package types

import (
	"bytes"
	"context"
	"math/big"

	block "github.com/ipfs/go-block-format"
	"github.com/ipfs/go-cid"
	"github.com/minio/sha256-simd"
	"github.com/multiformats/go-multihash"
	"go.opencensus.io/trace"
	xerrors "golang.org/x/xerrors"

	"github.com/filecoin-project/lotus/build"
	"github.com/filecoin-project/lotus/chain/address"
)

type Ticket struct {
	VRFProof []byte
}

type EPostTicket struct {
	Partial        []byte
	SectorID       uint64
	ChallengeIndex uint64
}

type EPostProof struct {
	Proof      []byte
	PostRand   []byte
	Candidates []EPostTicket
}

type BlockHeader struct {
	Miner address.Address

	Ticket *Ticket

	EPostProof EPostProof

	Parents []cid.Cid

	ParentWeight BigInt

	Height uint64

	ParentStateRoot cid.Cid

	ParentMessageReceipts cid.Cid

	Messages cid.Cid

	BLSAggregate Signature

	Timestamp uint64

	BlockSig *Signature
}

func (b *BlockHeader) ToStorageBlock() (block.Block, error) {
	data, err := b.Serialize()
	if err != nil {
		return nil, err
	}

	pref := cid.NewPrefixV1(cid.DagCBOR, multihash.BLAKE2B_MIN+31)
	c, err := pref.Sum(data)
	if err != nil {
		return nil, err
	}

	return block.NewBlockWithCid(data, c)
}

func (b *BlockHeader) Cid() cid.Cid {
	sb, err := b.ToStorageBlock()
	if err != nil {
		panic(err) // Not sure i'm entirely comfortable with this one, needs to be checked
	}

	return sb.Cid()
}

func DecodeBlock(b []byte) (*BlockHeader, error) {
	var blk BlockHeader
	if err := blk.UnmarshalCBOR(bytes.NewReader(b)); err != nil {
		return nil, err
	}

	return &blk, nil
}

func (blk *BlockHeader) Serialize() ([]byte, error) {
	buf := new(bytes.Buffer)
	if err := blk.MarshalCBOR(buf); err != nil {
		return nil, err
	}

	return buf.Bytes(), nil
}

func (blk *BlockHeader) LastTicket() *Ticket {
	return blk.Ticket
}

func (blk *BlockHeader) SigningBytes() ([]byte, error) {
	blkcopy := *blk
	blkcopy.BlockSig = nil

	return blkcopy.Serialize()
}

func (blk *BlockHeader) CheckBlockSignature(ctx context.Context, worker address.Address) error {
	_, span := trace.StartSpan(ctx, "checkBlockSignature")
	defer span.End()

	sigb, err := blk.SigningBytes()
	if err != nil {
		return xerrors.Errorf("failed to get block signing bytes: %w", err)
	}

	return blk.BlockSig.Verify(worker, sigb)
}

type MsgMeta struct {
	BlsMessages   cid.Cid
	SecpkMessages cid.Cid
}

func (mm *MsgMeta) Cid() cid.Cid {
	b, err := mm.ToStorageBlock()
	if err != nil {
		panic(err) // also maybe sketchy
	}
	return b.Cid()
}

func (mm *MsgMeta) ToStorageBlock() (block.Block, error) {
	buf := new(bytes.Buffer)
	if err := mm.MarshalCBOR(buf); err != nil {
		return nil, xerrors.Errorf("failed to marshal MsgMeta: %w", err)
	}

	pref := cid.NewPrefixV1(cid.DagCBOR, multihash.BLAKE2B_MIN+31)
	c, err := pref.Sum(buf.Bytes())
	if err != nil {
		return nil, err
	}

	return block.NewBlockWithCid(buf.Bytes(), c)
}

func CidArrsEqual(a, b []cid.Cid) bool {
	if len(a) != len(b) {
		return false
	}

	// order ignoring compare...
	s := make(map[cid.Cid]bool)
	for _, c := range a {
		s[c] = true
	}

	for _, c := range b {
		if !s[c] {
			return false
		}
	}
	return true
}

var blocksPerEpoch = NewInt(build.BlocksPerEpoch)

const sha256bits = 256

func IsTicketWinner(partialTicket []byte, ssizeI uint64, snum uint64, totpow BigInt) bool {
	ssize := NewInt(ssizeI)
	ssampled := ElectionPostChallengeCount(snum)
	/*
		Need to check that
		(h(vrfout) + 1) / (max(h) + 1) <= e * sectorSize / totalPower
		max(h) == 2^256-1
		which in terms of integer math means:
		(h(vrfout) + 1) * totalPower <= e * sectorSize * 2^256
		in 2^256 space, it is equivalent to:
		h(vrfout) * totalPower < e * sectorSize * 2^256

		Because of SectorChallengeRatioDiv sampling for proofs
		we need to scale this appropriately.

		Let c = ceil(numSectors/SectorChallengeRatioDiv)
		(c is the number of tickets a miner requests)
		Accordingly we check
		(h(vrfout) + 1) / 2^256 <= e * sectorSize / totalPower * snum / c
		or
		h(vrfout) * totalPower * c < e * sectorSize * 2^256 * snum
	*/

	h := sha256.Sum256(partialTicket)

	lhs := BigFromBytes(h[:]).Int
	lhs = lhs.Mul(lhs, totpow.Int)
	lhs = lhs.Mul(lhs, new(big.Int).SetUint64(ssampled))

	// rhs = sectorSize * 2^256
	// rhs = sectorSize << 256
	rhs := new(big.Int).Lsh(ssize.Int, sha256bits)
	rhs = rhs.Mul(rhs, new(big.Int).SetUint64(snum))
	rhs = rhs.Mul(rhs, blocksPerEpoch.Int)

	// h(vrfout) * totalPower < e * sectorSize * 2^256?
	return lhs.Cmp(rhs) < 0
}

func ElectionPostChallengeCount(sectors uint64) uint64 {
	if sectors == 0 {
		return 0
	}
	// ceil(sectors / build.SectorChallengeRatioDiv)
	return (sectors-1)/build.SectorChallengeRatioDiv + 1
}

func (t *Ticket) Equals(ot *Ticket) bool {
	return bytes.Equal(t.VRFProof, ot.VRFProof)
}