snowbridge_core/

location.rs

// SPDX-License-Identifier: Apache-2.0
// SPDX-FileCopyrightText: 2023 Snowfork <hello@snowfork.com>
//! # Location
//!
//! Location helpers for dealing with Tokens and Agents

pub use polkadot_parachain_primitives::primitives::{
	Id as ParaId, IsSystem, Sibling as SiblingParaId,
};
pub use sp_core::U256;

use codec::Encode;
use sp_core::H256;
use sp_std::prelude::*;
use xcm::prelude::{
	AccountId32, AccountKey20, GeneralIndex, GeneralKey, GlobalConsensus, Location, PalletInstance,
};
use xcm_builder::{
	DescribeAllTerminal, DescribeFamily, DescribeLocation, DescribeTerminus, HashedDescription,
};

pub type AgentId = H256;

/// Creates an AgentId from a Location. An AgentId is a unique mapping to an Agent contract on
/// Ethereum which acts as the sovereign account for the Location.
/// Resolves Polkadot locations (as seen by Ethereum) to unique `AgentId` identifiers.
pub type AgentIdOf = HashedDescription<
	AgentId,
	(
		DescribeHere,
		DescribeFamily<DescribeAllTerminal>,
		DescribeGlobalPrefix<(DescribeTerminus, DescribeFamily<DescribeTokenTerminal>)>,
	),
>;

pub type TokenId = H256;

/// Convert a token location (relative to Ethereum) to a stable ID that can be used on the Ethereum
/// side
pub type TokenIdOf = HashedDescription<
	TokenId,
	DescribeGlobalPrefix<(DescribeTerminus, DescribeFamily<DescribeTokenTerminal>)>,
>;

/// This looks like DescribeTerminus that was added to xcm-builder. However this does an extra
/// `encode` to the Vector producing a different output to DescribeTerminus. `DescribeHere`
/// should NOT be used for new code. This is left here for backwards compatibility of channels and
/// agents.
pub struct DescribeHere;
#[allow(deprecated)]
impl DescribeLocation for DescribeHere {
	fn describe_location(l: &Location) -> Option<Vec<u8>> {
		match l.unpack() {
			(0, []) => Some(Vec::<u8>::new().encode()),
			_ => None,
		}
	}
}
pub struct DescribeGlobalPrefix<DescribeInterior>(sp_std::marker::PhantomData<DescribeInterior>);
impl<Suffix: DescribeLocation> DescribeLocation for DescribeGlobalPrefix<Suffix> {
	fn describe_location(l: &Location) -> Option<Vec<u8>> {
		match (l.parent_count(), l.first_interior()) {
			(1, Some(GlobalConsensus(network))) => {
				let mut tail = l.clone().split_first_interior().0;
				tail.dec_parent();
				let interior = Suffix::describe_location(&tail)?;
				Some((b"GlobalConsensus", network, interior).encode())
			},
			_ => None,
		}
	}
}

pub struct DescribeTokenTerminal;
impl DescribeLocation for DescribeTokenTerminal {
	fn describe_location(l: &Location) -> Option<Vec<u8>> {
		match l.unpack().1 {
			[] => Some(Vec::<u8>::new().encode()),
			[GeneralIndex(index)] => Some((b"GeneralIndex", *index).encode()),
			[GeneralKey { length, data }] => Some((b"GeneralKey", *length, *data).encode()),
			[AccountKey20 { key, .. }] => Some((b"AccountKey20", *key).encode()),
			[AccountId32 { id, .. }] => Some((b"AccountId32", *id).encode()),

			// Pallet
			[PalletInstance(instance)] => Some((b"PalletInstance", *instance).encode()),
			[PalletInstance(instance), GeneralIndex(index)] => {
				Some((b"PalletInstance", *instance, b"GeneralIndex", *index).encode())
			},
			[PalletInstance(instance), GeneralKey { length, data }] => {
				Some((b"PalletInstance", *instance, b"GeneralKey", *length, *data).encode())
			},

			[PalletInstance(instance), AccountKey20 { key, .. }] => {
				Some((b"PalletInstance", *instance, b"AccountKey20", *key).encode())
			},
			[PalletInstance(instance), AccountId32 { id, .. }] => {
				Some((b"PalletInstance", *instance, b"AccountId32", *id).encode())
			},

			// Reject all other locations
			_ => None,
		}
	}
}

#[cfg(test)]
mod tests {
	use crate::TokenIdOf;
	use xcm::{
		latest::WESTEND_GENESIS_HASH,
		prelude::{
			GeneralIndex, GeneralKey, GlobalConsensus, Junction::*, Location, NetworkId::ByGenesis,
			PalletInstance, Parachain,
		},
	};
	use xcm_executor::traits::ConvertLocation;

	#[test]
	fn test_token_of_id() {
		let token_locations = [
			// Relay Chain cases
			// Relay Chain relative to Ethereum
			Location::new(1, [GlobalConsensus(ByGenesis(WESTEND_GENESIS_HASH))]),
			// Parachain cases
			// Parachain relative to Ethereum
			Location::new(1, [GlobalConsensus(ByGenesis(WESTEND_GENESIS_HASH)), Parachain(2000)]),
			// Parachain general index
			Location::new(
				1,
				[
					GlobalConsensus(ByGenesis(WESTEND_GENESIS_HASH)),
					Parachain(2000),
					GeneralIndex(1),
				],
			),
			// Parachain general key
			Location::new(
				1,
				[
					GlobalConsensus(ByGenesis(WESTEND_GENESIS_HASH)),
					Parachain(2000),
					GeneralKey { length: 32, data: [0; 32] },
				],
			),
			// Parachain account key 20
			Location::new(
				1,
				[
					GlobalConsensus(ByGenesis(WESTEND_GENESIS_HASH)),
					Parachain(2000),
					AccountKey20 { network: None, key: [0; 20] },
				],
			),
			// Parachain account id 32
			Location::new(
				1,
				[
					GlobalConsensus(ByGenesis(WESTEND_GENESIS_HASH)),
					Parachain(2000),
					AccountId32 { network: None, id: [0; 32] },
				],
			),
			// Parchain Pallet instance cases
			// Parachain pallet instance
			Location::new(
				1,
				[
					GlobalConsensus(ByGenesis(WESTEND_GENESIS_HASH)),
					Parachain(2000),
					PalletInstance(8),
				],
			),
			// Parachain Pallet general index
			Location::new(
				1,
				[
					GlobalConsensus(ByGenesis(WESTEND_GENESIS_HASH)),
					Parachain(2000),
					PalletInstance(8),
					GeneralIndex(1),
				],
			),
			// Parachain Pallet general key
			Location::new(
				1,
				[
					GlobalConsensus(ByGenesis(WESTEND_GENESIS_HASH)),
					Parachain(2000),
					PalletInstance(8),
					GeneralKey { length: 32, data: [0; 32] },
				],
			),
			// Parachain Pallet account key 20
			Location::new(
				1,
				[
					GlobalConsensus(ByGenesis(WESTEND_GENESIS_HASH)),
					Parachain(2000),
					PalletInstance(8),
					AccountKey20 { network: None, key: [0; 20] },
				],
			),
			// Parachain Pallet account id 32
			Location::new(
				1,
				[
					GlobalConsensus(ByGenesis(WESTEND_GENESIS_HASH)),
					Parachain(2000),
					PalletInstance(8),
					AccountId32 { network: None, id: [0; 32] },
				],
			),
		];

		for token in token_locations {
			assert!(
				TokenIdOf::convert_location(&token).is_some(),
				"Valid token = {token:?} yields no TokenId."
			);
		}

		let non_token_locations = [
			// Relative location for a token should fail.
			Location::new(1, []),
			// Relative location for a token should fail.
			Location::new(1, [Parachain(1000)]),
		];

		for token in non_token_locations {
			assert!(
				TokenIdOf::convert_location(&token).is_none(),
				"Invalid token = {token:?} yields a TokenId."
			);
		}
	}
}