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issuance.go
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/
issuance.go
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package transaction
import (
"bytes"
"encoding/json"
"errors"
"github.com/btcsuite/btcd/chaincfg/chainhash"
"github.com/vulpemventures/fastsha256"
"github.com/vulpemventures/go-elements/elementsutil"
"github.com/vulpemventures/go-elements/internal/bufferutil"
)
// IssuanceEntity defines one of the fields of the issuance contract
type IssuanceEntity struct {
Domain string `json:"domain"`
}
// IssuanceContract defines the structure of the Ricardian contract of the issuance
type IssuanceContract struct {
Name string `json:"name"`
Ticker string `json:"ticker"`
Version uint `json:"version"`
Precision uint `json:"precision"`
Entity IssuanceEntity `json:"entity"`
}
// TxIssuance defines the type for Issuance field in TxInput
type TxIssuance struct {
AssetBlindingNonce []byte
AssetEntropy []byte
AssetAmount []byte
TokenAmount []byte
}
// IsReissuance returns whether the issuance is an asset re-issuance
func (issuance *TxIssuance) IsReissuance() bool {
return !bytes.Equal(issuance.AssetBlindingNonce, Zero[:])
}
// HasTokenAmount returns whether the token amount is defined for the issuance
func (issuance *TxIssuance) HasTokenAmount() bool {
return len(issuance.TokenAmount) > 1
}
// TxIssuanceExtended adds fields to the issuance type that are not encoded in
// the transaction
type TxIssuanceExtended struct {
TxIssuance
Precision uint
ContractHash []byte
}
// NewTxIssuanceFromInput returns the extended issuance for the given input
func NewTxIssuanceFromInput(in *TxInput) (*TxIssuanceExtended, error) {
if in.Issuance.IsReissuance() {
return NewTxIssuanceFromEntropy(in.Issuance.AssetEntropy), nil
}
iss := NewTxIssuanceFromContractHash(in.Issuance.AssetEntropy)
if err := iss.GenerateEntropy(in.Hash, in.Index); err != nil {
return nil, err
}
return iss, nil
}
// NewTxIssuanceFromContractHash returns a new issuance instance from contract hash
func NewTxIssuanceFromContractHash(contractHash []byte) *TxIssuanceExtended {
return &TxIssuanceExtended{ContractHash: contractHash}
}
// NewTxIssuanceFromEntropy returns a new issuance instance from entropy
func NewTxIssuanceFromEntropy(entropy []byte) *TxIssuanceExtended {
issuance := &TxIssuanceExtended{
TxIssuance: TxIssuance{AssetEntropy: entropy},
}
return issuance
}
// NewTxIssuance returns a new issuance instance
func NewTxIssuance(
assetAmount uint64,
tokenAmount uint64,
precision uint,
contract *IssuanceContract,
) (*TxIssuanceExtended, error) {
if assetAmount < 0 {
return nil, errors.New("invalid asset amount")
}
if tokenAmount < 0 {
return nil, errors.New("invalid token amount")
}
if precision < 0 || precision > 8 {
return nil, errors.New("invalid precision")
}
// Use the default `0x00..00` 32-byte array if contract is not set
contractHash := make([]byte, 32)
if contract != nil {
if contract.Precision != precision {
return nil, errors.New(
"precision declared in contract does not match the one" +
"set as argument",
)
}
serializedContract, err := json.Marshal(contract)
if err != nil {
return nil, err
}
contractHash = chainhash.HashB(serializedContract)
}
confAssetAmount, err := toConfidentialAssetAmount(
assetAmount,
)
if err != nil {
return nil, err
}
confTokenAmount, err := toConfidentialTokenAmount(
tokenAmount,
)
if err != nil {
return nil, err
}
issuance := TxIssuance{
AssetAmount: confAssetAmount,
TokenAmount: confTokenAmount,
AssetBlindingNonce: make([]byte, 32),
}
return &TxIssuanceExtended{
TxIssuance: issuance,
Precision: precision,
ContractHash: contractHash,
}, nil
}
// GenerateEntropy generates the entropy from which the hash of the asset and
// of the reissuance token are calculated
func (issuance *TxIssuanceExtended) GenerateEntropy(inTxHash []byte, inTxIndex uint32) error {
if len(inTxHash) != 32 {
return errors.New("invalid tx hash length")
}
s, err := bufferutil.NewSerializer(nil)
if err != nil {
return err
}
err = s.WriteSlice(inTxHash)
if err != nil {
return err
}
err = s.WriteUint32(inTxIndex)
if err != nil {
return err
}
buf := chainhash.DoubleHashB(s.Bytes())
buf = append(buf, issuance.ContractHash...)
entropy := fastsha256.MidState256(buf)
issuance.TxIssuance.AssetEntropy = entropy[:]
return nil
}
// GenerateAsset calculates the asset hash for the given issuance
func (issuance *TxIssuanceExtended) GenerateAsset() ([]byte, error) {
if issuance.TxIssuance.AssetEntropy == nil || len(issuance.TxIssuance.AssetEntropy) <= 0 {
return nil, errors.New("issuance entropy must not be nil")
}
buf := append(issuance.TxIssuance.AssetEntropy, make([]byte, 32)...)
asset := fastsha256.MidState256(buf)
return asset[:], nil
}
// GenerateReissuanceToken calculates the asset hash for the given issuance
func (issuance *TxIssuanceExtended) GenerateReissuanceToken(flag uint) ([]byte, error) {
if issuance.TxIssuance.AssetEntropy == nil || len(issuance.TxIssuance.AssetEntropy) <= 0 {
return nil, errors.New("issuance entropy must not be nil")
}
if flag != 0 && flag != 1 {
return nil, errors.New("invalid flag for reissuance token")
}
buf := make([]byte, 32)
buf[0] = byte(flag + 1)
buf = append(issuance.TxIssuance.AssetEntropy, buf...)
token := fastsha256.MidState256(buf)
return token[:], nil
}
func toConfidentialAssetAmount(assetAmount uint64) ([]byte, error) {
confAmount, err := elementsutil.SatoshiToElementsValue(assetAmount)
if err != nil {
return nil, err
}
return confAmount[:], nil
}
func toConfidentialTokenAmount(tokenAmount uint64) ([]byte, error) {
if tokenAmount == 0 {
return []byte{0x00}, nil
}
confAmount, err := elementsutil.SatoshiToElementsValue(tokenAmount)
if err != nil {
return nil, err
}
return confAmount[:], nil
}