git.delta.rocks / unique-network / refs/commits / 374e37517d0d

1// Copyright 2019-2022 Unique Network (Gibraltar) Ltd.2// This file is part of Unique Network.34// Unique Network is free software: you can redistribute it and/or modify5// it under the terms of the GNU General Public License as published by6// the Free Software Foundation, either version 3 of the License, or7// (at your option) any later version.89// Unique Network is distributed in the hope that it will be useful,10// but WITHOUT ANY WARRANTY; without even the implied warranty of11// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the12// GNU General Public License for more details.1314// You should have received a copy of the GNU General Public License15// along with Unique Network. If not, see <http://www.gnu.org/licenses/>.1617//! # Fungible Pallet18//!19//! The Fungible pallet provides functionality for dealing with fungible assets.20//!21//! - [`CreateItemData`]22//! - [`Config`]23//! - [`FungibleHandle`]24//! - [`Pallet`]25//! - [`TotalSupply`]26//! - [`Balance`]27//! - [`Allowance`]28//! - [`Error`]29//!30//! ## Fungible tokens31//!32//! Fungible tokens or assets are divisible and non-unique. For instance,33//! fiat currencies like the dollar are fungible: A $1 bill34//! in New York City has the same value as a $1 bill in Miami.35//! A fungible token can also be a cryptocurrency like Bitcoin: 1 BTC is worth 1 BTC,36//! no matter where it is issued. Thus, the fungibility refers to a specific currency’s37//! ability to maintain one standard value. As well, it needs to have uniform acceptance.38//! This means that a currency’s history should not be able to affect its value,39//! and this is due to the fact that each piece that is a part of the currency is equal40//! in value when compared to every other piece of that exact same currency.41//! In the world of cryptocurrencies, this is essentially a coin or a token42//! that can be replaced by another identical coin or token, and they are43//! both mutually interchangeable. A popular implementation of fungible tokens is44//! the ERC-20 token standard.45//!46//! ### ERC-2047//!48//! The [ERC-20](https://ethereum.org/en/developers/docs/standards/tokens/erc-20/) (Ethereum Request for Comments 20), proposed by Fabian Vogelsteller in November 2015,49//! is a Token Standard that implements an API for tokens within Smart Contracts.50//!51//! Example functionalities ERC-20 provides:52//!53//! * transfer tokens from one account to another54//! * get the current token balance of an account55//! * get the total supply of the token available on the network56//! * approve whether an amount of token from an account can be spent by a third-party account57//!58//! ## Overview59//!60//! The module provides functionality for asset management of fungible asset, supports ERC-20 standart, includes:61//!62//! * Asset Issuance63//! * Asset Transferal64//! * Asset Destruction65//! * Delegated Asset Transfers66//!67//! **NOTE:** The created fungible asset always has `token_id` = 0.68//! So `tokenA` and `tokenB` will have different `collection_id`.69//!70//! ### Implementations71//!72//! The Fungible pallet provides implementations for the following traits.73//!74//! - [`WithRecorder`](pallet_evm_coder_substrate::WithRecorder): Trait for EVM support75//! - [`CommonCollectionOperations`](pallet_common::CommonCollectionOperations): Functions for dealing with collections76//!	- [`CommonWeightInfo`](pallet_common::CommonWeightInfo): Functions for retrieval of transaction weight77//! - [`CommonEvmHandler`](pallet_common::erc::CommonEvmHandler): Function for handling EVM runtime calls7879#![cfg_attr(not(feature = "std"), no_std)]8081use core::ops::Deref;82use evm_coder::ToLog;83use frame_support::ensure;84use pallet_evm::account::CrossAccountId;85use up_data_structs::{86	AccessMode, CollectionId, CollectionFlags, TokenId, CreateCollectionData,87	mapping::TokenAddressMapping, budget::Budget, PropertyKey, Property,88};89use pallet_common::{90	Error as CommonError, Event as CommonEvent, Pallet as PalletCommon,91	eth::collection_id_to_address,92};93use pallet_evm::Pallet as PalletEvm;94use pallet_structure::Pallet as PalletStructure;95use pallet_evm_coder_substrate::WithRecorder;96use sp_core::H160;97use sp_runtime::{ArithmeticError, DispatchError, DispatchResult};98use sp_std::{collections::btree_map::BTreeMap, vec::Vec};99100pub use pallet::*;101102use crate::erc::ERC20Events;103#[cfg(feature = "runtime-benchmarks")]104pub mod benchmarking;105pub mod common;106pub mod erc;107pub mod weights;108109pub type CreateItemData<T> = (<T as pallet_evm::Config>::CrossAccountId, u128);110pub(crate) type SelfWeightOf<T> = <T as Config>::WeightInfo;111112#[frame_support::pallet]113pub mod pallet {114	use frame_support::{Blake2_128, Blake2_128Concat, Twox64Concat, pallet_prelude::*, storage::Key};115	use up_data_structs::CollectionId;116	use super::weights::WeightInfo;117118	#[pallet::error]119	pub enum Error<T> {120		/// Not Fungible item data used to mint in Fungible collection.121		NotFungibleDataUsedToMintFungibleCollectionToken,122		/// Fungible tokens hold no ID, and the default value of TokenId for Fungible collection is 0.123		FungibleItemsHaveNoId,124		/// Tried to set data for fungible item.125		FungibleItemsDontHaveData,126		/// Fungible token does not support nesting.127		FungibleDisallowsNesting,128		/// Setting item properties is not allowed.129		SettingPropertiesNotAllowed,130		/// Setting allowance for all is not allowed.131		SettingAllowanceForAllNotAllowed,132		/// Only a fungible collection could be possibly broken; any fungible token is valid.133		FungibleTokensAreAlwaysValid,134	}135136	#[pallet::config]137	pub trait Config:138		frame_system::Config + pallet_common::Config + pallet_structure::Config + pallet_evm::Config139	{140		type WeightInfo: WeightInfo;141	}142143	#[pallet::pallet]144	pub struct Pallet<T>(_);145146	/// Total amount of fungible tokens inside a collection.147	#[pallet::storage]148	pub type TotalSupply<T: Config> =149		StorageMap<Hasher = Twox64Concat, Key = CollectionId, Value = u128, QueryKind = ValueQuery>;150151	/// Amount of tokens owned by an account inside a collection.152	#[pallet::storage]153	pub type Balance<T: Config> = StorageNMap<154		Key = (155			Key<Twox64Concat, CollectionId>,156			Key<Blake2_128Concat, T::CrossAccountId>,157		),158		Value = u128,159		QueryKind = ValueQuery,160	>;161162	/// Storage for assets delegated to a limited extent to other users.163	#[pallet::storage]164	pub type Allowance<T: Config> = StorageNMap<165		Key = (166			Key<Twox64Concat, CollectionId>,167			Key<Blake2_128, T::CrossAccountId>,       // Owner168			Key<Blake2_128Concat, T::CrossAccountId>, // Spender169		),170		Value = u128,171		QueryKind = ValueQuery,172	>;173}174175/// Wrapper around untyped collection handle, asserting inner collection is of fungible type.176/// Required for interaction with Fungible collections, type safety and implementation [`solidity_interface`][`evm_coder::solidity_interface`].177pub struct FungibleHandle<T: Config>(pallet_common::CollectionHandle<T>);178179/// Implementation of methods required for dispatching during runtime.180impl<T: Config> FungibleHandle<T> {181	/// Casts [`CollectionHandle`][`pallet_common::CollectionHandle`] into [`FungibleHandle`].182	pub fn cast(inner: pallet_common::CollectionHandle<T>) -> Self {183		Self(inner)184	}185186	/// Casts [`FungibleHandle`] into [`CollectionHandle`][`pallet_common::CollectionHandle`].187	pub fn into_inner(self) -> pallet_common::CollectionHandle<T> {188		self.0189	}190	/// Returns a mutable reference to the internal [`CollectionHandle`][`pallet_common::CollectionHandle`].191	pub fn common_mut(&mut self) -> &mut pallet_common::CollectionHandle<T> {192		&mut self.0193	}194}195impl<T: Config> WithRecorder<T> for FungibleHandle<T> {196	fn recorder(&self) -> &pallet_evm_coder_substrate::SubstrateRecorder<T> {197		self.0.recorder()198	}199	fn into_recorder(self) -> pallet_evm_coder_substrate::SubstrateRecorder<T> {200		self.0.into_recorder()201	}202}203impl<T: Config> Deref for FungibleHandle<T> {204	type Target = pallet_common::CollectionHandle<T>;205206	fn deref(&self) -> &Self::Target {207		&self.0208	}209}210211/// Pallet implementation for fungible assets212impl<T: Config> Pallet<T> {213	/// Initializes the collection. Returns [CollectionId] on success, [DispatchError] otherwise.214	pub fn init_collection(215		owner: T::CrossAccountId,216		payer: T::CrossAccountId,217		data: CreateCollectionData<T::AccountId>,218		flags: CollectionFlags,219	) -> Result<CollectionId, DispatchError> {220		<PalletCommon<T>>::init_collection(owner, payer, data, flags)221	}222223	/// Initializes the collection with ForeignCollection flag. Returns [CollectionId] on success, [DispatchError] otherwise.224	pub fn init_foreign_collection(225		owner: T::CrossAccountId,226		payer: T::CrossAccountId,227		data: CreateCollectionData<T::AccountId>,228	) -> Result<CollectionId, DispatchError> {229		let id = <PalletCommon<T>>::init_collection(230			owner,231			payer,232			data,233			CollectionFlags {234				foreign: true,235				..Default::default()236			},237		)?;238		Ok(id)239	}240241	/// Destroys a collection.242	pub fn destroy_collection(243		collection: FungibleHandle<T>,244		sender: &T::CrossAccountId,245	) -> DispatchResult {246		let id = collection.id;247248		if Self::collection_has_tokens(id) {249			return Err(<CommonError<T>>::CantDestroyNotEmptyCollection.into());250		}251252		// =========253254		PalletCommon::destroy_collection(collection.0, sender)?;255256		<TotalSupply<T>>::remove(id);257		let _ = <Balance<T>>::clear_prefix((id,), u32::MAX, None);258		let _ = <Allowance<T>>::clear_prefix((id,), u32::MAX, None);259		Ok(())260	}261262	/// Add properties to the collection.263	pub fn set_collection_properties(264		collection: &FungibleHandle<T>,265		sender: &T::CrossAccountId,266		properties: Vec<Property>,267	) -> DispatchResult {268		<PalletCommon<T>>::set_collection_properties(collection, sender, properties.into_iter())269	}270271	/// Delete properties of the collection, associated with the provided keys.272	pub fn delete_collection_properties(273		collection: &FungibleHandle<T>,274		sender: &T::CrossAccountId,275		property_keys: Vec<PropertyKey>,276	) -> DispatchResult {277		<PalletCommon<T>>::delete_collection_properties(278			collection,279			sender,280			property_keys.into_iter(),281		)282	}283284	/// Checks if collection has tokens. Return `true` if it has.285	fn collection_has_tokens(collection_id: CollectionId) -> bool {286		<TotalSupply<T>>::get(collection_id) != 0287	}288289	/// Burns the specified amount of the token. If the token balance290	/// or total supply is less than the given value,291	/// it will return [DispatchError].292	pub fn burn(293		collection: &FungibleHandle<T>,294		owner: &T::CrossAccountId,295		amount: u128,296	) -> DispatchResult {297		let total_supply = <TotalSupply<T>>::get(collection.id)298			.checked_sub(amount)299			.ok_or(<CommonError<T>>::TokenValueTooLow)?;300301		let balance = <Balance<T>>::get((collection.id, owner))302			.checked_sub(amount)303			.ok_or(<CommonError<T>>::TokenValueTooLow)?;304305		// Foreign collection check306		ensure!(!collection.flags.foreign, <CommonError<T>>::NoPermission);307308		if collection.permissions.access() == AccessMode::AllowList {309			collection.check_allowlist(owner)?;310		}311312		// =========313314		if balance == 0 {315			<Balance<T>>::remove((collection.id, owner));316			<PalletStructure<T>>::unnest_if_nested(owner, collection.id, TokenId::default());317		} else {318			<Balance<T>>::insert((collection.id, owner), balance);319		}320		<TotalSupply<T>>::insert(collection.id, total_supply);321322		<PalletEvm<T>>::deposit_log(323			ERC20Events::Transfer {324				from: *owner.as_eth(),325				to: H160::default(),326				value: amount.into(),327			}328			.to_log(collection_id_to_address(collection.id)),329		);330		<PalletCommon<T>>::deposit_event(CommonEvent::ItemDestroyed(331			collection.id,332			TokenId::default(),333			owner.clone(),334			amount,335		));336		Ok(())337	}338339	/// Burns the specified amount of the token.340	pub fn burn_foreign(341		collection: &FungibleHandle<T>,342		owner: &T::CrossAccountId,343		amount: u128,344	) -> DispatchResult {345		let total_supply = <TotalSupply<T>>::get(collection.id)346			.checked_sub(amount)347			.ok_or(<CommonError<T>>::TokenValueTooLow)?;348349		let balance = <Balance<T>>::get((collection.id, owner))350			.checked_sub(amount)351			.ok_or(<CommonError<T>>::TokenValueTooLow)?;352		// =========353354		if balance == 0 {355			<Balance<T>>::remove((collection.id, owner));356			<PalletStructure<T>>::unnest_if_nested(owner, collection.id, TokenId::default());357		} else {358			<Balance<T>>::insert((collection.id, owner), balance);359		}360		<TotalSupply<T>>::insert(collection.id, total_supply);361362		<PalletEvm<T>>::deposit_log(363			ERC20Events::Transfer {364				from: *owner.as_eth(),365				to: H160::default(),366				value: amount.into(),367			}368			.to_log(collection_id_to_address(collection.id)),369		);370		<PalletCommon<T>>::deposit_event(CommonEvent::ItemDestroyed(371			collection.id,372			TokenId::default(),373			owner.clone(),374			amount,375		));376		Ok(())377	}378379	/// Transfers the specified amount of tokens. Will check that380	/// the transfer is allowed for the token.381	///382	/// - `from`: Owner of tokens to transfer.383	/// - `to`: Recepient of transfered tokens.384	/// - `amount`: Amount of tokens to transfer.385	/// - `collection`: Collection that contains the token386	pub fn transfer(387		collection: &FungibleHandle<T>,388		from: &T::CrossAccountId,389		to: &T::CrossAccountId,390		amount: u128,391		nesting_budget: &dyn Budget,392	) -> DispatchResult {393		ensure!(394			collection.limits.transfers_enabled(),395			<CommonError<T>>::TransferNotAllowed,396		);397398		if collection.permissions.access() == AccessMode::AllowList {399			collection.check_allowlist(from)?;400			collection.check_allowlist(to)?;401		}402		<PalletCommon<T>>::ensure_correct_receiver(to)?;403404		let balance_from = <Balance<T>>::get((collection.id, from))405			.checked_sub(amount)406			.ok_or(<CommonError<T>>::TokenValueTooLow)?;407		let balance_to = if from != to && amount != 0 {408			Some(409				<Balance<T>>::get((collection.id, to))410					.checked_add(amount)411					.ok_or(ArithmeticError::Overflow)?,412			)413		} else {414			None415		};416417		// =========418419		if let Some(balance_to) = balance_to {420			// from != to && amount != 0421422			<PalletStructure<T>>::nest_if_sent_to_token(423				from.clone(),424				to,425				collection.id,426				TokenId::default(),427				nesting_budget,428			)?;429430			if balance_from == 0 {431				<Balance<T>>::remove((collection.id, from));432				<PalletStructure<T>>::unnest_if_nested(from, collection.id, TokenId::default());433			} else {434				<Balance<T>>::insert((collection.id, from), balance_from);435			}436			<Balance<T>>::insert((collection.id, to), balance_to);437		}438439		<PalletEvm<T>>::deposit_log(440			ERC20Events::Transfer {441				from: *from.as_eth(),442				to: *to.as_eth(),443				value: amount.into(),444			}445			.to_log(collection_id_to_address(collection.id)),446		);447		<PalletCommon<T>>::deposit_event(CommonEvent::Transfer(448			collection.id,449			TokenId::default(),450			from.clone(),451			to.clone(),452			amount,453		));454		Ok(())455	}456457	/// Minting tokens for multiple IDs.458	/// It is a utility function used in [`create_multiple_items`][`Pallet::create_multiple_items`]459	/// and [`create_multiple_items_foreign`][`Pallet::create_multiple_items_foreign`]460	pub fn create_multiple_items_common(461		collection: &FungibleHandle<T>,462		sender: &T::CrossAccountId,463		data: BTreeMap<T::CrossAccountId, u128>,464		nesting_budget: &dyn Budget,465	) -> DispatchResult {466		let total_supply = data467			.iter()468			.map(|(_, v)| *v)469			.try_fold(<TotalSupply<T>>::get(collection.id), |acc, v| {470				acc.checked_add(v)471			})472			.ok_or(ArithmeticError::Overflow)?;473474		for (to, _) in data.iter() {475			<PalletStructure<T>>::check_nesting(476				sender.clone(),477				to,478				collection.id,479				TokenId::default(),480				nesting_budget,481			)?;482		}483484		let updated_balances = data485			.into_iter()486			.map(|(user, amount)| {487				let updated_balance = <Balance<T>>::get((collection.id, &user))488					.checked_add(amount)489					.ok_or(ArithmeticError::Overflow)?;490				Ok((user, amount, updated_balance))491			})492			.collect::<Result<Vec<_>, DispatchError>>()?;493494		// =========495496		<TotalSupply<T>>::insert(collection.id, total_supply);497		for (user, amount, updated_balance) in updated_balances {498			<Balance<T>>::insert((collection.id, &user), updated_balance);499			<PalletStructure<T>>::nest_if_sent_to_token_unchecked(500				&user,501				collection.id,502				TokenId::default(),503			);504			<PalletEvm<T>>::deposit_log(505				ERC20Events::Transfer {506					from: H160::default(),507					to: *user.as_eth(),508					value: amount.into(),509				}510				.to_log(collection_id_to_address(collection.id)),511			);512			<PalletCommon<T>>::deposit_event(CommonEvent::ItemCreated(513				collection.id,514				TokenId::default(),515				user.clone(),516				amount,517			));518		}519520		Ok(())521	}522523	/// Minting tokens for multiple IDs.524	/// See [`create_item`][`Pallet::create_item`] for more details.525	pub fn create_multiple_items(526		collection: &FungibleHandle<T>,527		sender: &T::CrossAccountId,528		data: BTreeMap<T::CrossAccountId, u128>,529		nesting_budget: &dyn Budget,530	) -> DispatchResult {531		// Foreign collection check532		ensure!(!collection.flags.foreign, <CommonError<T>>::NoPermission);533534		if !collection.is_owner_or_admin(sender) {535			ensure!(536				collection.permissions.mint_mode(),537				<CommonError<T>>::PublicMintingNotAllowed538			);539			collection.check_allowlist(sender)?;540541			for (owner, _) in data.iter() {542				collection.check_allowlist(owner)?;543			}544		}545546		Self::create_multiple_items_common(collection, sender, data, nesting_budget)547	}548549	/// Minting tokens for multiple IDs.550	/// See [`create_item_foreign`][`Pallet::create_item_foreign`] for more details.551	pub fn create_multiple_items_foreign(552		collection: &FungibleHandle<T>,553		sender: &T::CrossAccountId,554		data: BTreeMap<T::CrossAccountId, u128>,555		nesting_budget: &dyn Budget,556	) -> DispatchResult {557		Self::create_multiple_items_common(collection, sender, data, nesting_budget)558	}559560	fn set_allowance_unchecked(561		collection: &FungibleHandle<T>,562		owner: &T::CrossAccountId,563		spender: &T::CrossAccountId,564		amount: u128,565	) {566		if amount == 0 {567			<Allowance<T>>::remove((collection.id, owner, spender));568		} else {569			<Allowance<T>>::insert((collection.id, owner, spender), amount);570		}571572		<PalletEvm<T>>::deposit_log(573			ERC20Events::Approval {574				owner: *owner.as_eth(),575				spender: *spender.as_eth(),576				value: amount.into(),577			}578			.to_log(collection_id_to_address(collection.id)),579		);580		<PalletCommon<T>>::deposit_event(CommonEvent::Approved(581			collection.id,582			TokenId(0),583			owner.clone(),584			spender.clone(),585			amount,586		));587	}588589	/// Set allowance for the spender to `transfer` or `burn` owner's tokens.590	///591	/// - `collection`: Collection that contains the token592	/// - `owner`: Owner of tokens that sets the allowance.593	/// - `spender`: Recipient of the allowance rights.594	/// - `amount`: Amount of tokens the spender is allowed to `transfer` or `burn`.595	pub fn set_allowance(596		collection: &FungibleHandle<T>,597		owner: &T::CrossAccountId,598		spender: &T::CrossAccountId,599		amount: u128,600	) -> DispatchResult {601		if collection.permissions.access() == AccessMode::AllowList {602			collection.check_allowlist(owner)?;603			collection.check_allowlist(spender)?;604		}605606		if <Balance<T>>::get((collection.id, owner)) < amount {607			ensure!(608				collection.ignores_owned_amount(owner),609				<CommonError<T>>::CantApproveMoreThanOwned610			);611		}612613		// =========614615		Self::set_allowance_unchecked(collection, owner, spender, amount);616		Ok(())617	}618619	/// Set allowance for the spender to `transfer` or `burn` owner's tokens from eth mirror.620	///621	/// - `collection`: Collection that contains the token622	/// - `sender`: Owner of tokens that sets the allowance.623	/// - `from`: Owner's eth mirror.624	/// - `to`: Recipient of the allowance rights.625	/// - `amount`: Amount of tokens the spender is allowed to `transfer` or `burn`.626	pub fn set_allowance_from(627		collection: &FungibleHandle<T>,628		sender: &T::CrossAccountId,629		from: &T::CrossAccountId,630		to: &T::CrossAccountId,631		amount: u128,632	) -> DispatchResult {633		if collection.permissions.access() == AccessMode::AllowList {634			collection.check_allowlist(sender)?;635			collection.check_allowlist(from)?;636			collection.check_allowlist(to)?;637		}638639		ensure!(640			sender.conv_eq(from),641			<CommonError<T>>::AddressIsNotEthMirror642		);643644		if <Balance<T>>::get((collection.id, from)) < amount {645			ensure!(646				collection.limits.owner_can_transfer()647					&& (collection.is_owner_or_admin(sender) || collection.is_owner_or_admin(from)),648				<CommonError<T>>::CantApproveMoreThanOwned649			);650		}651652		// =========653654		Self::set_allowance_unchecked(collection, from, to, amount);655		Ok(())656	}657658	/// Checks if a non-owner has (enough) allowance from the owner to perform operations on the tokens.659	/// Returns the expected remaining allowance - it should be set manually if the transaction proceeds.660	///661	/// - `collection`: Collection that contains the token.662	/// - `spender`: CrossAccountId who has the allowance rights.663	/// - `from`: The owner of the tokens who sets the allowance.664	/// - `amount`: Amount of tokens by which the allowance sholud be reduced.665	fn check_allowed(666		collection: &FungibleHandle<T>,667		spender: &T::CrossAccountId,668		from: &T::CrossAccountId,669		amount: u128,670		nesting_budget: &dyn Budget,671	) -> Result<Option<u128>, DispatchError> {672		if spender.conv_eq(from) {673			return Ok(None);674		}675		if collection.permissions.access() == AccessMode::AllowList {676			// `from`, `to` checked in [`transfer`]677			collection.check_allowlist(spender)?;678		}679680		if collection.ignores_token_restrictions(spender) {681			return Ok(Self::compute_allowance_decrease(682				collection, from, spender, amount,683			));684		}685686		if let Some(source) = T::CrossTokenAddressMapping::address_to_token(from) {687			ensure!(688				<PalletStructure<T>>::check_indirectly_owned(689					spender.clone(),690					source.0,691					source.1,692					None,693					nesting_budget694				)?,695				<CommonError<T>>::ApprovedValueTooLow,696			);697			return Ok(None);698		}699700		let allowance = Self::compute_allowance_decrease(collection, from, spender, amount);701		ensure!(allowance.is_some(), <CommonError<T>>::ApprovedValueTooLow);702703		Ok(allowance)704	}705706	/// Returns `Some(amount)` if the `spender` have allowance to spend this amount.707	/// Otherwise, it returns `None`.708	fn compute_allowance_decrease(709		collection: &FungibleHandle<T>,710		from: &T::CrossAccountId,711		spender: &T::CrossAccountId,712		amount: u128,713	) -> Option<u128> {714		<Allowance<T>>::get((collection.id, from, spender)).checked_sub(amount)715	}716717	/// Transfer fungible tokens from one account to another.718	/// Same as the [`transfer`][`Pallet::transfer`] but spender doesn't needs to be an owner of the token pieces.719	/// The owner should set allowance for the spender to transfer pieces.720	///	See [`set_allowance`][`Pallet::set_allowance`] for more details.721722	pub fn transfer_from(723		collection: &FungibleHandle<T>,724		spender: &T::CrossAccountId,725		from: &T::CrossAccountId,726		to: &T::CrossAccountId,727		amount: u128,728		nesting_budget: &dyn Budget,729	) -> DispatchResult {730		let allowance = Self::check_allowed(collection, spender, from, amount, nesting_budget)?;731732		// =========733734		Self::transfer(collection, from, to, amount, nesting_budget)?;735		if let Some(allowance) = allowance {736			Self::set_allowance_unchecked(collection, from, spender, allowance);737		}738		Ok(())739	}740741	/// Burn fungible tokens from the account.742	///743	/// Same as the [`burn`][`Pallet::burn`] but spender doesn't need to be an owner of the tokens. The `from` should744	/// set allowance for the spender to burn tokens.745	/// See [`set_allowance`][`Pallet::set_allowance`] for more details.746	pub fn burn_from(747		collection: &FungibleHandle<T>,748		spender: &T::CrossAccountId,749		from: &T::CrossAccountId,750		amount: u128,751		nesting_budget: &dyn Budget,752	) -> DispatchResult {753		let allowance = Self::check_allowed(collection, spender, from, amount, nesting_budget)?;754755		// =========756757		Self::burn(collection, from, amount)?;758		if let Some(allowance) = allowance {759			Self::set_allowance_unchecked(collection, from, spender, allowance);760		}761		Ok(())762	}763764	///	Creates fungible token.765	///766	/// The sender should be the owner/admin of the collection or collection should be configured767	/// to allow public minting.768	///769	/// - `data`: Contains user who will become the owners of the tokens and amount770	///   of tokens he will receive.771	pub fn create_item(772		collection: &FungibleHandle<T>,773		sender: &T::CrossAccountId,774		data: CreateItemData<T>,775		nesting_budget: &dyn Budget,776	) -> DispatchResult {777		Self::create_multiple_items(778			collection,779			sender,780			[(data.0, data.1)].into_iter().collect(),781			nesting_budget,782		)783	}784785	///	Creates fungible token.786	///787	/// - `data`: Contains user who will become the owners of the tokens and amount788	///   of tokens he will receive.789	pub fn create_item_foreign(790		collection: &FungibleHandle<T>,791		sender: &T::CrossAccountId,792		data: CreateItemData<T>,793		nesting_budget: &dyn Budget,794	) -> DispatchResult {795		Self::create_multiple_items_foreign(796			collection,797			sender,798			[(data.0, data.1)].into_iter().collect(),799			nesting_budget,800		)801	}802803	/// Returns 10 tokens owners in no particular order804	///805	/// There is no direct way to get token holders in ascending order,806	/// since `iter_prefix` returns values in no particular order.807	/// Therefore, getting the 10 largest holders with a large value of holders808	/// can lead to impact memory allocation + sorting with  `n * log (n)`.809	pub fn token_owners(810		collection: CollectionId,811		_token: TokenId,812	) -> Option<Vec<T::CrossAccountId>> {813		let res: Vec<T::CrossAccountId> = <Balance<T>>::iter_prefix((collection,))814			.map(|(owner, _amount)| owner)815			.take(10)816			.collect();817818		if res.is_empty() {819			None820		} else {821			Some(res)822		}823	}824}