Token-swap-over-bridge pallet (#944)

* token swap pallet

* token swap type (replay protection)

* post-merge fixes

* post-merge fix

* Update modules/token-swap/src/lib.rs

Co-authored-by: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

* Update modules/token-swap/src/lib.rs

Co-authored-by: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

* add missing comment part

* Update modules/token-swap/src/lib.rs

Co-authored-by: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

* starting claim after lock period is over is forbidden

* move spec_version and weight to arguments

Co-authored-by: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

bridges/primitives/token-swap/Cargo.toml

@@ -0,0 +1,23 @@
+[package]
+name = "bp-token-swap"
+description = "Primitives of the pallet-bridge-token-swap pallet"
+version = "0.1.0"
+authors = ["Parity Technologies <admin@parity.io>"]
+edition = "2018"
+license = "GPL-3.0-or-later WITH Classpath-exception-2.0"
+
+[dependencies]
+codec = { package = "parity-scale-codec", version = "2.0.0", default-features = false }
+
+# Substrate Dependencies
+
+frame-support = { git = "https://github.com/paritytech/substrate", branch = "master" , default-features = false }
+sp-core = { git = "https://github.com/paritytech/substrate", branch = "master" , default-features = false }
+
+[features]
+default = ["std"]
+std = [
+	"codec/std",
+	"frame-support/std",
+	"sp-core/std",
+]

bridges/primitives/token-swap/src/lib.rs

@@ -0,0 +1,64 @@
+// 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/>.
+
+use codec::{Decode, Encode};
+use frame_support::RuntimeDebug;
+use sp_core::U256;
+
+/// Token swap type.
+///
+/// Different swap types give a different guarantees regarding possible swap
+/// replay protection.
+#[derive(Encode, Decode, Clone, RuntimeDebug, PartialEq, Eq)]
+pub enum TokenSwapType<ThisBlockNumber> {
+	/// The `target_account_at_bridged_chain` is temporary and only have funds for single swap.
+	///
+	/// ***WARNING**: if `target_account_at_bridged_chain` still exists after the swap has been
+	/// completed (either by claiming or cancelling), the `source_account_at_this_chain` will be able
+	/// to restart the swap again and repeat the swap until `target_account_at_bridged_chain` depletes.
+	TemporaryTargetAccountAtBridgedChain,
+	/// This swap type prevents `source_account_at_this_chain` from restarting the swap after it has
+	/// been completed. There are two consequences:
+	///
+	/// 1) the `source_account_at_this_chain` won't be able to call `start_swap` after given <ThisBlockNumber>;
+	/// 2) the `target_account_at_bridged_chain` won't be able to call `claim_swap` (over the bridge) before
+	///    block `<ThisBlockNumber + 1>`.
+	///
+	/// The second element is the nonce of the swap. You must care about its uniqueness if you're
+	/// planning to perform another swap with exactly the same parameters (i.e. same amount, same accounts,
+	/// same `ThisBlockNumber`) to avoid collisions.
+	LockClaimUntilBlock(ThisBlockNumber, U256),
+}
+
+/// An intention to swap `source_balance_at_this_chain` owned by `source_account_at_this_chain`
+/// to `target_balance_at_bridged_chain` owned by `target_account_at_bridged_chain`.
+///
+/// **IMPORTANT NOTE**: this structure is always the same during single token swap. So even
+/// when chain changes, the meaning of This and Bridged are still used to point to the same chains.
+/// This chain is always the chain where swap has been started. And the Bridged chain is the other chain.
+#[derive(Encode, Decode, Clone, RuntimeDebug, PartialEq, Eq)]
+pub struct TokenSwap<ThisBlockNumber, ThisBalance, ThisAccountId, BridgedBalance, BridgedAccountId> {
+	/// The type of the swap.
+	pub swap_type: TokenSwapType<ThisBlockNumber>,
+	/// This chain balance to be swapped with `target_balance_at_bridged_chain`.
+	pub source_balance_at_this_chain: ThisBalance,
+	/// Account id of the party acting at This chain and owning the `source_account_at_this_chain`.
+	pub source_account_at_this_chain: ThisAccountId,
+	/// Bridged chain balance to be swapped with `source_balance_at_this_chain`.
+	pub target_balance_at_bridged_chain: BridgedBalance,
+	/// Account id of the party acting at the Bridged chain and owning the `target_balance_at_bridged_chain`.
+	pub target_account_at_bridged_chain: BridgedAccountId,
+}