block.go

// Copyright (c) 2020-2022 Blockwatch Data Inc.
// Author: alex@blockwatch.cc

package codec

import (
	"bytes"
	"encoding/binary"
	"strconv"
	"time"

	"blockwatch.cc/tzgo/tezos"
)

// BlockHeader represents a Tenderbake compatible block header
type BlockHeader struct {
	Level            int32                `json:"level"`
	Proto            byte                 `json:"proto"`
	Predecessor      tezos.BlockHash      `json:"predecessor"`
	Timestamp        time.Time            `json:"timestamp"`
	ValidationPass   byte                 `json:"validation_pass"`
	OperationsHash   tezos.OpListListHash `json:"operations_hash"`
	Fitness          []tezos.HexBytes     `json:"fitness"`
	Context          tezos.ContextHash    `json:"context"`
	PayloadHash      tezos.PayloadHash    `json:"payload_hash"`
	PayloadRound     int                  `json:"payload_round"`
	ProofOfWorkNonce tezos.HexBytes       `json:"proof_of_work_nonce"`
	SeedNonceHash    tezos.NonceHash      `json:"seed_nonce_hash"`
	LbVote           tezos.FeatureVote    `json:"liquidity_baking_toggle_vote"`
	AiVote           tezos.FeatureVote    `json:"adaptive_issuance_vote"`
	Signature        tezos.Signature      `json:"signature"`
	ChainId          *tezos.ChainIdHash   `json:"-"` // remote signer use only
}

// Bytes serializes the block header into binary form. When no signature is set, the
// result can be used as input for signing, if a signature is set the result is
// ready for broadcast.
func (h BlockHeader) Bytes() []byte {
	buf := bytes.NewBuffer(nil)
	_ = h.EncodeBuffer(buf)
	return buf.Bytes()
}

// WatermarkedBytes serializes the block header and prefixes it with a watermark.
// This format is only used for signing.
func (h BlockHeader) WatermarkedBytes() []byte {
	buf := bytes.NewBuffer(nil)
	buf.WriteByte(TenderbakeBlockWatermark)
	buf.Write(h.ChainId.Bytes())
	_ = h.EncodeBuffer(buf)
	return buf.Bytes()
}

// Digest returns a 32 byte blake2b hash for signing the block header. The pre-image
// is binary serialized (without signature) and prefixed with a watermark byte.
func (h BlockHeader) Digest() []byte {
	d := tezos.Digest(h.WatermarkedBytes())
	return d[:]
}

// Hash calculates the block hash. For the hash to be correct, the block
// must contain a valid signature.
func (h *BlockHeader) Hash() (s tezos.BlockHash) {
	d := tezos.Digest(h.Bytes())
	copy(s[:], d[:])
	return
}

// Sign signs the block header using a private key and generates a generic signature.
// If a valid signature already exists, this function is a noop.
func (h *BlockHeader) Sign(key tezos.PrivateKey) error {
	if h.Signature.IsValid() {
		return nil
	}
	sig, err := key.Sign(h.Digest())
	sig.Type = tezos.SignatureTypeGeneric
	if err != nil {
		return err
	}
	h.Signature = sig
	return nil
}

// WithChainId sets chain_id for this block to id. Use this only for remote signing
// of blocks as it creates an invalid binary encoding otherwise.
func (h *BlockHeader) WithChainId(id tezos.ChainIdHash) *BlockHeader {
	clone := id.Clone()
	h.ChainId = &clone
	return h
}

// WithSignature adds an externally created signature to the block header. Converts
// any non-generic signature first. No signature validation is performed, it is
// assumed the signature is correct.
func (h *BlockHeader) WithSignature(sig tezos.Signature) *BlockHeader {
	sig = sig.Clone()
	sig.Type = tezos.SignatureTypeGeneric
	h.Signature = sig
	return h
}

func (h BlockHeader) MarshalJSON() ([]byte, error) {
	buf := bytes.NewBuffer(nil)
	buf.WriteByte('{')
	buf.WriteString(`"level":`)
	buf.WriteString(strconv.FormatInt(int64(h.Level), 10))
	buf.WriteString(`,"proto":`)
	buf.WriteString(strconv.Itoa(int(h.Proto)))
	buf.WriteString(`,"predecessor":`)
	buf.WriteString(strconv.Quote(h.Predecessor.String()))
	buf.WriteString(`,"timestamp":`)
	buf.WriteString(strconv.Quote(h.Timestamp.UTC().Format("2006-01-02T15:04:05Z")))
	buf.WriteString(`,"validation_pass":`)
	buf.WriteString(strconv.Itoa(int(h.ValidationPass)))
	buf.WriteString(`,"operations_hash":`)
	buf.WriteString(strconv.Quote(h.OperationsHash.String()))
	buf.WriteString(`,"fitness":[`)
	for i, v := range h.Fitness {
		if i > 0 {
			buf.WriteByte(',')
		}
		buf.WriteString(strconv.Quote(v.String()))
	}
	buf.WriteString(`],"context":`)
	buf.WriteString(strconv.Quote(h.Context.String()))
	buf.WriteString(`,"payload_hash":`)
	buf.WriteString(strconv.Quote(h.PayloadHash.String()))
	buf.WriteString(`,"payload_round":`)
	buf.WriteString(strconv.Itoa(h.PayloadRound))
	buf.WriteString(`,"proof_of_work_nonce":`)
	buf.WriteString(strconv.Quote(h.ProofOfWorkNonce.String()))
	if h.SeedNonceHash.IsValid() {
		buf.WriteString(`,"seed_nonce_hash":`)
		buf.WriteString(strconv.Quote(h.SeedNonceHash.String()))
	}
	buf.WriteString(`,"liquidity_baking_toggle_vote":`)
	buf.WriteString(strconv.Quote(h.LbVote.String()))
	buf.WriteString(`,"adaptive_issuance_vote":`)
	buf.WriteString(strconv.Quote(h.AiVote.String()))
	if h.Signature.IsValid() {
		buf.WriteString(`,"signature":`)
		buf.WriteString(strconv.Quote(h.Signature.String()))
	}
	buf.WriteByte('}')
	return buf.Bytes(), nil
}

func (h *BlockHeader) EncodeBuffer(buf *bytes.Buffer) error {
	binary.Write(buf, enc, h.Level)
	buf.WriteByte(h.Proto)
	buf.Write(h.Predecessor.Bytes())
	binary.Write(buf, enc, h.Timestamp.Unix())
	buf.WriteByte(h.ValidationPass)
	buf.Write(h.OperationsHash.Bytes())
	var fitnessLen int
	for _, v := range h.Fitness {
		fitnessLen += len(v)
	}
	binary.Write(buf, enc, uint32(fitnessLen+4*len(h.Fitness)))
	for _, v := range h.Fitness {
		binary.Write(buf, enc, uint32(len(v)))
		buf.Write(v)
	}
	buf.Write(h.Context.Bytes())
	buf.Write(h.PayloadHash.Bytes())
	binary.Write(buf, enc, uint32(h.PayloadRound))
	buf.Write(h.ProofOfWorkNonce)
	if h.SeedNonceHash.IsValid() {
		buf.WriteByte(0xff)
		buf.Write(h.SeedNonceHash.Bytes())
	} else {
		buf.WriteByte(0x0)
	}
	// BROKEN: merging multiple vote flags is undocumented
	buf.WriteByte(h.LbVote.Tag() | (h.AiVote.Tag() << 2))
	if h.Signature.IsValid() {
		buf.Write(h.Signature.Data) // raw, no tag!
	}
	return nil
}

func (h *BlockHeader) DecodeBuffer(buf *bytes.Buffer) (err error) {
	h.Level, err = readInt32(buf.Next(4))
	if err != nil {
		return
	}
	h.Proto, err = readByte(buf.Next(1))
	if err != nil {
		return
	}
	if err = h.Predecessor.UnmarshalBinary(buf.Next(32)); err != nil {
		return
	}
	var i64 int64
	i64, err = readInt64(buf.Next(8))
	if err != nil {
		return
	}
	h.Timestamp = time.Unix(i64, 0).UTC()
	h.ValidationPass, err = readByte(buf.Next(1))
	if err != nil {
		return
	}
	if err = h.OperationsHash.UnmarshalBinary(buf.Next(32)); err != nil {
		return
	}
	var l int32
	l, err = readInt32(buf.Next(4))
	if err != nil {
		return
	}
	h.Fitness = make([]tezos.HexBytes, 0)
	for l > 0 {
		var n int32
		n, err = readInt32(buf.Next(4))
		if err != nil {
			return
		}
		b := make([]byte, int(n))
		copy(b, buf.Next(int(n)))
		h.Fitness = append(h.Fitness, b)
		l -= n + 4
	}
	if err = h.Context.UnmarshalBinary(buf.Next(32)); err != nil {
		return
	}
	if err = h.PayloadHash.UnmarshalBinary(buf.Next(32)); err != nil {
		return
	}
	l, err = readInt32(buf.Next(4))
	if err != nil {
		return
	}
	h.PayloadRound = int(l)
	h.ProofOfWorkNonce = make([]byte, 8)
	copy(h.ProofOfWorkNonce[:], buf.Next(8))
	var ok bool
	ok, err = readBool(buf.Next(1))
	if err != nil {
		return
	}
	if ok {
		if err = h.SeedNonceHash.UnmarshalBinary(buf.Next(32)); err != nil {
			return
		}
	}
	// BROKEN: merging multiple vote flags is undocumented
	b := buf.Next(1)
	if len(b) > 0 {
		if err = h.LbVote.UnmarshalBinary([]byte{b[0] & 3}); err != nil {
			return
		}
		if err = h.AiVote.UnmarshalBinary([]byte{(b[0] >> 2) & 3}); err != nil {
			return
		}
	}
	// conditionally read signature
	if buf.Len() > 0 {
		err = h.Signature.UnmarshalBinary(buf.Next(64))
		if err != nil {
			return
		}
	}
	return nil
}

func (h BlockHeader) MarshalBinary() ([]byte, error) {
	buf := bytes.NewBuffer(nil)
	err := h.EncodeBuffer(buf)
	return buf.Bytes(), err
}

func (h *BlockHeader) UnmarshalBinary(data []byte) error {
	return h.DecodeBuffer(bytes.NewBuffer(data))
}