// 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.

//! # Unique (Assets) Module
//!
//! A simple, secure module for dealing with non-fungible assets.
//!
//! ## Related Modules
//!
//! * [`System`](../frame_system/index.html)
//! * [`Support`](../frame_support/index.html)

// Ensure we're `no_std` when compiling for Wasm.
#![cfg_attr(not(feature = "std"), no_std)]

#[cfg(feature = "runtime-benchmarks")]
mod benchmarking;
#[cfg(test)]
pub mod mock;
#[cfg(test)]
mod tests;
pub mod weights;

mod functions;
mod impl_nonfungibles;
mod types;
pub use types::*;

use codec::{Decode, Encode, HasCompact};
use frame_support::traits::{BalanceStatus::Reserved, Currency, ReservableCurrency};
use frame_system::Config as SystemConfig;
use sp_runtime::{
	traits::{Saturating, StaticLookup, Zero},
	ArithmeticError, RuntimeDebug,
};
use sp_std::prelude::*;

pub use pallet::*;
pub use weights::WeightInfo;

#[frame_support::pallet]
pub mod pallet {
	use super::*;
	use frame_support::pallet_prelude::*;
	use frame_system::pallet_prelude::*;

	#[pallet::pallet]
	#[pallet::generate_store(pub(super) trait Store)]
	pub struct Pallet<T, I = ()>(_);

	#[pallet::config]
	/// The module configuration trait.
	pub trait Config<I: 'static = ()>: frame_system::Config {
		/// The overarching event type.
		type Event: From<Event<Self, I>> + IsType<<Self as frame_system::Config>::Event>;

		/// Identifier for the class of asset.
		type ClassId: Member + Parameter + Default + Copy + HasCompact;

		/// The type used to identify a unique asset within an asset class.
		type InstanceId: Member + Parameter + Default + Copy + HasCompact + From<u16>;

		/// The currency mechanism, used for paying for reserves.
		type Currency: ReservableCurrency<Self::AccountId>;

		/// The origin which may forcibly create or destroy an asset or otherwise alter privileged
		/// attributes.
		type ForceOrigin: EnsureOrigin<Self::Origin>;

		/// The basic amount of funds that must be reserved for an asset class.
		#[pallet::constant]
		type ClassDeposit: Get<DepositBalanceOf<Self, I>>;

		/// The basic amount of funds that must be reserved for an asset instance.
		#[pallet::constant]
		type InstanceDeposit: Get<DepositBalanceOf<Self, I>>;

		/// The basic amount of funds that must be reserved when adding metadata to your asset.
		#[pallet::constant]
		type MetadataDepositBase: Get<DepositBalanceOf<Self, I>>;

		/// The basic amount of funds that must be reserved when adding an attribute to an asset.
		#[pallet::constant]
		type AttributeDepositBase: Get<DepositBalanceOf<Self, I>>;

		/// The additional funds that must be reserved for the number of bytes store in metadata,
		/// either "normal" metadata or attribute metadata.
		#[pallet::constant]
		type DepositPerByte: Get<DepositBalanceOf<Self, I>>;

		/// The maximum length of data stored on-chain.
		#[pallet::constant]
		type StringLimit: Get<u32>;

		/// The maximum length of an attribute key.
		#[pallet::constant]
		type KeyLimit: Get<u32>;

		/// The maximum length of an attribute value.
		#[pallet::constant]
		type ValueLimit: Get<u32>;

		/// Weight information for extrinsics in this pallet.
		type WeightInfo: WeightInfo;
	}

	#[pallet::storage]
	/// Details of an asset class.
	pub(super) type Class<T: Config<I>, I: 'static = ()> = StorageMap<
		_,
		Blake2_128Concat,
		T::ClassId,
		ClassDetails<T::AccountId, DepositBalanceOf<T, I>>,
	>;

	#[pallet::storage]
	/// The assets held by any given account; set out this way so that assets owned by a single
	/// account can be enumerated.
	pub(super) type Account<T: Config<I>, I: 'static = ()> = StorageNMap<
		_,
		(
			NMapKey<Blake2_128Concat, T::AccountId>, // owner
			NMapKey<Blake2_128Concat, T::ClassId>,
			NMapKey<Blake2_128Concat, T::InstanceId>,
		),
		(),
		OptionQuery,
	>;

	#[pallet::storage]
	/// The assets in existence and their ownership details.
	pub(super) type Asset<T: Config<I>, I: 'static = ()> = StorageDoubleMap<
		_,
		Blake2_128Concat,
		T::ClassId,
		Blake2_128Concat,
		T::InstanceId,
		InstanceDetails<T::AccountId, DepositBalanceOf<T, I>>,
		OptionQuery,
	>;

	#[pallet::storage]
	/// Metadata of an asset class.
	pub(super) type ClassMetadataOf<T: Config<I>, I: 'static = ()> = StorageMap<
		_,
		Blake2_128Concat,
		T::ClassId,
		ClassMetadata<DepositBalanceOf<T, I>, T::StringLimit>,
		OptionQuery,
	>;

	#[pallet::storage]
	/// Metadata of an asset instance.
	pub(super) type InstanceMetadataOf<T: Config<I>, I: 'static = ()> = StorageDoubleMap<
		_,
		Blake2_128Concat,
		T::ClassId,
		Blake2_128Concat,
		T::InstanceId,
		InstanceMetadata<DepositBalanceOf<T, I>, T::StringLimit>,
		OptionQuery,
	>;

	#[pallet::storage]
	/// Metadata of an asset class.
	pub(super) type Attribute<T: Config<I>, I: 'static = ()> = StorageNMap<
		_,
		(
			NMapKey<Blake2_128Concat, T::ClassId>,
			NMapKey<Blake2_128Concat, Option<T::InstanceId>>,
			NMapKey<Blake2_128Concat, BoundedVec<u8, T::KeyLimit>>,
		),
		(BoundedVec<u8, T::ValueLimit>, DepositBalanceOf<T, I>),
		OptionQuery,
	>;

	#[pallet::event]
	#[pallet::generate_deposit(pub(super) fn deposit_event)]
	#[pallet::metadata(
		T::AccountId = "AccountId",
		T::ClassId = "ClassId",
		T::InstanceId = "InstanceId"
	)]
	pub enum Event<T: Config<I>, I: 'static = ()> {
		/// An asset class was created. \[ class, creator, owner \]
		Created(T::ClassId, T::AccountId, T::AccountId),
		/// An asset class was force-created. \[ class, owner \]
		ForceCreated(T::ClassId, T::AccountId),
		/// An asset `class` was destroyed. \[ class \]
		Destroyed(T::ClassId),
		/// An asset `instace` was issued. \[ class, instance, owner \]
		Issued(T::ClassId, T::InstanceId, T::AccountId),
		/// An asset `instace` was transferred. \[ class, instance, from, to \]
		Transferred(T::ClassId, T::InstanceId, T::AccountId, T::AccountId),
		/// An asset `instance` was destroyed. \[ class, instance, owner \]
		Burned(T::ClassId, T::InstanceId, T::AccountId),
		/// Some asset `instance` was frozen. \[ class, instance \]
		Frozen(T::ClassId, T::InstanceId),
		/// Some asset `instance` was thawed. \[ class, instance \]
		Thawed(T::ClassId, T::InstanceId),
		/// Some asset `class` was frozen. \[ class \]
		ClassFrozen(T::ClassId),
		/// Some asset `class` was thawed. \[ class \]
		ClassThawed(T::ClassId),
		/// The owner changed \[ class, new_owner \]
		OwnerChanged(T::ClassId, T::AccountId),
		/// The management team changed \[ class, issuer, admin, freezer \]
		TeamChanged(T::ClassId, T::AccountId, T::AccountId, T::AccountId),
		/// An `instance` of an asset `class` has been approved by the `owner` for transfer by a
		/// `delegate`.
		/// \[ class, instance, owner, delegate \]
		ApprovedTransfer(T::ClassId, T::InstanceId, T::AccountId, T::AccountId),
		/// An approval for a `delegate` account to transfer the `instance` of an asset `class` was
		/// cancelled by its `owner`.
		/// \[ class, instance, owner, delegate \]
		ApprovalCancelled(T::ClassId, T::InstanceId, T::AccountId, T::AccountId),
		/// An asset `class` has had its attributes changed by the `Force` origin.
		/// \[ class \]
		AssetStatusChanged(T::ClassId),
		/// New metadata has been set for an asset class. \[ class, data, is_frozen \]
		ClassMetadataSet(T::ClassId, BoundedVec<u8, T::StringLimit>, bool),
		/// Metadata has been cleared for an asset class. \[ class \]
		ClassMetadataCleared(T::ClassId),
		/// New metadata has been set for an asset instance.
		/// \[ class, instance, data, is_frozen \]
		MetadataSet(T::ClassId, T::InstanceId, BoundedVec<u8, T::StringLimit>, bool),
		/// Metadata has been cleared for an asset instance. \[ class, instance \]
		MetadataCleared(T::ClassId, T::InstanceId),
		/// Metadata has been cleared for an asset instance. \[ class, successful_instances \]
		Redeposited(T::ClassId, Vec<T::InstanceId>),
		/// New attribute metadata has been set for an asset class or instance.
		/// \[ class, maybe_instance, key, value \]
		AttributeSet(
			T::ClassId,
			Option<T::InstanceId>,
			BoundedVec<u8, T::KeyLimit>,
			BoundedVec<u8, T::ValueLimit>,
		),
		/// Attribute metadata has been cleared for an asset class or instance.
		/// \[ class, maybe_instance, key, maybe_value \]
		AttributeCleared(T::ClassId, Option<T::InstanceId>, BoundedVec<u8, T::KeyLimit>),
	}

	#[pallet::error]
	pub enum Error<T, I = ()> {
		/// The signing account has no permission to do the operation.
		NoPermission,
		/// The given asset ID is unknown.
		Unknown,
		/// The asset instance ID has already been used for an asset.
		AlreadyExists,
		/// The owner turned out to be different to what was expected.
		WrongOwner,
		/// Invalid witness data given.
		BadWitness,
		/// The asset ID is already taken.
		InUse,
		/// The asset instance or class is frozen.
		Frozen,
		/// The delegate turned out to be different to what was expected.
		WrongDelegate,
		/// There is no delegate approved.
		NoDelegate,
		/// No approval exists that would allow the transfer.
		Unapproved,
	}

	#[pallet::hooks]
	impl<T: Config<I>, I: 'static> Hooks<BlockNumberFor<T>> for Pallet<T, I> {}

	impl<T: Config<I>, I: 'static> Pallet<T, I> {
		/// Get the owner of the asset instance, if the asset exists.
		pub fn owner(class: T::ClassId, instance: T::InstanceId) -> Option<T::AccountId> {
			Asset::<T, I>::get(class, instance).map(|i| i.owner)
		}
	}

	#[pallet::call]
	impl<T: Config<I>, I: 'static> Pallet<T, I> {
		/// Issue a new class of non-fungible assets from a public origin.
		///
		/// This new asset class has no assets initially and its owner is the origin.
		///
		/// The origin must be Signed and the sender must have sufficient funds free.
		///
		/// `AssetDeposit` funds of sender are reserved.
		///
		/// Parameters:
		/// - `class`: The identifier of the new asset class. This must not be currently in use.
		/// - `admin`: The admin of this class of assets. The admin is the initial address of each
		/// member of the asset class's admin team.
		///
		/// Emits `Created` event when successful.
		///
		/// Weight: `O(1)`
		#[pallet::weight(T::WeightInfo::create())]
		pub fn create(
			origin: OriginFor<T>,
			#[pallet::compact] class: T::ClassId,
			admin: <T::Lookup as StaticLookup>::Source,
		) -> DispatchResult {
			let owner = ensure_signed(origin)?;
			let admin = T::Lookup::lookup(admin)?;

			Self::do_create_class(
				class,
				owner.clone(),
				admin.clone(),
				T::ClassDeposit::get(),
				false,
				Event::Created(class, owner, admin),
			)
		}

		/// Issue a new class of non-fungible assets from a privileged origin.
		///
		/// This new asset class has no assets initially.
		///
		/// The origin must conform to `ForceOrigin`.
		///
		/// Unlike `create`, no funds are reserved.
		///
		/// - `class`: The identifier of the new asset. This must not be currently in use.
		/// - `owner`: The owner of this class of assets. The owner has full superuser permissions
		/// over this asset, but may later change and configure the permissions using
		/// `transfer_ownership` and `set_team`.
		///
		/// Emits `ForceCreated` event when successful.
		///
		/// Weight: `O(1)`
		#[pallet::weight(T::WeightInfo::force_create())]
		pub fn force_create(
			origin: OriginFor<T>,
			#[pallet::compact] class: T::ClassId,
			owner: <T::Lookup as StaticLookup>::Source,
			free_holding: bool,
		) -> DispatchResult {
			T::ForceOrigin::ensure_origin(origin)?;
			let owner = T::Lookup::lookup(owner)?;

			Self::do_create_class(
				class,
				owner.clone(),
				owner.clone(),
				Zero::zero(),
				free_holding,
				Event::ForceCreated(class, owner),
			)
		}

		/// Destroy a class of fungible assets.
		///
		/// The origin must conform to `ForceOrigin` or must be `Signed` and the sender must be the
		/// owner of the asset `class`.
		///
		/// - `class`: The identifier of the asset class to be destroyed.
		/// - `witness`: Information on the instances minted in the asset class. This must be
		/// correct.
		///
		/// Emits `Destroyed` event when successful.
		///
		/// Weight: `O(n + m)` where:
		/// - `n = witness.instances`
		/// - `m = witness.instance_metadatas`
		/// - `a = witness.attributes`
		#[pallet::weight(T::WeightInfo::destroy(
			witness.instances,
 			witness.instance_metadatas,
			witness.attributes,
 		))]
		pub fn destroy(
			origin: OriginFor<T>,
			#[pallet::compact] class: T::ClassId,
			witness: DestroyWitness,
		) -> DispatchResult {
			let maybe_check_owner = match T::ForceOrigin::try_origin(origin) {
				Ok(_) => None,
				Err(origin) => Some(ensure_signed(origin)?),
			};
			Class::<T, I>::try_mutate_exists(class, |maybe_details| {
				let class_details = maybe_details.take().ok_or(Error::<T, I>::Unknown)?;
				if let Some(check_owner) = maybe_check_owner {
					ensure!(class_details.owner == check_owner, Error::<T, I>::NoPermission);
				}
				ensure!(class_details.instances == witness.instances, Error::<T, I>::BadWitness);
				ensure!(
					class_details.instance_metadatas == witness.instance_metadatas,
					Error::<T, I>::BadWitness
				);
				ensure!(class_details.attributes == witness.attributes, Error::<T, I>::BadWitness);

				for (instance, details) in Asset::<T, I>::drain_prefix(&class) {
					Account::<T, I>::remove((&details.owner, &class, &instance));
				}
				InstanceMetadataOf::<T, I>::remove_prefix(&class, None);
				ClassMetadataOf::<T, I>::remove(&class);
				Attribute::<T, I>::remove_prefix((&class,), None);
				T::Currency::unreserve(&class_details.owner, class_details.total_deposit);

				Self::deposit_event(Event::Destroyed(class));

				// NOTE: could use postinfo to reflect the actual number of
				// accounts/sufficient/approvals
				Ok(())
			})
		}

		/// Mint an asset instance of a particular class.
		///
		/// The origin must be Signed and the sender must be the Issuer of the asset `class`.
		///
		/// - `class`: The class of the asset to be minted.
		/// - `instance`: The instance value of the asset to be minted.
		/// - `beneficiary`: The initial owner of the minted asset.
		///
		/// Emits `Issued` event when successful.
		///
		/// Weight: `O(1)`
		#[pallet::weight(T::WeightInfo::mint())]
		pub fn mint(
			origin: OriginFor<T>,
			#[pallet::compact] class: T::ClassId,
			#[pallet::compact] instance: T::InstanceId,
			owner: <T::Lookup as StaticLookup>::Source,
		) -> DispatchResult {
			let origin = ensure_signed(origin)?;
			let owner = T::Lookup::lookup(owner)?;

			Self::do_mint(class, instance, owner, |class_details| {
				ensure!(class_details.issuer == origin, Error::<T, I>::NoPermission);
				Ok(())
			})
		}

		/// Destroy a single asset instance.
		///
		/// Origin must be Signed and the sender should be the Admin of the asset `class`.
		///
		/// - `class`: The class of the asset to be burned.
		/// - `instance`: The instance of the asset to be burned.
		/// - `check_owner`: If `Some` then the operation will fail with `WrongOwner` unless the
		///   asset is owned by this value.
		///
		/// Emits `Burned` with the actual amount burned.
		///
		/// Weight: `O(1)`
		/// Modes: `check_owner.is_some()`.
		#[pallet::weight(T::WeightInfo::burn())]
		pub fn burn(
			origin: OriginFor<T>,
			#[pallet::compact] class: T::ClassId,
			#[pallet::compact] instance: T::InstanceId,
			check_owner: Option<<T::Lookup as StaticLookup>::Source>,
		) -> DispatchResult {
			let origin = ensure_signed(origin)?;
			let check_owner = check_owner.map(T::Lookup::lookup).transpose()?;

			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
				);
				Ok(())
			})
		}

		/// Move an asset from the sender account to another.
		///
		/// Origin must be Signed and the signing account must be either:
		/// - the Admin of the asset `class`;
		/// - the Owner of the asset `instance`;
		/// - the approved delegate for the asset `instance` (in this case, the approval is reset).
		///
		/// Arguments:
		/// - `class`: The class of the asset to be transferred.
		/// - `instance`: The instance of the asset to be transferred.
		/// - `dest`: The account to receive ownership of the asset.
		///
		/// Emits `Transferred`.
		///
		/// Weight: `O(1)`
		#[pallet::weight(T::WeightInfo::transfer())]
		pub fn transfer(
			origin: OriginFor<T>,
			#[pallet::compact] class: T::ClassId,
			#[pallet::compact] instance: T::InstanceId,
			dest: <T::Lookup as StaticLookup>::Source,
		) -> DispatchResult {
			let origin = ensure_signed(origin)?;
			let dest = T::Lookup::lookup(dest)?;

			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.
		///
		/// Origin must be Signed and the sender should be the Owner of the asset `class`.
		///
		/// - `class`: The class of the asset to be frozen.
		/// - `instances`: The instances of the asset class whose deposits will be reevaluated.
		///
		/// NOTE: This exists as a best-effort function. Any asset instances which are unknown or
		/// in the case that the owner account does not have reservable funds to pay for a
		/// deposit increase are ignored. Generally the owner isn't going to call this on instances
		/// whose existing deposit is less than the refreshed deposit as it would only cost them,
		/// so it's of little consequence.
		///
		/// It will still return an error in the case that the class is unknown of the signer is
		/// not permitted to call it.
		///
		/// Weight: `O(instances.len())`
		#[pallet::weight(T::WeightInfo::redeposit(instances.len() as u32))]
		pub fn redeposit(
			origin: OriginFor<T>,
			#[pallet::compact] class: T::ClassId,
			instances: Vec<T::InstanceId>,
		) -> DispatchResult {
			let origin = ensure_signed(origin)?;

			let mut class_details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::Unknown)?;
			ensure!(class_details.owner == origin, Error::<T, I>::NoPermission);
			let deposit = match class_details.free_holding {
				true => Zero::zero(),
				false => T::InstanceDeposit::get(),
			};

			let mut successful = Vec::with_capacity(instances.len());
			for instance in instances.into_iter() {
				let mut details = match Asset::<T, I>::get(&class, &instance) {
					Some(x) => x,
					None => continue,
				};
				let old = details.deposit;
				if old > deposit {
					T::Currency::unreserve(&class_details.owner, old - deposit);
				} else if deposit > old {
					if T::Currency::reserve(&class_details.owner, deposit - old).is_err() {
						// NOTE: No alterations made to class_details in this iteration so far, so
						// this is OK to do.
						continue
					}
				} else {
					continue
				}
				class_details.total_deposit.saturating_accrue(deposit);
				class_details.total_deposit.saturating_reduce(old);
				details.deposit = deposit;
				Asset::<T, I>::insert(&class, &instance, &details);
				successful.push(instance);
			}
			Class::<T, I>::insert(&class, &class_details);

			Self::deposit_event(Event::<T, I>::Redeposited(class, successful));

			Ok(())
		}

		/// Disallow further unprivileged transfer of an asset instance.
		///
		/// Origin must be Signed and the sender should be the Freezer of the asset `class`.
		///
		/// - `class`: The class of the asset to be frozen.
		/// - `instance`: The instance of the asset to be frozen.
		///
		/// Emits `Frozen`.
		///
		/// Weight: `O(1)`
		#[pallet::weight(T::WeightInfo::freeze())]
		pub fn freeze(
			origin: OriginFor<T>,
			#[pallet::compact] class: T::ClassId,
			#[pallet::compact] instance: T::InstanceId,
		) -> DispatchResult {
			let origin = ensure_signed(origin)?;

			let mut details =
				Asset::<T, I>::get(&class, &instance).ok_or(Error::<T, I>::Unknown)?;
			let class_details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::Unknown)?;
			ensure!(class_details.freezer == origin, Error::<T, I>::NoPermission);

			details.is_frozen = true;
			Asset::<T, I>::insert(&class, &instance, &details);

			Self::deposit_event(Event::<T, I>::Frozen(class, instance));
			Ok(())
		}

		/// Re-allow unprivileged transfer of an asset instance.
		///
		/// Origin must be Signed and the sender should be the Freezer of the asset `class`.
		///
		/// - `class`: The class of the asset to be thawed.
		/// - `instance`: The instance of the asset to be thawed.
		///
		/// Emits `Thawed`.
		///
		/// Weight: `O(1)`
		#[pallet::weight(T::WeightInfo::thaw())]
		pub fn thaw(
			origin: OriginFor<T>,
			#[pallet::compact] class: T::ClassId,
			#[pallet::compact] instance: T::InstanceId,
		) -> DispatchResult {
			let origin = ensure_signed(origin)?;

			let mut details =
				Asset::<T, I>::get(&class, &instance).ok_or(Error::<T, I>::Unknown)?;
			let class_details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::Unknown)?;
			ensure!(class_details.admin == origin, Error::<T, I>::NoPermission);

			details.is_frozen = false;
			Asset::<T, I>::insert(&class, &instance, &details);

			Self::deposit_event(Event::<T, I>::Thawed(class, instance));
			Ok(())
		}

		/// Disallow further unprivileged transfers for a whole asset class.
		///
		/// Origin must be Signed and the sender should be the Freezer of the asset `class`.
		///
		/// - `class`: The asset class to be frozen.
		///
		/// Emits `ClassFrozen`.
		///
		/// Weight: `O(1)`
		#[pallet::weight(T::WeightInfo::freeze_class())]
		pub fn freeze_class(
			origin: OriginFor<T>,
			#[pallet::compact] class: T::ClassId,
		) -> DispatchResult {
			let origin = ensure_signed(origin)?;

			Class::<T, I>::try_mutate(class, |maybe_details| {
				let details = maybe_details.as_mut().ok_or(Error::<T, I>::Unknown)?;
				ensure!(&origin == &details.freezer, Error::<T, I>::NoPermission);

				details.is_frozen = true;

				Self::deposit_event(Event::<T, I>::ClassFrozen(class));
				Ok(())
			})
		}

		/// Re-allow unprivileged transfers for a whole asset class.
		///
		/// Origin must be Signed and the sender should be the Admin of the asset `class`.
		///
		/// - `class`: The class to be thawed.
		///
		/// Emits `ClassThawed`.
		///
		/// Weight: `O(1)`
		#[pallet::weight(T::WeightInfo::thaw_class())]
		pub fn thaw_class(
			origin: OriginFor<T>,
			#[pallet::compact] class: T::ClassId,
		) -> DispatchResult {
			let origin = ensure_signed(origin)?;

			Class::<T, I>::try_mutate(class, |maybe_details| {
				let details = maybe_details.as_mut().ok_or(Error::<T, I>::Unknown)?;
				ensure!(&origin == &details.admin, Error::<T, I>::NoPermission);

				details.is_frozen = false;

				Self::deposit_event(Event::<T, I>::ClassThawed(class));
				Ok(())
			})
		}

		/// Change the Owner of an asset class.
		///
		/// Origin must be Signed and the sender should be the Owner of the asset `class`.
		///
		/// - `class`: The asset class whose owner should be changed.
		/// - `owner`: The new Owner of this asset class.
		///
		/// Emits `OwnerChanged`.
		///
		/// Weight: `O(1)`
		#[pallet::weight(T::WeightInfo::transfer_ownership())]
		pub fn transfer_ownership(
			origin: OriginFor<T>,
			#[pallet::compact] class: T::ClassId,
			owner: <T::Lookup as StaticLookup>::Source,
		) -> DispatchResult {
			let origin = ensure_signed(origin)?;
			let owner = T::Lookup::lookup(owner)?;

			Class::<T, I>::try_mutate(class, |maybe_details| {
				let details = maybe_details.as_mut().ok_or(Error::<T, I>::Unknown)?;
				ensure!(&origin == &details.owner, Error::<T, I>::NoPermission);
				if details.owner == owner {
					return Ok(())
				}

				// Move the deposit to the new owner.
				T::Currency::repatriate_reserved(
					&details.owner,
					&owner,
					details.total_deposit,
					Reserved,
				)?;
				details.owner = owner.clone();

				Self::deposit_event(Event::OwnerChanged(class, owner));
				Ok(())
			})
		}

		/// Change the Issuer, Admin and Freezer of an asset class.
		///
		/// Origin must be Signed and the sender should be the Owner of the asset `class`.
		///
		/// - `class`: The asset class whose team should be changed.
		/// - `issuer`: The new Issuer of this asset class.
		/// - `admin`: The new Admin of this asset class.
		/// - `freezer`: The new Freezer of this asset class.
		///
		/// Emits `TeamChanged`.
		///
		/// Weight: `O(1)`
		#[pallet::weight(T::WeightInfo::set_team())]
		pub fn set_team(
			origin: OriginFor<T>,
			#[pallet::compact] class: T::ClassId,
			issuer: <T::Lookup as StaticLookup>::Source,
			admin: <T::Lookup as StaticLookup>::Source,
			freezer: <T::Lookup as StaticLookup>::Source,
		) -> DispatchResult {
			let origin = ensure_signed(origin)?;
			let issuer = T::Lookup::lookup(issuer)?;
			let admin = T::Lookup::lookup(admin)?;
			let freezer = T::Lookup::lookup(freezer)?;

			Class::<T, I>::try_mutate(class, |maybe_details| {
				let details = maybe_details.as_mut().ok_or(Error::<T, I>::Unknown)?;
				ensure!(&origin == &details.owner, Error::<T, I>::NoPermission);

				details.issuer = issuer.clone();
				details.admin = admin.clone();
				details.freezer = freezer.clone();

				Self::deposit_event(Event::TeamChanged(class, issuer, admin, freezer));
				Ok(())
			})
		}

		/// Approve an instance to be transferred by a delegated third-party account.
		///
		/// Origin must be Signed and must be the owner of the asset `instance`.
		///
		/// - `class`: The class of the asset to be approved for delegated transfer.
		/// - `instance`: The instance of the asset to be approved for delegated transfer.
		/// - `delegate`: The account to delegate permission to transfer the asset.
		///
		/// Emits `ApprovedTransfer` on success.
		///
		/// Weight: `O(1)`
		#[pallet::weight(T::WeightInfo::approve_transfer())]
		pub fn approve_transfer(
			origin: OriginFor<T>,
			#[pallet::compact] class: T::ClassId,
			#[pallet::compact] instance: T::InstanceId,
			delegate: <T::Lookup as StaticLookup>::Source,
		) -> DispatchResult {
			let maybe_check: Option<T::AccountId> = T::ForceOrigin::try_origin(origin)
				.map(|_| None)
				.or_else(|origin| ensure_signed(origin).map(Some).map_err(DispatchError::from))?;

			let delegate = T::Lookup::lookup(delegate)?;

			let class_details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::Unknown)?;
			let mut details =
				Asset::<T, I>::get(&class, &instance).ok_or(Error::<T, I>::Unknown)?;

			if let Some(check) = maybe_check {
				let permitted = &check == &class_details.admin || &check == &details.owner;
				ensure!(permitted, Error::<T, I>::NoPermission);
			}

			details.approved = Some(delegate);
			Asset::<T, I>::insert(&class, &instance, &details);

			let delegate = details.approved.expect("set as Some above; qed");
			Self::deposit_event(Event::ApprovedTransfer(class, instance, details.owner, delegate));

			Ok(())
		}

		/// Cancel the prior approval for the transfer of an asset by a delegate.
		///
		/// Origin must be either:
		/// - the `Force` origin;
		/// - `Signed` with the signer being the Admin of the asset `class`;
		/// - `Signed` with the signer being the Owner of the asset `instance`;
		///
		/// Arguments:
		/// - `class`: The class of the asset of whose approval will be cancelled.
		/// - `instance`: The instance of the asset of whose approval will be cancelled.
		/// - `maybe_check_delegate`: If `Some` will ensure that the given account is the one to
		///   which permission of transfer is delegated.
		///
		/// Emits `ApprovalCancelled` on success.
		///
		/// Weight: `O(1)`
		#[pallet::weight(T::WeightInfo::cancel_approval())]
		pub fn cancel_approval(
			origin: OriginFor<T>,
			#[pallet::compact] class: T::ClassId,
			#[pallet::compact] instance: T::InstanceId,
			maybe_check_delegate: Option<<T::Lookup as StaticLookup>::Source>,
		) -> DispatchResult {
			let maybe_check: Option<T::AccountId> = T::ForceOrigin::try_origin(origin)
				.map(|_| None)
				.or_else(|origin| ensure_signed(origin).map(Some).map_err(DispatchError::from))?;

			let class_details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::Unknown)?;
			let mut details =
				Asset::<T, I>::get(&class, &instance).ok_or(Error::<T, I>::Unknown)?;
			if let Some(check) = maybe_check {
				let permitted = &check == &class_details.admin || &check == &details.owner;
				ensure!(permitted, Error::<T, I>::NoPermission);
			}
			let maybe_check_delegate = maybe_check_delegate.map(T::Lookup::lookup).transpose()?;
			let old = details.approved.take().ok_or(Error::<T, I>::NoDelegate)?;
			if let Some(check_delegate) = maybe_check_delegate {
				ensure!(check_delegate == old, Error::<T, I>::WrongDelegate);
			}

			Asset::<T, I>::insert(&class, &instance, &details);
			Self::deposit_event(Event::ApprovalCancelled(class, instance, details.owner, old));

			Ok(())
		}

		/// Alter the attributes of a given asset.
		///
		/// Origin must be `ForceOrigin`.
		///
		/// - `class`: The identifier of the asset.
		/// - `owner`: The new Owner of this asset.
		/// - `issuer`: The new Issuer of this asset.
		/// - `admin`: The new Admin of this asset.
		/// - `freezer`: The new Freezer of this asset.
		/// - `free_holding`: Whether a deposit is taken for holding an instance of this asset
		///   class.
		/// - `is_frozen`: Whether this asset class is frozen except for permissioned/admin
		/// instructions.
		///
		/// Emits `AssetStatusChanged` with the identity of the asset.
		///
		/// Weight: `O(1)`
		#[pallet::weight(T::WeightInfo::force_asset_status())]
		pub fn force_asset_status(
			origin: OriginFor<T>,
			#[pallet::compact] class: T::ClassId,
			owner: <T::Lookup as StaticLookup>::Source,
			issuer: <T::Lookup as StaticLookup>::Source,
			admin: <T::Lookup as StaticLookup>::Source,
			freezer: <T::Lookup as StaticLookup>::Source,
			free_holding: bool,
			is_frozen: bool,
		) -> DispatchResult {
			T::ForceOrigin::ensure_origin(origin)?;

			Class::<T, I>::try_mutate(class, |maybe_asset| {
				let mut asset = maybe_asset.take().ok_or(Error::<T, I>::Unknown)?;
				asset.owner = T::Lookup::lookup(owner)?;
				asset.issuer = T::Lookup::lookup(issuer)?;
				asset.admin = T::Lookup::lookup(admin)?;
				asset.freezer = T::Lookup::lookup(freezer)?;
				asset.free_holding = free_holding;
				asset.is_frozen = is_frozen;
				*maybe_asset = Some(asset);

				Self::deposit_event(Event::AssetStatusChanged(class));
				Ok(())
			})
		}

		/// Set an attribute for an asset class or instance.
		///
		/// Origin must be either `ForceOrigin` or Signed and the sender should be the Owner of the
		/// asset `class`.
		///
		/// If the origin is Signed, then funds of signer are reserved according to the formula:
		/// `MetadataDepositBase + DepositPerByte * (key.len + value.len)` taking into
		/// account any already reserved funds.
		///
		/// - `class`: The identifier of the asset class whose instance's metadata to set.
		/// - `maybe_instance`: The identifier of the asset instance whose metadata to set.
		/// - `key`: The key of the attribute.
		/// - `value`: The value to which to set the attribute.
		///
		/// Emits `AttributeSet`.
		///
		/// Weight: `O(1)`
		#[pallet::weight(T::WeightInfo::set_attribute())]
		pub fn set_attribute(
			origin: OriginFor<T>,
			#[pallet::compact] class: T::ClassId,
			maybe_instance: Option<T::InstanceId>,
			key: BoundedVec<u8, T::KeyLimit>,
			value: BoundedVec<u8, T::ValueLimit>,
		) -> DispatchResult {
			let maybe_check_owner = T::ForceOrigin::try_origin(origin)
				.map(|_| None)
				.or_else(|origin| ensure_signed(origin).map(Some))?;

			let mut class_details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::Unknown)?;
			if let Some(check_owner) = &maybe_check_owner {
				ensure!(check_owner == &class_details.owner, Error::<T, I>::NoPermission);
			}
			let maybe_is_frozen = match maybe_instance {
				None => ClassMetadataOf::<T, I>::get(class).map(|v| v.is_frozen),
				Some(instance) =>
					InstanceMetadataOf::<T, I>::get(class, instance).map(|v| v.is_frozen),
			};
			ensure!(!maybe_is_frozen.unwrap_or(false), Error::<T, I>::Frozen);

			let attribute = Attribute::<T, I>::get((class, maybe_instance, &key));
			if attribute.is_none() {
				class_details.attributes.saturating_inc();
			}
			let old_deposit = attribute.map_or(Zero::zero(), |m| m.1);
			class_details.total_deposit.saturating_reduce(old_deposit);
			let mut deposit = Zero::zero();
			if !class_details.free_holding && maybe_check_owner.is_some() {
				deposit = T::DepositPerByte::get()
					.saturating_mul(((key.len() + value.len()) as u32).into())
					.saturating_add(T::AttributeDepositBase::get());
			}
			class_details.total_deposit.saturating_accrue(deposit);
			if deposit > old_deposit {
				T::Currency::reserve(&class_details.owner, deposit - old_deposit)?;
			} else if deposit < old_deposit {
				T::Currency::unreserve(&class_details.owner, old_deposit - deposit);
			}

			Attribute::<T, I>::insert((&class, maybe_instance, &key), (&value, deposit));
			Class::<T, I>::insert(class, &class_details);
			Self::deposit_event(Event::AttributeSet(class, maybe_instance, key, value));
			Ok(())
		}

		/// Set an attribute for an asset class or instance.
		///
		/// Origin must be either `ForceOrigin` or Signed and the sender should be the Owner of the
		/// asset `class`.
		///
		/// If the origin is Signed, then funds of signer are reserved according to the formula:
		/// `MetadataDepositBase + DepositPerByte * (key.len + value.len)` taking into
		/// account any already reserved funds.
		///
		/// - `class`: The identifier of the asset class whose instance's metadata to set.
		/// - `instance`: The identifier of the asset instance whose metadata to set.
		/// - `key`: The key of the attribute.
		/// - `value`: The value to which to set the attribute.
		///
		/// Emits `AttributeSet`.
		///
		/// Weight: `O(1)`
		#[pallet::weight(T::WeightInfo::clear_attribute())]
		pub fn clear_attribute(
			origin: OriginFor<T>,
			#[pallet::compact] class: T::ClassId,
			maybe_instance: Option<T::InstanceId>,
			key: BoundedVec<u8, T::KeyLimit>,
		) -> DispatchResult {
			let maybe_check_owner = T::ForceOrigin::try_origin(origin)
				.map(|_| None)
				.or_else(|origin| ensure_signed(origin).map(Some))?;

			let mut class_details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::Unknown)?;
			if let Some(check_owner) = &maybe_check_owner {
				ensure!(check_owner == &class_details.owner, Error::<T, I>::NoPermission);
			}
			let maybe_is_frozen = match maybe_instance {
				None => ClassMetadataOf::<T, I>::get(class).map(|v| v.is_frozen),
				Some(instance) =>
					InstanceMetadataOf::<T, I>::get(class, instance).map(|v| v.is_frozen),
			};
			ensure!(!maybe_is_frozen.unwrap_or(false), Error::<T, I>::Frozen);

			if let Some((_, deposit)) = Attribute::<T, I>::take((class, maybe_instance, &key)) {
				class_details.attributes.saturating_dec();
				class_details.total_deposit.saturating_reduce(deposit);
				T::Currency::unreserve(&class_details.owner, deposit);
				Class::<T, I>::insert(class, &class_details);
				Self::deposit_event(Event::AttributeCleared(class, maybe_instance, key));
			}
			Ok(())
		}

		/// Set the metadata for an asset instance.
		///
		/// Origin must be either `ForceOrigin` or Signed and the sender should be the Owner of the
		/// asset `class`.
		///
		/// If the origin is Signed, then funds of signer are reserved according to the formula:
		/// `MetadataDepositBase + DepositPerByte * data.len` taking into
		/// account any already reserved funds.
		///
		/// - `class`: The identifier of the asset class whose instance's metadata to set.
		/// - `instance`: The identifier of the asset instance whose metadata to set.
		/// - `data`: The general information of this asset. Limited in length by `StringLimit`.
		/// - `is_frozen`: Whether the metadata should be frozen against further changes.
		///
		/// Emits `MetadataSet`.
		///
		/// Weight: `O(1)`
		#[pallet::weight(T::WeightInfo::set_metadata())]
		pub fn set_metadata(
			origin: OriginFor<T>,
			#[pallet::compact] class: T::ClassId,
			#[pallet::compact] instance: T::InstanceId,
			data: BoundedVec<u8, T::StringLimit>,
			is_frozen: bool,
		) -> DispatchResult {
			let maybe_check_owner = T::ForceOrigin::try_origin(origin)
				.map(|_| None)
				.or_else(|origin| ensure_signed(origin).map(Some))?;

			let mut class_details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::Unknown)?;

			if let Some(check_owner) = &maybe_check_owner {
				ensure!(check_owner == &class_details.owner, Error::<T, I>::NoPermission);
			}

			InstanceMetadataOf::<T, I>::try_mutate_exists(class, instance, |metadata| {
				let was_frozen = metadata.as_ref().map_or(false, |m| m.is_frozen);
				ensure!(maybe_check_owner.is_none() || !was_frozen, Error::<T, I>::Frozen);

				if metadata.is_none() {
					class_details.instance_metadatas.saturating_inc();
				}
				let old_deposit = metadata.take().map_or(Zero::zero(), |m| m.deposit);
				class_details.total_deposit.saturating_reduce(old_deposit);
				let mut deposit = Zero::zero();
				if !class_details.free_holding && maybe_check_owner.is_some() {
					deposit = T::DepositPerByte::get()
						.saturating_mul(((data.len()) as u32).into())
						.saturating_add(T::MetadataDepositBase::get());
				}
				if deposit > old_deposit {
					T::Currency::reserve(&class_details.owner, deposit - old_deposit)?;
				} else if deposit < old_deposit {
					T::Currency::unreserve(&class_details.owner, old_deposit - deposit);
				}
				class_details.total_deposit.saturating_accrue(deposit);

				*metadata = Some(InstanceMetadata { deposit, data: data.clone(), is_frozen });

				Class::<T, I>::insert(&class, &class_details);
				Self::deposit_event(Event::MetadataSet(class, instance, data, is_frozen));
				Ok(())
			})
		}

		/// Clear the metadata for an asset instance.
		///
		/// Origin must be either `ForceOrigin` or Signed and the sender should be the Owner of the
		/// asset `instance`.
		///
		/// Any deposit is freed for the asset class owner.
		///
		/// - `class`: The identifier of the asset class whose instance's metadata to clear.
		/// - `instance`: The identifier of the asset instance whose metadata to clear.
		///
		/// Emits `MetadataCleared`.
		///
		/// Weight: `O(1)`
		#[pallet::weight(T::WeightInfo::clear_metadata())]
		pub fn clear_metadata(
			origin: OriginFor<T>,
			#[pallet::compact] class: T::ClassId,
			#[pallet::compact] instance: T::InstanceId,
		) -> DispatchResult {
			let maybe_check_owner = T::ForceOrigin::try_origin(origin)
				.map(|_| None)
				.or_else(|origin| ensure_signed(origin).map(Some))?;

			let mut class_details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::Unknown)?;
			if let Some(check_owner) = &maybe_check_owner {
				ensure!(check_owner == &class_details.owner, Error::<T, I>::NoPermission);
			}

			InstanceMetadataOf::<T, I>::try_mutate_exists(class, instance, |metadata| {
				let was_frozen = metadata.as_ref().map_or(false, |m| m.is_frozen);
				ensure!(maybe_check_owner.is_none() || !was_frozen, Error::<T, I>::Frozen);

				if metadata.is_some() {
					class_details.instance_metadatas.saturating_dec();
				}
				let deposit = metadata.take().ok_or(Error::<T, I>::Unknown)?.deposit;
				T::Currency::unreserve(&class_details.owner, deposit);
				class_details.total_deposit.saturating_reduce(deposit);

				Class::<T, I>::insert(&class, &class_details);
				Self::deposit_event(Event::MetadataCleared(class, instance));
				Ok(())
			})
		}

		/// Set the metadata for an asset class.
		///
		/// Origin must be either `ForceOrigin` or `Signed` and the sender should be the Owner of
		/// the asset `class`.
		///
		/// If the origin is `Signed`, then funds of signer are reserved according to the formula:
		/// `MetadataDepositBase + DepositPerByte * data.len` taking into
		/// account any already reserved funds.
		///
		/// - `class`: The identifier of the asset whose metadata to update.
		/// - `data`: The general information of this asset. Limited in length by `StringLimit`.
		/// - `is_frozen`: Whether the metadata should be frozen against further changes.
		///
		/// Emits `ClassMetadataSet`.
		///
		/// Weight: `O(1)`
		#[pallet::weight(T::WeightInfo::set_class_metadata())]
		pub fn set_class_metadata(
			origin: OriginFor<T>,
			#[pallet::compact] class: T::ClassId,
			data: BoundedVec<u8, T::StringLimit>,
			is_frozen: bool,
		) -> DispatchResult {
			let maybe_check_owner = T::ForceOrigin::try_origin(origin)
				.map(|_| None)
				.or_else(|origin| ensure_signed(origin).map(Some))?;

			let mut details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::Unknown)?;
			if let Some(check_owner) = &maybe_check_owner {
				ensure!(check_owner == &details.owner, Error::<T, I>::NoPermission);
			}

			ClassMetadataOf::<T, I>::try_mutate_exists(class, |metadata| {
				let was_frozen = metadata.as_ref().map_or(false, |m| m.is_frozen);
				ensure!(maybe_check_owner.is_none() || !was_frozen, Error::<T, I>::Frozen);

				let old_deposit = metadata.take().map_or(Zero::zero(), |m| m.deposit);
				details.total_deposit.saturating_reduce(old_deposit);
				let mut deposit = Zero::zero();
				if maybe_check_owner.is_some() && !details.free_holding {
					deposit = T::DepositPerByte::get()
						.saturating_mul(((data.len()) as u32).into())
						.saturating_add(T::MetadataDepositBase::get());
				}
				if deposit > old_deposit {
					T::Currency::reserve(&details.owner, deposit - old_deposit)?;
				} else if deposit < old_deposit {
					T::Currency::unreserve(&details.owner, old_deposit - deposit);
				}
				details.total_deposit.saturating_accrue(deposit);

				Class::<T, I>::insert(&class, details);

				*metadata = Some(ClassMetadata { deposit, data: data.clone(), is_frozen });

				Self::deposit_event(Event::ClassMetadataSet(class, data, is_frozen));
				Ok(())
			})
		}

		/// Clear the metadata for an asset class.
		///
		/// Origin must be either `ForceOrigin` or `Signed` and the sender should be the Owner of
		/// the asset `class`.
		///
		/// Any deposit is freed for the asset class owner.
		///
		/// - `class`: The identifier of the asset class whose metadata to clear.
		///
		/// Emits `ClassMetadataCleared`.
		///
		/// Weight: `O(1)`
		#[pallet::weight(T::WeightInfo::clear_class_metadata())]
		pub fn clear_class_metadata(
			origin: OriginFor<T>,
			#[pallet::compact] class: T::ClassId,
		) -> DispatchResult {
			let maybe_check_owner = T::ForceOrigin::try_origin(origin)
				.map(|_| None)
				.or_else(|origin| ensure_signed(origin).map(Some))?;

			let details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::Unknown)?;
			if let Some(check_owner) = &maybe_check_owner {
				ensure!(check_owner == &details.owner, Error::<T, I>::NoPermission);
			}

			ClassMetadataOf::<T, I>::try_mutate_exists(class, |metadata| {
				let was_frozen = metadata.as_ref().map_or(false, |m| m.is_frozen);
				ensure!(maybe_check_owner.is_none() || !was_frozen, Error::<T, I>::Frozen);

				let deposit = metadata.take().ok_or(Error::<T, I>::Unknown)?.deposit;
				T::Currency::unreserve(&details.owner, deposit);
				Self::deposit_event(Event::ClassMetadataCleared(class));
				Ok(())
			})
		}
	}
}