Initial validator trait. (#14)

* Initial validator trait.

* Add missing docs warning.

* Fix formatting.

* Fix validator output and serialization.

* Get rid of redundant ValidationCode type.

substrate/validator/src/parachains.rs

@@ -0,0 +1,46 @@
+// Copyright 2017 Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Polkadot is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+use std::fmt;
+
+use primitives::validator;
+use serde::de::DeserializeOwned;
+
+/// Parachain code implementation.
+pub trait ParachainCode: fmt::Debug {
+	/// Deserialized messages type.
+	type Messages: DeserializeOwned;
+	/// Deserialized proof type.
+	type Proof: DeserializeOwned;
+
+	/// Given decoded messages and proof validate it and return egress posts.
+	fn check(&self, messages: Self::Messages, proof: Self::Proof) ->
+		Option<(validator::IngressPostsDelta, validator::EgressPosts)>;
+}
+
+/// Dummy implementation of the first parachain validation.
+#[derive(Debug)]
+pub struct ParaChain1;
+
+impl ParachainCode for ParaChain1 {
+	type Messages = ();
+	type Proof = ();
+
+	fn check(&self, _messages: Self::Messages, _proof: Self::Proof)
+		-> Option<(validator::IngressPostsDelta, validator::EgressPosts)> {
+		None
+	}
+}