core,dao: save contract metadata on migration

After contract is migrated there is no way to retrieve it's state.
This commit implements some metadata for NEP5 contracts, so that
values important for diplaying transfer log aren't lost.

pkg/core/blockchain.go

@@ -994,6 +994,12 @@ func (bc *Blockchain) GetNEP5Balances(acc util.Uint160) *state.NEP5Balances {
 	return bs
 }
 
+// GetNEP5Metadata returns NEP5 metadata for the contract h.
+// Note: it is currently saved only for migrated contracts.
+func (bc *Blockchain) GetNEP5Metadata(h util.Uint160) (*state.NEP5Metadata, error) {
+	return bc.dao.GetNEP5Metadata(h)
+}
+
 // LastBatch returns last persisted storage batch.
 func (bc *Blockchain) LastBatch() *storage.MemBatch {
 	return bc.lastBatch

pkg/core/blockchainer.go

@@ -35,6 +35,7 @@ type Blockchainer interface {
 	GetAssetState(util.Uint256) *state.Asset
 	GetAccountState(util.Uint160) *state.Account
 	GetAppExecResult(util.Uint256) (*state.AppExecResult, error)
+	GetNEP5Metadata(util.Uint160) (*state.NEP5Metadata, error)
 	GetNEP5TransferLog(util.Uint160) *state.NEP5TransferLog
 	GetNEP5Balances(util.Uint160) *state.NEP5Balances
 	GetValidators(txes ...*transaction.Transaction) ([]*keys.PublicKey, error)

pkg/core/dao/dao.go

@@ -35,6 +35,7 @@ type DAO interface {
 	GetCurrentStateRootHeight() (uint32, error)
 	GetHeaderHashes() ([]util.Uint256, error)
 	GetNEP5Balances(acc util.Uint160) (*state.NEP5Balances, error)
+	GetNEP5Metadata(h util.Uint160) (*state.NEP5Metadata, error)
 	GetNEP5TransferLog(acc util.Uint160, index uint32) (*state.NEP5TransferLog, error)
 	GetStateRoot(height uint32) (*state.MPTRootState, error)
 	PutStateRoot(root *state.MPTRootState) error
@@ -58,6 +59,7 @@ type DAO interface {
 	PutContractState(cs *state.Contract) error
 	PutCurrentHeader(hashAndIndex []byte) error
 	PutNEP5Balances(acc util.Uint160, bs *state.NEP5Balances) error
+	PutNEP5Metadata(h util.Uint160, meta *state.NEP5Metadata) error
 	PutNEP5TransferLog(acc util.Uint160, index uint32, lg *state.NEP5TransferLog) error
 	PutStorageItem(scripthash util.Uint160, key []byte, si *state.StorageItem) error
 	PutUnspentCoinState(hash util.Uint256, ucs *state.UnspentCoin) error
@@ -215,6 +217,22 @@ func (dao *Simple) DeleteContractState(hash util.Uint160) error {
 	return dao.Store.Delete(key)
 }
 
+// GetNEP5Metadata returns saved NEP5 metadata for the contract h.
+func (dao *Simple) GetNEP5Metadata(h util.Uint160) (*state.NEP5Metadata, error) {
+	key := storage.AppendPrefix(storage.STMigration, h.BytesBE())
+	m := new(state.NEP5Metadata)
+	if err := dao.GetAndDecode(m, key); err != nil {
+		return nil, err
+	}
+	return m, nil
+}
+
+// PutNEP5Metadata saves NEP5 metadata for the contract h.
+func (dao *Simple) PutNEP5Metadata(h util.Uint160, m *state.NEP5Metadata) error {
+	key := storage.AppendPrefix(storage.STMigration, h.BytesBE())
+	return dao.Put(m, key)
+}
+
 // -- end contracts.
 
 // -- start nep5 balances.

pkg/core/interop_neo.go

@@ -12,10 +12,12 @@ import (
 	"github.com/nspcc-dev/neo-go/pkg/core/storage"
 	"github.com/nspcc-dev/neo-go/pkg/core/transaction"
 	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
+	"github.com/nspcc-dev/neo-go/pkg/io"
 	"github.com/nspcc-dev/neo-go/pkg/smartcontract"
 	"github.com/nspcc-dev/neo-go/pkg/smartcontract/trigger"
 	"github.com/nspcc-dev/neo-go/pkg/util"
 	"github.com/nspcc-dev/neo-go/pkg/vm"
+	"github.com/nspcc-dev/neo-go/pkg/vm/emit"
 	gherr "github.com/pkg/errors"
 )
 
@@ -583,8 +585,8 @@ func (ic *interopContext) contractMigrate(v *vm.VM) error {
 		if err != nil {
 			return err
 		}
+		hash := getContextScriptHash(v, 0)
 		if contract.HasStorage() {
-			hash := getContextScriptHash(v, 0)
 			siMap, err := ic.dao.GetStorageItems(hash, nil)
 			if err != nil {
 				return err
@@ -598,6 +600,26 @@ func (ic *interopContext) contractMigrate(v *vm.VM) error {
 				}
 			}
 			ic.dao.MigrateNEP5Balances(hash, contract.ScriptHash())
+
+			// save NEP5 metadata if any
+			v := ic.bc.GetTestVM()
+			w := io.NewBufBinWriter()
+			emit.AppCallWithOperationAndArgs(w.BinWriter, hash, "decimals")
+			v.SetGasLimit(ic.bc.GetConfig().FreeGasLimit)
+			v.Load(w.Bytes())
+			if err := v.Run(); err == nil && v.Estack().Len() == 1 {
+				res := v.Estack().Pop().Item().ToContractParameter(map[vm.StackItem]bool{})
+				d := int64(-1)
+				switch res.Type {
+				case smartcontract.IntegerType:
+					d = res.Value.(int64)
+				case smartcontract.ByteArrayType:
+					d = emit.BytesToInt(res.Value.([]byte)).Int64()
+				}
+				if d >= 0 {
+					ic.dao.PutNEP5Metadata(hash, &state.NEP5Metadata{Decimals: d})
+				}
+			}
 		}
 	}
 	v.Estack().PushVal(vm.NewInteropItem(contract))

pkg/core/state/nep5.go

@@ -49,6 +49,11 @@ type NEP5Balances struct {
 	NextTransferBatch uint32
 }
 
+// NEP5Metadata is a metadata for NEP5 contracts.
+type NEP5Metadata struct {
+	Decimals int64
+}
+
 // NewNEP5Balances returns new NEP5Balances.
 func NewNEP5Balances() *NEP5Balances {
 	return &NEP5Balances{
@@ -81,6 +86,16 @@ func (bs *NEP5Balances) EncodeBinary(w *io.BinWriter) {
 	}
 }
 
+// DecodeBinary implements io.Serializable interface.
+func (bs *NEP5Metadata) DecodeBinary(r *io.BinReader) {
+	bs.Decimals = int64(r.ReadU64LE())
+}
+
+// EncodeBinary implements io.Serializable interface.
+func (bs *NEP5Metadata) EncodeBinary(w *io.BinWriter) {
+	w.WriteU64LE(uint64(bs.Decimals))
+}
+
 // Append appends single transfer to a log.
 func (lg *NEP5TransferLog) Append(tr *NEP5Transfer) error {
 	w := io.NewBufBinWriter()

pkg/core/storage/store.go

@@ -17,6 +17,7 @@ const (
 	STAsset           KeyPrefix = 0x4c
 	STNotification    KeyPrefix = 0x4d
 	STContract        KeyPrefix = 0x50
+	STMigration       KeyPrefix = 0x51
 	STStorage         KeyPrefix = 0x70
 	STNEP5Transfers   KeyPrefix = 0x72
 	STNEP5Balances    KeyPrefix = 0x73

pkg/network/helper_test.go

@@ -93,6 +93,9 @@ func (chain testChain) GetAssetState(util.Uint256) *state.Asset {
 func (chain testChain) GetAccountState(util.Uint160) *state.Account {
 	panic("TODO")
 }
+func (chain testChain) GetNEP5Metadata(util.Uint160) (*state.NEP5Metadata, error) {
+	panic("TODO")
+}
 func (chain testChain) GetNEP5TransferLog(util.Uint160) *state.NEP5TransferLog {
 	panic("TODO")
 }