Approval types (#2111)

* start approval types

* doc

* finish basic types

* add debug and codec impls to approval types

* grumbles

* remove unused AssignmentId

* remove aux-schema file

polkadot/node/primitives/src/approval.rs

@@ -0,0 +1,105 @@
+// Copyright 2017-2020 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/>.
+
+//! Types relevant for approval.
+
+pub use sp_consensus_vrf::schnorrkel::{VRFOutput, VRFProof};
+
+use polkadot_primitives::v1::{
+	CandidateHash, Hash, ValidatorIndex, Signed, ValidatorSignature, CoreIndex,
+};
+use parity_scale_codec::{Encode, Decode};
+
+/// Validators assigning to check a particular candidate are split up into tranches.
+/// Earlier tranches of validators check first, with later tranches serving as backup.
+pub type DelayTranche = u32;
+
+/// A static context used for all relay-vrf-modulo VRFs.
+pub const RELAY_VRF_MODULO_CONTEXT: &str = "A&V MOD";
+
+/// A static context used for all relay-vrf-delay VRFs.
+pub const RELAY_VRF_DELAY_CONTEXT: &str = "A&V TRANCHE";
+
+/// random bytes derived from the VRF submitted within the block by the
+/// block author as a credential and used as input to approval assignment criteria.
+#[derive(Debug, Clone, Encode, Decode)]
+pub struct RelayVRF(pub [u8; 32]);
+
+/// Different kinds of input data or criteria that can prove a validator's assignment
+/// to check a particular parachain.
+#[derive(Debug, Clone, Encode, Decode)]
+pub enum AssignmentCertKind {
+	/// An assignment story based on the VRF that authorized the relay-chain block where the
+	/// candidate was included combined with a sample number.
+	///
+	/// The context used to produce bytes is [`RELAY_VRF_MODULO_CONTEXT`]
+	RelayVRFModulo {
+		/// The sample number used in this cert.
+		sample: u32,
+	},
+	/// An assignment story based on the VRF that authorized the relay-chain block where the
+	/// candidate was included combined with the index of a particular core.
+	///
+	/// The context is [`RELAY_VRF_DELAY_CONTEXT`]
+	RelayVRFDelay {
+		/// The core index chosen in this cert.
+		core_index: CoreIndex,
+	},
+}
+
+/// A certification of assignment.
+#[derive(Debug, Clone, Encode, Decode)]
+pub struct AssignmentCert {
+	/// The criterion which is claimed to be met by this cert.
+	pub kind: AssignmentCertKind,
+	/// The VRF showing the criterion is met.
+	pub vrf: (VRFOutput, VRFProof),
+}
+
+/// An assignment crt which refers to the candidate under which the assignment is
+/// relevant by block hash.
+#[derive(Debug, Clone, Encode, Decode)]
+pub struct IndirectAssignmentCert {
+	/// A block hash where the candidate appears.
+	pub block_hash: Hash,
+	/// The validator index.
+	pub validator: ValidatorIndex,
+	/// The cert itself.
+	pub cert: AssignmentCert,
+}
+
+/// A vote of approval on a candidate.
+#[derive(Debug, Clone, Encode, Decode)]
+pub struct ApprovalVote(pub CandidateHash);
+
+/// An approval vote signed by some validator.
+pub type SignedApprovalVote = Signed<ApprovalVote>;
+
+/// A signed approval vote which references the candidate indirectly via the block.
+///
+/// In practice, we have a look-up from block hash and candidate index to candidate hash,
+/// so this can be transformed into a `SignedApprovalVote`.
+#[derive(Debug, Clone, Encode, Decode)]
+pub struct IndirectSignedApprovalVote {
+	/// A block hash where the candidate appears.
+	pub block_hash: Hash,
+	/// The index of the candidate in the list of candidates fully included as-of the block.
+	pub candidate_index: u32,
+	/// The validator index.
+	pub validator: ValidatorIndex,
+	/// The signature by the validator.
+	pub signature: ValidatorSignature,
+}