git.delta.rocks / unique-network / refs/commits / 2eecdab55d8c

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::{84	ensure,85	pallet_prelude::{DispatchResultWithPostInfo, Pays},86	dispatch::PostDispatchInfo,87};88use pallet_evm::account::CrossAccountId;89use up_data_structs::{90	AccessMode, CollectionId, CollectionFlags, TokenId, CreateCollectionData,91	mapping::TokenAddressMapping, budget::Budget, PropertyKey, Property,92};93use pallet_common::{94	Error as CommonError, Event as CommonEvent, Pallet as PalletCommon,95	eth::collection_id_to_address, SelfWeightOf as PalletCommonWeightOf,96	weights::WeightInfo as CommonWeightInfo, helpers::add_weight_to_post_info,97};98use pallet_evm::Pallet as PalletEvm;99use pallet_structure::Pallet as PalletStructure;100use pallet_evm_coder_substrate::WithRecorder;101use sp_core::H160;102use sp_runtime::{ArithmeticError, DispatchError, DispatchResult};103use sp_std::{collections::btree_map::BTreeMap, vec::Vec};104use weights::WeightInfo;105pub use pallet::*;106107use crate::erc::ERC20Events;108#[cfg(feature = "runtime-benchmarks")]109pub mod benchmarking;110pub mod common;111pub mod erc;112pub mod weights;113114pub type CreateItemData<T> = (<T as pallet_evm::Config>::CrossAccountId, u128);115pub(crate) type SelfWeightOf<T> = <T as Config>::WeightInfo;116117#[frame_support::pallet]118pub mod pallet {119	use frame_support::{Blake2_128, Blake2_128Concat, Twox64Concat, pallet_prelude::*, storage::Key};120	use up_data_structs::CollectionId;121	use super::weights::WeightInfo;122123	#[pallet::error]124	pub enum Error<T> {125		/// Not Fungible item data used to mint in Fungible collection.126		NotFungibleDataUsedToMintFungibleCollectionToken,127		/// Fungible tokens hold no ID, and the default value of TokenId for Fungible collection is 0.128		FungibleItemsHaveNoId,129		/// Tried to set data for fungible item.130		FungibleItemsDontHaveData,131		/// Fungible token does not support nesting.132		FungibleDisallowsNesting,133		/// Setting item properties is not allowed.134		SettingPropertiesNotAllowed,135		/// Setting allowance for all is not allowed.136		SettingAllowanceForAllNotAllowed,137		/// Only a fungible collection could be possibly broken; any fungible token is valid.138		FungibleTokensAreAlwaysValid,139	}140141	#[pallet::config]142	pub trait Config:143		frame_system::Config + pallet_common::Config + pallet_structure::Config + pallet_evm::Config144	{145		type WeightInfo: WeightInfo;146	}147148	#[pallet::pallet]149	pub struct Pallet<T>(_);150151	/// Total amount of fungible tokens inside a collection.152	#[pallet::storage]153	pub type TotalSupply<T: Config> =154		StorageMap<Hasher = Twox64Concat, Key = CollectionId, Value = u128, QueryKind = ValueQuery>;155156	/// Amount of tokens owned by an account inside a collection.157	#[pallet::storage]158	pub type Balance<T: Config> = StorageNMap<159		Key = (160			Key<Twox64Concat, CollectionId>,161			Key<Blake2_128Concat, T::CrossAccountId>,162		),163		Value = u128,164		QueryKind = ValueQuery,165	>;166167	/// Storage for assets delegated to a limited extent to other users.168	#[pallet::storage]169	pub type Allowance<T: Config> = StorageNMap<170		Key = (171			Key<Twox64Concat, CollectionId>,172			Key<Blake2_128, T::CrossAccountId>,       // Owner173			Key<Blake2_128Concat, T::CrossAccountId>, // Spender174		),175		Value = u128,176		QueryKind = ValueQuery,177	>;178}179180/// Wrapper around untyped collection handle, asserting inner collection is of fungible type.181/// Required for interaction with Fungible collections, type safety and implementation [`solidity_interface`][`evm_coder::solidity_interface`].182pub struct FungibleHandle<T: Config>(pallet_common::CollectionHandle<T>);183184/// Implementation of methods required for dispatching during runtime.185impl<T: Config> FungibleHandle<T> {186	/// Casts [`CollectionHandle`][`pallet_common::CollectionHandle`] into [`FungibleHandle`].187	pub fn cast(inner: pallet_common::CollectionHandle<T>) -> Self {188		Self(inner)189	}190191	/// Casts [`FungibleHandle`] into [`CollectionHandle`][`pallet_common::CollectionHandle`].192	pub fn into_inner(self) -> pallet_common::CollectionHandle<T> {193		self.0194	}195	/// Returns a mutable reference to the internal [`CollectionHandle`][`pallet_common::CollectionHandle`].196	pub fn common_mut(&mut self) -> &mut pallet_common::CollectionHandle<T> {197		&mut self.0198	}199}200impl<T: Config> WithRecorder<T> for FungibleHandle<T> {201	fn recorder(&self) -> &pallet_evm_coder_substrate::SubstrateRecorder<T> {202		self.0.recorder()203	}204	fn into_recorder(self) -> pallet_evm_coder_substrate::SubstrateRecorder<T> {205		self.0.into_recorder()206	}207}208impl<T: Config> Deref for FungibleHandle<T> {209	type Target = pallet_common::CollectionHandle<T>;210211	fn deref(&self) -> &Self::Target {212		&self.0213	}214}215216/// Pallet implementation for fungible assets217impl<T: Config> Pallet<T> {218	/// Initializes the collection. Returns [CollectionId] on success, [DispatchError] otherwise.219	pub fn init_collection(220		owner: T::CrossAccountId,221		payer: T::CrossAccountId,222		data: CreateCollectionData<T::AccountId>,223		flags: CollectionFlags,224	) -> Result<CollectionId, DispatchError> {225		<PalletCommon<T>>::init_collection(owner, payer, data, flags)226	}227228	/// Initializes the collection with ForeignCollection flag. Returns [CollectionId] on success, [DispatchError] otherwise.229	pub fn init_foreign_collection(230		owner: T::CrossAccountId,231		payer: T::CrossAccountId,232		data: CreateCollectionData<T::AccountId>,233	) -> Result<CollectionId, DispatchError> {234		let id = <PalletCommon<T>>::init_collection(235			owner,236			payer,237			data,238			CollectionFlags {239				foreign: true,240				..Default::default()241			},242		)?;243		Ok(id)244	}245246	/// Destroys a collection.247	pub fn destroy_collection(248		collection: FungibleHandle<T>,249		sender: &T::CrossAccountId,250	) -> DispatchResult {251		let id = collection.id;252253		if Self::collection_has_tokens(id) {254			return Err(<CommonError<T>>::CantDestroyNotEmptyCollection.into());255		}256257		// =========258259		PalletCommon::destroy_collection(collection.0, sender)?;260261		<TotalSupply<T>>::remove(id);262		let _ = <Balance<T>>::clear_prefix((id,), u32::MAX, None);263		let _ = <Allowance<T>>::clear_prefix((id,), u32::MAX, None);264		Ok(())265	}266267	/// Add properties to the collection.268	pub fn set_collection_properties(269		collection: &FungibleHandle<T>,270		sender: &T::CrossAccountId,271		properties: Vec<Property>,272	) -> DispatchResult {273		<PalletCommon<T>>::set_collection_properties(collection, sender, properties.into_iter())274	}275276	/// Delete properties of the collection, associated with the provided keys.277	pub fn delete_collection_properties(278		collection: &FungibleHandle<T>,279		sender: &T::CrossAccountId,280		property_keys: Vec<PropertyKey>,281	) -> DispatchResult {282		<PalletCommon<T>>::delete_collection_properties(283			collection,284			sender,285			property_keys.into_iter(),286		)287	}288289	/// Checks if collection has tokens. Return `true` if it has.290	fn collection_has_tokens(collection_id: CollectionId) -> bool {291		<TotalSupply<T>>::get(collection_id) != 0292	}293294	/// Burns the specified amount of the token. If the token balance295	/// or total supply is less than the given value,296	/// it will return [DispatchError].297	pub fn burn(298		collection: &FungibleHandle<T>,299		owner: &T::CrossAccountId,300		amount: u128,301	) -> DispatchResult {302		let total_supply = <TotalSupply<T>>::get(collection.id)303			.checked_sub(amount)304			.ok_or(<CommonError<T>>::TokenValueTooLow)?;305306		let balance = <Balance<T>>::get((collection.id, owner))307			.checked_sub(amount)308			.ok_or(<CommonError<T>>::TokenValueTooLow)?;309310		// Foreign collection check311		ensure!(!collection.flags.foreign, <CommonError<T>>::NoPermission);312313		if collection.permissions.access() == AccessMode::AllowList {314			collection.check_allowlist(owner)?;315		}316317		// =========318319		if balance == 0 {320			<Balance<T>>::remove((collection.id, owner));321			<PalletStructure<T>>::unnest_if_nested(owner, collection.id, TokenId::default());322		} else {323			<Balance<T>>::insert((collection.id, owner), balance);324		}325		<TotalSupply<T>>::insert(collection.id, total_supply);326327		<PalletEvm<T>>::deposit_log(328			ERC20Events::Transfer {329				from: *owner.as_eth(),330				to: H160::default(),331				value: amount.into(),332			}333			.to_log(collection_id_to_address(collection.id)),334		);335		<PalletCommon<T>>::deposit_event(CommonEvent::ItemDestroyed(336			collection.id,337			TokenId::default(),338			owner.clone(),339			amount,340		));341		Ok(())342	}343344	/// Burns the specified amount of the token.345	pub fn burn_foreign(346		collection: &FungibleHandle<T>,347		owner: &T::CrossAccountId,348		amount: u128,349	) -> DispatchResult {350		let total_supply = <TotalSupply<T>>::get(collection.id)351			.checked_sub(amount)352			.ok_or(<CommonError<T>>::TokenValueTooLow)?;353354		let balance = <Balance<T>>::get((collection.id, owner))355			.checked_sub(amount)356			.ok_or(<CommonError<T>>::TokenValueTooLow)?;357		// =========358359		if balance == 0 {360			<Balance<T>>::remove((collection.id, owner));361			<PalletStructure<T>>::unnest_if_nested(owner, collection.id, TokenId::default());362		} else {363			<Balance<T>>::insert((collection.id, owner), balance);364		}365		<TotalSupply<T>>::insert(collection.id, total_supply);366367		<PalletEvm<T>>::deposit_log(368			ERC20Events::Transfer {369				from: *owner.as_eth(),370				to: H160::default(),371				value: amount.into(),372			}373			.to_log(collection_id_to_address(collection.id)),374		);375		<PalletCommon<T>>::deposit_event(CommonEvent::ItemDestroyed(376			collection.id,377			TokenId::default(),378			owner.clone(),379			amount,380		));381		Ok(())382	}383384	/// Transfers the specified amount of tokens. Will check that385	/// the transfer is allowed for the token.386	///387	/// - `from`: Owner of tokens to transfer.388	/// - `to`: Recepient of transfered tokens.389	/// - `amount`: Amount of tokens to transfer.390	/// - `collection`: Collection that contains the token391	pub fn transfer(392		collection: &FungibleHandle<T>,393		from: &T::CrossAccountId,394		to: &T::CrossAccountId,395		amount: u128,396		nesting_budget: &dyn Budget,397	) -> DispatchResultWithPostInfo {398		ensure!(399			collection.limits.transfers_enabled(),400			<CommonError<T>>::TransferNotAllowed,401		);402403		let mut actual_weight = <SelfWeightOf<T>>::transfer_raw();404405		if collection.permissions.access() == AccessMode::AllowList {406			collection.check_allowlist(from)?;407			collection.check_allowlist(to)?;408			actual_weight += <PalletCommonWeightOf<T>>::check_accesslist() * 2;409		}410		<PalletCommon<T>>::ensure_correct_receiver(to)?;411		let balance_from = <Balance<T>>::get((collection.id, from))412			.checked_sub(amount)413			.ok_or(<CommonError<T>>::TokenValueTooLow)?;414		let balance_to = if from != to && amount != 0 {415			Some(416				<Balance<T>>::get((collection.id, to))417					.checked_add(amount)418					.ok_or(ArithmeticError::Overflow)?,419			)420		} else {421			None422		};423424		// =========425426		if let Some(balance_to) = balance_to {427			// from != to && amount != 0428429			<PalletStructure<T>>::nest_if_sent_to_token(430				from.clone(),431				to,432				collection.id,433				TokenId::default(),434				nesting_budget,435			)?;436437			if balance_from == 0 {438				<Balance<T>>::remove((collection.id, from));439				<PalletStructure<T>>::unnest_if_nested(from, collection.id, TokenId::default());440			} else {441				<Balance<T>>::insert((collection.id, from), balance_from);442			}443			<Balance<T>>::insert((collection.id, to), balance_to);444		}445446		<PalletEvm<T>>::deposit_log(447			ERC20Events::Transfer {448				from: *from.as_eth(),449				to: *to.as_eth(),450				value: amount.into(),451			}452			.to_log(collection_id_to_address(collection.id)),453		);454		<PalletCommon<T>>::deposit_event(CommonEvent::Transfer(455			collection.id,456			TokenId::default(),457			from.clone(),458			to.clone(),459			amount,460		));461462		Ok(PostDispatchInfo {463			actual_weight: Some(actual_weight),464			pays_fee: Pays::Yes,465		})466	}467468	/// Minting tokens for multiple IDs.469	/// It is a utility function used in [`create_multiple_items`][`Pallet::create_multiple_items`]470	/// and [`create_multiple_items_foreign`][`Pallet::create_multiple_items_foreign`]471	pub fn create_multiple_items_common(472		collection: &FungibleHandle<T>,473		sender: &T::CrossAccountId,474		data: BTreeMap<T::CrossAccountId, u128>,475		nesting_budget: &dyn Budget,476	) -> DispatchResult {477		let total_supply = data478			.values()479			.copied()480			.try_fold(<TotalSupply<T>>::get(collection.id), |acc, v| {481				acc.checked_add(v)482			})483			.ok_or(ArithmeticError::Overflow)?;484485		for (to, _) in data.iter() {486			<PalletStructure<T>>::check_nesting(487				sender.clone(),488				to,489				collection.id,490				TokenId::default(),491				nesting_budget,492			)?;493		}494495		let updated_balances = data496			.into_iter()497			.map(|(user, amount)| {498				let updated_balance = <Balance<T>>::get((collection.id, &user))499					.checked_add(amount)500					.ok_or(ArithmeticError::Overflow)?;501				Ok((user, amount, updated_balance))502			})503			.collect::<Result<Vec<_>, DispatchError>>()?;504505		// =========506507		<TotalSupply<T>>::insert(collection.id, total_supply);508		for (user, amount, updated_balance) in updated_balances {509			<Balance<T>>::insert((collection.id, &user), updated_balance);510			<PalletStructure<T>>::nest_if_sent_to_token_unchecked(511				&user,512				collection.id,513				TokenId::default(),514			);515			<PalletEvm<T>>::deposit_log(516				ERC20Events::Transfer {517					from: H160::default(),518					to: *user.as_eth(),519					value: amount.into(),520				}521				.to_log(collection_id_to_address(collection.id)),522			);523			<PalletCommon<T>>::deposit_event(CommonEvent::ItemCreated(524				collection.id,525				TokenId::default(),526				user.clone(),527				amount,528			));529		}530531		Ok(())532	}533534	/// Minting tokens for multiple IDs.535	/// See [`create_item`][`Pallet::create_item`] for more details.536	pub fn create_multiple_items(537		collection: &FungibleHandle<T>,538		sender: &T::CrossAccountId,539		data: BTreeMap<T::CrossAccountId, u128>,540		nesting_budget: &dyn Budget,541	) -> DispatchResult {542		// Foreign collection check543		ensure!(!collection.flags.foreign, <CommonError<T>>::NoPermission);544545		if !collection.is_owner_or_admin(sender) {546			ensure!(547				collection.permissions.mint_mode(),548				<CommonError<T>>::PublicMintingNotAllowed549			);550			collection.check_allowlist(sender)?;551552			for (owner, _) in data.iter() {553				collection.check_allowlist(owner)?;554			}555		}556557		Self::create_multiple_items_common(collection, sender, data, nesting_budget)558	}559560	/// Minting tokens for multiple IDs.561	/// See [`create_item_foreign`][`Pallet::create_item_foreign`] for more details.562	pub fn create_multiple_items_foreign(563		collection: &FungibleHandle<T>,564		sender: &T::CrossAccountId,565		data: BTreeMap<T::CrossAccountId, u128>,566		nesting_budget: &dyn Budget,567	) -> DispatchResult {568		Self::create_multiple_items_common(collection, sender, data, nesting_budget)569	}570571	fn set_allowance_unchecked(572		collection: &FungibleHandle<T>,573		owner: &T::CrossAccountId,574		spender: &T::CrossAccountId,575		amount: u128,576	) {577		if amount == 0 {578			<Allowance<T>>::remove((collection.id, owner, spender));579		} else {580			<Allowance<T>>::insert((collection.id, owner, spender), amount);581		}582583		<PalletEvm<T>>::deposit_log(584			ERC20Events::Approval {585				owner: *owner.as_eth(),586				spender: *spender.as_eth(),587				value: amount.into(),588			}589			.to_log(collection_id_to_address(collection.id)),590		);591		<PalletCommon<T>>::deposit_event(CommonEvent::Approved(592			collection.id,593			TokenId(0),594			owner.clone(),595			spender.clone(),596			amount,597		));598	}599600	/// Set allowance for the spender to `transfer` or `burn` owner's tokens.601	///602	/// - `collection`: Collection that contains the token603	/// - `owner`: Owner of tokens that sets the allowance.604	/// - `spender`: Recipient of the allowance rights.605	/// - `amount`: Amount of tokens the spender is allowed to `transfer` or `burn`.606	pub fn set_allowance(607		collection: &FungibleHandle<T>,608		owner: &T::CrossAccountId,609		spender: &T::CrossAccountId,610		amount: u128,611	) -> DispatchResult {612		if collection.permissions.access() == AccessMode::AllowList {613			collection.check_allowlist(owner)?;614			collection.check_allowlist(spender)?;615		}616617		if <Balance<T>>::get((collection.id, owner)) < amount {618			ensure!(619				collection.ignores_owned_amount(owner),620				<CommonError<T>>::CantApproveMoreThanOwned621			);622		}623624		// =========625626		Self::set_allowance_unchecked(collection, owner, spender, amount);627		Ok(())628	}629630	/// Set allowance for the spender to `transfer` or `burn` owner's tokens from eth mirror.631	///632	/// - `collection`: Collection that contains the token633	/// - `sender`: Owner of tokens that sets the allowance.634	/// - `from`: Owner's eth mirror.635	/// - `to`: Recipient of the allowance rights.636	/// - `amount`: Amount of tokens the spender is allowed to `transfer` or `burn`.637	pub fn set_allowance_from(638		collection: &FungibleHandle<T>,639		sender: &T::CrossAccountId,640		from: &T::CrossAccountId,641		to: &T::CrossAccountId,642		amount: u128,643	) -> DispatchResult {644		if collection.permissions.access() == AccessMode::AllowList {645			collection.check_allowlist(sender)?;646			collection.check_allowlist(from)?;647			collection.check_allowlist(to)?;648		}649650		ensure!(651			sender.conv_eq(from),652			<CommonError<T>>::AddressIsNotEthMirror653		);654655		if <Balance<T>>::get((collection.id, from)) < amount {656			ensure!(657				collection.limits.owner_can_transfer()658					&& (collection.is_owner_or_admin(sender) || collection.is_owner_or_admin(from)),659				<CommonError<T>>::CantApproveMoreThanOwned660			);661		}662663		// =========664665		Self::set_allowance_unchecked(collection, from, to, amount);666		Ok(())667	}668669	/// Checks if a non-owner has (enough) allowance from the owner to perform operations on the tokens.670	/// Returns the expected remaining allowance - it should be set manually if the transaction proceeds.671	///672	/// - `collection`: Collection that contains the token.673	/// - `spender`: CrossAccountId who has the allowance rights.674	/// - `from`: The owner of the tokens who sets the allowance.675	/// - `amount`: Amount of tokens by which the allowance sholud be reduced.676	fn check_allowed(677		collection: &FungibleHandle<T>,678		spender: &T::CrossAccountId,679		from: &T::CrossAccountId,680		amount: u128,681		nesting_budget: &dyn Budget,682	) -> Result<Option<u128>, DispatchError> {683		if spender.conv_eq(from) {684			return Ok(None);685		}686		if collection.permissions.access() == AccessMode::AllowList {687			// `from`, `to` checked in [`transfer`]688			collection.check_allowlist(spender)?;689		}690691		if collection.ignores_token_restrictions(spender) {692			return Ok(Self::compute_allowance_decrease(693				collection, from, spender, amount,694			));695		}696697		if let Some(source) = T::CrossTokenAddressMapping::address_to_token(from) {698			ensure!(699				<PalletStructure<T>>::check_indirectly_owned(700					spender.clone(),701					source.0,702					source.1,703					None,704					nesting_budget705				)?,706				<CommonError<T>>::ApprovedValueTooLow,707			);708			return Ok(None);709		}710711		let allowance = Self::compute_allowance_decrease(collection, from, spender, amount);712		ensure!(allowance.is_some(), <CommonError<T>>::ApprovedValueTooLow);713714		Ok(allowance)715	}716717	/// Returns `Some(amount)` if the `spender` have allowance to spend this amount.718	/// Otherwise, it returns `None`.719	fn compute_allowance_decrease(720		collection: &FungibleHandle<T>,721		from: &T::CrossAccountId,722		spender: &T::CrossAccountId,723		amount: u128,724	) -> Option<u128> {725		<Allowance<T>>::get((collection.id, from, spender)).checked_sub(amount)726	}727728	/// Transfer fungible tokens from one account to another.729	/// Same as the [`transfer`][`Pallet::transfer`] but spender doesn't needs to be an owner of the token pieces.730	/// The owner should set allowance for the spender to transfer pieces.731	///	See [`set_allowance`][`Pallet::set_allowance`] for more details.732	pub fn transfer_from(733		collection: &FungibleHandle<T>,734		spender: &T::CrossAccountId,735		from: &T::CrossAccountId,736		to: &T::CrossAccountId,737		amount: u128,738		nesting_budget: &dyn Budget,739	) -> DispatchResultWithPostInfo {740		let allowance = Self::check_allowed(collection, spender, from, amount, nesting_budget)?;741742		// =========743744		let mut result = Self::transfer(collection, from, to, amount, nesting_budget);745		add_weight_to_post_info(&mut result, <SelfWeightOf<T>>::check_allowed_raw());746		result?;747748		if let Some(allowance) = allowance {749			Self::set_allowance_unchecked(collection, from, spender, allowance);750			add_weight_to_post_info(751				&mut result,752				<SelfWeightOf<T>>::set_allowance_unchecked_raw(),753			)754		}755		result756	}757758	/// Burn fungible tokens from the account.759	///760	/// Same as the [`burn`][`Pallet::burn`] but spender doesn't need to be an owner of the tokens. The `from` should761	/// set allowance for the spender to burn tokens.762	/// See [`set_allowance`][`Pallet::set_allowance`] for more details.763	pub fn burn_from(764		collection: &FungibleHandle<T>,765		spender: &T::CrossAccountId,766		from: &T::CrossAccountId,767		amount: u128,768		nesting_budget: &dyn Budget,769	) -> DispatchResult {770		let allowance = Self::check_allowed(collection, spender, from, amount, nesting_budget)?;771772		// =========773774		Self::burn(collection, from, amount)?;775		if let Some(allowance) = allowance {776			Self::set_allowance_unchecked(collection, from, spender, allowance);777		}778		Ok(())779	}780781	///	Creates fungible token.782	///783	/// The sender should be the owner/admin of the collection or collection should be configured784	/// to allow public minting.785	///786	/// - `data`: Contains user who will become the owners of the tokens and amount787	///   of tokens he will receive.788	pub fn create_item(789		collection: &FungibleHandle<T>,790		sender: &T::CrossAccountId,791		data: CreateItemData<T>,792		nesting_budget: &dyn Budget,793	) -> DispatchResult {794		Self::create_multiple_items(795			collection,796			sender,797			[(data.0, data.1)].into_iter().collect(),798			nesting_budget,799		)800	}801802	///	Creates fungible token.803	///804	/// - `data`: Contains user who will become the owners of the tokens and amount805	///   of tokens he will receive.806	pub fn create_item_foreign(807		collection: &FungibleHandle<T>,808		sender: &T::CrossAccountId,809		data: CreateItemData<T>,810		nesting_budget: &dyn Budget,811	) -> DispatchResult {812		Self::create_multiple_items_foreign(813			collection,814			sender,815			[(data.0, data.1)].into_iter().collect(),816			nesting_budget,817		)818	}819820	/// Returns 10 tokens owners in no particular order821	///822	/// There is no direct way to get token holders in ascending order,823	/// since `iter_prefix` returns values in no particular order.824	/// Therefore, getting the 10 largest holders with a large value of holders825	/// can lead to impact memory allocation + sorting with  `n * log (n)`.826	pub fn token_owners(827		collection: CollectionId,828		_token: TokenId,829	) -> Option<Vec<T::CrossAccountId>> {830		let res: Vec<T::CrossAccountId> = <Balance<T>>::iter_prefix((collection,))831			.map(|(owner, _amount)| owner)832			.take(10)833			.collect();834835		if res.is_empty() {836			None837		} else {838			Some(res)839		}840	}841}