package native import ( "errors" "fmt" "math/big" "github.com/nspcc-dev/neo-go/pkg/core/dao" "github.com/nspcc-dev/neo-go/pkg/core/interop" "github.com/nspcc-dev/neo-go/pkg/core/interop/runtime" "github.com/nspcc-dev/neo-go/pkg/core/state" "github.com/nspcc-dev/neo-go/pkg/encoding/bigint" "github.com/nspcc-dev/neo-go/pkg/smartcontract" "github.com/nspcc-dev/neo-go/pkg/smartcontract/manifest" "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/stackitem" ) // prefixAccount is the standard prefix used to store account data. const prefixAccount = 20 // makeAccountKey creates a key from account script hash. func makeAccountKey(h util.Uint160) []byte { k := make([]byte, util.Uint160Size+1) k[0] = prefixAccount copy(k[1:], h.BytesBE()) return k } // nep5TokenNative represents NEP-5 token contract. type nep5TokenNative struct { interop.ContractMD symbol string decimals int64 factor int64 onPersist func(*interop.Context) error incBalance func(*interop.Context, util.Uint160, *state.StorageItem, *big.Int) error } // totalSupplyKey is the key used to store totalSupply value. var totalSupplyKey = []byte{11} func (c *nep5TokenNative) Metadata() *interop.ContractMD { return &c.ContractMD } var _ interop.Contract = (*nep5TokenNative)(nil) func newNEP5Native(name string) *nep5TokenNative { n := &nep5TokenNative{ContractMD: *interop.NewContractMD(name)} n.Manifest.SupportedStandards = []string{manifest.NEP5StandardName} desc := newDescriptor("name", smartcontract.StringType) md := newMethodAndPrice(n.Name, 0, smartcontract.NoneFlag) n.AddMethod(md, desc, true) desc = newDescriptor("symbol", smartcontract.StringType) md = newMethodAndPrice(n.Symbol, 0, smartcontract.NoneFlag) n.AddMethod(md, desc, true) desc = newDescriptor("decimals", smartcontract.IntegerType) md = newMethodAndPrice(n.Decimals, 0, smartcontract.NoneFlag) n.AddMethod(md, desc, true) desc = newDescriptor("totalSupply", smartcontract.IntegerType) md = newMethodAndPrice(n.TotalSupply, 1000000, smartcontract.AllowStates) n.AddMethod(md, desc, true) desc = newDescriptor("balanceOf", smartcontract.IntegerType, manifest.NewParameter("account", smartcontract.Hash160Type)) md = newMethodAndPrice(n.balanceOf, 1000000, smartcontract.AllowStates) n.AddMethod(md, desc, true) desc = newDescriptor("transfer", smartcontract.BoolType, manifest.NewParameter("from", smartcontract.Hash160Type), manifest.NewParameter("to", smartcontract.Hash160Type), manifest.NewParameter("amount", smartcontract.IntegerType), ) md = newMethodAndPrice(n.Transfer, 8000000, smartcontract.AllowModifyStates) n.AddMethod(md, desc, false) desc = newDescriptor("onPersist", smartcontract.VoidType) md = newMethodAndPrice(getOnPersistWrapper(n.OnPersist), 0, smartcontract.AllowModifyStates) n.AddMethod(md, desc, false) n.AddEvent("Transfer", desc.Parameters...) return n } func (c *nep5TokenNative) Initialize(_ *interop.Context) error { return nil } func (c *nep5TokenNative) Name(_ *interop.Context, _ []stackitem.Item) stackitem.Item { return stackitem.NewByteArray([]byte(c.ContractMD.Name)) } func (c *nep5TokenNative) Symbol(_ *interop.Context, _ []stackitem.Item) stackitem.Item { return stackitem.NewByteArray([]byte(c.symbol)) } func (c *nep5TokenNative) Decimals(_ *interop.Context, _ []stackitem.Item) stackitem.Item { return stackitem.NewBigInteger(big.NewInt(c.decimals)) } func (c *nep5TokenNative) TotalSupply(ic *interop.Context, _ []stackitem.Item) stackitem.Item { return stackitem.NewBigInteger(c.getTotalSupply(ic.DAO)) } func (c *nep5TokenNative) getTotalSupply(d dao.DAO) *big.Int { si := d.GetStorageItem(c.ContractID, totalSupplyKey) if si == nil { return big.NewInt(0) } return bigint.FromBytes(si.Value) } func (c *nep5TokenNative) saveTotalSupply(d dao.DAO, supply *big.Int) error { si := &state.StorageItem{Value: bigint.ToBytes(supply)} return d.PutStorageItem(c.ContractID, totalSupplyKey, si) } func (c *nep5TokenNative) Transfer(ic *interop.Context, args []stackitem.Item) stackitem.Item { from := toUint160(args[0]) to := toUint160(args[1]) amount := toBigInt(args[2]) err := c.TransferInternal(ic, from, to, amount) return stackitem.NewBool(err == nil) } func addrToStackItem(u *util.Uint160) stackitem.Item { if u == nil { return stackitem.Null{} } return stackitem.NewByteArray(u.BytesBE()) } func (c *nep5TokenNative) emitTransfer(ic *interop.Context, from, to *util.Uint160, amount *big.Int) { ne := state.NotificationEvent{ ScriptHash: c.Hash, Name: "Transfer", Item: stackitem.NewArray([]stackitem.Item{ addrToStackItem(from), addrToStackItem(to), stackitem.NewBigInteger(amount), }), } ic.Notifications = append(ic.Notifications, ne) } func (c *nep5TokenNative) updateAccBalance(ic *interop.Context, acc util.Uint160, amount *big.Int) error { key := makeAccountKey(acc) si := ic.DAO.GetStorageItem(c.ContractID, key) if si == nil { if amount.Sign() <= 0 { return errors.New("insufficient funds") } si = new(state.StorageItem) } err := c.incBalance(ic, acc, si, amount) if err != nil { return err } if si.Value == nil { err = ic.DAO.DeleteStorageItem(c.ContractID, key) } else { err = ic.DAO.PutStorageItem(c.ContractID, key, si) } return err } // TransferInternal transfers NEO between accounts. func (c *nep5TokenNative) TransferInternal(ic *interop.Context, from, to util.Uint160, amount *big.Int) error { if amount.Sign() == -1 { return errors.New("negative amount") } caller := ic.VM.GetCallingScriptHash() if caller.Equals(util.Uint160{}) || !from.Equals(caller) { ok, err := runtime.CheckHashedWitness(ic, from) if err != nil { return err } else if !ok { return errors.New("invalid signature") } } isEmpty := from.Equals(to) || amount.Sign() == 0 inc := amount if isEmpty { inc = big.NewInt(0) } else { inc = new(big.Int).Neg(inc) } if err := c.updateAccBalance(ic, from, inc); err != nil { return err } if !isEmpty { if err := c.updateAccBalance(ic, to, amount); err != nil { return err } } c.emitTransfer(ic, &from, &to, amount) return nil } func (c *nep5TokenNative) balanceOf(ic *interop.Context, args []stackitem.Item) stackitem.Item { h := toUint160(args[0]) bs, err := ic.DAO.GetNEP5Balances(h) if err != nil { panic(err) } balance := bs.Trackers[c.ContractID].Balance return stackitem.NewBigInteger(&balance) } func (c *nep5TokenNative) mint(ic *interop.Context, h util.Uint160, amount *big.Int) { if amount.Sign() == 0 { return } c.addTokens(ic, h, amount) c.emitTransfer(ic, nil, &h, amount) } func (c *nep5TokenNative) burn(ic *interop.Context, h util.Uint160, amount *big.Int) { if amount.Sign() == 0 { return } c.addTokens(ic, h, new(big.Int).Neg(amount)) c.emitTransfer(ic, &h, nil, amount) } func (c *nep5TokenNative) addTokens(ic *interop.Context, h util.Uint160, amount *big.Int) { if amount.Sign() == 0 { return } key := makeAccountKey(h) si := ic.DAO.GetStorageItem(c.ContractID, key) if si == nil { si = new(state.StorageItem) } if err := c.incBalance(ic, h, si, amount); err != nil { panic(err) } if err := ic.DAO.PutStorageItem(c.ContractID, key, si); err != nil { panic(err) } supply := c.getTotalSupply(ic.DAO) supply.Add(supply, amount) err := c.saveTotalSupply(ic.DAO, supply) if err != nil { panic(err) } } func (c *nep5TokenNative) OnPersist(ic *interop.Context) error { if ic.Trigger != trigger.System { return errors.New("onPersist should be triggerred by system") } return nil } func newDescriptor(name string, ret smartcontract.ParamType, ps ...manifest.Parameter) *manifest.Method { return &manifest.Method{ Name: name, Parameters: ps, ReturnType: ret, } } func newMethodAndPrice(f interop.Method, price int64, flags smartcontract.CallFlag) *interop.MethodAndPrice { return &interop.MethodAndPrice{ Func: f, Price: price, RequiredFlags: flags, } } func toBigInt(s stackitem.Item) *big.Int { bi, err := s.TryInteger() if err != nil { panic(err) } return bi } func toUint160(s stackitem.Item) util.Uint160 { buf, err := s.TryBytes() if err != nil { panic(err) } u, err := util.Uint160DecodeBytesBE(buf) if err != nil { panic(err) } return u } func getOnPersistWrapper(f func(ic *interop.Context) error) interop.Method { return func(ic *interop.Context, _ []stackitem.Item) stackitem.Item { err := f(ic) if err != nil { panic(fmt.Errorf("OnPersist for native contract: %w", err)) } return stackitem.Null{} } }