Remove optional from load result

Makes loading of data well-defined for arbitrary object contents.
Introduce zero reference and object to represent missing or mismatched
parts.

12 files changed, 184 insertions, 182 deletions

diff --git a/include/erebos/message.h b/include/erebos/message.h
index 0b5e257..c94e8c3 100644
--- a/include/erebos/message.h
+++ b/include/erebos/message.h
@@ -14,9 +14,9 @@ class Identity;
 class DirectMessage
 {
 public:
-	const Identity & from() const;
-	const struct ZonedTime & time() const;
-	const std::string & text() const;
+	const std::optional<Identity> & from() const;
+	const std::optional<struct ZonedTime> & time() const;
+	std::string text() const;
 
 private:
 	friend class DirectMessageThread;
diff --git a/include/erebos/storage.h b/include/erebos/storage.h
index d5ae45a..d46c056 100644
--- a/include/erebos/storage.h
+++ b/include/erebos/storage.h
@@ -72,6 +72,7 @@ public:
 	PartialStorage derivePartialStorage() const;
 
 	std::optional<Ref> ref(const Digest &) const;
+	Ref zref() const;
 
 	std::optional<Object> loadObject(const Digest &) const;
 	Ref storeObject(const Object &) const;
@@ -103,6 +104,7 @@ public:
 	explicit Digest(std::array<uint8_t, size> value): value(value) {}
 	explicit Digest(const std::string &);
 	explicit operator std::string() const;
+	bool isZero() const;
 
 	const std::array<uint8_t, size> & arr() const { return value; }
 
@@ -151,6 +153,7 @@ public:
 	Ref & operator=(Ref &&) = default;
 
 	static std::optional<Ref> create(Storage, const Digest &);
+	static Ref zcreate(Storage);
 
 	constexpr operator bool() const { return true; }
 	const Object operator*() const;
@@ -265,7 +268,8 @@ class ObjectT
 public:
 	typedef std::variant<
 		RecordT<S>,
-		Blob> Variants;
+		Blob,
+		std::monostate> Variants;
 
 	ObjectT(const ObjectT<S> &) = default;
 	ObjectT(Variants content): content(content) {}
@@ -282,7 +286,7 @@ public:
 			std::vector<uint8_t>::const_iterator);
 	static std::vector<ObjectT<S>> decodeMany(const S &, const std::vector<uint8_t> &);
 	std::vector<uint8_t> encode() const;
-	static std::optional<ObjectT<S>> load(const typename S::Ref &);
+	static ObjectT<S> load(const typename S::Ref &);
 
 	std::optional<RecordT<S>> asRecord() const;
 	std::optional<Blob> asBlob() const;
@@ -317,7 +321,7 @@ public:
 	Stored & operator=(const Stored &) = default;
 	Stored & operator=(Stored &&) = default;
 
-	static std::optional<Stored<T>> load(const Ref &);
+	static Stored<T> load(const Ref &);
 	Ref store(const Storage &) const;
 
 	bool operator==(const Stored<T> & other) const
@@ -354,11 +358,9 @@ Stored<T> Storage::store(const T & val) const
 }
 
 template<typename T>
-std::optional<Stored<T>> Stored<T>::load(const Ref & ref)
+Stored<T> Stored<T>::load(const Ref & ref)
 {
-	if (auto val = T::load(ref))
-		return Stored(ref, std::make_shared<T>(val.value()));
-	return std::nullopt;
+	return Stored(ref, std::make_shared<T>(T::load(ref)));
 }
 
 template<typename T>
diff --git a/src/channel.cpp b/src/channel.cpp
index 50c5f97..b13a71e 100644
--- a/src/channel.cpp
+++ b/src/channel.cpp
@@ -22,28 +22,25 @@ Ref ChannelRequestData::store(const Storage & st) const
 	return st.storeObject(Record(std::move(items)));
 }
 
-optional<ChannelRequestData> ChannelRequestData::load(const Ref & ref)
+ChannelRequestData ChannelRequestData::load(const Ref & ref)
 {
-	auto rec = ref->asRecord();
-	if (!rec)
-		return nullopt;
-
-	remove_const<decltype(peers)>::type peers;
-	for (const auto & i : rec->items("peer"))
-		if (auto p = i.as<Signed<IdentityData>>())
-			peers.push_back(*p);
-
-	auto enc = rec->item("enc").asText();
-	if (!enc || enc != "aes-128-gcm")
-		return nullopt;
-
-	auto key = rec->item("key").as<PublicKexKey>();
-	if (!key)
-		return nullopt;
+	if (auto rec = ref->asRecord()) {
+		remove_const<decltype(peers)>::type peers;
+		for (const auto & i : rec->items("peer"))
+			if (auto p = i.as<Signed<IdentityData>>())
+				peers.push_back(*p);
+
+		if (rec->item("enc").asText() == "aes-128-gcm")
+			if (auto key = rec->item("key").as<PublicKexKey>())
+				return ChannelRequestData {
+					.peers = std::move(peers),
+					.key = *key,
+				};
+	}
 
 	return ChannelRequestData {
-		.peers = std::move(peers),
-		.key = *key,
+		.peers = {},
+		.key = Stored<PublicKexKey>::load(ref.storage().zref()),
 	};
 }
 
@@ -58,27 +55,18 @@ Ref ChannelAcceptData::store(const Storage & st) const
 	return st.storeObject(Record(std::move(items)));
 }
 
-optional<ChannelAcceptData> ChannelAcceptData::load(const Ref & ref)
+ChannelAcceptData ChannelAcceptData::load(const Ref & ref)
 {
-	auto rec = ref->asRecord();
-	if (!rec)
-		return nullopt;
-
-	auto request = rec->item("req").as<ChannelRequest>();
-	if (!request)
-		return nullopt;
-
-	auto enc = rec->item("enc").asText();
-	if (!enc || enc != "aes-128-gcm")
-		return nullopt;
-
-	auto key = rec->item("key").as<PublicKexKey>();
-	if (!key)
-		return nullopt;
+	if (auto rec = ref->asRecord())
+		if (rec->item("enc").asText() == "aes-128-gcm")
+			return ChannelAcceptData {
+				.request = *rec->item("req").as<ChannelRequest>(),
+				.key = *rec->item("key").as<PublicKexKey>(),
+			};
 
 	return ChannelAcceptData {
-		.request = *request,
-		.key = *key,
+		.request = Stored<ChannelRequest>::load(ref.storage().zref()),
+		.key = Stored<PublicKexKey>::load(ref.storage().zref()),
 	};
 }
 
@@ -114,26 +102,20 @@ Ref Channel::store(const Storage & st) const
 	return st.storeObject(Record(std::move(items)));
 }
 
-optional<Channel> Channel::load(const Ref & ref)
+Channel Channel::load(const Ref & ref)
 {
-	auto rec = ref->asRecord();
-	if (!rec)
-		return nullopt;
-
-	remove_const<decltype(peers)>::type peers;
-	for (const auto & i : rec->items("peer"))
-		if (auto p = i.as<Signed<IdentityData>>())
-			peers.push_back(*p);
-
-	auto enc = rec->item("enc").asText();
-	if (!enc || enc != "aes-128-gcm")
-		return nullopt;
-
-	auto key = rec->item("key").asBinary();
-	if (!key)
-		return nullopt;
-
-	return Channel(peers, std::move(*key));
+	if (auto rec = ref->asRecord()) {
+		remove_const<decltype(peers)>::type peers;
+		for (const auto & i : rec->items("peer"))
+			if (auto p = i.as<Signed<IdentityData>>())
+				peers.push_back(*p);
+
+		if (rec->item("enc").asText() == "aes-128-gcm")
+			if (auto key = rec->item("key").asBinary())
+				return Channel(peers, std::move(*key));
+	}
+
+	return Channel({}, {});
 }
 
 Stored<ChannelRequest> Channel::generateRequest(const Storage & st,
@@ -146,12 +128,12 @@ Stored<ChannelRequest> Channel::generateRequest(const Storage & st,
 	return signKey->sign(st.store(ChannelRequestData {
 		.peers = self.ref()->digest() < peer.ref()->digest() ?
 			vector<Stored<Signed<IdentityData>>> {
-				*Stored<Signed<IdentityData>>::load(*self.ref()),
-				*Stored<Signed<IdentityData>>::load(*peer.ref()),
+				Stored<Signed<IdentityData>>::load(*self.ref()),
+				Stored<Signed<IdentityData>>::load(*peer.ref()),
 			} :
 			vector<Stored<Signed<IdentityData>>> {
-				*Stored<Signed<IdentityData>>::load(*peer.ref()),
-				*Stored<Signed<IdentityData>>::load(*self.ref()),
+				Stored<Signed<IdentityData>>::load(*peer.ref()),
+				Stored<Signed<IdentityData>>::load(*self.ref()),
 			},
 		.key = SecretKexKey::generate(st).pub(),
 	}));
diff --git a/src/channel.h b/src/channel.h
index 100003c..1c7df30 100644
--- a/src/channel.h
+++ b/src/channel.h
@@ -9,7 +9,7 @@ namespace erebos {
 struct ChannelRequestData
 {
 	Ref store(const Storage & st) const;
-	static optional<ChannelRequestData> load(const Ref &);
+	static ChannelRequestData load(const Ref &);
 
 	const vector<Stored<Signed<IdentityData>>> peers;
 	const Stored<PublicKexKey> key;
@@ -20,7 +20,7 @@ typedef Signed<ChannelRequestData> ChannelRequest;
 struct ChannelAcceptData
 {
 	Ref store(const Storage & st) const;
-	static optional<ChannelAcceptData> load(const Ref &);
+	static ChannelAcceptData load(const Ref &);
 
 	Stored<class Channel> channel() const;
 
@@ -40,7 +40,7 @@ public:
 	{}
 
 	Ref store(const Storage & st) const;
-	static optional<Channel> load(const Ref &);
+	static Channel load(const Ref &);
 
 	static Stored<ChannelRequest> generateRequest(const Storage &,
 			const Identity & self, const Identity & peer);
diff --git a/src/identity.cpp b/src/identity.cpp
index 3cba97c..2396b9f 100644
--- a/src/identity.cpp
+++ b/src/identity.cpp
@@ -24,12 +24,8 @@ optional<Identity> Identity::load(const vector<Ref> & refs)
 	vector<Stored<Signed<IdentityData>>> data;
 	data.reserve(refs.size());
 
-	for (const auto & ref : refs) {
-		auto d = Stored<Signed<IdentityData>>::load(ref);
-		if (!d)
-			return nullopt;
-		data.push_back(*d);
-	}
+	for (const auto & ref : refs)
+		data.push_back(Stored<Signed<IdentityData>>::load(ref));
 
 	if (auto ptr = Priv::validate(data))
 		return Identity(ptr);
@@ -124,27 +120,30 @@ void Identity::Builder::owner(const Identity & val)
 	p->owner.emplace(val);
 }
 
-optional<IdentityData> IdentityData::load(const Ref & ref)
+IdentityData IdentityData::load(const Ref & ref)
 {
-	auto rec = ref->asRecord();
-	if (!rec)
-		return nullopt;
-
-	vector<Stored<Signed<IdentityData>>> prev;
-	for (auto p : rec->items("SPREV"))
-		if (const auto & x = p.as<Signed<IdentityData>>())
-			prev.push_back(x.value());
+	if (auto rec = ref->asRecord()) {
+		vector<Stored<Signed<IdentityData>>> prev;
+		for (auto p : rec->items("SPREV"))
+			if (const auto & x = p.as<Signed<IdentityData>>())
+				prev.push_back(x.value());
 
-	auto keyIdentity = rec->item("key-id").as<PublicKey>();
-	if (!keyIdentity)
-		return nullopt;
+		if (auto keyIdentity = rec->item("key-id").as<PublicKey>())
+			return IdentityData {
+				.prev = std::move(prev),
+				.name = rec->item("name").asText(),
+				.owner = rec->item("owner").as<Signed<IdentityData>>(),
+				.keyIdentity = keyIdentity.value(),
+				.keyMessage = rec->item("key-msg").as<PublicKey>(),
+			};
+	}
 
 	return IdentityData {
-		.prev = std::move(prev),
-		.name = rec->item("name").asText(),
-		.owner = rec->item("owner").as<Signed<IdentityData>>(),
-		.keyIdentity = keyIdentity.value(),
-		.keyMessage = rec->item("key-msg").as<PublicKey>(),
+		.prev = {},
+		.name = nullopt,
+		.owner = nullopt,
+		.keyIdentity = Stored<PublicKey>::load(ref.storage().zref()),
+		.keyMessage = nullopt,
 	};
 }
 
diff --git a/src/identity.h b/src/identity.h
index 92ac34f..1dfc193 100644
--- a/src/identity.h
+++ b/src/identity.h
@@ -13,7 +13,7 @@ namespace erebos {
 class IdentityData
 {
 public:
-	static optional<IdentityData> load(const Ref &);
+	static IdentityData load(const Ref &);
 	Ref store(const Storage & st) const;
 
 	const vector<Stored<Signed<IdentityData>>> prev;
diff --git a/src/message.cpp b/src/message.cpp
index b7d4bda..354703e 100644
--- a/src/message.cpp
+++ b/src/message.cpp
@@ -48,11 +48,11 @@ DirectMessage::DirectMessage(Priv * p):
 	p(p)
 {}
 
-optional<DirectMessageData> DirectMessageData::load(const Ref & ref)
+DirectMessageData DirectMessageData::load(const Ref & ref)
 {
 	auto rec = ref->asRecord();
 	if (!rec)
-		return nullopt;
+		return DirectMessageData();
 
 	vector<Stored<DirectMessageData>> prev;
 	for (auto p : rec->items("PREV"))
@@ -60,16 +60,10 @@ optional<DirectMessageData> DirectMessageData::load(const Ref & ref)
 			prev.push_back(*x);
 
 	auto fref = rec->item("from").asRef();
-	if (!fref)
-		return nullopt;
-
-	auto from = Identity::load(*fref);
-	if (!from)
-		return nullopt;
 
 	return DirectMessageData {
 		.prev = std::move(prev),
-		.from = *from,
+		.from = fref ? Identity::load(*fref) : nullopt,
 		.time = *rec->item("time").asDate(),
 		.text = rec->item("text").asText().value(),
 	};
@@ -81,27 +75,32 @@ Ref DirectMessageData::store(const Storage & st) const
 
 	for (const auto prev : prev)
 		items.emplace_back("PREV", prev.ref());
-	items.emplace_back("from", from.ref().value());
-	items.emplace_back("time", time);
-	items.emplace_back("text", text);
+	if (from)
+		items.emplace_back("from", from->ref().value());
+	if (time)
+		items.emplace_back("time", *time);
+	if (text)
+		items.emplace_back("text", *text);
 
 	return st.storeObject(Record(std::move(items)));
 }
 
 
-const Identity & DirectMessage::from() const
+const optional<Identity> & DirectMessage::from() const
 {
 	return p->data->from;
 }
 
-const ZonedTime & DirectMessage::time() const
+const optional<ZonedTime> & DirectMessage::time() const
 {
 	return p->data->time;
 }
 
-const string & DirectMessage::text() const
+string DirectMessage::text() const
 {
-	return p->data->text;
+	if (p->data->text)
+		return p->data->text.value();
+	return "";
 }
 
 
@@ -138,7 +137,7 @@ DirectMessageThread::Iterator & DirectMessageThread::Iterator::operator++()
 		auto ncur = p->next[0];
 
 		for (const auto & m : p->next)
-			if (m->time.time >= ncur->time.time)
+			if (!ncur->time || (m->time && m->time->time >= ncur->time->time))
 				ncur = m;
 
 		p->current.emplace(DirectMessage(new DirectMessage::Priv {
@@ -216,10 +215,6 @@ UUID DirectMessageService::uuid() const
 
 void DirectMessageService::handle(Context & ctx) const
 {
-	auto dm = Stored<DirectMessageData>::load(ctx.ref());
-	if (!dm)
-		return;
-
 	auto pid = ctx.peer().identity();
 	if (!pid)
 		return;
@@ -228,7 +223,7 @@ void DirectMessageService::handle(Context & ctx) const
 	unique_lock lock(threadLock);
 
 	vector<Stored<DirectMessageData>> head(DirectMessageThread::Priv::getThreadLocked(powner).p->head);
-	head.push_back(*dm);
+	head.push_back(Stored<DirectMessageData>::load(ctx.ref()));
 	filterAncestors(head);
 	auto dmt = DirectMessageThread::Priv::updateThreadLocked(powner, std::move(head));
 
diff --git a/src/message.h b/src/message.h
index 7e0f597..c4a3549 100644
--- a/src/message.h
+++ b/src/message.h
@@ -19,13 +19,13 @@ namespace erebos {
 
 struct DirectMessageData
 {
-	static optional<DirectMessageData> load(const Ref &);
+	static DirectMessageData load(const Ref &);
 	Ref store(const Storage &) const;
 
 	vector<Stored<DirectMessageData>> prev;
-	Identity from;
-	ZonedTime time;
-	string text;
+	optional<Identity> from;
+	optional<ZonedTime> time;
+	optional<string> text;
 };
 
 struct DirectMessage::Priv
diff --git a/src/network.cpp b/src/network.cpp
index b31d949..91f1923 100644
--- a/src/network.cpp
+++ b/src/network.cpp
@@ -298,7 +298,7 @@ Server::Peer & Server::Priv::getPeer(const sockaddr_in & paddr)
 void Server::Priv::handlePacket(Server::Peer & peer, const TransportHeader & header, ReplyBuilder & reply)
 {
 	unordered_set<Digest> plaintextRefs;
-	for (const auto & obj : collectStoredObjects(*Stored<Object>::load(*self.ref())))
+	for (const auto & obj : collectStoredObjects(Stored<Object>::load(*self.ref())))
 		plaintextRefs.insert(obj.ref().digest());
 
 	optional<UUID> serviceType;
@@ -397,9 +397,11 @@ void Server::Priv::handlePacket(Server::Peer & peer, const TransportHeader & hea
 
 				auto cres = peer.tempStorage.copy(pref);
 				if (auto r = std::get_if<Ref>(&cres)) {
-					if (auto acc = ChannelAccept::load(*r)) {
+					auto acc = ChannelAccept::load(*r);
+					if (holds_alternative<Identity>(peer.identity) &&
+							acc.isSignedBy(std::get<Identity>(peer.identity).keyMessage())) {
 						reply.header({ TransportHeader::Type::Acknowledged, pref });
-						peer.channel.emplace<Stored<Channel>>(acc->data->channel());
+						peer.channel.emplace<Stored<Channel>>(acc.data->channel());
 					}
 				}
 			}
@@ -485,8 +487,10 @@ void Server::Peer::updateChannel(ReplyBuilder & reply)
 
 	if (holds_alternative<shared_ptr<WaitingRef>>(channel)) {
 		if (auto ref = std::get<shared_ptr<WaitingRef>>(channel)->check(reply)) {
-			if (auto req = Stored<ChannelRequest>::load(*ref)) {
-				if (auto acc = Channel::acceptRequest(server.self, std::get<Identity>(identity), *req)) {
+			auto req = Stored<ChannelRequest>::load(*ref);
+			if (holds_alternative<Identity>(identity) &&
+					req->isSignedBy(std::get<Identity>(identity).keyMessage())) {
+				if (auto acc = Channel::acceptRequest(server.self, std::get<Identity>(identity), req)) {
 					channel.emplace<Stored<ChannelAccept>>(*acc);
 					reply.header({ TransportHeader::Type::ChannelAccept, acc->ref() });
 					reply.body(acc->ref());
diff --git a/src/pubkey.cpp b/src/pubkey.cpp
index 0e83136..6d85d33 100644
--- a/src/pubkey.cpp
+++ b/src/pubkey.cpp
@@ -8,11 +8,11 @@ using std::string;
 
 using namespace erebos;
 
-optional<PublicKey> PublicKey::load(const Ref & ref)
+PublicKey PublicKey::load(const Ref & ref)
 {
 	auto rec = ref->asRecord();
 	if (!rec)
-		return nullopt;
+		return PublicKey(nullptr);
 
 	if (auto ktype = rec->item("type").asText())
 		if (ktype.value() != "ed25519")
@@ -22,7 +22,7 @@ optional<PublicKey> PublicKey::load(const Ref & ref)
 		return PublicKey(EVP_PKEY_new_raw_public_key(EVP_PKEY_ED25519, nullptr,
 					pubkey.value().data(), pubkey.value().size()));
 
-	return nullopt;
+	return PublicKey(nullptr);
 }
 
 Ref PublicKey::store(const Storage & st) const
@@ -31,12 +31,14 @@ Ref PublicKey::store(const Storage & st) const
 
 	items.emplace_back("type", "ed25519");
 
-	vector<uint8_t> keyData;
-	size_t keyLen;
-	EVP_PKEY_get_raw_public_key(key.get(), nullptr, &keyLen);
-	keyData.resize(keyLen);
-	EVP_PKEY_get_raw_public_key(key.get(), keyData.data(), &keyLen);
-	items.emplace_back("pubkey", keyData);
+	if (key) {
+		vector<uint8_t> keyData;
+		size_t keyLen;
+		EVP_PKEY_get_raw_public_key(key.get(), nullptr, &keyLen);
+		keyData.resize(keyLen);
+		EVP_PKEY_get_raw_public_key(key.get(), keyData.data(), &keyLen);
+		items.emplace_back("pubkey", keyData);
+	}
 
 	return st.storeObject(Record(std::move(items)));
 }
@@ -110,19 +112,14 @@ vector<uint8_t> SecretKey::sign(const Digest & dgst) const
 	return sigData;
 }
 
-optional<Signature> Signature::load(const Ref & ref)
+Signature Signature::load(const Ref & ref)
 {
-	auto rec = ref->asRecord();
-	if (!rec)
-		return nullopt;
+	if (auto rec = ref->asRecord())
+		if (auto key = rec->item("key").as<PublicKey>())
+			if (auto sig = rec->item("sig").asBinary())
+				return Signature(*key, *sig);
 
-	auto key = rec->item("key").as<PublicKey>();
-	auto sig = rec->item("sig").asBinary();
-
-	if (!key || !sig)
-		return nullopt;
-
-	return Signature(*key, *sig);
+	return Signature(Stored<PublicKey>::load(ref.storage().zref()), {});
 }
 
 Ref Signature::store(const Storage & st) const
@@ -151,11 +148,11 @@ bool Signature::verify(const Ref & ref) const
 }
 
 
-optional<PublicKexKey> PublicKexKey::load(const Ref & ref)
+PublicKexKey PublicKexKey::load(const Ref & ref)
 {
 	auto rec = ref->asRecord();
 	if (!rec)
-		return nullopt;
+		return PublicKexKey(nullptr);
 
 	if (auto ktype = rec->item("type").asText())
 		if (ktype.value() != "x25519")
@@ -165,7 +162,7 @@ optional<PublicKexKey> PublicKexKey::load(const Ref & ref)
 		return PublicKexKey(EVP_PKEY_new_raw_public_key(EVP_PKEY_X25519, nullptr,
 					pubkey.value().data(), pubkey.value().size()));
 
-	return nullopt;
+	return PublicKexKey(nullptr);
 }
 
 Ref PublicKexKey::store(const Storage & st) const
@@ -174,12 +171,14 @@ Ref PublicKexKey::store(const Storage & st) const
 
 	items.emplace_back("type", "x25519");
 
-	vector<uint8_t> keyData;
-	size_t keyLen;
-	EVP_PKEY_get_raw_public_key(key.get(), nullptr, &keyLen);
-	keyData.resize(keyLen);
-	EVP_PKEY_get_raw_public_key(key.get(), keyData.data(), &keyLen);
-	items.emplace_back("pubkey", keyData);
+	if (key) {
+		vector<uint8_t> keyData;
+		size_t keyLen;
+		EVP_PKEY_get_raw_public_key(key.get(), nullptr, &keyLen);
+		keyData.resize(keyLen);
+		EVP_PKEY_get_raw_public_key(key.get(), keyData.data(), &keyLen);
+		items.emplace_back("pubkey", keyData);
+	}
 
 	return st.storeObject(Record(std::move(items)));
 }
diff --git a/src/pubkey.h b/src/pubkey.h
index c922dc7..7b80752 100644
--- a/src/pubkey.h
+++ b/src/pubkey.h
@@ -18,7 +18,7 @@ class PublicKey
 		key(key, EVP_PKEY_free) {}
 	friend class SecretKey;
 public:
-	static optional<PublicKey> load(const Ref &);
+	static PublicKey load(const Ref &);
 	Ref store(const Storage &) const;
 
 	const shared_ptr<EVP_PKEY> key;
@@ -49,7 +49,7 @@ private:
 class Signature
 {
 public:
-	static optional<Signature> load(const Ref &);
+	static Signature load(const Ref &);
 	Ref store(const Storage &) const;
 
 	bool verify(const Ref &) const;
@@ -67,7 +67,7 @@ template<typename T>
 class Signed
 {
 public:
-	static optional<Signed<T>> load(const Ref &);
+	static Signed<T> load(const Ref &);
 	Ref store(const Storage &) const;
 
 	bool isSignedBy(const Stored<PublicKey> &) const;
@@ -90,23 +90,20 @@ Stored<Signed<T>> SecretKey::sign(const Stored<T> & val) const
 }
 
 template<typename T>
-optional<Signed<T>> Signed<T>::load(const Ref & ref)
+Signed<T> Signed<T>::load(const Ref & ref)
 {
-	auto rec = ref->asRecord();
-	if (!rec)
-		return nullopt;
-
-	auto data = rec->item("SDATA").as<T>();
-	if (!data)
-		return nullopt;
-
-	vector<Stored<Signature>> sigs;
-	for (auto item : rec->items("sig"))
-		if (auto sig = item.as<Signature>())
-			if (sig.value()->verify(data.value().ref()))
-				sigs.push_back(sig.value());
-
-	return Signed(*data, sigs);
+	if (auto rec = ref->asRecord())
+		if (auto data = rec->item("SDATA").as<T>()) {
+			vector<Stored<Signature>> sigs;
+			for (auto item : rec->items("sig"))
+				if (auto sig = item.as<Signature>())
+					if (sig.value()->verify(data.value().ref()))
+						sigs.push_back(sig.value());
+
+			return Signed(*data, sigs);
+		}
+
+	return Signed(Stored<T>::load(ref.storage().zref()), {});
 }
 
 template<typename T>
@@ -137,7 +134,7 @@ class PublicKexKey
 		key(key, EVP_PKEY_free) {}
 	friend class SecretKexKey;
 public:
-	static optional<PublicKexKey> load(const Ref &);
+	static PublicKexKey load(const Ref &);
 	Ref store(const Storage &) const;
 
 	const shared_ptr<EVP_PKEY> key;
diff --git a/src/storage.cpp b/src/storage.cpp
index 81a70e1..6a0669c 100644
--- a/src/storage.cpp
+++ b/src/storage.cpp
@@ -315,6 +315,11 @@ optional<Ref> Storage::ref(const Digest & digest) const
 	return Ref::create(*this, digest);
 }
 
+Ref Storage::zref() const
+{
+	return Ref::zcreate(*this);
+}
+
 Digest PartialStorage::Priv::storeBytes(const vector<uint8_t> & content) const
 {
 	array<uint8_t, Digest::size> arr;
@@ -346,6 +351,8 @@ optional<vector<uint8_t>> PartialStorage::Priv::loadBytes(const Digest & digest)
 
 optional<PartialObject> PartialStorage::loadObject(const Digest & digest) const
 {
+	if (digest.isZero())
+		return PartialObject(monostate());
 	if (auto content = p->loadBytes(digest))
 		return PartialObject::decode(*this, *content);
 	return nullopt;
@@ -362,6 +369,8 @@ PartialRef PartialStorage::storeObject(const Blob & val) const
 
 optional<Object> Storage::loadObject(const Digest & digest) const
 {
+	if (digest.isZero())
+		return Object(monostate());
 	if (auto content = p->loadBytes(digest))
 		return Object::decode(*this, *content);
 	return nullopt;
@@ -466,6 +475,13 @@ Digest::operator string() const
 	return res;
 }
 
+bool Digest::isZero() const
+{
+	for (uint8_t x : value)
+		if (x) return false;
+	return true;
+}
+
 
 PartialRef PartialRef::create(PartialStorage st, const Digest & digest)
 {
@@ -517,6 +533,16 @@ optional<Ref> Ref::create(Storage st, const Digest & digest)
 	return Ref(shared_ptr<Priv>(p));
 }
 
+Ref Ref::zcreate(Storage st)
+{
+	auto p = new Priv {
+		.storage = make_unique<PartialStorage>(st),
+		.digest = Digest(array<uint8_t, Digest::size> {}),
+	};
+
+	return Ref(shared_ptr<Priv>(p));
+}
+
 const Object Ref::operator*() const
 {
 	if (auto res = static_cast<Storage*>(p->storage.get())->loadObject(p->digest))
@@ -854,11 +880,9 @@ vector<uint8_t> ObjectT<S>::encode() const
 }
 
 template<class S>
-optional<ObjectT<S>> ObjectT<S>::load(const typename S::Ref & ref)
+ObjectT<S> ObjectT<S>::load(const typename S::Ref & ref)
 {
-	if (ref)
-		return *ref;
-	return nullopt;
+	return *ref;
 }
 
 template<class S>
@@ -899,7 +923,7 @@ vector<Stored<Object>> erebos::collectStoredObjects(const Stored<Object> & from)
 		if (auto rec = cur->asRecord())
 			for (const auto & item : rec->items())
 				if (auto ref = item.asRef())
-					queue.push_back(*Stored<Object>::load(*ref));
+					queue.push_back(Stored<Object>::load(*ref));
 	}
 
 	return res;