golang.org/x/xerrors"
)

type StorageMinerActor struct{}

type StorageMinerActorState struct {
	// PreCommittedSectors is the set of sectors that have been committed to but not
	// yet had their proofs submitted
	PreCommittedSectors map[string]*PreCommittedSector

	// All sectors this miner has committed.
	Sectors cid.Cid

	// TODO: Spec says 'StagedCommittedSectors', which one is it?

	// Sectors this miner is currently mining. It is only updated
	// when a PoSt is submitted (not as each new sector commitment is added).
	ProvingSet cid.Cid

	// TODO: these:
	//    SectorTable
	//    SectorExpirationQueue
	//    ChallengeStatus

	// Contains mostly static info about this miner
	Info cid.Cid

	// Faulty sectors reported since last SubmitPost,
	// up to the current proving period's challenge time.
	CurrentFaultSet types.BitField

	// Faults submitted after the current proving period's challenge time,
	// but before the PoSt for that period is submitted.
	// These become the currentFaultSet when a PoSt is submitted.
	NextFaultSet types.BitField

	// Sectors reported during the last PoSt submission as being 'done'.
	// The collateral for them is still being held until
	// the next PoSt submission in case early sector
	// removal penalization is needed.
	NextDoneSet types.BitField

	// Amount of power this miner has.
	Power types.BigInt

	// The height at which this miner was slashed at.
	SlashedAt uint64

	ProvingPeriodEnd uint64
}

type MinerInfo struct {
	// Account that owns this miner.
	// - Income and returned collateral are paid to this address.
	// - This address is also allowed to change the worker address for the miner.
	Owner address.Address

	// Worker account for this miner.
	// This will be the key that is used to sign blocks created by this miner, and
	// sign messages sent on behalf of this miner to commit sectors, submit PoSts, and
	// other day to day miner activities.
	Worker address.Address

	// Libp2p identity that should be used when connecting to this miner.
	PeerID peer.ID

	// Amount of space in each sector committed to the network by this miner.
	SectorSize uint64

	// SubsectorCount
}

type PreCommittedSector struct {
	Info          SectorPreCommitInfo
	ReceivedEpoch uint64
}

type StorageMinerConstructorParams struct {
	Owner      address.Address
	Worker     address.Address
	SectorSize uint64
	PeerID     peer.ID
}

type SectorPreCommitInfo struct {
	SectorNumber uint64

	CommR     []byte // TODO: Spec says CID
	SealEpoch uint64
	DealIDs   []uint64
}

type maMethods struct {
	Constructor          uint64
	PreCommitSector      uint64
	ProveCommitSector    uint64
	SubmitPoSt           uint64
	SlashStorageFault    uint64
	GetCurrentProvingSet uint64
	ArbitrateDeal        uint64
	DePledge             uint64
	GetOwner             uint64
	GetWorkerAddr        uint64
	GetPower             uint64
	GetPeerID            uint64
	GetSectorSize        uint64
	UpdatePeerID         uint64
	ChangeWorker         uint64
	IsLate uint64
	CheckMiner               uint64
	DeclareFaults        uint64
	SlashConsensusFault  uint64
}

var MAMethods = maMethods{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19}

func (sma StorageMinerActor) Exports() []interface{} {
	return []interface{}{
		1: sma.StorageMinerConstructor,
		2: sma.PreCommitSector,
		3: sma.ProveCommitSector,
		4: sma.SubmitPoSt,
		//5: sma.SlashStorageFault,
		//6: sma.GetCurrentProvingSet,
		//7:  sma.ArbitrateDeal,
		//8:  sma.DePledge,
		9:  sma.GetOwner,
		10: sma.GetWorkerAddr,
		11: sma.GetPower, // TODO: Remove
		12: sma.GetPeerID,
		13: sma.GetSectorSize,
		14: sma.UpdatePeerID,
		//15: sma.ChangeWorker,
		16: sma.IsLate,
		17: sma.CheckMiner,
		18: sma.DeclareFaults,
		19: sma.SlashConsensusFault,
	}
}

func loadState(vmctx types.VMContext) (cid.Cid, *StorageMinerActorState, ActorError) {
	var self StorageMinerActorState
	oldstate := vmctx.Storage().GetHead()
	if err := vmctx.Storage().Get(oldstate, &self); err != nil {
		return cid.Undef, nil, err
	}

	return oldstate, &self, nil
}

func loadMinerInfo(vmctx types.VMContext, m *StorageMinerActorState) (*MinerInfo, ActorError) {
	var mi MinerInfo
	if err := vmctx.Storage().Get(m.Info, &mi); err != nil {
		return nil, err
	}

	return &mi, nil
}

func (sma StorageMinerActor) StorageMinerConstructor(act *types.Actor, vmctx types.VMContext, params *StorageMinerConstructorParams) ([]byte, ActorError) {
	minerInfo := &MinerInfo{
		Owner:      params.Owner,
		Worker:     params.Worker,
		PeerID:     params.PeerID,
		SectorSize: params.SectorSize,
	}

	minfocid, err := vmctx.Storage().Put(minerInfo)
	if err != nil {
		return nil, err
	}

	var self StorageMinerActorState
	sectors := amt.NewAMT(types.WrapStorage(vmctx.Storage()))
	scid, serr := sectors.Flush()
	if serr != nil {
		return nil, aerrors.HandleExternalError(serr, "initializing AMT")
	}

	self.Sectors = scid
	self.ProvingSet = scid
	self.Info = minfocid

	storage := vmctx.Storage()
	c, err := storage.Put(&self)
	if err != nil {
		return nil, err
	}

	if err := storage.Commit(EmptyCBOR, c); err != nil {
		return nil, err
	}

	return nil, nil
}

func (sma StorageMinerActor) PreCommitSector(act *types.Actor, vmctx types.VMContext, params *SectorPreCommitInfo) ([]byte, ActorError) {
	ctx := vmctx.Context()
	oldstate, self, err := loadState(vmctx)
	if err != nil {
		return nil, err
	}

	if params.SealEpoch >= vmctx.BlockHeight()+build.SealRandomnessLookback {
		return nil, aerrors.Newf(1, "sector commitment must be based off past randomness (%d >= %d)", params.SealEpoch, vmctx.BlockHeight()+build.SealRandomnessLookback)
	}

	if vmctx.BlockHeight()-params.SealEpoch+build.SealRandomnessLookback > build.SealRandomnessLookbackLimit {
		return nil, aerrors.Newf(2, "sector commitment must be recent enough (was %d)", vmctx.BlockHeight()-params.SealEpoch+build.SealRandomnessLookback)
	}

	mi, err := loadMinerInfo(vmctx, self)
	if err != nil {
		return nil, err
	}

	if vmctx.Message().From != mi.Worker {
		return nil, aerrors.New(1, "not authorized to commit sector for miner")
	}

	// make sure the miner isnt trying to submit a pre-existing sector
	unique, err := SectorIsUnique(ctx, vmctx.Storage(), self.Sectors, params.SectorNumber)
	if err != nil {
		return nil, err
	}
	if !unique {
		return nil, aerrors.New(3, "sector already committed!")
	}

	// Power of the miner after adding this sector
	futurePower := types.BigAdd(self.Power, types.NewInt(mi.SectorSize))
	collateralRequired := CollateralForPower(futurePower)

	// TODO: grab from market?
	if act.Balance.LessThan(collateralRequired) {
		return nil, aerrors.New(4, "not enough collateral")
	}

	self.PreCommittedSectors[uintToStringKey(params.SectorNumber)] = &PreCommittedSector{
		Info:          *params,
		ReceivedEpoch: vmctx.BlockHeight(),
	}

	nstate, err := vmctx.Storage().Put(self)
	if err != nil {
		return nil, err
	}
	if err := vmctx.Storage().Commit(oldstate, nstate); err != nil {
		return nil, err
	}

	return nil, nil
}

func uintToStringKey(i uint64) string {
	buf := make([]byte, 10)
	n := binary.PutUvarint(buf, i)
	return string(buf[:n])
}

type SectorProveCommitInfo struct {
	Proof    []byte
	SectorID uint64
	DealIDs  []uint64
}

func (sma StorageMinerActor) ProveCommitSector(act *types.Actor, vmctx types.VMContext, params *SectorProveCommitInfo) ([]byte, ActorError) {
	ctx := vmctx.Context()
	oldstate, self, err := loadState(vmctx)
	if err != nil {
		return nil, err
	}

	mi, err := loadMinerInfo(vmctx, self)
	if err != nil {
		return nil, err
	}

	us, ok := self.PreCommittedSectors[uintToStringKey(params.SectorID)]
	if !ok {
		return nil, aerrors.New(1, "no pre-commitment found for sector")
	}

	if us.ReceivedEpoch+build.InteractivePoRepDelay >= vmctx.BlockHeight() {
		return nil, aerrors.New(2, "too early for proof submission")
	}

	delete(self.PreCommittedSectors, uintToStringKey(params.SectorID))

	// TODO: ensure normalization to ID address
	maddr := vmctx.Message().To

	ticket, err := vmctx.GetRandomness(us.Info.SealEpoch - build.SealRandomnessLookback)
	if err != nil {
		return nil, aerrors.Wrap(err, "failed to get ticket randomness")
	}

	seed, err := vmctx.GetRandomness(us.ReceivedEpoch + build.InteractivePoRepDelay)
	if err != nil {
		return nil, aerrors.Wrap(err, "failed to get randomness for prove sector commitment")
	}

	enc, err := SerializeParams(&ComputeDataCommitmentParams{
		DealIDs:    params.DealIDs,
		SectorSize: mi.SectorSize,
	})
	if err != nil {
		return nil, aerrors.Wrap(err, "failed to serialize ComputeDataCommitmentParams")
	}

	commD, err := vmctx.Send(StorageMarketAddress, SMAMethods.ComputeDataCommitment, types.NewInt(0), enc)
	if err != nil {
		return nil, aerrors.Wrap(err, "failed to compute data commitment")
	}

	if ok, err := ValidatePoRep(ctx, maddr, mi.SectorSize, commD, us.Info.CommR, ticket, params.Proof, seed, params.SectorID); err != nil {
		return nil, err
	} else if !ok {
		return nil, aerrors.Newf(2, "porep proof was invalid (t:%x; s:%x(%d); p:%x)", ticket, seed, us.ReceivedEpoch+build.InteractivePoRepDelay, params.Proof)
	}

	// Note: There must exist a unique index in the miner's sector set for each
	// sector ID. The `faults`, `recovered`, and `done` parameters of the
	// SubmitPoSt method express indices into this sector set.
	nssroot, err := AddToSectorSet(ctx, vmctx.Storage(), self.Sectors, params.SectorID, us.Info.CommR, commD)
	if err != nil {
		return nil, err
	}
	self.Sectors = nssroot

	// if miner is not mining, start their proving period now
	// Note: As written here, every miners first PoSt will only be over one sector.
	// We could set up a 'grace period' for starting mining that would allow miners
	// to submit several sectors for their first proving period. Alternatively, we
	// could simply make the 'PreCommitSector' call take multiple sectors at a time.
	//
	// Note: Proving period is a function of sector size; small sectors take less
	// time to prove than large sectors do. Sector size is selected when pledging.
	pss, lerr := amt.LoadAMT(types.WrapStorage(vmctx.Storage()), self.ProvingSet)
	if lerr != nil {
		return nil, aerrors.HandleExternalError(lerr, "could not load proving set node")
	}

	if pss.Count == 0 {
		self.ProvingSet = self.Sectors
		self.ProvingPeriodEnd = vmctx.BlockHeight() + build.ProvingPeriodDuration
	}

	nstate, err := vmctx.Storage().Put(self)
	if err != nil {
		return nil, err
	}
	if err := vmctx.Storage().Commit(oldstate, nstate); err != nil {
		return nil, err
	}

	activateParams, err := SerializeParams(&ActivateStorageDealsParams{
		Deals: params.DealIDs,
	})
	if err != nil {
		return nil, err
	}

	_, err = vmctx.Send(StorageMarketAddress, SMAMethods.ActivateStorageDeals, types.NewInt(0), activateParams)
	return nil, err
}

type SubmitPoStParams struct {
	Proof   []byte
	DoneSet types.BitField
	// TODO: once the spec changes finish, we have more work to do here...
}

func ProvingPeriodEnd(setPeriodEnd, height uint64) (uint64, uint64) {
	offset := setPeriodEnd % build.ProvingPeriodDuration
	period := ((height - offset - 1) / build.ProvingPeriodDuration) + 1
	end := (period * build.ProvingPeriodDuration) + offset

	return end, period
}

// TODO: this is a dummy method that allows us to plumb in other parts of the
// system for now.
func (sma StorageMinerActor) SubmitPoSt(act *types.Actor, vmctx types.VMContext, params *SubmitPoStParams) ([]byte, ActorError) {
	oldstate, self, err := loadState(vmctx)
	if err != nil {
		return nil, err
	}

	mi, err := loadMinerInfo(vmctx, self)
	if err != nil {
		return nil, err
	}

	if vmctx.Message().From != mi.Worker {
		return nil, aerrors.New(1, "not authorized to submit post for miner")
	}

	currentProvingPeriodEnd, _ := ProvingPeriodEnd(self.ProvingPeriodEnd, vmctx.BlockHeight())

	feesRequired := types.NewInt(0)

	if currentProvingPeriodEnd > self.ProvingPeriodEnd {
		//TODO late fee calc
		feesRequired = types.BigAdd(feesRequired, types.NewInt(1000))
	}

	//TODO temporary sector failure fees

	msgVal := vmctx.Message().Value
	if msgVal.LessThan(feesRequired) {
		return nil, aerrors.New(2, "not enough funds to pay post submission fees")
	}

	if msgVal.GreaterThan(feesRequired) {
		_, err := vmctx.Send(vmctx.Message().From, 0,
			types.BigSub(msgVal, feesRequired), nil)
		if err != nil {
			return nil, aerrors.Wrap(err, "could not refund excess fees")
		}
	}

	var seed [sectorbuilder.CommLen]byte
	{
		randHeight := currentProvingPeriodEnd - build.PoStChallangeTime - build.PoStRandomnessLookback
		if vmctx.BlockHeight() <= randHeight {
			// TODO: spec, retcode
			return nil, aerrors.Newf(1, "submit PoSt called outside submission window (%d < %d)", vmctx.BlockHeight(), randHeight)
		}

		rand, err := vmctx.GetRandomness(randHeight)

		if err != nil {
			return nil, aerrors.Wrap(err, "could not get randomness for PoST")
		}
		if len(rand) < len(seed) {
			return nil, aerrors.Escalate(fmt.Errorf("randomness too small (%d < %d)",
				len(rand), len(seed)), "improper randomness")
		}
		copy(seed[:], rand)
	}

	pss, lerr := amt.LoadAMT(types.WrapStorage(vmctx.Storage()), self.ProvingSet)
	if lerr != nil {
		return nil, aerrors.HandleExternalError(lerr, "could not load proving set node")
	}

	var sectorInfos []sectorbuilder.SectorInfo
	if err := pss.ForEach(func(id uint64, v *cbg.Deferred) error {
		var comms [][]byte
		if err := cbor.DecodeInto(v.Raw, &comms); err != nil {
			return xerrors.New("could not decode comms")
		}
		si := sectorbuilder.SectorInfo{
			SectorID: id,
		}
		commR := comms[0]
		if len(commR) != len(si.CommR) {
			return xerrors.Errorf("commR length is wrong: %d", len(commR))
		}
		copy(si.CommR[:], commR)

		sectorInfos = append(sectorInfos, si)

		return nil
	}); err != nil {
		return nil, aerrors.Absorb(err, 3, "could not decode sectorset")
	}

	faults := self.CurrentFaultSet.All()

	if ok, lerr := sectorbuilder.VerifyPost(vmctx.Context(), mi.SectorSize,
		sectorbuilder.NewSortedSectorInfo(sectorInfos), seed, params.Proof,
		faults); !ok || lerr != nil {
		if lerr != nil {
			// TODO: study PoST errors
			return nil, aerrors.Absorb(lerr, 4, "PoST error")
		}
		if !ok {
			return nil, aerrors.New(4, "PoST invalid")
		}
	}
	self.CurrentFaultSet = self.NextFaultSet
	self.NextFaultSet = types.NewBitField()

	ss, lerr := amt.LoadAMT(types.WrapStorage(vmctx.Storage()), self.ProvingSet)
	if lerr != nil {
		return nil, aerrors.HandleExternalError(lerr, "could not load proving set node")
	}

	if err := ss.BatchDelete(params.DoneSet.All()); err != nil {
		// TODO: this could fail for system reasons (block not found) or for
		// bad user input reasons (e.g. bad doneset). The latter should be a
		// non-fatal error
		return nil, aerrors.HandleExternalError(err, "failed to delete sectors in done set")
	}

	self.ProvingSet, lerr = ss.Flush()
	if lerr != nil {
		return nil, aerrors.HandleExternalError(lerr, "could not flush AMT")
	}

	oldPower := self.Power
	self.Power = types.BigMul(types.NewInt(pss.Count-uint64(len(faults))),
		types.NewInt(mi.SectorSize))

	delta := types.BigSub(self.Power, oldPower)
	if self.SlashedAt != 0 {
		self.SlashedAt = 0
		delta = self.Power
	}

	enc, err := SerializeParams(&UpdateStorageParams{
		Delta:                    delta,
		NextProvingPeriodEnd:     currentProvingPeriodEnd + build.ProvingPeriodDuration,
		PreviousProvingPeriodEnd: currentProvingPeriodEnd,
	})
	if err != nil {
		return nil, err
	}

	_, err = vmctx.Send(StoragePowerAddress, SPAMethods.UpdateStorage, types.NewInt(0), enc)
	if err != nil {
		return nil, err
	}

	self.ProvingSet = self.Sectors
	self.ProvingPeriodEnd = currentProvingPeriodEnd + build.ProvingPeriodDuration
	self.NextDoneSet = params.DoneSet

	c, err := vmctx.Storage().Put(self)
	if err != nil {
		return nil, err
	}

	if err := vmctx.Storage().Commit(oldstate, c); err != nil {
		return nil, err
	}

	return nil, nil
}

func (sma StorageMinerActor) GetPower(act *types.Actor, vmctx types.VMContext, params *struct{}) ([]byte, ActorError) {
	_, self, err := loadState(vmctx)
	if err != nil {
		return nil, err
	}
	return self.Power.Bytes(), nil
}

func SectorIsUnique(ctx context.Context, s types.Storage, sroot cid.Cid, sid uint64) (bool, ActorError) {
	found, _, _, err := GetFromSectorSet(ctx, s, sroot, sid)
	if err != nil {
		return false, err
	}

	return !found, nil
}

func AddToSectorSet(ctx context.Context, s types.Storage, ss cid.Cid, sectorID uint64, commR, commD []byte) (cid.Cid, ActorError) {
	ssr, err := amt.LoadAMT(types.WrapStorage(s), ss)
	if err != nil {
		return cid.Undef, aerrors.HandleExternalError(err, "could not load sector set node")
	}

	// TODO: Spec says to use SealCommitment, and construct commD from deals each time,
	//  but that would make SubmitPoSt way, way more expensive
	if err := ssr.Set(sectorID, [][]byte{commR, commD}); err != nil {
		return cid.Undef, aerrors.HandleExternalError(err, "failed to set commitment in sector set")
	}

	ncid, err := ssr.Flush()
	if err != nil {
		return cid.Undef, aerrors.HandleExternalError(err, "failed to flush sector set")
	}

	return ncid, nil
}

func GetFromSectorSet(ctx context.Context, s types.Storage, ss cid.Cid, sectorID uint64) (bool, []byte, []byte, ActorError) {
	ssr, err := amt.LoadAMT(types.WrapStorage(s), ss)
	if err != nil {
		return false, nil, nil, aerrors.HandleExternalError(err, "could not load sector set node")
	}

	var comms [][]byte
	err = ssr.Get(sectorID, &comms)
	if err != nil {
		if _, ok := err.(*amt.ErrNotFound); ok {
			return false, nil, nil, nil
		}
		return false, nil, nil, aerrors.HandleExternalError(err, "failed to find sector in sector set")
	}

	if len(comms) != 2 {
		return false, nil, nil, aerrors.Newf(20, "sector set entry should only have 2 elements")
	}

	return true, comms[0], comms[1], nil
}

func ValidatePoRep(ctx context.Context, maddr address.Address, ssize uint64, commD, commR, ticket, proof, seed []byte, sectorID uint64) (bool, ActorError) {
	_, span := trace.StartSpan(ctx, "ValidatePoRep")
	defer span.End()
	ok, err := sectorbuilder.VerifySeal(ssize, commR, commD, maddr, ticket, seed, sectorID, proof)
	if err != nil {
		return false, aerrors.Absorb(err, 25, "verify seal failed")
	}

	return ok, nil
}

func CollateralForPower(power types.BigInt) types.BigInt {
	return types.BigMul(power, types.NewInt(10))
	/* TODO: this
	availableFil = FakeGlobalMethods.GetAvailableFil()
	totalNetworkPower = StorageMinerActor.GetTotalStorage()
	numMiners = StorageMarket.GetMinerCount()
	powerCollateral = availableFil * NetworkConstants.POWER_COLLATERAL_PROPORTION * power / totalNetworkPower
	perCapitaCollateral = availableFil * NetworkConstants.PER_CAPITA_COLLATERAL_PROPORTION / numMiners
	collateralRequired = math.Ceil(minerPowerCollateral + minerPerCapitaCollateral)
	return collateralRequired
	*/
}

func (sma StorageMinerActor) GetWorkerAddr(act *types.Actor, vmctx types.VMContext, params *struct{}) ([]byte, ActorError) {
	_, self, err := loadState(vmctx)
	if err != nil {
		return nil, err
	}

	mi, err := loadMinerInfo(vmctx, self)
	if err != nil {
		return nil, err
	}

	return mi.Worker.Bytes(), nil
}

func (sma StorageMinerActor) GetOwner(act *types.Actor, vmctx types.VMContext, params *struct{}) ([]byte, ActorError) {
	_, self, err := loadState(vmctx)
	if err != nil {
		return nil, err
	}

	mi, err := loadMinerInfo(vmctx, self)
	if err != nil {
		return nil, err
	}

	return mi.Owner.Bytes(), nil
}

func (sma StorageMinerActor) GetPeerID(act *types.Actor, vmctx types.VMContext, params *struct{}) ([]byte, ActorError) {
	_, self, err := loadState(vmctx)
	if err != nil {
		return nil, err
	}

	mi, err := loadMinerInfo(vmctx, self)
	if err != nil {
		return nil, err
	}

	return []byte(mi.PeerID), nil
}

type UpdatePeerIDParams struct {
	PeerID peer.ID
}

func (sma StorageMinerActor) UpdatePeerID(act *types.Actor, vmctx types.VMContext, params *UpdatePeerIDParams) ([]byte, ActorError) {
	oldstate, self, err := loadState(vmctx)
	if err != nil {
		return nil, err
	}

	mi, err := loadMinerInfo(vmctx, self)
	if err != nil {
		return nil, err
	}

	if vmctx.Message().From != mi.Worker {
		return nil, aerrors.New(2, "only the mine worker may update the peer ID")
	}

	mi.PeerID = params.PeerID

	mic, err := vmctx.Storage().Put(mi)
	if err != nil {
		return nil, err
	}

	self.Info = mic

	c, err := vmctx.Storage().Put(self)
	if err != nil {
		return nil, err
	}

	if err := vmctx.Storage().Commit(oldstate, c); err != nil {
		return nil, err
	}

	return nil, nil
}

func (sma StorageMinerActor) GetSectorSize(act *types.Actor, vmctx types.VMContext, params *struct{}) ([]byte, ActorError) {
	_, self, err := loadState(vmctx)
	if err != nil {
		return nil, err
	}

	mi, err := loadMinerInfo(vmctx, self)
	if err != nil {
		return nil, err
	}

	return types.NewInt(mi.SectorSize).Bytes(), nil
}

func isLate(height uint64, self *StorageMinerActorState) bool {
	return height >= self.ProvingPeriodEnd // TODO: review: maybe > ?
}

func (sma StorageMinerActor) IsLate(act *types.Actor, vmctx types.VMContext, params *struct{}) ([]byte, ActorError) {
	_, self, err := loadState(vmctx)
	if err != nil {
		return nil, err
	}

	return cbg.EncodeBool(isLate(vmctx.BlockHeight(), self)), nil
}

// TODO: better name
func (sma StorageMinerActor) CheckMiner(act *types.Actor, vmctx types.VMContext, params *struct{}) ([]byte, ActorError) {
	if vmctx.Message().From != StoragePowerAddress {
		return nil, aerrors.New(2, "only the storage power actor can check miner")
	}

	oldstate, self, err := loadState(vmctx)
	if err != nil {
		return nil, err
	}

	if !isLate(vmctx.BlockHeight(), self) {
		// Everything's fine
		return cbg.EncodeBool(true), nil
	}

	if self.SlashedAt != 0 {
		// Don't slash more than necessary
		return nil, nil
	}

	// Slash for being late

	self.SlashedAt = vmctx.BlockHeight()

	nstate, err := vmctx.Storage().Put(self)
	if err != nil {
		return nil, err
	}
	if err := vmctx.Storage().Commit(oldstate, nstate); err != nil {
		return nil, err
	}

	return self.Power.Bytes(), nil
}

type DeclareFaultsParams struct {
	Faults types.BitField
}

func (sma StorageMinerActor) DeclareFaults(act *types.Actor, vmctx types.VMContext, params *DeclareFaultsParams) ([]byte, ActorError) {
	oldstate, self, aerr := loadState(vmctx)
	if aerr != nil {
		return nil, aerr
	}

	challengeHeight := self.ProvingPeriodEnd - build.PoStChallangeTime

	if vmctx.BlockHeight() < challengeHeight {
		// TODO: optimized bitfield methods
		for _, v := range params.Faults.All() {
			self.CurrentFaultSet.Set(v)
		}
	} else {
		for _, v := range params.Faults.All() {
			self.NextFaultSet.Set(v)
		}
	}

	nstate, err := vmctx.Storage().Put(self)
	if err != nil {
		return nil, err
	}
	if err := vmctx.Storage().Commit(oldstate, nstate); err != nil {
		return nil, err
	}

	return nil, nil
}

type MinerSlashConsensusFault struct {
	Slasher           address.Address
	AtHeight          uint64
	SlashedCollateral types.BigInt
}

func (sma StorageMinerActor) SlashConsensusFault(act *types.Actor, vmctx types.VMContext, params *MinerSlashConsensusFault) ([]byte, ActorError) {
	if vmctx.Message().From != StoragePowerAddress {
		return nil, aerrors.New(1, "SlashConsensusFault may only be called by the storage market actor")
	}

	slashedCollateral := params.SlashedCollateral
	if slashedCollateral.LessThan(act.Balance) {
		slashedCollateral = act.Balance
	}

	// Some of the slashed collateral should be paid to the slasher
	// GROWTH_RATE determines how fast the slasher share of slashed collateral will increase as block elapses
	// current GROWTH_RATE results in SLASHER_SHARE reaches 1 after 30 blocks
	// TODO: define arithmetic precision and rounding for this operation
	blockElapsed := vmctx.BlockHeight() - params.AtHeight

	slasherShare := slasherShare(params.SlashedCollateral, blockElapsed)

	burnPortion := types.BigSub(slashedCollateral, slasherShare)

	_, err := vmctx.Send(vmctx.Message().From, 0, slasherShare, nil)
	if err != nil {
		return nil, aerrors.Wrap(err, "failed to pay slasher")
	}

	_, err = vmctx.Send(BurntFundsAddress, 0, burnPortion, nil)
	if err != nil {
		return nil, aerrors.Wrap(err, "failed to burn funds")
	}

	// TODO: this still allows the miner to commit sectors and submit posts,
	// their users could potentially be unaffected, but the miner will never be
	// able to mine a block again
	// One potential issue: the miner will have to pay back the slashed
	// collateral to continue submitting PoSts, which includes pledge
	// collateral that they no longer really 'need'

	return nil, nil
}

func slasherShare(total types.BigInt, elapsed uint64) types.BigInt {
	// [int(pow(1.26, n) * 10) for n in range(30)]
	fracs := []uint64{10, 12, 15, 20, 25, 31, 40, 50, 63, 80, 100, 127, 160, 201, 254, 320, 403, 508, 640, 807, 1017, 1281, 1614, 2034, 2563, 3230, 4070, 5128, 6462, 8142}
	const precision = 10000

	var frac uint64
	if elapsed >= uint64(len(fracs)) {
		return total
	} else {
		frac = fracs[elapsed]
	}

	return types.BigDiv(
		types.BigMul(
			types.NewInt(frac),
			total,
		),
		types.NewInt(precision),
	)
}