package actors

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

	ffi "github.com/filecoin-project/filecoin-ffi"

	"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"
)

const MaxSectors = 1 << 48

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.
	//
	// AMT[sectorID]ffi.PublicSectorInfo
	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).
	//
	// AMT[sectorID]ffi.PublicSectorInfo
	ProvingSet cid.Cid

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

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

	// Faulty sectors reported since last SubmitPost
	FaultSet types.BitField

	LastFaultSubmission uint64

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

	// Active is set to true after the miner has submitted their first PoSt
	Active bool

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

	ElectionPeriodStart 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
	SubmitFallbackPoSt   uint64
	SlashStorageFault    uint64
	GetCurrentProvingSet uint64
	ArbitrateDeal        uint64
	DePledge             uint64
	GetOwner             uint64
	GetWorkerAddr        uint64
	GetPower             uint64
	GetPeerID            uint64
	GetSectorSize        uint64
	UpdatePeerID         uint64
	ChangeWorker         uint64
	IsSlashed            uint64
	CheckMiner           uint64
	DeclareFaults        uint64
	SlashConsensusFault  uint64
	SubmitElectionPoSt   uint64
}

var MAMethods = maMethods{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20}

func (sma StorageMinerActor) Exports() []interface{} {
	return []interface{}{
		1: sma.StorageMinerConstructor,
		2: sma.PreCommitSector,
		3: sma.ProveCommitSector,
		4: sma.SubmitFallbackPoSt,
		//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.IsSlashed,
		17: sma.CheckMiner,
		18: sma.DeclareFaults,
		19: sma.SlashConsensusFault,
		20: sma.SubmitElectionPoSt,
	}
}

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.Wrapf(err, "failed to compute data commitment (sector %d, deals: %v)", params.SectorID, params.DealIDs)
	}

	if ok, err := vmctx.Sys().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:%s)", ticket, seed, us.ReceivedEpoch+build.InteractivePoRepDelay, truncateHexPrint(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, types.WrapStorage(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
		// TODO: probably want to wait until the miner is above a certain
		//  threshold before starting this
		self.ElectionPeriodStart = 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
	}

	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
}

func truncateHexPrint(b []byte) string {
	s := fmt.Sprintf("%x", b)
	if len(s) > 60 {
		return s[:20] + "..." + s[len(s)-20:]
	}
	return s
}

type SubmitFallbackPoStParams struct {
	Proof      []byte
	Candidates []types.EPostTicket
}

func (sma StorageMinerActor) SubmitFallbackPoSt(act *types.Actor, vmctx types.VMContext, params *SubmitFallbackPoStParams) ([]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")
	}

	/*
		// TODO: handle 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 := self.ElectionPeriodStart + build.FallbackPoStDelay
		if vmctx.BlockHeight() <= randHeight {
			// TODO: spec, retcode
			return nil, aerrors.Newf(1, "submit fallback PoSt called too early (%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")
	}

	faults, nerr := self.FaultSet.AllMap()
	if nerr != nil {
		return nil, aerrors.Absorb(err, 5, "RLE+ invalid")
	}

	var sectorInfos []ffi.PublicSectorInfo
	if err := pss.ForEach(func(id uint64, v *cbg.Deferred) error {
		if faults[id] {
			return nil
		}

		var comms [][]byte
		if err := cbor.DecodeInto(v.Raw, &comms); err != nil {
			return xerrors.New("could not decode comms")
		}
		si := ffi.PublicSectorInfo{
			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")
	}

	proverID := vmctx.Message().To // TODO: normalize to ID address

	var candidates []sectorbuilder.EPostCandidate
	for _, t := range params.Candidates {
		var partial [32]byte
		copy(partial[:], t.Partial)
		candidates = append(candidates, sectorbuilder.EPostCandidate{
			PartialTicket:        partial,
			SectorID:             t.SectorID,
			SectorChallengeIndex: t.ChallengeIndex,
		})
	}

	if ok, lerr := sectorbuilder.VerifyFallbackPost(vmctx.Context(), mi.SectorSize,
		sectorbuilder.NewSortedPublicSectorInfo(sectorInfos), seed[:], params.Proof, candidates, proverID); !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")
		}
	}

	// Post submission is successful!
	if err := onSuccessfulPoSt(self, vmctx); err != nil {
		return nil, err
	}

	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, blks amt.Blocks, ss cid.Cid, sectorID uint64, commR, commD []byte) (cid.Cid, ActorError) {
	if sectorID >= MaxSectors {
		return cid.Undef, aerrors.Newf(25, "sector ID out of range: %d", sectorID)
	}
	ssr, err := amt.LoadAMT(blks, 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) {
	if sectorID >= MaxSectors {
		return false, nil, nil, aerrors.Newf(25, "sector ID out of range: %d", sectorID)
	}

	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 RemoveFromSectorSet(ctx context.Context, s types.Storage, ss cid.Cid, ids []uint64) (cid.Cid, aerrors.ActorError) {

	ssr, err := amt.LoadAMT(types.WrapStorage(s), ss)
	if err != nil {
		return cid.Undef, aerrors.HandleExternalError(err, "could not load sector set node")
	}

	if err := ssr.BatchDelete(ids); err != nil {
		return cid.Undef, aerrors.HandleExternalError(err, "failed to delete from sector set")
	}

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

	return ncid, 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 self.ElectionPeriodStart > 0 && height >= self.ElectionPeriodStart+build.SlashablePowerDelay
}

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

	return cbg.EncodeBool(self.SlashedAt != 0), nil
}

type CheckMinerParams struct {
	NetworkPower types.BigInt
}

// TODO: better name
func (sma StorageMinerActor) CheckMiner(act *types.Actor, vmctx types.VMContext, params *CheckMinerParams) ([]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 nil, nil
	}

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

	if params.NetworkPower.Equals(self.Power) {
		// Don't break the network when there's only one miner left

		log.Warnf("can't slash miner %s for missed PoSt, no power would be left in the network", vmctx.Message().To)
		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
	}

	var out bytes.Buffer
	if err := self.Power.MarshalCBOR(&out); err != nil {
		return nil, aerrors.HandleExternalError(err, "marshaling return value")
	}
	return out.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
	}

	nfaults, err := types.MergeBitFields(params.Faults, self.FaultSet)
	if err != nil {
		return nil, aerrors.Absorb(err, 1, "failed to merge bitfields")
	}

	self.FaultSet = nfaults

	self.LastFaultSubmission = vmctx.BlockHeight()

	nstate, aerr := vmctx.Storage().Put(self)
	if err != nil {
		return nil, aerr
	}
	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 (sma StorageMinerActor) SubmitElectionPoSt(act *types.Actor, vmctx types.VMContext, params *struct{}) ([]byte, aerrors.ActorError) {
	if vmctx.Message().From != NetworkAddress {
		return nil, aerrors.Newf(1, "submit election post can only be called by the storage power actor")
	}

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

	if self.SlashedAt != 0 {
		return nil, aerrors.New(1, "slashed miners can't perform election PoSt")
	}

	if err := onSuccessfulPoSt(self, vmctx); err != nil {
		return nil, err
	}

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

	return nil, nil
}

func onSuccessfulPoSt(self *StorageMinerActorState, vmctx types.VMContext) aerrors.ActorError {
	// TODO: some sector upkeep stuff that is very haphazard and unclear in the spec

	var mi MinerInfo
	if err := vmctx.Storage().Get(self.Info, &mi); err != nil {
		return err
	}

	pss, nerr := amt.LoadAMT(types.WrapStorage(vmctx.Storage()), self.ProvingSet)
	if nerr != nil {
		return aerrors.HandleExternalError(nerr, "failed to load proving set")
	}

	faults, nerr := self.FaultSet.All()
	if nerr != nil {
		return aerrors.Absorb(nerr, 1, "invalid bitfield (fatal?)")
	}

	self.FaultSet = types.NewBitField()

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

	// If below the minimum size requirement, miners have zero power
	if newPower.LessThan(types.NewInt(build.MinimumMinerPower)) {
		newPower = types.NewInt(0)
	}

	self.Power = newPower

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

	prevSlashingDeadline := self.ElectionPeriodStart + build.SlashablePowerDelay
	if !self.Active && newPower.GreaterThan(types.NewInt(0)) {
		self.Active = true
		prevSlashingDeadline = 0
	}

	if !(oldPower.IsZero() && newPower.IsZero()) {
		enc, err := SerializeParams(&UpdateStorageParams{
			Delta:                    delta,
			NextProvingPeriodEnd:     vmctx.BlockHeight() + build.SlashablePowerDelay,
			PreviousProvingPeriodEnd: prevSlashingDeadline,
		})
		if err != nil {
			return err
		}

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

	ncid, err := RemoveFromSectorSet(vmctx.Context(), vmctx.Storage(), self.Sectors, faults)
	if err != nil {
		return err
	}

	self.Sectors = ncid
	self.ProvingSet = ncid
	self.ElectionPeriodStart = vmctx.BlockHeight()
	return 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),
	)
}