Non-fungible token traits (#8993)

* Non-fungible token traits

* Docs

* Fixes

* Implement non-fungible trait for Uniques

* Update frame/uniques/src/impl_nonfungibles.rs

Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>

* Update frame/uniques/src/impl_nonfungibles.rs

Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>

Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>

substrate/frame/uniques/src/functions.rs

@@ -0,0 +1,115 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2017-2021 Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Various pieces of common functionality.
+
+use super::*;
+use frame_support::{ensure, traits::Get};
+use sp_runtime::{DispatchResult, DispatchError};
+
+impl<T: Config<I>, I: 'static> Pallet<T, I> {
+	pub(crate) fn do_transfer(
+		class: T::ClassId,
+		instance: T::InstanceId,
+		dest: T::AccountId,
+		with_details: impl FnOnce(
+			&ClassDetailsFor<T, I>,
+			&mut InstanceDetailsFor<T, I>,
+		) -> DispatchResult,
+	) -> DispatchResult {
+		let class_details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::Unknown)?;
+		ensure!(!class_details.is_frozen, Error::<T, I>::Frozen);
+
+		let mut details = Asset::<T, I>::get(&class, &instance).ok_or(Error::<T, I>::Unknown)?;
+		ensure!(!details.is_frozen, Error::<T, I>::Frozen);
+		with_details(&class_details, &mut details)?;
+
+		Account::<T, I>::remove((&details.owner, &class, &instance));
+		Account::<T, I>::insert((&dest, &class, &instance), ());
+		let origin = details.owner;
+		details.owner = dest;
+		Asset::<T, I>::insert(&class, &instance, &details);
+
+		Self::deposit_event(Event::Transferred(class, instance, origin, details.owner));
+		Ok(())
+	}
+
+	pub(super) fn do_mint(
+		class: T::ClassId,
+		instance: T::InstanceId,
+		owner: T::AccountId,
+		with_details: impl FnOnce(
+			&ClassDetailsFor<T, I>,
+		) -> DispatchResult,
+	) -> DispatchResult {
+		ensure!(!Asset::<T, I>::contains_key(class, instance), Error::<T, I>::AlreadyExists);
+
+		Class::<T, I>::try_mutate(&class, |maybe_class_details| -> DispatchResult {
+			let class_details = maybe_class_details.as_mut().ok_or(Error::<T, I>::Unknown)?;
+
+			with_details(&class_details)?;
+
+			let instances = class_details.instances.checked_add(1)
+				.ok_or(ArithmeticError::Overflow)?;
+			class_details.instances = instances;
+
+			let deposit = match class_details.free_holding {
+				true => Zero::zero(),
+				false => T::InstanceDeposit::get(),
+			};
+			T::Currency::reserve(&class_details.owner, deposit)?;
+			class_details.total_deposit += deposit;
+
+			let owner = owner.clone();
+			Account::<T, I>::insert((&owner, &class, &instance), ());
+			let details = InstanceDetails { owner, approved: None, is_frozen: false, deposit};
+			Asset::<T, I>::insert(&class, &instance, details);
+			Ok(())
+		})?;
+
+		Self::deposit_event(Event::Issued(class, instance, owner));
+		Ok(())
+	}
+
+	pub(super) fn do_burn(
+		class: T::ClassId,
+		instance: T::InstanceId,
+		with_details: impl FnOnce(
+			&ClassDetailsFor<T, I>,
+			&InstanceDetailsFor<T, I>,
+		) -> DispatchResult,
+	) -> DispatchResult {
+		let owner = Class::<T, I>::try_mutate(&class, |maybe_class_details| -> Result<T::AccountId, DispatchError> {
+			let class_details = maybe_class_details.as_mut().ok_or(Error::<T, I>::Unknown)?;
+			let details = Asset::<T, I>::get(&class, &instance)
+				.ok_or(Error::<T, I>::Unknown)?;
+			with_details(&class_details, &details)?;
+
+			// Return the deposit.
+			T::Currency::unreserve(&class_details.owner, details.deposit);
+			class_details.total_deposit.saturating_reduce(details.deposit);
+			class_details.instances.saturating_dec();
+			Ok(details.owner)
+		})?;
+
+		Asset::<T, I>::remove(&class, &instance);
+		Account::<T, I>::remove((&owner, &class, &instance));
+
+		Self::deposit_event(Event::Burned(class, instance, owner));
+		Ok(())
+	}
+}

substrate/frame/uniques/src/impl_nonfungibles.rs

@@ -0,0 +1,108 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2017-2021 Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Implementations for `nonfungibles` traits.
+
+use super::*;
+use sp_std::convert::TryFrom;
+use frame_support::traits::tokens::nonfungibles::{Inspect, Mutate, Transfer};
+use frame_support::BoundedSlice;
+use sp_runtime::DispatchResult;
+
+impl<T: Config<I>, I: 'static> Inspect<<T as SystemConfig>::AccountId> for Pallet<T, I> {
+	type InstanceId = T::InstanceId;
+	type ClassId = T::ClassId;
+
+	fn owner(
+		class: &Self::ClassId,
+		instance: &Self::InstanceId,
+	) -> Option<<T as SystemConfig>::AccountId> {
+		Asset::<T, I>::get(class, instance).map(|a| a.owner)
+	}
+
+	fn class_owner(class: &Self::ClassId) -> Option<<T as SystemConfig>::AccountId> {
+		Class::<T, I>::get(class).map(|a| a.owner)
+	}
+
+	/// Returns the attribute value of `instance` of `class` corresponding to `key`.
+	///
+	/// When `key` is empty, we return the instance metadata value.
+	///
+	/// By default this is `None`; no attributes are defined.
+	fn attribute(class: &Self::ClassId, instance: &Self::InstanceId, key: &[u8])
+		-> Option<Vec<u8>>
+	{
+		if key.is_empty() {
+			// We make the empty key map to the instance metadata value.
+			InstanceMetadataOf::<T, I>::get(class, instance).map(|m| m.data.into())
+		} else {
+			let key = BoundedSlice::<_, _>::try_from(key).ok()?;
+			Attribute::<T, I>::get((class, Some(instance), key)).map(|a| a.0.into())
+		}
+	}
+
+	/// Returns the attribute value of `instance` of `class` corresponding to `key`.
+	///
+	/// When `key` is empty, we return the instance metadata value.
+	///
+	/// By default this is `None`; no attributes are defined.
+	fn class_attribute(class: &Self::ClassId, key: &[u8])
+		-> Option<Vec<u8>>
+	{
+		if key.is_empty() {
+			// We make the empty key map to the instance metadata value.
+			ClassMetadataOf::<T, I>::get(class).map(|m| m.data.into())
+		} else {
+			let key = BoundedSlice::<_, _>::try_from(key).ok()?;
+			Attribute::<T, I>::get((class, Option::<T::InstanceId>::None, key)).map(|a| a.0.into())
+		}
+	}
+
+	/// Returns `true` if the asset `instance` of `class` may be transferred.
+	///
+	/// Default implementation is that all assets are transferable.
+	fn can_transfer(class: &Self::ClassId, instance: &Self::InstanceId) -> bool {
+		match (Class::<T, I>::get(class), Asset::<T, I>::get(class, instance)) {
+			(Some(cd), Some(id)) if !cd.is_frozen && !id.is_frozen => true,
+			_ => false,
+		}
+	}
+}
+
+impl<T: Config<I>, I: 'static> Mutate<<T as SystemConfig>::AccountId> for Pallet<T, I> {
+	fn mint_into(
+		class: &Self::ClassId,
+		instance: &Self::InstanceId,
+		who: &T::AccountId,
+	) -> DispatchResult {
+		Self::do_mint(class.clone(), instance.clone(), who.clone(), |_| Ok(()))
+	}
+
+	fn burn_from(class: &Self::ClassId, instance: &Self::InstanceId) -> DispatchResult {
+		Self::do_burn(class.clone(), instance.clone(), |_, _| Ok(()))
+	}
+}
+
+impl<T: Config<I>, I: 'static> Transfer<T::AccountId> for Pallet<T, I> {
+	fn transfer(
+		class: &Self::ClassId,
+		instance: &Self::InstanceId,
+		destination: &T::AccountId,
+	) -> DispatchResult {
+		Self::do_transfer(class.clone(), instance.clone(), destination.clone(), |_, _| Ok(()))
+	}
+}

substrate/frame/uniques/src/lib.rs

@@ -36,6 +36,8 @@ pub mod mock;
 mod tests;
 
 mod types;
+mod functions;
+mod impl_nonfungibles;
 pub use types::*;
 
 use sp_std::prelude::*;
@@ -448,32 +450,10 @@ pub mod pallet {
 			let origin = ensure_signed(origin)?;
 			let owner = T::Lookup::lookup(owner)?;
 
-			ensure!(!Asset::<T, I>::contains_key(class, instance), Error::<T, I>::AlreadyExists);
-
-			Class::<T, I>::try_mutate(&class, |maybe_class_details| -> DispatchResult {
-				let class_details = maybe_class_details.as_mut().ok_or(Error::<T, I>::Unknown)?;
+			Self::do_mint(class, instance, owner, |class_details| {
 				ensure!(class_details.issuer == origin, Error::<T, I>::NoPermission);
-
-				let instances = class_details.instances.checked_add(1)
-					.ok_or(ArithmeticError::Overflow)?;
-				class_details.instances = instances;
-
-				let deposit = match class_details.free_holding {
-					true => Zero::zero(),
-					false => T::InstanceDeposit::get(),
-				};
-				T::Currency::reserve(&class_details.owner, deposit)?;
-				class_details.total_deposit += deposit;
-
-				let owner = owner.clone();
-				Account::<T, I>::insert((&owner, &class, &instance), ());
-				let details = InstanceDetails { owner, approved: None, is_frozen: false, deposit};
-				Asset::<T, I>::insert(&class, &instance, details);
 				Ok(())
-			})?;
-
-			Self::deposit_event(Event::Issued(class, instance, owner));
-			Ok(())
+			})
 		}
 
 		/// Destroy a single asset instance.
@@ -499,27 +479,12 @@ pub mod pallet {
 			let origin = ensure_signed(origin)?;
 			let check_owner = check_owner.map(T::Lookup::lookup).transpose()?;
 
-			let owner = Class::<T, I>::try_mutate(&class, |maybe_class_details| -> Result<T::AccountId, DispatchError> {
-				let class_details = maybe_class_details.as_mut().ok_or(Error::<T, I>::Unknown)?;
-				let details = Asset::<T, I>::get(&class, &instance)
-					.ok_or(Error::<T, I>::Unknown)?;
+			Self::do_burn(class, instance, |class_details, details| {
 				let is_permitted = class_details.admin == origin || details.owner == origin;
 				ensure!(is_permitted, Error::<T, I>::NoPermission);
 				ensure!(check_owner.map_or(true, |o| o == details.owner), Error::<T, I>::WrongOwner);
-
-				// Return the deposit.
-				T::Currency::unreserve(&class_details.owner, details.deposit);
-				class_details.total_deposit.saturating_reduce(details.deposit);
-				class_details.instances.saturating_dec();
-				Ok(details.owner)
-			})?;
-
-
-			Asset::<T, I>::remove(&class, &instance);
-			Account::<T, I>::remove((&owner, &class, &instance));
-
-			Self::deposit_event(Event::Burned(class, instance, owner));
-			Ok(())
+				Ok(())
+			})
 		}
 
 		/// Move an asset from the sender account to another.
@@ -547,24 +512,13 @@ pub mod pallet {
 			let origin = ensure_signed(origin)?;
 			let dest = T::Lookup::lookup(dest)?;
 
-			let class_details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::Unknown)?;
-			ensure!(!class_details.is_frozen, Error::<T, I>::Frozen);
-
-			let mut details = Asset::<T, I>::get(&class, &instance).ok_or(Error::<T, I>::Unknown)?;
-			ensure!(!details.is_frozen, Error::<T, I>::Frozen);
-			if details.owner != origin && class_details.admin != origin {
-				let approved = details.approved.take().map_or(false, |i| i == origin);
-				ensure!(approved, Error::<T, I>::NoPermission);
-			}
-
-			Account::<T, I>::remove((&details.owner, &class, &instance));
-			Account::<T, I>::insert((&dest, &class, &instance), ());
-			details.owner = dest;
-			Asset::<T, I>::insert(&class, &instance, &details);
-
-			Self::deposit_event(Event::Transferred(class, instance, origin, details.owner));
-
-			Ok(())
+			Self::do_transfer(class, instance, dest, |class_details, details| {
+				if details.owner != origin && class_details.admin != origin {
+					let approved = details.approved.take().map_or(false, |i| i == origin);
+					ensure!(approved, Error::<T, I>::NoPermission);
+				}
+				Ok(())
+			})
 		}
 
 		/// Reevaluate the deposits on some assets.

substrate/frame/uniques/src/types.rs

@@ -22,6 +22,11 @@ use frame_support::{traits::Get, BoundedVec};
 
 pub(super) type DepositBalanceOf<T, I = ()> =
 	<<T as Config<I>>::Currency as Currency<<T as SystemConfig>::AccountId>>::Balance;
+pub(super) type ClassDetailsFor<T, I> =
+	ClassDetails<<T as SystemConfig>::AccountId, DepositBalanceOf<T, I>>;
+pub(super) type InstanceDetailsFor<T, I> =
+	InstanceDetails<<T as SystemConfig>::AccountId, DepositBalanceOf<T, I>>;
+
 
 #[derive(Clone, Encode, Decode, Eq, PartialEq, RuntimeDebug)]
 pub struct ClassDetails<