// 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/>.

//! XCM `MultiLocation` datatype.

use super::{Junction, Junctions};

use crate::{

	v2::MultiLocation as OldMultiLocation, v4::Location as NewMultiLocation, VersionedLocation,

};

use codec::{Decode, Encode, MaxEncodedLen};

use core::result;

use scale_info::TypeInfo;

/// A relative path between state-bearing consensus systems.

///

/// A location in a consensus system is defined as an *isolatable state machine* held within global

/// consensus. The location in question need not have a sophisticated consensus algorithm of its

/// own; a single account within Ethereum, for example, could be considered a location.

///

/// A very-much non-exhaustive list of types of location include:

/// - A (normal, layer-1) block chain, e.g. the Bitcoin mainnet or a parachain.

/// - A layer-0 super-chain, e.g. the Polkadot Relay chain.

/// - A layer-2 smart contract, e.g. an ERC-20 on Ethereum.

/// - A logical functional component of a chain, e.g. a single instance of a pallet on a Frame-based

///   Substrate chain.

/// - An account.

///

/// A `MultiLocation` is a *relative identifier*, meaning that it can only be used to define the

/// relative path between two locations, and cannot generally be used to refer to a location

/// universally. It is comprised of an integer number of parents specifying the number of times to

/// "escape" upwards into the containing consensus system and then a number of *junctions*, each

/// diving down and specifying some interior portion of state (which may be considered a

/// "sub-consensus" system).

///

/// This specific `MultiLocation` implementation uses a `Junctions` datatype which is a Rust `enum`

/// in order to make pattern matching easier. There are occasions where it is important to ensure

/// that a value is strictly an interior location, in those cases, `Junctions` may be used.

///

/// The `MultiLocation` value of `Null` simply refers to the interpreting consensus system.

#[derive(

	Copy,

	Clone,

	Decode,

	Encode,

	Eq,

	PartialEq,

	Ord,

	PartialOrd,

	Debug,

	serde::Serialize,

)]

#[cfg_attr(feature = "json-schema", derive(schemars::JsonSchema))]

pub struct MultiLocation {

	/// The number of parent junctions at the beginning of this `MultiLocation`.

	pub parents: u8,

	/// The interior (i.e. non-parent) junctions that this `MultiLocation` contains.

	pub interior: Junctions,

}

/// Type alias for a better transition to V4.

pub type Location = MultiLocation;

impl Default for MultiLocation {

}

/// A relative location which is constrained to be an interior location of the context.

///

/// See also `MultiLocation`.

pub type InteriorMultiLocation = Junctions;

impl MultiLocation {

	/// Creates a new `MultiLocation` with the given number of parents and interior junctions.

	/// Consume `self` and return the equivalent `VersionedLocation` value.

	/// Creates a new `MultiLocation` with 0 parents and a `Here` interior.

	///

	/// The resulting `MultiLocation` can be interpreted as the "current consensus system".

	/// Creates a new `MultiLocation` which evaluates to the parent context.

	/// Creates a new `MultiLocation` which evaluates to the grand parent context.

	/// Creates a new `MultiLocation` with `parents` and an empty (`Here`) interior.

	/// Whether the `MultiLocation` has no parents and has a `Here` interior.

	/// Remove the `NetworkId` value in any interior `Junction`s.

	/// Return a reference to the interior field.

	/// Return a mutable reference to the interior field.

	/// Returns the number of `Parent` junctions at the beginning of `self`.

	/// Returns boolean indicating whether `self` contains only the specified amount of

	/// parents and no interior junctions.

	/// Returns the number of parents and junctions in `self`.

	/// Returns the first interior junction, or `None` if the location is empty or contains only

	/// parents.

	/// Returns last junction, or `None` if the location is empty or contains only parents.

	/// Splits off the first interior junction, returning the remaining suffix (first item in tuple)

	/// and the first element (second item in tuple) or `None` if it was empty.

	/// Splits off the last interior junction, returning the remaining prefix (first item in tuple)

	/// and the last element (second item in tuple) or `None` if it was empty or if `self` only

	/// contains parents.

	/// Mutates `self`, suffixing its interior junctions with `new`. Returns `Err` with `new` in

	/// case of overflow.

	/// Mutates `self`, prefixing its interior junctions with `new`. Returns `Err` with `new` in

	/// case of overflow.

	/// Consumes `self` and returns a `MultiLocation` suffixed with `new`, or an `Err` with

	/// the original value of `self` in case of overflow.

		}

	/// Consumes `self` and returns a `MultiLocation` prefixed with `new`, or an `Err` with the

	/// original value of `self` in case of overflow.

		}

	/// Returns the junction at index `i`, or `None` if the location is a parent or if the location

	/// does not contain that many elements.

	/// Returns a mutable reference to the junction at index `i`, or `None` if the location is a

	/// parent or if it doesn't contain that many elements.

	/// Decrements the parent count by 1.

	/// Removes the first interior junction from `self`, returning it

	/// (or `None` if it was empty or if `self` contains only parents).

	/// Removes the last element from `interior`, returning it (or `None` if it was empty or if

	/// `self` only contains parents).

	/// Ensures that `self` has the same number of parents as `prefix`, its junctions begins with

	/// the junctions of `prefix` and that it has a single `Junction` item following.

	/// If so, returns a reference to this `Junction` item.

	///

	/// # Example

	/// ```rust

	/// # use staging_xcm::v3::{Junctions::*, Junction::*, MultiLocation};

	/// let mut m = MultiLocation::new(1, X2(PalletInstance(3), OnlyChild));

	/// assert_eq!(

	///     m.match_and_split(&MultiLocation::new(1, X1(PalletInstance(3)))),

	///     Some(&OnlyChild),

	/// );

	/// assert_eq!(m.match_and_split(&MultiLocation::new(1, Here)), None);

	/// ```

	/// Mutate `self` so that it is suffixed with `suffix`.

	///

	/// Does not modify `self` and returns `Err` with `suffix` in case of overflow.

	///

	/// # Example

	/// ```rust

	/// # use staging_xcm::v3::{Junctions::*, Junction::*, MultiLocation, Parent};

	/// let mut m: MultiLocation = (Parent, Parachain(21), 69u64).into();

	/// assert_eq!(m.append_with((Parent, PalletInstance(3))), Ok(()));

	/// assert_eq!(m, MultiLocation::new(1, X2(Parachain(21), PalletInstance(3))));

	/// ```

		}

	/// Consume `self` and return its value suffixed with `suffix`.

	///

	/// Returns `Err` with the original value of `self` and `suffix` in case of overflow.

	///

	/// # Example

	/// ```rust

	/// # use staging_xcm::v3::{Junctions::*, Junction::*, MultiLocation, Parent};

	/// let mut m: MultiLocation = (Parent, Parachain(21), 69u64).into();

	/// let r = m.appended_with((Parent, PalletInstance(3))).unwrap();

	/// assert_eq!(r, MultiLocation::new(1, X2(Parachain(21), PalletInstance(3))));

	/// ```

		}

	/// Mutate `self` so that it is prefixed with `prefix`.

	///

	/// Does not modify `self` and returns `Err` with `prefix` in case of overflow.

	///

	/// # Example

	/// ```rust

	/// # use staging_xcm::v3::{Junctions::*, Junction::*, MultiLocation, Parent};

	/// let mut m: MultiLocation = (Parent, Parent, PalletInstance(3)).into();

	/// assert_eq!(m.prepend_with((Parent, Parachain(21), OnlyChild)), Ok(()));

	/// assert_eq!(m, MultiLocation::new(1, X1(PalletInstance(3))));

	/// ```

		// cancel out the final item on the prefix interior for one of the suffix's parents.

		// now we have either removed all suffix's parents or prefix interior.

		// this means we can combine the prefix's and suffix's remaining parents/interior since

		// we know that with at least one empty, the overall order will be respected:

		//     prefix     self (suffix)

		// P .. P   (I)   p .. p i .. i => P + p .. (no I) i

		//  -- or --

		// P .. P I .. I    (p)  i .. i => P (no p) .. I + i

	/// Consume `self` and return its value prefixed with `prefix`.

	///

	/// Returns `Err` with the original value of `self` and `prefix` in case of overflow.

	///

	/// # Example

	/// ```rust

	/// # use staging_xcm::v3::{Junctions::*, Junction::*, MultiLocation, Parent};

	/// let m: MultiLocation = (Parent, Parent, PalletInstance(3)).into();

	/// let r = m.prepended_with((Parent, Parachain(21), OnlyChild)).unwrap();

	/// assert_eq!(r, MultiLocation::new(1, X1(PalletInstance(3))));

	/// ```

		}

	/// Mutate `self` so that it represents the same location from the point of view of `target`.

	/// The context of `self` is provided as `context`.

	///

	/// Does not modify `self` in case of overflow.

		// TODO: https://github.com/paritytech/polkadot/issues/4489 Optimize this.

		// 1. Use our `context` to figure out how the `target` would address us.

		// 2. Prepend `inverted_target` to `self` to get self's location from the perspective of

		// `target`.

		// 3. Given that we know some of `target` context, ensure that any parents in `self` are

		// strictly needed.

	/// Consume `self` and return a new value representing the same location from the point of view

	/// of `target`. The context of `self` is provided as `context`.

	///

	/// Returns the original `self` in case of overflow.

		}

	/// Remove any unneeded parents/junctions in `self` based on the given context it will be

	/// interpreted in.

			// Not enough context

			}

		}

	/// Return the MultiLocation subsection identifying the chain that `self` points to.

		// start popping junctions until we reach chain identifier

				// return chain subsection

		}

}

impl TryFrom<OldMultiLocation> for MultiLocation {

	type Error = ();

}

impl TryFrom<NewMultiLocation> for Option<MultiLocation> {

	type Error = ();

}

impl TryFrom<NewMultiLocation> for MultiLocation {

	type Error = ();

		})

}

/// A unit struct which can be converted into a `MultiLocation` of `parents` value 1.

#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Debug)]

pub struct Parent;

impl From<Parent> for MultiLocation {

}

/// A tuple struct which can be converted into a `MultiLocation` of `parents` value 1 with the inner

/// interior.

#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Debug)]

pub struct ParentThen(pub Junctions);

impl From<ParentThen> for MultiLocation {

}

/// A unit struct which can be converted into a `MultiLocation` of the inner `parents` value.

#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Debug)]

pub struct Ancestor(pub u8);

impl From<Ancestor> for MultiLocation {

}

/// A unit struct which can be converted into a `MultiLocation` of the inner `parents` value and the

/// inner interior.

#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Debug)]

pub struct AncestorThen<Interior>(pub u8, pub Interior);

impl<Interior: Into<Junctions>> From<AncestorThen<Interior>> for MultiLocation {

}

#[cfg(test)]

mod tests {

	use crate::v3::prelude::*;

	use codec::{Decode, Encode};

	#[test]

	fn conversion_works() {

		let x: MultiLocation = Parent.into();

		assert_eq!(x, MultiLocation { parents: 1, interior: Here });

		//		let x: MultiLocation = (Parent,).into();

		//		assert_eq!(x, MultiLocation { parents: 1, interior: Here });

		//		let x: MultiLocation = (Parent, Parent).into();

		//		assert_eq!(x, MultiLocation { parents: 2, interior: Here });

		let x: MultiLocation = (Parent, Parent, OnlyChild).into();

		assert_eq!(x, MultiLocation { parents: 2, interior: OnlyChild.into() });

		let x: MultiLocation = OnlyChild.into();

		assert_eq!(x, MultiLocation { parents: 0, interior: OnlyChild.into() });

		let x: MultiLocation = (OnlyChild,).into();

		assert_eq!(x, MultiLocation { parents: 0, interior: OnlyChild.into() });

	}

	#[test]

	fn simplify_basic_works() {

		let mut location: MultiLocation =

			(Parent, Parent, Parachain(1000), PalletInstance(42), GeneralIndex(69)).into();

		let context = X2(Parachain(1000), PalletInstance(42));

		let expected = GeneralIndex(69).into();

		location.simplify(&context);

		assert_eq!(location, expected);

		let mut location: MultiLocation = (Parent, PalletInstance(42), GeneralIndex(69)).into();

		let context = X1(PalletInstance(42));

		let expected = GeneralIndex(69).into();

		location.simplify(&context);

		assert_eq!(location, expected);

		let mut location: MultiLocation = (Parent, PalletInstance(42), GeneralIndex(69)).into();

		let context = X2(Parachain(1000), PalletInstance(42));

		let expected = GeneralIndex(69).into();

		location.simplify(&context);

		assert_eq!(location, expected);

		let mut location: MultiLocation =

			(Parent, Parent, Parachain(1000), PalletInstance(42), GeneralIndex(69)).into();

		let context = X3(OnlyChild, Parachain(1000), PalletInstance(42));

		let expected = GeneralIndex(69).into();

		location.simplify(&context);

		assert_eq!(location, expected);

	}

	#[test]

	fn simplify_incompatible_location_fails() {

		let mut location: MultiLocation =

			(Parent, Parent, Parachain(1000), PalletInstance(42), GeneralIndex(69)).into();

		let context = X3(Parachain(1000), PalletInstance(42), GeneralIndex(42));

		let expected =

			(Parent, Parent, Parachain(1000), PalletInstance(42), GeneralIndex(69)).into();

		location.simplify(&context);

		assert_eq!(location, expected);

		let mut location: MultiLocation =

			(Parent, Parent, Parachain(1000), PalletInstance(42), GeneralIndex(69)).into();

		let context = X1(Parachain(1000));

		let expected =

			(Parent, Parent, Parachain(1000), PalletInstance(42), GeneralIndex(69)).into();

		location.simplify(&context);

		assert_eq!(location, expected);

	}

	#[test]

	fn reanchor_works() {

		let mut id: MultiLocation = (Parent, Parachain(1000), GeneralIndex(42)).into();

		let context = Parachain(2000).into();

		let target = (Parent, Parachain(1000)).into();

		let expected = GeneralIndex(42).into();

		id.reanchor(&target, context).unwrap();

		assert_eq!(id, expected);

	}

	#[test]

	fn encode_and_decode_works() {

		let m = MultiLocation {

			parents: 1,

			interior: X2(Parachain(42), AccountIndex64 { network: None, index: 23 }),

		};

		let encoded = m.encode();

		assert_eq!(encoded, [1, 2, 0, 168, 2, 0, 92].to_vec());

		let decoded = MultiLocation::decode(&mut &encoded[..]);

		assert_eq!(decoded, Ok(m));

	}

	#[test]

	fn match_and_split_works() {

		let m = MultiLocation {

			parents: 1,

			interior: X2(Parachain(42), AccountIndex64 { network: None, index: 23 }),

		};

		assert_eq!(m.match_and_split(&MultiLocation { parents: 1, interior: Here }), None);

		assert_eq!(

			m.match_and_split(&MultiLocation { parents: 1, interior: X1(Parachain(42)) }),

			Some(&AccountIndex64 { network: None, index: 23 })

		);

		assert_eq!(m.match_and_split(&m), None);

	}

	#[test]

	fn append_with_works() {

		let acc = AccountIndex64 { network: None, index: 23 };

		let mut m = MultiLocation { parents: 1, interior: X1(Parachain(42)) };

		assert_eq!(m.append_with(X2(PalletInstance(3), acc)), Ok(()));

		assert_eq!(

			m,

			MultiLocation { parents: 1, interior: X3(Parachain(42), PalletInstance(3), acc) }

		);

		// cannot append to create overly long multilocation

		let acc = AccountIndex64 { network: None, index: 23 };

		let m = MultiLocation {

			parents: 254,

			interior: X5(Parachain(42), OnlyChild, OnlyChild, OnlyChild, OnlyChild),

		};

		let suffix: MultiLocation = (PalletInstance(3), acc, OnlyChild, OnlyChild).into();

		assert_eq!(m.clone().append_with(suffix), Err(suffix));

	}

	#[test]

	fn prepend_with_works() {

		let mut m = MultiLocation {

			parents: 1,

			interior: X2(Parachain(42), AccountIndex64 { network: None, index: 23 }),

		};

		assert_eq!(m.prepend_with(MultiLocation { parents: 1, interior: X1(OnlyChild) }), Ok(()));

		assert_eq!(

			m,

			MultiLocation {

				parents: 1,

				interior: X2(Parachain(42), AccountIndex64 { network: None, index: 23 })

			}

		);

		// cannot prepend to create overly long multilocation

		let mut m = MultiLocation { parents: 254, interior: X1(Parachain(42)) };

		let prefix = MultiLocation { parents: 2, interior: Here };

		assert_eq!(m.prepend_with(prefix), Err(prefix));

		let prefix = MultiLocation { parents: 1, interior: Here };

		assert_eq!(m.prepend_with(prefix), Ok(()));

		assert_eq!(m, MultiLocation { parents: 255, interior: X1(Parachain(42)) });

	}

	#[test]

	fn double_ended_ref_iteration_works() {

		let m = X3(Parachain(1000), Parachain(3), PalletInstance(5));

		let mut iter = m.iter();

		let first = iter.next().unwrap();

		assert_eq!(first, &Parachain(1000));

		let third = iter.next_back().unwrap();

		assert_eq!(third, &PalletInstance(5));

		let second = iter.next_back().unwrap();

		assert_eq!(iter.next(), None);

		assert_eq!(iter.next_back(), None);

		assert_eq!(second, &Parachain(3));

		let res = Here

			.pushed_with(*first)

			.unwrap()

			.pushed_with(*second)

			.unwrap()

			.pushed_with(*third)

			.unwrap();

		assert_eq!(m, res);

		// make sure there's no funny business with the 0 indexing

		let m = Here;

		let mut iter = m.iter();

		assert_eq!(iter.next(), None);

		assert_eq!(iter.next_back(), None);

	}

	#[test]

	fn chain_location_works() {

		// Relay-chain or parachain context pointing to local resource,

		let relay_to_local = MultiLocation::new(0, (PalletInstance(42), GeneralIndex(42)));

		assert_eq!(relay_to_local.chain_location(), MultiLocation::here());

		// Relay-chain context pointing to child parachain,

		let relay_to_child =

			MultiLocation::new(0, (Parachain(42), PalletInstance(42), GeneralIndex(42)));

		let expected = MultiLocation::new(0, Parachain(42));

		assert_eq!(relay_to_child.chain_location(), expected);

		// Relay-chain context pointing to different consensus relay,

		let relay_to_remote_relay =

			MultiLocation::new(1, (GlobalConsensus(Kusama), PalletInstance(42), GeneralIndex(42)));

		let expected = MultiLocation::new(1, GlobalConsensus(Kusama));

		assert_eq!(relay_to_remote_relay.chain_location(), expected);

		// Relay-chain context pointing to different consensus parachain,

		let relay_to_remote_para = MultiLocation::new(

			1,

			(GlobalConsensus(Kusama), Parachain(42), PalletInstance(42), GeneralIndex(42)),

		);

		let expected = MultiLocation::new(1, (GlobalConsensus(Kusama), Parachain(42)));

		assert_eq!(relay_to_remote_para.chain_location(), expected);

		// Parachain context pointing to relay chain,

		let para_to_relay = MultiLocation::new(1, (PalletInstance(42), GeneralIndex(42)));

		assert_eq!(para_to_relay.chain_location(), MultiLocation::parent());

		// Parachain context pointing to sibling parachain,

		let para_to_sibling =

			MultiLocation::new(1, (Parachain(42), PalletInstance(42), GeneralIndex(42)));

		let expected = MultiLocation::new(1, Parachain(42));

		assert_eq!(para_to_sibling.chain_location(), expected);

		// Parachain context pointing to different consensus relay,

		let para_to_remote_relay =

			MultiLocation::new(2, (GlobalConsensus(Kusama), PalletInstance(42), GeneralIndex(42)));

		let expected = MultiLocation::new(2, GlobalConsensus(Kusama));

		assert_eq!(para_to_remote_relay.chain_location(), expected);

		// Parachain context pointing to different consensus parachain,

		let para_to_remote_para = MultiLocation::new(

			2,

			(GlobalConsensus(Kusama), Parachain(42), PalletInstance(42), GeneralIndex(42)),

		);

		let expected = MultiLocation::new(2, (GlobalConsensus(Kusama), Parachain(42)));

		assert_eq!(para_to_remote_para.chain_location(), expected);

	}

	#[test]

	fn conversion_from_other_types_works() {

		use crate::v2;

		fn takes_multilocation<Arg: Into<MultiLocation>>(_arg: Arg) {}

		takes_multilocation(Parent);

		takes_multilocation(Here);

		takes_multilocation(X1(Parachain(42)));

		takes_multilocation((Ancestor(255), PalletInstance(8)));

		takes_multilocation((Ancestor(5), Parachain(1), PalletInstance(3)));

		takes_multilocation((Ancestor(2), Here));

		takes_multilocation(AncestorThen(

			3,

			X2(Parachain(43), AccountIndex64 { network: None, index: 155 }),

		));

		takes_multilocation((Parent, AccountId32 { network: None, id: [0; 32] }));

		takes_multilocation((Parent, Here));

		takes_multilocation(ParentThen(X1(Parachain(75))));

		takes_multilocation([Parachain(100), PalletInstance(3)]);

		assert_eq!(

			v2::MultiLocation::from(v2::Junctions::Here).try_into(),

			Ok(MultiLocation::here())

		);

		assert_eq!(v2::MultiLocation::from(v2::Parent).try_into(), Ok(MultiLocation::parent()));

		assert_eq!(

			v2::MultiLocation::from((v2::Parent, v2::Parent, v2::Junction::GeneralIndex(42u128),))

				.try_into(),

			Ok(MultiLocation { parents: 2, interior: X1(GeneralIndex(42u128)) }),

		);

	}

}