junction.rs

// Copyright (C) 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/>.

//! Support data structures for `MultiLocation`, primarily the `Junction` datatype.

use super::{Junctions, MultiLocation};
use crate::{
	v2::{
		BodyId as OldBodyId, BodyPart as OldBodyPart, Junction as OldJunction,
		NetworkId as OldNetworkId,
	},
	VersionedMultiLocation,
};
use bounded_collections::{BoundedSlice, BoundedVec, ConstU32};
use core::convert::{TryFrom, TryInto};
use parity_scale_codec::{self, Decode, Encode, MaxEncodedLen};
use scale_info::TypeInfo;
use serde::{Deserialize, Serialize};

/// A global identifier of a data structure existing within consensus.
///
/// Maintenance note: Networks with global consensus and which are practically bridgeable within the
/// Polkadot ecosystem are given preference over explicit naming in this enumeration.
#[derive(
	Copy,
	Clone,
	Eq,
	PartialEq,
	Ord,
	PartialOrd,
	Encode,
	Decode,
	Debug,
	TypeInfo,
	MaxEncodedLen,
	Serialize,
	Deserialize,
)]
#[scale_info(replace_segment("staging_xcm", "xcm"))]
pub enum NetworkId {
	/// Network specified by the first 32 bytes of its genesis block.
	ByGenesis([u8; 32]),
	/// Network defined by the first 32-bytes of the hash and number of some block it contains.
	ByFork { block_number: u64, block_hash: [u8; 32] },
	/// The Polkadot mainnet Relay-chain.
	Polkadot,
	/// The Kusama canary-net Relay-chain.
	Kusama,
	/// The Westend testnet Relay-chain.
	Westend,
	/// The Rococo testnet Relay-chain.
	Rococo,
	/// The Wococo testnet Relay-chain.
	Wococo,
	/// An Ethereum network specified by its chain ID.
	Ethereum {
		/// The EIP-155 chain ID.
		#[codec(compact)]
		chain_id: u64,
	},
	/// The Bitcoin network, including hard-forks supported by Bitcoin Core development team.
	BitcoinCore,
	/// The Bitcoin network, including hard-forks supported by Bitcoin Cash developers.
	BitcoinCash,
}

impl From<OldNetworkId> for Option<NetworkId> {
	fn from(old: OldNetworkId) -> Option<NetworkId> {
		use OldNetworkId::*;
		match old {
			Any => None,
			Named(_) => None,
			Polkadot => Some(NetworkId::Polkadot),
			Kusama => Some(NetworkId::Kusama),
		}
	}
}

impl TryFrom<OldNetworkId> for NetworkId {
	type Error = ();
	fn try_from(old: OldNetworkId) -> Result<Self, Self::Error> {
		use OldNetworkId::*;
		match old {
			Any | Named(_) => Err(()),
			Polkadot => Ok(NetworkId::Polkadot),
			Kusama => Ok(NetworkId::Kusama),
		}
	}
}

/// An identifier of a pluralistic body.
#[derive(
	Copy,
	Clone,
	Eq,
	PartialEq,
	Ord,
	PartialOrd,
	Encode,
	Decode,
	Debug,
	TypeInfo,
	MaxEncodedLen,
	Serialize,
	Deserialize,
)]
#[scale_info(replace_segment("staging_xcm", "xcm"))]
pub enum BodyId {
	/// The only body in its context.
	Unit,
	/// A named body.
	Moniker([u8; 4]),
	/// An indexed body.
	Index(#[codec(compact)] u32),
	/// The unambiguous executive body (for Polkadot, this would be the Polkadot council).
	Executive,
	/// The unambiguous technical body (for Polkadot, this would be the Technical Committee).
	Technical,
	/// The unambiguous legislative body (for Polkadot, this could be considered the opinion of a
	/// majority of lock-voters).
	Legislative,
	/// The unambiguous judicial body (this doesn't exist on Polkadot, but if it were to get a
	/// "grand oracle", it may be considered as that).
	Judicial,
	/// The unambiguous defense body (for Polkadot, an opinion on the topic given via a public
	/// referendum on the `staking_admin` track).
	Defense,
	/// The unambiguous administration body (for Polkadot, an opinion on the topic given via a
	/// public referendum on the `general_admin` track).
	Administration,
	/// The unambiguous treasury body (for Polkadot, an opinion on the topic given via a public
	/// referendum on the `treasurer` track).
	Treasury,
}

impl TryFrom<OldBodyId> for BodyId {
	type Error = ();
	fn try_from(value: OldBodyId) -> Result<Self, ()> {
		use OldBodyId::*;
		Ok(match value {
			Unit => Self::Unit,
			Named(n) =>
				if n.len() == 4 {
					let mut r = [0u8; 4];
					r.copy_from_slice(&n[..]);
					Self::Moniker(r)
				} else {
					return Err(())
				},
			Index(n) => Self::Index(n),
			Executive => Self::Executive,
			Technical => Self::Technical,
			Legislative => Self::Legislative,
			Judicial => Self::Judicial,
			Defense => Self::Defense,
			Administration => Self::Administration,
			Treasury => Self::Treasury,
		})
	}
}

/// A part of a pluralistic body.
#[derive(
	Copy,
	Clone,
	Eq,
	PartialEq,
	Ord,
	PartialOrd,
	Encode,
	Decode,
	Debug,
	TypeInfo,
	MaxEncodedLen,
	Serialize,
	Deserialize,
)]
#[scale_info(replace_segment("staging_xcm", "xcm"))]
pub enum BodyPart {
	/// The body's declaration, under whatever means it decides.
	Voice,
	/// A given number of members of the body.
	Members {
		#[codec(compact)]
		count: u32,
	},
	/// A given number of members of the body, out of some larger caucus.
	Fraction {
		#[codec(compact)]
		nom: u32,
		#[codec(compact)]
		denom: u32,
	},
	/// No less than the given proportion of members of the body.
	AtLeastProportion {
		#[codec(compact)]
		nom: u32,
		#[codec(compact)]
		denom: u32,
	},
	/// More than than the given proportion of members of the body.
	MoreThanProportion {
		#[codec(compact)]
		nom: u32,
		#[codec(compact)]
		denom: u32,
	},
}

impl BodyPart {
	/// Returns `true` if the part represents a strict majority (> 50%) of the body in question.
	pub fn is_majority(&self) -> bool {
		match self {
			BodyPart::Fraction { nom, denom } if *nom * 2 > *denom => true,
			BodyPart::AtLeastProportion { nom, denom } if *nom * 2 > *denom => true,
			BodyPart::MoreThanProportion { nom, denom } if *nom * 2 >= *denom => true,
			_ => false,
		}
	}
}

impl TryFrom<OldBodyPart> for BodyPart {
	type Error = ();
	fn try_from(value: OldBodyPart) -> Result<Self, ()> {
		use OldBodyPart::*;
		Ok(match value {
			Voice => Self::Voice,
			Members { count } => Self::Members { count },
			Fraction { nom, denom } => Self::Fraction { nom, denom },
			AtLeastProportion { nom, denom } => Self::AtLeastProportion { nom, denom },
			MoreThanProportion { nom, denom } => Self::MoreThanProportion { nom, denom },
		})
	}
}

/// A single item in a path to describe the relative location of a consensus system.
///
/// Each item assumes a pre-existing location as its context and is defined in terms of it.
#[derive(
	Copy,
	Clone,
	Eq,
	PartialEq,
	Ord,
	PartialOrd,
	Encode,
	Decode,
	Debug,
	TypeInfo,
	MaxEncodedLen,
	Serialize,
	Deserialize,
)]
#[scale_info(replace_segment("staging_xcm", "xcm"))]
pub enum Junction {
	/// An indexed parachain belonging to and operated by the context.
	///
	/// Generally used when the context is a Polkadot Relay-chain.
	Parachain(#[codec(compact)] u32),
	/// A 32-byte identifier for an account of a specific network that is respected as a sovereign
	/// endpoint within the context.
	///
	/// Generally used when the context is a Substrate-based chain.
	AccountId32 { network: Option<NetworkId>, id: [u8; 32] },
	/// An 8-byte index for an account of a specific network that is respected as a sovereign
	/// endpoint within the context.
	///
	/// May be used when the context is a Frame-based chain and includes e.g. an indices pallet.
	AccountIndex64 {
		network: Option<NetworkId>,
		#[codec(compact)]
		index: u64,
	},
	/// A 20-byte identifier for an account of a specific network that is respected as a sovereign
	/// endpoint within the context.
	///
	/// May be used when the context is an Ethereum or Bitcoin chain or smart-contract.
	AccountKey20 { network: Option<NetworkId>, key: [u8; 20] },
	/// An instanced, indexed pallet that forms a constituent part of the context.
	///
	/// Generally used when the context is a Frame-based chain.
	// TODO XCMv4 inner should be `Compact<u32>`.
	PalletInstance(u8),
	/// A non-descript index within the context location.
	///
	/// Usage will vary widely owing to its generality.
	///
	/// NOTE: Try to avoid using this and instead use a more specific item.
	GeneralIndex(#[codec(compact)] u128),
	/// A nondescript array datum, 32 bytes, acting as a key within the context
	/// location.
	///
	/// Usage will vary widely owing to its generality.
	///
	/// NOTE: Try to avoid using this and instead use a more specific item.
	// Note this is implemented as an array with a length rather than using `BoundedVec` owing to
	// the bound for `Copy`.
	GeneralKey { length: u8, data: [u8; 32] },
	/// The unambiguous child.
	///
	/// Not currently used except as a fallback when deriving context.
	OnlyChild,
	/// A pluralistic body existing within consensus.
	///
	/// Typical to be used to represent a governance origin of a chain, but could in principle be
	/// used to represent things such as multisigs also.
	Plurality { id: BodyId, part: BodyPart },
	/// A global network capable of externalizing its own consensus. This is not generally
	/// meaningful outside of the universal level.
	GlobalConsensus(NetworkId),
}

impl From<NetworkId> for Junction {
	fn from(n: NetworkId) -> Self {
		Self::GlobalConsensus(n)
	}
}

impl From<[u8; 32]> for Junction {
	fn from(id: [u8; 32]) -> Self {
		Self::AccountId32 { network: None, id }
	}
}

impl From<BoundedVec<u8, ConstU32<32>>> for Junction {
	fn from(key: BoundedVec<u8, ConstU32<32>>) -> Self {
		key.as_bounded_slice().into()
	}
}

impl<'a> From<BoundedSlice<'a, u8, ConstU32<32>>> for Junction {
	fn from(key: BoundedSlice<'a, u8, ConstU32<32>>) -> Self {
		let mut data = [0u8; 32];
		data[..key.len()].copy_from_slice(&key[..]);
		Self::GeneralKey { length: key.len() as u8, data }
	}
}

impl<'a> TryFrom<&'a Junction> for BoundedSlice<'a, u8, ConstU32<32>> {
	type Error = ();
	fn try_from(key: &'a Junction) -> Result<Self, ()> {
		match key {
			Junction::GeneralKey { length, data } =>
				BoundedSlice::try_from(&data[..data.len().min(*length as usize)]).map_err(|_| ()),
			_ => Err(()),
		}
	}
}

impl From<[u8; 20]> for Junction {
	fn from(key: [u8; 20]) -> Self {
		Self::AccountKey20 { network: None, key }
	}
}

impl From<u64> for Junction {
	fn from(index: u64) -> Self {
		Self::AccountIndex64 { network: None, index }
	}
}

impl From<u128> for Junction {
	fn from(id: u128) -> Self {
		Self::GeneralIndex(id)
	}
}

impl TryFrom<OldJunction> for Junction {
	type Error = ();
	fn try_from(value: OldJunction) -> Result<Self, ()> {
		use OldJunction::*;
		Ok(match value {
			Parachain(id) => Self::Parachain(id),
			AccountId32 { network, id } => Self::AccountId32 { network: network.into(), id },
			AccountIndex64 { network, index } =>
				Self::AccountIndex64 { network: network.into(), index },
			AccountKey20 { network, key } => Self::AccountKey20 { network: network.into(), key },
			PalletInstance(index) => Self::PalletInstance(index),
			GeneralIndex(id) => Self::GeneralIndex(id),
			GeneralKey(key) => match key.len() {
				len @ 0..=32 => Self::GeneralKey {
					length: len as u8,
					data: {
						let mut data = [0u8; 32];
						data[..len].copy_from_slice(&key[..]);
						data
					},
				},
				_ => return Err(()),
			},
			OnlyChild => Self::OnlyChild,
			Plurality { id, part } =>
				Self::Plurality { id: id.try_into()?, part: part.try_into()? },
		})
	}
}

impl Junction {
	/// Convert `self` into a `MultiLocation` containing 0 parents.
	///
	/// Similar to `Into::into`, except that this method can be used in a const evaluation context.
	pub const fn into_location(self) -> MultiLocation {
		MultiLocation { parents: 0, interior: Junctions::X1(self) }
	}

	/// Convert `self` into a `MultiLocation` containing `n` parents.
	///
	/// Similar to `Self::into_location`, with the added ability to specify the number of parent
	/// junctions.
	pub const fn into_exterior(self, n: u8) -> MultiLocation {
		MultiLocation { parents: n, interior: Junctions::X1(self) }
	}

	/// Convert `self` into a `VersionedMultiLocation` containing 0 parents.
	///
	/// Similar to `Into::into`, except that this method can be used in a const evaluation context.
	pub const fn into_versioned(self) -> VersionedMultiLocation {
		self.into_location().into_versioned()
	}

	/// Remove the `NetworkId` value.
	pub fn remove_network_id(&mut self) {
		use Junction::*;
		match self {
			AccountId32 { ref mut network, .. } |
			AccountIndex64 { ref mut network, .. } |
			AccountKey20 { ref mut network, .. } => *network = None,
			_ => {},
		}
	}
}

#[cfg(test)]
mod tests {
	use super::*;
	use alloc::vec;

	#[test]
	fn junction_round_trip_works() {
		let j = Junction::GeneralKey { length: 32, data: [1u8; 32] };
		let k = Junction::try_from(OldJunction::try_from(j).unwrap()).unwrap();
		assert_eq!(j, k);

		let j = OldJunction::GeneralKey(vec![1u8; 32].try_into().unwrap());
		let k = OldJunction::try_from(Junction::try_from(j.clone()).unwrap()).unwrap();
		assert_eq!(j, k);

		let j = Junction::from(BoundedVec::try_from(vec![1u8, 2, 3, 4]).unwrap());
		let k = Junction::try_from(OldJunction::try_from(j).unwrap()).unwrap();
		assert_eq!(j, k);
		let s: BoundedSlice<_, _> = (&k).try_into().unwrap();
		assert_eq!(s, &[1u8, 2, 3, 4][..]);

		let j = OldJunction::GeneralKey(vec![1u8, 2, 3, 4].try_into().unwrap());
		let k = OldJunction::try_from(Junction::try_from(j.clone()).unwrap()).unwrap();
		assert_eq!(j, k);
	}
}