[#54] morph: Introduce ContractStorageReader

* Implement MorphRuleChainStorageReader interface to make
  possible to read from Policy contract without wallets.

Signed-off-by: Airat Arifullin <aarifullin@yadro.com>

pkg/engine/chain_router.go

@@ -6,18 +6,18 @@ import (
 )
 
 type defaultChainRouter struct {
-	morph MorphRuleChainStorage
+	morph MorphRuleChainStorageReader
 
 	local LocalOverrideStorage
 }
 
-func NewDefaultChainRouter(morph MorphRuleChainStorage) ChainRouter {
+func NewDefaultChainRouter(morph MorphRuleChainStorageReader) ChainRouter {
 	return &defaultChainRouter{
 		morph: morph,
 	}
 }
 
-func NewDefaultChainRouterWithLocalOverrides(morph MorphRuleChainStorage, local LocalOverrideStorage) ChainRouter {
+func NewDefaultChainRouterWithLocalOverrides(morph MorphRuleChainStorageReader, local LocalOverrideStorage) ChainRouter {
 	return &defaultChainRouter{
 		morph: morph,
 		local: local,

pkg/morph/policy/policy_contract_storage.go

@@ -22,13 +22,20 @@ var (
 	ErrEngineTargetTypeUnsupported = errors.New("this target type is not supported yet")
 )
 
-// ContractStorage is the interface to manage chain rules within the policy contract.
+// ContractStorage is the interface to manage chain rules within Policy contract.
 type ContractStorage struct {
 	contractInterface *client.Contract
 }
 
 var _ engine.MorphRuleChainStorage = (*ContractStorage)(nil)
 
+// ContractStorageReader is the interface to read data from Policy contract.
+type ContractStorageReader struct {
+	contractReaderInterface *client.ContractReader
+}
+
+var _ engine.MorphRuleChainStorageReader = (*ContractStorageReader)(nil)
+
 func NewContractStorage(actor client.Actor, contract util.Uint160) *ContractStorage {
 	return &ContractStorage{
 		contractInterface: client.New(actor, contract),
@@ -112,6 +119,43 @@ func (s *ContractStorage) SetAdmin(addr util.Uint160) (util.Uint256, uint32, err
 	return s.contractInterface.SetAdmin(addr)
 }
 
+func NewContractStorageReader(inv client.Invoker, contract util.Uint160) *ContractStorageReader {
+	return &ContractStorageReader{
+		contractReaderInterface: client.NewReader(inv, contract),
+	}
+}
+
+func (s *ContractStorageReader) ListMorphRuleChains(name chain.Name, target engine.Target) ([]*chain.Chain, error) {
+	kind, err := policyKind(target.Type)
+	if err != nil {
+		return nil, err
+	}
+
+	items, err := s.contractReaderInterface.ListChainsByPrefix(big.NewInt(int64(kind)), target.Name, []byte(name))
+	if err != nil {
+		return nil, err
+	}
+
+	var chains []*chain.Chain
+	for _, item := range items {
+		serialized, err := bytesFromStackItem(item)
+		if err != nil {
+			return nil, err
+		}
+		c := new(chain.Chain)
+		if err := c.DecodeBytes(serialized); err != nil {
+			return nil, err
+		}
+		chains = append(chains, c)
+	}
+
+	return chains, nil
+}
+
+func (s *ContractStorageReader) GetAdmin() (util.Uint160, error) {
+	return s.contractReaderInterface.GetAdmin()
+}
+
 func bytesFromStackItem(param stackitem.Item) ([]byte, error) {
 	switch param.Type() {
 	case stackitem.BufferT, stackitem.ByteArrayT, stackitem.IntegerT: