package gen

import (
	"bytes"
	"context"
	"crypto/sha256"
	"fmt"
	"io/ioutil"
	"sync/atomic"

	"github.com/filecoin-project/go-address"
	commcid "github.com/filecoin-project/go-fil-commcid"
	sectorbuilder "github.com/filecoin-project/go-sectorbuilder"
	"github.com/filecoin-project/specs-actors/actors/abi"
	"github.com/filecoin-project/specs-actors/actors/crypto"
	"github.com/filecoin-project/specs-storage/storage"
	block "github.com/ipfs/go-block-format"
	"github.com/ipfs/go-blockservice"
	"github.com/ipfs/go-car"
	"github.com/ipfs/go-cid"
	blockstore "github.com/ipfs/go-ipfs-blockstore"
	offline "github.com/ipfs/go-ipfs-exchange-offline"
	format "github.com/ipfs/go-ipld-format"
	logging "github.com/ipfs/go-log/v2"
	"github.com/ipfs/go-merkledag"

	"github.com/filecoin-project/lotus/api"
	"github.com/filecoin-project/lotus/build"
	genesis2 "github.com/filecoin-project/lotus/chain/gen/genesis"
	"github.com/filecoin-project/lotus/chain/stmgr"
	"github.com/filecoin-project/lotus/chain/store"
	"github.com/filecoin-project/lotus/chain/types"
	"github.com/filecoin-project/lotus/chain/vm"
	"github.com/filecoin-project/lotus/chain/wallet"
	"github.com/filecoin-project/lotus/cmd/lotus-seed/seed"
	"github.com/filecoin-project/lotus/genesis"
	"github.com/filecoin-project/lotus/lib/sigs"
	"github.com/filecoin-project/lotus/node/repo"
	"github.com/filecoin-project/lotus/storage/sbmock"

	"go.opencensus.io/trace"
	"golang.org/x/xerrors"
)

var log = logging.Logger("gen")

const msgsPerBlock = 20

type ChainGen struct {
	msgsPerBlock int

	bs blockstore.Blockstore

	cs *store.ChainStore

	sm *stmgr.StateManager

	genesis   *types.BlockHeader
	CurTipset *store.FullTipSet

	Timestamper func(*types.TipSet, abi.ChainEpoch) uint64

	GetMessages func(*ChainGen) ([]*types.SignedMessage, error)

	w *wallet.Wallet

	eppProvs    map[address.Address]ElectionPoStProver
	Miners      []address.Address
	receivers   []address.Address
	banker      address.Address
	bankerNonce uint64

	r  repo.Repo
	lr repo.LockedRepo
}

type mybs struct {
	blockstore.Blockstore
}

func (m mybs) Get(c cid.Cid) (block.Block, error) {
	b, err := m.Blockstore.Get(c)
	if err != nil {
		return nil, err
	}

	return b, nil
}

func NewGenerator() (*ChainGen, error) {
	mr := repo.NewMemory(nil)
	lr, err := mr.Lock(repo.StorageMiner)
	if err != nil {
		return nil, xerrors.Errorf("taking mem-repo lock failed: %w", err)
	}

	ds, err := lr.Datastore("/metadata")
	if err != nil {
		return nil, xerrors.Errorf("failed to get metadata datastore: %w", err)
	}

	bds, err := lr.Datastore("/blocks")
	if err != nil {
		return nil, xerrors.Errorf("failed to get blocks datastore: %w", err)
	}

	bs := mybs{blockstore.NewIdStore(blockstore.NewBlockstore(bds))}

	ks, err := lr.KeyStore()
	if err != nil {
		return nil, xerrors.Errorf("getting repo keystore failed: %w", err)
	}

	w, err := wallet.NewWallet(ks)
	if err != nil {
		return nil, xerrors.Errorf("creating memrepo wallet failed: %w", err)
	}

	banker, err := w.GenerateKey(crypto.SigTypeSecp256k1)
	if err != nil {
		return nil, xerrors.Errorf("failed to generate banker key: %w", err)
	}

	receievers := make([]address.Address, msgsPerBlock)
	for r := range receievers {
		receievers[r], err = w.GenerateKey(crypto.SigTypeBLS)
		if err != nil {
			return nil, xerrors.Errorf("failed to generate receiver key: %w", err)
		}
	}

	maddr1 := genesis2.MinerAddress(0)

	m1temp, err := ioutil.TempDir("", "preseal")
	if err != nil {
		return nil, err
	}

	genm1, k1, err := seed.PreSeal(maddr1, abi.RegisteredProof_StackedDRG2KiBPoSt, 0, 1, m1temp, []byte("some randomness"), nil)
	if err != nil {
		return nil, err
	}

	maddr2 := genesis2.MinerAddress(1)

	m2temp, err := ioutil.TempDir("", "preseal")
	if err != nil {
		return nil, err
	}

	genm2, k2, err := seed.PreSeal(maddr2, abi.RegisteredProof_StackedDRG2KiBPoSt, 0, 1, m2temp, []byte("some randomness"), nil)
	if err != nil {
		return nil, err
	}

	mk1, err := w.Import(k1)
	if err != nil {
		return nil, err
	}
	mk2, err := w.Import(k2)
	if err != nil {
		return nil, err
	}

	sys := vm.Syscalls(&genFakeVerifier{})

	tpl := genesis.Template{
		Accounts: []genesis.Actor{
			{
				Type:    genesis.TAccount,
				Balance: types.FromFil(40000),
				Meta:    (&genesis.AccountMeta{Owner: mk1}).ActorMeta(),
			},
			{
				Type:    genesis.TAccount,
				Balance: types.FromFil(40000),
				Meta:    (&genesis.AccountMeta{Owner: mk2}).ActorMeta(),
			},
			{
				Type:    genesis.TAccount,
				Balance: types.FromFil(50000),
				Meta:    (&genesis.AccountMeta{Owner: banker}).ActorMeta(),
			},
		},
		Miners: []genesis.Miner{
			*genm1,
			*genm2,
		},
		NetworkName: "",
		Timestamp:   100000,
	}

	genb, err := genesis2.MakeGenesisBlock(context.TODO(), bs, sys, tpl)
	if err != nil {
		return nil, xerrors.Errorf("make genesis block failed: %w", err)
	}

	cs := store.NewChainStore(bs, ds, sys)

	genfb := &types.FullBlock{Header: genb.Genesis}
	gents := store.NewFullTipSet([]*types.FullBlock{genfb})

	if err := cs.SetGenesis(genb.Genesis); err != nil {
		return nil, xerrors.Errorf("set genesis failed: %w", err)
	}

	mgen := make(map[address.Address]ElectionPoStProver)
	for i := range tpl.Miners {
		mgen[genesis2.MinerAddress(uint64(i))] = &eppProvider{}
	}

	sm := stmgr.NewStateManager(cs)

	miners := []address.Address{maddr1, maddr2}

	gen := &ChainGen{
		bs:           bs,
		cs:           cs,
		sm:           sm,
		msgsPerBlock: msgsPerBlock,
		genesis:      genb.Genesis,
		w:            w,

		GetMessages: getRandomMessages,
		Miners:      miners,
		eppProvs:    mgen,
		banker:      banker,
		receivers:   receievers,

		CurTipset: gents,

		r:  mr,
		lr: lr,
	}

	return gen, nil
}

func (cg *ChainGen) SetStateManager(sm *stmgr.StateManager) {
	cg.sm = sm
}

func (cg *ChainGen) ChainStore() *store.ChainStore {
	return cg.cs
}

func (cg *ChainGen) Genesis() *types.BlockHeader {
	return cg.genesis
}

func (cg *ChainGen) GenesisCar() ([]byte, error) {
	offl := offline.Exchange(cg.bs)
	blkserv := blockservice.New(cg.bs, offl)
	dserv := merkledag.NewDAGService(blkserv)

	out := new(bytes.Buffer)

	if err := car.WriteCarWithWalker(context.TODO(), dserv, []cid.Cid{cg.Genesis().Cid()}, out, CarWalkFunc); err != nil {
		return nil, xerrors.Errorf("genesis car write car failed: %w", err)
	}

	return out.Bytes(), nil
}

func CarWalkFunc(nd format.Node) (out []*format.Link, err error) {
	for _, link := range nd.Links() {
		if link.Cid.Prefix().MhType == uint64(commcid.FC_SEALED_V1) || link.Cid.Prefix().MhType == uint64(commcid.FC_UNSEALED_V1) {
			continue
		}
		out = append(out, link)
	}

	return out, nil
}

func (cg *ChainGen) nextBlockProof(ctx context.Context, pts *types.TipSet, m address.Address, round int64) (*types.EPostProof, *types.Ticket, error) {
	mc := &mca{w: cg.w, sm: cg.sm}

	// TODO: REVIEW: Am I doing this correctly?
	ticketRand, err := mc.ChainGetRandomness(ctx, pts.Key(), crypto.DomainSeparationTag_TicketProduction, pts.Height(), m.Bytes())
	if err != nil {
		return nil, nil, err
	}

	st := pts.ParentState()

	worker, err := stmgr.GetMinerWorkerRaw(ctx, cg.sm, st, m)
	if err != nil {
		return nil, nil, xerrors.Errorf("get miner worker: %w", err)
	}

	vrfout, err := ComputeVRF(ctx, cg.w.Sign, worker, ticketRand)
	if err != nil {
		return nil, nil, xerrors.Errorf("compute VRF: %w", err)
	}

	tick := &types.Ticket{
		VRFProof: vrfout,
	}

	eproofin, err := IsRoundWinner(ctx, pts, round, m, cg.eppProvs[m], mc)
	if err != nil {
		return nil, nil, xerrors.Errorf("checking round winner failed: %w", err)
	}
	if eproofin == nil {
		return nil, tick, nil
	}
	eproof, err := ComputeProof(ctx, cg.eppProvs[m], eproofin)
	if err != nil {
		return nil, nil, xerrors.Errorf("computing proof: %w", err)
	}

	return eproof, tick, nil
}

type MinedTipSet struct {
	TipSet   *store.FullTipSet
	Messages []*types.SignedMessage
}

func (cg *ChainGen) NextTipSet() (*MinedTipSet, error) {
	mts, err := cg.NextTipSetFromMiners(cg.CurTipset.TipSet(), cg.Miners)
	if err != nil {
		return nil, err
	}

	cg.CurTipset = mts.TipSet
	return mts, nil
}

func (cg *ChainGen) NextTipSetFromMiners(base *types.TipSet, miners []address.Address) (*MinedTipSet, error) {
	var blks []*types.FullBlock

	msgs, err := cg.GetMessages(cg)
	if err != nil {
		return nil, xerrors.Errorf("get random messages: %w", err)
	}

	for round := int64(base.Height() + 1); len(blks) == 0; round++ {
		for _, m := range miners {
			proof, t, err := cg.nextBlockProof(context.TODO(), base, m, round)
			if err != nil {
				return nil, xerrors.Errorf("next block proof: %w", err)
			}

			if proof != nil {
				fblk, err := cg.makeBlock(base, m, proof, t, abi.ChainEpoch(round), msgs)
				if err != nil {
					return nil, xerrors.Errorf("making a block for next tipset failed: %w", err)
				}

				if err := cg.cs.PersistBlockHeaders(fblk.Header); err != nil {
					return nil, xerrors.Errorf("chainstore AddBlock: %w", err)
				}

				blks = append(blks, fblk)
			}
		}
	}

	fts := store.NewFullTipSet(blks)

	return &MinedTipSet{
		TipSet:   fts,
		Messages: msgs,
	}, nil
}

func (cg *ChainGen) makeBlock(parents *types.TipSet, m address.Address, eproof *types.EPostProof, ticket *types.Ticket, height abi.ChainEpoch, msgs []*types.SignedMessage) (*types.FullBlock, error) {

	var ts uint64
	if cg.Timestamper != nil {
		ts = cg.Timestamper(parents, height-parents.Height())
	} else {
		ts = parents.MinTimestamp() + uint64((height-parents.Height())*build.BlockDelay)
	}

	fblk, err := MinerCreateBlock(context.TODO(), cg.sm, cg.w, m, parents, ticket, eproof, msgs, height, ts)
	if err != nil {
		return nil, err
	}

	return fblk, err
}

// This function is awkward. It's used to deal with messages made when
// simulating forks
func (cg *ChainGen) ResyncBankerNonce(ts *types.TipSet) error {
	act, err := cg.sm.GetActor(cg.banker, ts)
	if err != nil {
		return err
	}

	cg.bankerNonce = act.Nonce
	return nil
}

func (cg *ChainGen) Banker() address.Address {
	return cg.banker
}

func (cg *ChainGen) Wallet() *wallet.Wallet {
	return cg.w
}

func getRandomMessages(cg *ChainGen) ([]*types.SignedMessage, error) {
	msgs := make([]*types.SignedMessage, cg.msgsPerBlock)
	for m := range msgs {
		msg := types.Message{
			To:   cg.receivers[m%len(cg.receivers)],
			From: cg.banker,

			Nonce: atomic.AddUint64(&cg.bankerNonce, 1) - 1,

			Value: types.NewInt(uint64(m + 1)),

			Method: 0,

			GasLimit: types.NewInt(10000),
			GasPrice: types.NewInt(0),
		}

		sig, err := cg.w.Sign(context.TODO(), cg.banker, msg.Cid().Bytes())
		if err != nil {
			return nil, err
		}

		msgs[m] = &types.SignedMessage{
			Message:   msg,
			Signature: *sig,
		}
	}

	return msgs, nil
}

func (cg *ChainGen) YieldRepo() (repo.Repo, error) {
	if err := cg.lr.Close(); err != nil {
		return nil, err
	}
	return cg.r, nil
}

type MiningCheckAPI interface {
	ChainGetRandomness(ctx context.Context, tsk types.TipSetKey, personalization crypto.DomainSeparationTag, randEpoch abi.ChainEpoch, entropy []byte) (abi.Randomness, error)

	StateMinerPower(context.Context, address.Address, types.TipSetKey) (*api.MinerPower, error)

	StateMinerWorker(context.Context, address.Address, types.TipSetKey) (address.Address, error)

	StateMinerSectorSize(context.Context, address.Address, types.TipSetKey) (abi.SectorSize, error)

	StateMinerProvingSet(context.Context, address.Address, types.TipSetKey) ([]*api.ChainSectorInfo, error)

	WalletSign(context.Context, address.Address, []byte) (*crypto.Signature, error)
}

type mca struct {
	w  *wallet.Wallet
	sm *stmgr.StateManager
}

func (mca mca) ChainGetRandomness(ctx context.Context, tsk types.TipSetKey, personalization crypto.DomainSeparationTag, randEpoch abi.ChainEpoch, entropy []byte) (abi.Randomness, error) {
	pts, err := mca.sm.ChainStore().LoadTipSet(tsk)
	if err != nil {
		return nil, xerrors.Errorf("loading tipset key: %w", err)
	}

	return mca.sm.ChainStore().GetRandomness(ctx, pts.Cids(), personalization, int64(randEpoch), entropy)
}

func (mca mca) StateMinerPower(ctx context.Context, maddr address.Address, tsk types.TipSetKey) (*api.MinerPower, error) {
	ts, err := mca.sm.ChainStore().LoadTipSet(tsk)
	if err != nil {
		return nil, xerrors.Errorf("loading tipset %s: %w", tsk, err)
	}
	mpow, tpow, err := stmgr.GetPower(ctx, mca.sm, ts, maddr)
	if err != nil {
		return nil, err
	}

	return &api.MinerPower{
		MinerPower: mpow,
		TotalPower: tpow,
	}, err
}

func (mca mca) StateMinerWorker(ctx context.Context, maddr address.Address, tsk types.TipSetKey) (address.Address, error) {
	ts, err := mca.sm.ChainStore().LoadTipSet(tsk)
	if err != nil {
		return address.Undef, xerrors.Errorf("loading tipset %s: %w", tsk, err)
	}
	return stmgr.GetMinerWorkerRaw(ctx, mca.sm, ts.ParentState(), maddr)
}

func (mca mca) StateMinerSectorSize(ctx context.Context, maddr address.Address, tsk types.TipSetKey) (abi.SectorSize, error) {
	ts, err := mca.sm.ChainStore().LoadTipSet(tsk)
	if err != nil {
		return 0, xerrors.Errorf("loading tipset %s: %w", tsk, err)
	}
	return stmgr.GetMinerSectorSize(ctx, mca.sm, ts, maddr)
}

func (mca mca) StateMinerProvingSet(ctx context.Context, maddr address.Address, tsk types.TipSetKey) ([]*api.ChainSectorInfo, error) {
	ts, err := mca.sm.ChainStore().LoadTipSet(tsk)
	if err != nil {
		return nil, xerrors.Errorf("loading tipset %s: %w", tsk, err)
	}
	return stmgr.GetMinerProvingSet(ctx, mca.sm, ts, maddr)
}

func (mca mca) WalletSign(ctx context.Context, a address.Address, v []byte) (*crypto.Signature, error) {
	return mca.w.Sign(ctx, a, v)
}

type ElectionPoStProver interface {
	GenerateCandidates(context.Context, []abi.SectorInfo, abi.PoStRandomness) ([]storage.PoStCandidateWithTicket, error)
	ComputeProof(context.Context, []abi.SectorInfo, []byte, []storage.PoStCandidateWithTicket) ([]abi.PoStProof, error)
}

type eppProvider struct{}

func (epp *eppProvider) GenerateCandidates(ctx context.Context, _ []abi.SectorInfo, eprand abi.PoStRandomness) ([]storage.PoStCandidateWithTicket, error) {
	return []storage.PoStCandidateWithTicket{
		{
			Candidate: abi.PoStCandidate{
				RegisteredProof: abi.RegisteredProof_StackedDRG2KiBPoSt,
				SectorID:        abi.SectorID{Number: 1},
				PartialTicket:   abi.PartialTicket{},
				PrivateProof:    abi.PrivatePoStCandidateProof{},
				ChallengeIndex:  1,
			},
		},
	}, nil
}

func (epp *eppProvider) ComputeProof(ctx context.Context, _ []abi.SectorInfo, eprand []byte, winners []storage.PoStCandidateWithTicket) ([]abi.PoStProof, error) {

	return []abi.PoStProof{{
		ProofBytes: []byte("valid proof"),
	}}, nil
}

type ProofInput struct {
	sectors []abi.SectorInfo
	hvrf    []byte
	winners []storage.PoStCandidateWithTicket
	vrfout  []byte
}

func IsRoundWinner(ctx context.Context, ts *types.TipSet, round int64, miner address.Address, epp ElectionPoStProver, a MiningCheckAPI) (*ProofInput, error) {
	epostRand, err := a.ChainGetRandomness(ctx, ts.Key(), crypto.DomainSeparationTag_ElectionPoStChallengeSeed, abi.ChainEpoch(round-build.EcRandomnessLookback), miner.Bytes())
	if err != nil {
		return nil, xerrors.Errorf("chain get randomness: %w", err)
	}

	mworker, err := a.StateMinerWorker(ctx, miner, ts.Key())
	if err != nil {
		return nil, xerrors.Errorf("failed to get miner worker: %w", err)
	}

	vrfout, err := ComputeVRF(ctx, a.WalletSign, mworker, epostRand)
	if err != nil {
		return nil, xerrors.Errorf("failed to compute VRF: %w", err)
	}

	pset, err := a.StateMinerProvingSet(ctx, miner, ts.Key())
	if err != nil {
		return nil, xerrors.Errorf("failed to load proving set for miner: %w", err)
	}
	if len(pset) == 0 {
		return nil, nil
	}

	var sinfos []abi.SectorInfo
	for _, s := range pset {
		if s.Info.Info.RegisteredProof == 0 {
			return nil, xerrors.Errorf("sector %d in proving set had registered type of zero", s.ID)
		}
		sinfos = append(sinfos, abi.SectorInfo{
			SectorNumber:    s.ID,
			SealedCID:       s.Info.Info.SealedCID,
			RegisteredProof: s.Info.Info.RegisteredProof,
		})
	}

	hvrf := sha256.Sum256(vrfout)
	candidates, err := epp.GenerateCandidates(ctx, sinfos, hvrf[:])
	if err != nil {
		return nil, xerrors.Errorf("failed to generate electionPoSt candidates: %w", err)
	}

	pow, err := a.StateMinerPower(ctx, miner, ts.Key())
	if err != nil {
		return nil, xerrors.Errorf("failed to check power: %w", err)
	}

	ssize, err := a.StateMinerSectorSize(ctx, miner, ts.Key())
	if err != nil {
		return nil, xerrors.Errorf("failed to look up miners sector size: %w", err)
	}

	var winners []storage.PoStCandidateWithTicket
	for _, c := range candidates {
		if types.IsTicketWinner(c.Candidate.PartialTicket, ssize, uint64(len(sinfos)), pow.TotalPower) {
			winners = append(winners, c)
		}
	}

	// no winners, sad
	if len(winners) == 0 {
		return nil, nil
	}

	return &ProofInput{
		sectors: sinfos,
		hvrf:    hvrf[:],
		winners: winners,
		vrfout:  vrfout,
	}, nil
}

func ComputeProof(ctx context.Context, epp ElectionPoStProver, pi *ProofInput) (*types.EPostProof, error) {
	proof, err := epp.ComputeProof(ctx, pi.sectors, pi.hvrf, pi.winners)
	if err != nil {
		return nil, xerrors.Errorf("failed to compute snark for election proof: %w", err)
	}

	ept := types.EPostProof{
		Proofs:   proof,
		PostRand: pi.vrfout,
	}
	for _, win := range pi.winners {
		part := make([]byte, 32)
		copy(part, win.Candidate.PartialTicket)
		ept.Candidates = append(ept.Candidates, types.EPostTicket{
			Partial:        part,
			SectorID:       win.Candidate.SectorID.Number,
			ChallengeIndex: uint64(win.Candidate.ChallengeIndex),
		})
	}

	return &ept, nil
}

type SignFunc func(context.Context, address.Address, []byte) (*crypto.Signature, error)

func VerifyVRF(ctx context.Context, worker address.Address, vrfBase, vrfproof []byte) error {
	_, span := trace.StartSpan(ctx, "VerifyVRF")
	defer span.End()

	sig := &crypto.Signature{
		Type: crypto.SigTypeBLS,
		Data: vrfproof,
	}

	if err := sigs.Verify(sig, worker, vrfBase); err != nil {
		return xerrors.Errorf("vrf was invalid: %w", err)
	}

	return nil
}

func ComputeVRF(ctx context.Context, sign SignFunc, worker address.Address, sigInput []byte) ([]byte, error) {
	sig, err := sign(ctx, worker, sigInput)
	if err != nil {
		return nil, err
	}

	if sig.Type != crypto.SigTypeBLS {
		return nil, fmt.Errorf("miner worker address was not a BLS key")
	}

	return sig.Data, nil
}

type genFakeVerifier struct{}

var _ sectorbuilder.Verifier = (*genFakeVerifier)(nil)

func (m genFakeVerifier) VerifyElectionPost(ctx context.Context, pvi abi.PoStVerifyInfo) (bool, error) {
	panic("nyi")
}
func (m genFakeVerifier) GenerateDataCommitment(ssize abi.PaddedPieceSize, pieces []abi.PieceInfo) (cid.Cid, error) {
	return sbmock.MockVerifier.GenerateDataCommitment(ssize, pieces)
}

func (m genFakeVerifier) VerifySeal(svi abi.SealVerifyInfo) (bool, error) {
	return true, nil
}

func (m genFakeVerifier) VerifyFallbackPost(ctx context.Context, pvi abi.PoStVerifyInfo) (bool, error) {
	panic("nyi")
}