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/error.rs

@@ -0,0 +1,33 @@
+// 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 serializer;
+
+error_chain! {
+	foreign_links {
+		Serialization(serializer::Error);
+	}
+	errors {
+		Timeout {
+			description("Validation task has timed-out."),
+			display("Validation timeout."),
+		}
+		InvalidCode(details: String) {
+			description("The code is invalid."),
+			display("invalid code: '{}'", details),
+		}
+	}
+}

substrate/validator/src/lib.rs

@@ -0,0 +1,33 @@
+// 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/>.
+
+//! Validator implementation.
+
+#[warn(missing_docs)]
+
+extern crate polkadot_primitives as primitives;
+extern crate polkadot_serializer as serializer;
+extern crate serde;
+
+#[macro_use]
+extern crate error_chain;
+
+mod error;
+mod parachains;
+mod validator;
+
+pub use error::{Error, ErrorKind, Result};
+pub use validator::Validator;

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
+	}
+}

substrate/validator/src/validator.rs

@@ -0,0 +1,79 @@
+// 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, parachain};
+use serde::de::DeserializeOwned;
+use serializer;
+
+use error::{Error, ErrorKind, Result};
+use parachains::{ParachainCode, ParaChain1};
+
+/// A dummy validator implementation.
+#[derive(Debug)]
+pub struct Validator {
+	codes: Vec<Box<Code>>,
+}
+
+impl Validator {
+	/// Create a new validator.
+	pub fn new() -> Self {
+		Validator {
+			codes: vec![
+				Box::new(ParaChain1) as Box<Code>
+			],
+		}
+	}
+}
+
+impl validator::Validator for Validator {
+	type Error = Error;
+
+	fn validate(
+		&self,
+		messages: &validator::IngressPosts,
+		proof: &parachain::Proof,
+		code: &[u8],
+	) -> Result<validator::ProofValidity> {
+		ensure!(code.len() == 1, ErrorKind::InvalidCode(format!("The code should be a single byte.")));
+
+		match self.codes.get(code[0] as usize) {
+			Some(code) => code.check(messages, proof),
+			None => bail!(ErrorKind::InvalidCode(format!("Unknown parachain code."))),
+		}
+	}
+}
+
+/// Simplified parachain code verification
+trait Code: fmt::Debug {
+	/// Given bytes of messages and proof determine if the proof is valid and return egress posts.
+	fn check(&self, messages: &validator::IngressPosts, proof: &parachain::Proof) -> Result<validator::ProofValidity>;
+}
+
+impl<M, P, T> Code for T where
+	M: DeserializeOwned,
+	P: DeserializeOwned,
+	T: ParachainCode<Messages=M, Proof=P>,
+{
+	fn check(&self, messages: &validator::IngressPosts, proof: &parachain::Proof) -> Result<validator::ProofValidity> {
+		let messages = serializer::from_slice(&messages.0)?;
+		let proof = serializer::from_slice(&proof.raw().0)?;
+
+		Ok(self.check(messages, proof).into())
+	}
+}
+