channel: Implement channel.Backend interface

channel/backend.go

@@ -0,0 +1,54 @@
+package channel
+
+import (
+	"crypto/sha256"
+	"perun.network/go-perun/channel"
+	"perun.network/go-perun/wallet"
+	"perun.network/perun-stellar-backend/channel/types"
+	"perun.network/perun-stellar-backend/wire"
+)
+
+type backend struct{}
+
+var Backend = backend{}
+
+func init() {
+	channel.SetBackend(Backend)
+}
+
+func (b backend) CalcID(params *channel.Params) channel.ID {
+	wp := wire.MustMakeParams(*params)
+	bytes, err := wp.MarshalBinary()
+	if err != nil {
+		panic(err)
+	}
+	return sha256.Sum256(bytes)
+}
+
+func (b backend) Sign(account wallet.Account, state *channel.State) (wallet.Sig, error) {
+	bytes, err := EncodeState(state)
+	if err != nil {
+		return nil, err
+	}
+	return account.SignData(bytes)
+}
+
+func (b backend) Verify(addr wallet.Address, state *channel.State, sig wallet.Sig) (bool, error) {
+	bytes, err := EncodeState(state)
+	if err != nil {
+		return false, err
+	}
+	return wallet.VerifySignature(bytes, sig, addr)
+}
+
+func (b backend) NewAsset() channel.Asset {
+	return &types.StellarAsset{}
+}
+
+func EncodeState(state *channel.State) ([]byte, error) {
+	ws, err := wire.MakeState(*state)
+	if err != nil {
+		return nil, err
+	}
+	return ws.MarshalBinary()
+}