Parachains finality pallet (#1068)

* parachains finality

* parachains pallet test

* demo of how to configure GRANDPA pallet instance

* allow instances in parachains pallet

* spellcheck

* TODO + fix

* fmt

* removed invalid storage_keys file

* change all hashers to Blake2_128Concat

* use Twox64Concat for insertion position

* fix build

* fix compilation

* change ParaId and ParaHead types

* TODOs -> TODOs with issues refs

bridges/primitives/polkadot-core/Cargo.toml

@@ -8,7 +8,9 @@ license = "GPL-3.0-or-later WITH Classpath-exception-2.0"
 
 [dependencies]
 parity-scale-codec = { version = "3.0.0", default-features = false, features = ["derive"] }
+parity-util-mem = { version = "0.11.0", optional = true }
 scale-info = { version = "2.1.1", default-features = false, features = ["derive"] }
+serde = { version = "1.0", optional = true, features = ["derive"] }
 
 # Bridge Dependencies
 
@@ -36,7 +38,9 @@ std = [
 	"frame-support/std",
 	"frame-system/std",
 	"parity-scale-codec/std",
+	"parity-util-mem",
 	"scale-info/std",
+	"serde",
 	"sp-api/std",
 	"sp-core/std",
 	"sp-runtime/std",

bridges/primitives/polkadot-core/src/lib.rs

@@ -43,6 +43,8 @@ use sp_std::prelude::Vec;
 pub use frame_support::{weights::constants::ExtrinsicBaseWeight, Parameter};
 pub use sp_runtime::{traits::Convert, Perbill};
 
+pub mod parachains;
+
 /// Number of extra bytes (excluding size of storage value itself) of storage proof, built at
 /// Polkadot-like chain. This mostly depends on number of entries in the storage trie.
 /// Some reserve is reserved to account future chain growth.

bridges/primitives/polkadot-core/src/parachains.rs

@@ -0,0 +1,82 @@
+// Copyright 2019-2021 Parity Technologies (UK) Ltd.
+// This file is part of Parity Bridges Common.
+
+// Parity Bridges Common 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.
+
+// Parity Bridges Common 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 Parity Bridges Common.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Primitives of polkadot-like chains, that are related to parachains functionality.
+//!
+//! Even though this (bridges) repository references polkadot repository, we can't
+//! reference polkadot crates from pallets. That's because bridges repository is
+//! included in the polkadot repository and included pallets are used by polkadot
+//! chains. Having pallets that are referencing polkadot, would mean that there may
+//! be two versions of polkadot crates included in the runtime. Which is bad.
+
+use frame_support::RuntimeDebug;
+use parity_scale_codec::{CompactAs, Decode, Encode, MaxEncodedLen};
+use scale_info::TypeInfo;
+use sp_core::Hasher;
+use sp_std::vec::Vec;
+
+#[cfg(feature = "std")]
+use serde::{Deserialize, Serialize};
+
+#[cfg(feature = "std")]
+use parity_util_mem::MallocSizeOf;
+
+/// Parachain id.
+///
+/// This is an equivalent of the `polkadot_parachain::Id`, which is a compact-encoded `u32`.
+#[derive(
+	Clone,
+	CompactAs,
+	Copy,
+	Decode,
+	Default,
+	Encode,
+	Eq,
+	Hash,
+	MaxEncodedLen,
+	Ord,
+	PartialEq,
+	PartialOrd,
+	RuntimeDebug,
+	TypeInfo,
+)]
+pub struct ParaId(pub u32);
+
+/// Parachain head.
+///
+/// This is an equivalent of the `polkadot_parachain::HeadData`.
+///
+/// The parachain head means (at least in Cumulus) a SCALE-encoded parachain header. Keep in mind
+/// that in Polkadot it is twice-encoded (so `header.encode().encode()`). We'll also do it to keep
+/// it binary-compatible (implies hash-compatibility) with other parachain pallets.
+#[derive(
+	PartialEq, Eq, Clone, PartialOrd, Ord, Encode, Decode, RuntimeDebug, TypeInfo, Default,
+)]
+#[cfg_attr(feature = "std", derive(Serialize, Deserialize, Hash, MallocSizeOf))]
+pub struct ParaHead(pub Vec<u8>);
+
+impl ParaHead {
+	/// Returns the hash of this head data.
+	pub fn hash(&self) -> crate::Hash {
+		sp_runtime::traits::BlakeTwo256::hash(&self.0)
+	}
+}
+
+/// Parachain head hash.
+pub type ParaHash = crate::Hash;
+
+/// Raw storage proof of parachain heads, stored in polkadot-like chain runtime.
+pub type ParachainHeadsProof = Vec<Vec<u8>>;