Buy&Sell methods for Uniques (#11398)

* Allow to set item's price

* Clean the state when we transfer/burn an item or destroy a collection

* Allow to buy an item

* Remove redundant checks

* Improve events

* Cover with tests

* Add comments

* Apply suggestions

* Fmt

* Improvements for price validation

* Improve validation

* Update to use the new terminology

* Remove multi-assets support

* Chore

* Weights + benchmarking

* Shield against human error

* Test when we pass the higher item's price

* fmt fix

* Chore

* cargo run --quiet --profile=production  --features=runtime-benchmarks --manifest-path=bin/node/cli/Cargo.toml -- benchmark pallet --chain=dev --steps=50 --repeat=20 --pallet=pallet_uniques --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --output=./frame/uniques/src/weights.rs --template=./.maintain/frame-weight-template.hbs

* Remove is_frozen check when setting the price

* Try to fix benchmarking

* Fix benchmarking

* cargo run --quiet --profile=production  --features=runtime-benchmarks --manifest-path=bin/node/cli/Cargo.toml -- benchmark pallet --chain=dev --steps=50 --repeat=20 --pallet=pallet_uniques --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --output=./frame/uniques/src/weights.rs --template=./.maintain/frame-weight-template.hbs

* Add transactional

* Add 'allow deprecated' flag for transactional

* Remove #[allow(deprecated)]

* ".git/.scripts/bench-bot.sh" pallet dev pallet_uniques

Co-authored-by: Parity Bot <admin@parity.io>
Co-authored-by: command-bot <>

frame/uniques/src/benchmarking.rs

@@ -408,5 +408,41 @@ benchmarks_instance_pallet! {
 		}.into());
 	}
 
+	set_price {
+		let (collection, caller, _) = create_collection::<T, I>();
+		let (item, ..) = mint_item::<T, I>(0);
+		let delegate: T::AccountId = account("delegate", 0, SEED);
+		let delegate_lookup = T::Lookup::unlookup(delegate.clone());
+		let price = ItemPrice::<T, I>::from(100u32);
+	}: _(SystemOrigin::Signed(caller.clone()), collection, item, Some(price), Some(delegate_lookup))
+	verify {
+		assert_last_event::<T, I>(Event::ItemPriceSet {
+			collection,
+			item,
+			price,
+			whitelisted_buyer: Some(delegate),
+		}.into());
+	}
+
+	buy_item {
+		let (collection, seller, _) = create_collection::<T, I>();
+		let (item, ..) = mint_item::<T, I>(0);
+		let buyer: T::AccountId = account("buyer", 0, SEED);
+		let buyer_lookup = T::Lookup::unlookup(buyer.clone());
+		let price = ItemPrice::<T, I>::from(0u32);
+		let origin = SystemOrigin::Signed(seller.clone()).into();
+		Uniques::<T, I>::set_price(origin, collection, item, Some(price.clone()), Some(buyer_lookup))?;
+		T::Currency::make_free_balance_be(&buyer, DepositBalanceOf::<T, I>::max_value());
+	}: _(SystemOrigin::Signed(buyer.clone()), collection, item, price.clone())
+	verify {
+		assert_last_event::<T, I>(Event::ItemBought {
+			collection,
+			item,
+			price,
+			seller,
+			buyer,
+		}.into());
+	}
+
 	impl_benchmark_test_suite!(Uniques, crate::mock::new_test_ext(), crate::mock::Test);
 }

frame/uniques/src/functions.rs

@@ -18,7 +18,10 @@
 //! Various pieces of common functionality.
 
 use super::*;
-use frame_support::{ensure, traits::Get};
+use frame_support::{
+	ensure,
+	traits::{ExistenceRequirement, Get},
+};
 use sp_runtime::{DispatchError, DispatchResult};
 
 impl<T: Config<I>, I: 'static> Pallet<T, I> {
@@ -46,6 +49,7 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 		let origin = details.owner;
 		details.owner = dest;
 		Item::<T, I>::insert(&collection, &item, &details);
+		ItemPriceOf::<T, I>::remove(&collection, &item);
 
 		Self::deposit_event(Event::Transferred {
 			collection,
@@ -112,6 +116,8 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 			}
 			#[allow(deprecated)]
 			ItemMetadataOf::<T, I>::remove_prefix(&collection, None);
+			#[allow(deprecated)]
+			ItemPriceOf::<T, I>::remove_prefix(&collection, None);
 			CollectionMetadataOf::<T, I>::remove(&collection);
 			#[allow(deprecated)]
 			Attribute::<T, I>::remove_prefix((&collection,), None);
@@ -196,8 +202,79 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 
 		Item::<T, I>::remove(&collection, &item);
 		Account::<T, I>::remove((&owner, &collection, &item));
+		ItemPriceOf::<T, I>::remove(&collection, &item);
 
 		Self::deposit_event(Event::Burned { collection, item, owner });
 		Ok(())
 	}
+
+	pub fn do_set_price(
+		collection: T::CollectionId,
+		item: T::ItemId,
+		sender: T::AccountId,
+		price: Option<ItemPrice<T, I>>,
+		whitelisted_buyer: Option<T::AccountId>,
+	) -> DispatchResult {
+		let details = Item::<T, I>::get(&collection, &item).ok_or(Error::<T, I>::UnknownItem)?;
+		ensure!(details.owner == sender, Error::<T, I>::NoPermission);
+
+		if let Some(ref price) = price {
+			ItemPriceOf::<T, I>::insert(
+				&collection,
+				&item,
+				(price.clone(), whitelisted_buyer.clone()),
+			);
+			Self::deposit_event(Event::ItemPriceSet {
+				collection,
+				item,
+				price: price.clone(),
+				whitelisted_buyer,
+			});
+		} else {
+			ItemPriceOf::<T, I>::remove(&collection, &item);
+			Self::deposit_event(Event::ItemPriceRemoved { collection, item });
+		}
+
+		Ok(())
+	}
+
+	pub fn do_buy_item(
+		collection: T::CollectionId,
+		item: T::ItemId,
+		buyer: T::AccountId,
+		bid_price: ItemPrice<T, I>,
+	) -> DispatchResult {
+		let details = Item::<T, I>::get(&collection, &item).ok_or(Error::<T, I>::UnknownItem)?;
+		ensure!(details.owner != buyer, Error::<T, I>::NoPermission);
+
+		let price_info =
+			ItemPriceOf::<T, I>::get(&collection, &item).ok_or(Error::<T, I>::NotForSale)?;
+
+		ensure!(bid_price >= price_info.0, Error::<T, I>::BidTooLow);
+
+		if let Some(only_buyer) = price_info.1 {
+			ensure!(only_buyer == buyer, Error::<T, I>::NoPermission);
+		}
+
+		T::Currency::transfer(
+			&buyer,
+			&details.owner,
+			price_info.0,
+			ExistenceRequirement::KeepAlive,
+		)?;
+
+		let old_owner = details.owner.clone();
+
+		Self::do_transfer(collection, item, buyer.clone(), |_, _| Ok(()))?;
+
+		Self::deposit_event(Event::ItemBought {
+			collection,
+			item,
+			price: price_info.0,
+			seller: old_owner,
+			buyer,
+		});
+
+		Ok(())
+	}
 }

frame/uniques/src/lib.rs

@@ -24,6 +24,7 @@
 //! * [`System`](../frame_system/index.html)
 //! * [`Support`](../frame_support/index.html)
 
+#![recursion_limit = "256"]
 // Ensure we're `no_std` when compiling for Wasm.
 #![cfg_attr(not(feature = "std"), no_std)]
 
@@ -42,8 +43,11 @@ pub mod migration;
 pub mod weights;
 
 use codec::{Decode, Encode};
-use frame_support::traits::{
-	tokens::Locker, BalanceStatus::Reserved, Currency, EnsureOriginWithArg, ReservableCurrency,
+use frame_support::{
+	traits::{
+		tokens::Locker, BalanceStatus::Reserved, Currency, EnsureOriginWithArg, ReservableCurrency,
+	},
+	transactional,
 };
 use frame_system::Config as SystemConfig;
 use sp_runtime::{
@@ -245,6 +249,18 @@ pub mod pallet {
 		OptionQuery,
 	>;
 
+	#[pallet::storage]
+	/// Price of an asset instance.
+	pub(super) type ItemPriceOf<T: Config<I>, I: 'static = ()> = StorageDoubleMap<
+		_,
+		Blake2_128Concat,
+		T::CollectionId,
+		Blake2_128Concat,
+		T::ItemId,
+		(ItemPrice<T, I>, Option<T::AccountId>),
+		OptionQuery,
+	>;
+
 	#[pallet::storage]
 	/// Keeps track of the number of items a collection might have.
 	pub(super) type CollectionMaxSupply<T: Config<I>, I: 'static = ()> =
@@ -341,6 +357,23 @@ pub mod pallet {
 		OwnershipAcceptanceChanged { who: T::AccountId, maybe_collection: Option<T::CollectionId> },
 		/// Max supply has been set for a collection.
 		CollectionMaxSupplySet { collection: T::CollectionId, max_supply: u32 },
+		/// The price was set for the instance.
+		ItemPriceSet {
+			collection: T::CollectionId,
+			item: T::ItemId,
+			price: ItemPrice<T, I>,
+			whitelisted_buyer: Option<T::AccountId>,
+		},
+		/// The price for the instance was removed.
+		ItemPriceRemoved { collection: T::CollectionId, item: T::ItemId },
+		/// An item was bought.
+		ItemBought {
+			collection: T::CollectionId,
+			item: T::ItemId,
+			price: ItemPrice<T, I>,
+			seller: T::AccountId,
+			buyer: T::AccountId,
+		},
 	}
 
 	#[pallet::error]
@@ -375,6 +408,12 @@ pub mod pallet {
 		MaxSupplyAlreadySet,
 		/// The provided max supply is less to the amount of items a collection already has.
 		MaxSupplyTooSmall,
+		/// The given item ID is unknown.
+		UnknownItem,
+		/// Item is not for sale.
+		NotForSale,
+		/// The provided bid is too low.
+		BidTooLow,
 	}
 
 	impl<T: Config<I>, I: 'static> Pallet<T, I> {
@@ -1408,5 +1447,50 @@ pub mod pallet {
 			Self::deposit_event(Event::CollectionMaxSupplySet { collection, max_supply });
 			Ok(())
 		}
+
+		/// Set (or reset) the price for an item.
+		///
+		/// Origin must be Signed and must be the owner of the asset `item`.
+		///
+		/// - `collection`: The collection of the item.
+		/// - `item`: The item to set the price for.
+		/// - `price`: The price for the item. Pass `None`, to reset the price.
+		/// - `buyer`: Restricts the buy operation to a specific account.
+		///
+		/// Emits `ItemPriceSet` on success if the price is not `None`.
+		/// Emits `ItemPriceRemoved` on success if the price is `None`.
+		#[pallet::weight(T::WeightInfo::set_price())]
+		pub fn set_price(
+			origin: OriginFor<T>,
+			collection: T::CollectionId,
+			item: T::ItemId,
+			price: Option<ItemPrice<T, I>>,
+			whitelisted_buyer: Option<<T::Lookup as StaticLookup>::Source>,
+		) -> DispatchResult {
+			let origin = ensure_signed(origin)?;
+			let whitelisted_buyer = whitelisted_buyer.map(T::Lookup::lookup).transpose()?;
+			Self::do_set_price(collection, item, origin, price, whitelisted_buyer)
+		}
+
+		/// Allows to buy an item if it's up for sale.
+		///
+		/// Origin must be Signed and must not be the owner of the `item`.
+		///
+		/// - `collection`: The collection of the item.
+		/// - `item`: The item the sender wants to buy.
+		/// - `bid_price`: The price the sender is willing to pay.
+		///
+		/// Emits `ItemBought` on success.
+		#[pallet::weight(T::WeightInfo::buy_item())]
+		#[transactional]
+		pub fn buy_item(
+			origin: OriginFor<T>,
+			collection: T::CollectionId,
+			item: T::ItemId,
+			bid_price: ItemPrice<T, I>,
+		) -> DispatchResult {
+			let origin = ensure_signed(origin)?;
+			Self::do_buy_item(collection, item, origin, bid_price)
+		}
 	}
 }