git.delta.rocks / unique-network / refs/commits / 8162cc088fb8

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	#[pallet::generate_store(pub(super) trait Store)]145	pub struct Pallet<T>(_);146147	/// Total amount of fungible tokens inside a collection.148	#[pallet::storage]149	pub type TotalSupply<T: Config> =150		StorageMap<Hasher = Twox64Concat, Key = CollectionId, Value = u128, QueryKind = ValueQuery>;151152	/// Amount of tokens owned by an account inside a collection.153	#[pallet::storage]154	pub type Balance<T: Config> = StorageNMap<155		Key = (156			Key<Twox64Concat, CollectionId>,157			Key<Blake2_128Concat, T::CrossAccountId>,158		),159		Value = u128,160		QueryKind = ValueQuery,161	>;162163	/// Storage for assets delegated to a limited extent to other users.164	#[pallet::storage]165	pub type Allowance<T: Config> = StorageNMap<166		Key = (167			Key<Twox64Concat, CollectionId>,168			Key<Blake2_128, T::CrossAccountId>,169			Key<Blake2_128Concat, T::CrossAccountId>,170		),171		Value = u128,172		QueryKind = ValueQuery,173	>;174}175176/// Wrapper around untyped collection handle, asserting inner collection is of fungible type.177/// Required for interaction with Fungible collections, type safety and implementation [`solidity_interface`][`evm_coder::solidity_interface`].178pub struct FungibleHandle<T: Config>(pallet_common::CollectionHandle<T>);179180/// Implementation of methods required for dispatching during runtime.181impl<T: Config> FungibleHandle<T> {182	/// Casts [`CollectionHandle`][`pallet_common::CollectionHandle`] into [`FungibleHandle`].183	pub fn cast(inner: pallet_common::CollectionHandle<T>) -> Self {184		Self(inner)185	}186187	/// Casts [`FungibleHandle`] into [`CollectionHandle`][`pallet_common::CollectionHandle`].188	pub fn into_inner(self) -> pallet_common::CollectionHandle<T> {189		self.0190	}191	/// Returns a mutable reference to the internal [`CollectionHandle`][`pallet_common::CollectionHandle`].192	pub fn common_mut(&mut self) -> &mut pallet_common::CollectionHandle<T> {193		&mut self.0194	}195}196impl<T: Config> WithRecorder<T> for FungibleHandle<T> {197	fn recorder(&self) -> &pallet_evm_coder_substrate::SubstrateRecorder<T> {198		self.0.recorder()199	}200	fn into_recorder(self) -> pallet_evm_coder_substrate::SubstrateRecorder<T> {201		self.0.into_recorder()202	}203}204impl<T: Config> Deref for FungibleHandle<T> {205	type Target = pallet_common::CollectionHandle<T>;206207	fn deref(&self) -> &Self::Target {208		&self.0209	}210}211212/// Pallet implementation for fungible assets213impl<T: Config> Pallet<T> {214	/// Initializes the collection. Returns [CollectionId] on success, [DispatchError] otherwise.215	pub fn init_collection(216		owner: T::CrossAccountId,217		payer: T::CrossAccountId,218		data: CreateCollectionData<T::AccountId>,219		flags: CollectionFlags,220	) -> Result<CollectionId, DispatchError> {221		<PalletCommon<T>>::init_collection(owner, payer, data, flags)222	}223224	/// Initializes the collection with ForeignCollection flag. Returns [CollectionId] on success, [DispatchError] otherwise.225	pub fn init_foreign_collection(226		owner: T::CrossAccountId,227		payer: T::CrossAccountId,228		data: CreateCollectionData<T::AccountId>,229	) -> Result<CollectionId, DispatchError> {230		let id = <PalletCommon<T>>::init_collection(231			owner,232			payer,233			data,234			CollectionFlags {235				foreign: true,236				..Default::default()237			},238		)?;239		Ok(id)240	}241242	/// Destroys a collection.243	pub fn destroy_collection(244		collection: FungibleHandle<T>,245		sender: &T::CrossAccountId,246	) -> DispatchResult {247		let id = collection.id;248249		if Self::collection_has_tokens(id) {250			return Err(<CommonError<T>>::CantDestroyNotEmptyCollection.into());251		}252253		// =========254255		PalletCommon::destroy_collection(collection.0, sender)?;256257		<TotalSupply<T>>::remove(id);258		let _ = <Balance<T>>::clear_prefix((id,), u32::MAX, None);259		let _ = <Allowance<T>>::clear_prefix((id,), u32::MAX, None);260		Ok(())261	}262263	/// Add properties to the collection.264	pub fn set_collection_properties(265		collection: &FungibleHandle<T>,266		sender: &T::CrossAccountId,267		properties: Vec<Property>,268	) -> DispatchResult {269		<PalletCommon<T>>::set_collection_properties(collection, sender, properties)270	}271272	/// Delete properties of the collection, associated with the provided keys.273	pub fn delete_collection_properties(274		collection: &FungibleHandle<T>,275		sender: &T::CrossAccountId,276		property_keys: Vec<PropertyKey>,277	) -> DispatchResult {278		<PalletCommon<T>>::delete_collection_properties(collection, sender, property_keys)279	}280281	/// Checks if collection has tokens. Return `true` if it has.282	fn collection_has_tokens(collection_id: CollectionId) -> bool {283		<TotalSupply<T>>::get(collection_id) != 0284	}285286	/// Burns the specified amount of the token. If the token balance287	/// or total supply is less than the given value,288	/// it will return [DispatchError].289	pub fn burn(290		collection: &FungibleHandle<T>,291		owner: &T::CrossAccountId,292		amount: u128,293	) -> DispatchResult {294		let total_supply = <TotalSupply<T>>::get(collection.id)295			.checked_sub(amount)296			.ok_or(<CommonError<T>>::TokenValueTooLow)?;297298		let balance = <Balance<T>>::get((collection.id, owner))299			.checked_sub(amount)300			.ok_or(<CommonError<T>>::TokenValueTooLow)?;301302		// Foreign collection check303		ensure!(!collection.flags.foreign, <CommonError<T>>::NoPermission);304305		if collection.permissions.access() == AccessMode::AllowList {306			collection.check_allowlist(owner)?;307		}308309		// =========310311		if balance == 0 {312			<Balance<T>>::remove((collection.id, owner));313			<PalletStructure<T>>::unnest_if_nested(owner, collection.id, TokenId::default());314		} else {315			<Balance<T>>::insert((collection.id, owner), balance);316		}317		<TotalSupply<T>>::insert(collection.id, total_supply);318319		<PalletEvm<T>>::deposit_log(320			ERC20Events::Transfer {321				from: *owner.as_eth(),322				to: H160::default(),323				value: amount.into(),324			}325			.to_log(collection_id_to_address(collection.id)),326		);327		<PalletCommon<T>>::deposit_event(CommonEvent::ItemDestroyed(328			collection.id,329			TokenId::default(),330			owner.clone(),331			amount,332		));333		Ok(())334	}335336	/// Burns the specified amount of the token.337	pub fn burn_foreign(338		collection: &FungibleHandle<T>,339		owner: &T::CrossAccountId,340		amount: u128,341	) -> DispatchResult {342		let total_supply = <TotalSupply<T>>::get(collection.id)343			.checked_sub(amount)344			.ok_or(<CommonError<T>>::TokenValueTooLow)?;345346		let balance = <Balance<T>>::get((collection.id, owner))347			.checked_sub(amount)348			.ok_or(<CommonError<T>>::TokenValueTooLow)?;349		// =========350351		if balance == 0 {352			<Balance<T>>::remove((collection.id, owner));353			<PalletStructure<T>>::unnest_if_nested(owner, collection.id, TokenId::default());354		} else {355			<Balance<T>>::insert((collection.id, owner), balance);356		}357		<TotalSupply<T>>::insert(collection.id, total_supply);358359		<PalletEvm<T>>::deposit_log(360			ERC20Events::Transfer {361				from: *owner.as_eth(),362				to: H160::default(),363				value: amount.into(),364			}365			.to_log(collection_id_to_address(collection.id)),366		);367		<PalletCommon<T>>::deposit_event(CommonEvent::ItemDestroyed(368			collection.id,369			TokenId::default(),370			owner.clone(),371			amount,372		));373		Ok(())374	}375376	/// Transfers the specified amount of tokens. Will check that377	/// the transfer is allowed for the token.378	///379	/// - `from`: Owner of tokens to transfer.380	/// - `to`: Recepient of transfered tokens.381	/// - `amount`: Amount of tokens to transfer.382	/// - `collection`: Collection that contains the token383	pub fn transfer(384		collection: &FungibleHandle<T>,385		from: &T::CrossAccountId,386		to: &T::CrossAccountId,387		amount: u128,388		nesting_budget: &dyn Budget,389	) -> DispatchResult {390		ensure!(391			collection.limits.transfers_enabled(),392			<CommonError<T>>::TransferNotAllowed,393		);394395		if collection.permissions.access() == AccessMode::AllowList {396			collection.check_allowlist(from)?;397			collection.check_allowlist(to)?;398		}399		<PalletCommon<T>>::ensure_correct_receiver(to)?;400401		let balance_from = <Balance<T>>::get((collection.id, from))402			.checked_sub(amount)403			.ok_or(<CommonError<T>>::TokenValueTooLow)?;404		let balance_to = if from != to && amount != 0 {405			Some(406				<Balance<T>>::get((collection.id, to))407					.checked_add(amount)408					.ok_or(ArithmeticError::Overflow)?,409			)410		} else {411			None412		};413414		// =========415416		if let Some(balance_to) = balance_to {417			// from != to && amount != 0418419			<PalletStructure<T>>::nest_if_sent_to_token(420				from.clone(),421				to,422				collection.id,423				TokenId::default(),424				nesting_budget,425			)?;426427			if balance_from == 0 {428				<Balance<T>>::remove((collection.id, from));429				<PalletStructure<T>>::unnest_if_nested(from, collection.id, TokenId::default());430			} else {431				<Balance<T>>::insert((collection.id, from), balance_from);432			}433			<Balance<T>>::insert((collection.id, to), balance_to);434		}435436		<PalletEvm<T>>::deposit_log(437			ERC20Events::Transfer {438				from: *from.as_eth(),439				to: *to.as_eth(),440				value: amount.into(),441			}442			.to_log(collection_id_to_address(collection.id)),443		);444		<PalletCommon<T>>::deposit_event(CommonEvent::Transfer(445			collection.id,446			TokenId::default(),447			from.clone(),448			to.clone(),449			amount,450		));451		Ok(())452	}453454	/// Minting tokens for multiple IDs.455	/// It is a utility function used in [`create_multiple_items`][`Pallet::create_multiple_items`]456	/// and [`create_multiple_items_foreign`][`Pallet::create_multiple_items_foreign`]457	pub fn create_multiple_items_common(458		collection: &FungibleHandle<T>,459		sender: &T::CrossAccountId,460		data: BTreeMap<T::CrossAccountId, u128>,461		nesting_budget: &dyn Budget,462	) -> DispatchResult {463		let total_supply = data464			.iter()465			.map(|(_, v)| *v)466			.try_fold(<TotalSupply<T>>::get(collection.id), |acc, v| {467				acc.checked_add(v)468			})469			.ok_or(ArithmeticError::Overflow)?;470471		for (to, _) in data.iter() {472			<PalletStructure<T>>::check_nesting(473				sender.clone(),474				to,475				collection.id,476				TokenId::default(),477				nesting_budget,478			)?;479		}480481		let updated_balances = data482			.into_iter()483			.map(|(user, amount)| {484				let updated_balance = <Balance<T>>::get((collection.id, &user))485					.checked_add(amount)486					.ok_or(ArithmeticError::Overflow)?;487				Ok((user, amount, updated_balance))488			})489			.collect::<Result<Vec<_>, DispatchError>>()?;490491		// =========492493		<TotalSupply<T>>::insert(collection.id, total_supply);494		for (user, amount, updated_balance) in updated_balances {495			<Balance<T>>::insert((collection.id, &user), updated_balance);496			<PalletStructure<T>>::nest_if_sent_to_token_unchecked(497				&user,498				collection.id,499				TokenId::default(),500			);501			<PalletEvm<T>>::deposit_log(502				ERC20Events::Transfer {503					from: H160::default(),504					to: *user.as_eth(),505					value: amount.into(),506				}507				.to_log(collection_id_to_address(collection.id)),508			);509			<PalletCommon<T>>::deposit_event(CommonEvent::ItemCreated(510				collection.id,511				TokenId::default(),512				user.clone(),513				amount,514			));515		}516517		Ok(())518	}519520	/// Minting tokens for multiple IDs.521	/// See [`create_item`][`Pallet::create_item`] for more details.522	pub fn create_multiple_items(523		collection: &FungibleHandle<T>,524		sender: &T::CrossAccountId,525		data: BTreeMap<T::CrossAccountId, u128>,526		nesting_budget: &dyn Budget,527	) -> DispatchResult {528		// Foreign collection check529		ensure!(!collection.flags.foreign, <CommonError<T>>::NoPermission);530531		if !collection.is_owner_or_admin(sender) {532			ensure!(533				collection.permissions.mint_mode(),534				<CommonError<T>>::PublicMintingNotAllowed535			);536			collection.check_allowlist(sender)?;537538			for (owner, _) in data.iter() {539				collection.check_allowlist(owner)?;540			}541		}542543		Self::create_multiple_items_common(collection, sender, data, nesting_budget)544	}545546	/// Minting tokens for multiple IDs.547	/// See [`create_item_foreign`][`Pallet::create_item_foreign`] for more details.548	pub fn create_multiple_items_foreign(549		collection: &FungibleHandle<T>,550		sender: &T::CrossAccountId,551		data: BTreeMap<T::CrossAccountId, u128>,552		nesting_budget: &dyn Budget,553	) -> DispatchResult {554		Self::create_multiple_items_common(collection, sender, data, nesting_budget)555	}556557	fn set_allowance_unchecked(558		collection: &FungibleHandle<T>,559		owner: &T::CrossAccountId,560		spender: &T::CrossAccountId,561		amount: u128,562	) {563		if amount == 0 {564			<Allowance<T>>::remove((collection.id, owner, spender));565		} else {566			<Allowance<T>>::insert((collection.id, owner, spender), amount);567		}568569		<PalletEvm<T>>::deposit_log(570			ERC20Events::Approval {571				owner: *owner.as_eth(),572				spender: *spender.as_eth(),573				value: amount.into(),574			}575			.to_log(collection_id_to_address(collection.id)),576		);577		<PalletCommon<T>>::deposit_event(CommonEvent::Approved(578			collection.id,579			TokenId(0),580			owner.clone(),581			spender.clone(),582			amount,583		));584	}585586	/// Set allowance for the spender to `transfer` or `burn` owner's tokens.587	///588	/// - `collection`: Collection that contains the token589	/// - `owner`: Owner of tokens that sets the allowance.590	/// - `spender`: Recipient of the allowance rights.591	/// - `amount`: Amount of tokens the spender is allowed to `transfer` or `burn`.592	pub fn set_allowance(593		collection: &FungibleHandle<T>,594		owner: &T::CrossAccountId,595		spender: &T::CrossAccountId,596		amount: u128,597	) -> DispatchResult {598		if collection.permissions.access() == AccessMode::AllowList {599			collection.check_allowlist(owner)?;600			collection.check_allowlist(spender)?;601		}602603		if <Balance<T>>::get((collection.id, owner)) < amount {604			ensure!(605				collection.ignores_owned_amount(owner),606				<CommonError<T>>::CantApproveMoreThanOwned607			);608		}609610		// =========611612		Self::set_allowance_unchecked(collection, owner, spender, amount);613		Ok(())614	}615616	/// Set allowance for the spender to `transfer` or `burn` owner's tokens from eth mirror.617	///618	/// - `collection`: Collection that contains the token619	/// - `sender`: Owner of tokens that sets the allowance.620	/// - `from`: Owner's eth mirror.621	/// - `to`: Recipient of the allowance rights.622	/// - `amount`: Amount of tokens the spender is allowed to `transfer` or `burn`.623	pub fn set_allowance_from(624		collection: &FungibleHandle<T>,625		sender: &T::CrossAccountId,626		from: &T::CrossAccountId,627		to: &T::CrossAccountId,628		amount: u128,629	) -> DispatchResult {630		if collection.permissions.access() == AccessMode::AllowList {631			collection.check_allowlist(sender)?;632			collection.check_allowlist(from)?;633			collection.check_allowlist(to)?;634		}635636		ensure!(637			*sender.as_eth() == *from.as_eth(),638			<CommonError<T>>::AddressIsNotEthMirror639		);640641		if <Balance<T>>::get((collection.id, from)) < amount {642			ensure!(643				collection.limits.owner_can_transfer()644					&& (collection.is_owner_or_admin(sender) || collection.is_owner_or_admin(from)),645				<CommonError<T>>::CantApproveMoreThanOwned646			);647		}648649		// =========650651		Self::set_allowance_unchecked(collection, from, to, amount);652		Ok(())653	}654655	/// Checks if a non-owner has (enough) allowance from the owner to perform operations on the tokens.656	/// Returns the expected remaining allowance - it should be set manually if the transaction proceeds.657	///658	/// - `collection`: Collection that contains the token.659	/// - `spender`: CrossAccountId who has the allowance rights.660	/// - `from`: The owner of the tokens who sets the allowance.661	/// - `amount`: Amount of tokens by which the allowance sholud be reduced.662	fn check_allowed(663		collection: &FungibleHandle<T>,664		spender: &T::CrossAccountId,665		from: &T::CrossAccountId,666		amount: u128,667		nesting_budget: &dyn Budget,668	) -> Result<Option<u128>, DispatchError> {669		if spender.conv_eq(from) {670			return Ok(None);671		}672		if collection.permissions.access() == AccessMode::AllowList {673			// `from`, `to` checked in [`transfer`]674			collection.check_allowlist(spender)?;675		}676		if let Some(source) = T::CrossTokenAddressMapping::address_to_token(from) {677			// TODO: should collection owner be allowed to perform this transfer?678			ensure!(679				<PalletStructure<T>>::check_indirectly_owned(680					spender.clone(),681					source.0,682					source.1,683					None,684					nesting_budget685				)?,686				<CommonError<T>>::ApprovedValueTooLow,687			);688			return Ok(None);689		}690		let allowance = <Allowance<T>>::get((collection.id, from, spender)).checked_sub(amount);691		if allowance.is_none() {692			ensure!(693				collection.ignores_allowance(spender),694				<CommonError<T>>::ApprovedValueTooLow695			);696		}697698		Ok(allowance)699	}700701	/// Transfer fungible tokens from one account to another.702	/// Same as the [`transfer`][`Pallet::transfer`] but spender doesn't needs to be an owner of the token pieces.703	/// The owner should set allowance for the spender to transfer pieces.704	///	See [`set_allowance`][`Pallet::set_allowance`] for more details.705706	pub fn transfer_from(707		collection: &FungibleHandle<T>,708		spender: &T::CrossAccountId,709		from: &T::CrossAccountId,710		to: &T::CrossAccountId,711		amount: u128,712		nesting_budget: &dyn Budget,713	) -> DispatchResult {714		let allowance = Self::check_allowed(collection, spender, from, amount, nesting_budget)?;715716		// =========717718		Self::transfer(collection, from, to, amount, nesting_budget)?;719		if let Some(allowance) = allowance {720			Self::set_allowance_unchecked(collection, from, spender, allowance);721		}722		Ok(())723	}724725	/// Burn fungible tokens from the account.726	///727	/// Same as the [`burn`][`Pallet::burn`] but spender doesn't need to be an owner of the tokens. The `from` should728	/// set allowance for the spender to burn tokens.729	/// See [`set_allowance`][`Pallet::set_allowance`] for more details.730	pub fn burn_from(731		collection: &FungibleHandle<T>,732		spender: &T::CrossAccountId,733		from: &T::CrossAccountId,734		amount: u128,735		nesting_budget: &dyn Budget,736	) -> DispatchResult {737		let allowance = Self::check_allowed(collection, spender, from, amount, nesting_budget)?;738739		// =========740741		Self::burn(collection, from, amount)?;742		if let Some(allowance) = allowance {743			Self::set_allowance_unchecked(collection, from, spender, allowance);744		}745		Ok(())746	}747748	///	Creates fungible token.749	///750	/// The sender should be the owner/admin of the collection or collection should be configured751	/// to allow public minting.752	///753	/// - `data`: Contains user who will become the owners of the tokens and amount754	///   of tokens he will receive.755	pub fn create_item(756		collection: &FungibleHandle<T>,757		sender: &T::CrossAccountId,758		data: CreateItemData<T>,759		nesting_budget: &dyn Budget,760	) -> DispatchResult {761		Self::create_multiple_items(762			collection,763			sender,764			[(data.0, data.1)].into_iter().collect(),765			nesting_budget,766		)767	}768769	///	Creates fungible token.770	///771	/// - `data`: Contains user who will become the owners of the tokens and amount772	///   of tokens he will receive.773	pub fn create_item_foreign(774		collection: &FungibleHandle<T>,775		sender: &T::CrossAccountId,776		data: CreateItemData<T>,777		nesting_budget: &dyn Budget,778	) -> DispatchResult {779		Self::create_multiple_items_foreign(780			collection,781			sender,782			[(data.0, data.1)].into_iter().collect(),783			nesting_budget,784		)785	}786787	/// Returns 10 tokens owners in no particular order788	///789	/// There is no direct way to get token holders in ascending order,790	/// since `iter_prefix` returns values in no particular order.791	/// Therefore, getting the 10 largest holders with a large value of holders792	/// can lead to impact memory allocation + sorting with  `n * log (n)`.793	pub fn token_owners(794		collection: CollectionId,795		_token: TokenId,796	) -> Option<Vec<T::CrossAccountId>> {797		let res: Vec<T::CrossAccountId> = <Balance<T>>::iter_prefix((collection,))798			.map(|(owner, _amount)| owner)799			.take(10)800			.collect();801802		if res.is_empty() {803			None804		} else {805			Some(res)806		}807	}808}