// 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.

//! An index is a short form of an address. This module handles allocation
//! of indices for a newly created accounts.

#![cfg_attr(not(feature = "std"), no_std)]

mod mock;
mod tests;
mod benchmarking;
pub mod weights;

use sp_std::prelude::*;
use codec::Codec;
use sp_runtime::MultiAddress;
use sp_runtime::traits::{
	StaticLookup, LookupError, Zero, Saturating, AtLeast32Bit
};
use frame_support::traits::{Currency, ReservableCurrency, BalanceStatus::Reserved};
pub use weights::WeightInfo;

type BalanceOf<T> = <<T as Config>::Currency as Currency<<T as frame_system::Config>::AccountId>>::Balance;

pub use pallet::*;

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

	/// The module's config trait.
	#[pallet::config]
	pub trait Config: frame_system::Config {
		/// Type used for storing an account's index; implies the maximum number of accounts the system
		/// can hold.
		type AccountIndex: Parameter + Member + MaybeSerializeDeserialize + Codec + Default + AtLeast32Bit + Copy;

		/// The currency trait.
		type Currency: ReservableCurrency<Self::AccountId>;

		/// The deposit needed for reserving an index.
		#[pallet::constant]
		type Deposit: Get<BalanceOf<Self>>;

		/// The overarching event type.
		type Event: From<Event<Self>> + IsType<<Self as frame_system::Config>::Event>;

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

	#[pallet::pallet]
	#[pallet::generate_store(pub(super) trait Store)]
	pub struct Pallet<T>(PhantomData<T>);

	#[pallet::call]
	impl<T: Config> Pallet<T> {
		/// Assign an previously unassigned index.
		///
		/// Payment: `Deposit` is reserved from the sender account.
		///
		/// The dispatch origin for this call must be _Signed_.
		///
		/// - `index`: the index to be claimed. This must not be in use.
		///
		/// Emits `IndexAssigned` if successful.
		///
		/// # <weight>
		/// - `O(1)`.
		/// - One storage mutation (codec `O(1)`).
		/// - One reserve operation.
		/// - One event.
		/// -------------------
		/// - DB Weight: 1 Read/Write (Accounts)
		/// # </weight>
		#[pallet::weight(T::WeightInfo::claim())]
		pub fn claim(origin: OriginFor<T>, index: T::AccountIndex) -> DispatchResult {
			let who = ensure_signed(origin)?;

			Accounts::<T>::try_mutate(index, |maybe_value| {
				ensure!(maybe_value.is_none(), Error::<T>::InUse);
				*maybe_value = Some((who.clone(), T::Deposit::get(), false));
				T::Currency::reserve(&who, T::Deposit::get())
			})?;
			Self::deposit_event(Event::IndexAssigned(who, index));
			Ok(())
		}

		/// Assign an index already owned by the sender to another account. The balance reservation
		/// is effectively transferred to the new account.
		///
		/// The dispatch origin for this call must be _Signed_.
		///
		/// - `index`: the index to be re-assigned. This must be owned by the sender.
		/// - `new`: the new owner of the index. This function is a no-op if it is equal to sender.
		///
		/// Emits `IndexAssigned` if successful.
		///
		/// # <weight>
		/// - `O(1)`.
		/// - One storage mutation (codec `O(1)`).
		/// - One transfer operation.
		/// - One event.
		/// -------------------
		/// - DB Weight:
		///    - Reads: Indices Accounts, System Account (recipient)
		///    - Writes: Indices Accounts, System Account (recipient)
		/// # </weight>
		#[pallet::weight(T::WeightInfo::transfer())]
		pub fn transfer(
			origin: OriginFor<T>,
			new: T::AccountId,
			index: T::AccountIndex,
		) -> DispatchResult {
			let who = ensure_signed(origin)?;
			ensure!(who != new, Error::<T>::NotTransfer);

			Accounts::<T>::try_mutate(index, |maybe_value| -> DispatchResult {
				let (account, amount, perm) = maybe_value.take().ok_or(Error::<T>::NotAssigned)?;
				ensure!(!perm, Error::<T>::Permanent);
				ensure!(&account == &who, Error::<T>::NotOwner);
				let lost = T::Currency::repatriate_reserved(&who, &new, amount, Reserved)?;
				*maybe_value = Some((new.clone(), amount.saturating_sub(lost), false));
				Ok(())
			})?;
			Self::deposit_event(Event::IndexAssigned(new, index));
			Ok(())
		}

		/// Free up an index owned by the sender.
		///
		/// Payment: Any previous deposit placed for the index is unreserved in the sender account.
		///
		/// The dispatch origin for this call must be _Signed_ and the sender must own the index.
		///
		/// - `index`: the index to be freed. This must be owned by the sender.
		///
		/// Emits `IndexFreed` if successful.
		///
		/// # <weight>
		/// - `O(1)`.
		/// - One storage mutation (codec `O(1)`).
		/// - One reserve operation.
		/// - One event.
		/// -------------------
		/// - DB Weight: 1 Read/Write (Accounts)
		/// # </weight>
		#[pallet::weight(T::WeightInfo::free())]
		pub fn free(origin: OriginFor<T>, index: T::AccountIndex) -> DispatchResult {
			let who = ensure_signed(origin)?;

			Accounts::<T>::try_mutate(index, |maybe_value| -> DispatchResult {
				let (account, amount, perm) = maybe_value.take().ok_or(Error::<T>::NotAssigned)?;
				ensure!(!perm, Error::<T>::Permanent);
				ensure!(&account == &who, Error::<T>::NotOwner);
				T::Currency::unreserve(&who, amount);
				Ok(())
			})?;
			Self::deposit_event(Event::IndexFreed(index));
			Ok(())
		}

		/// Force an index to an account. This doesn't require a deposit. If the index is already
		/// held, then any deposit is reimbursed to its current owner.
		///
		/// The dispatch origin for this call must be _Root_.
		///
		/// - `index`: the index to be (re-)assigned.
		/// - `new`: the new owner of the index. This function is a no-op if it is equal to sender.
		/// - `freeze`: if set to `true`, will freeze the index so it cannot be transferred.
		///
		/// Emits `IndexAssigned` if successful.
		///
		/// # <weight>
		/// - `O(1)`.
		/// - One storage mutation (codec `O(1)`).
		/// - Up to one reserve operation.
		/// - One event.
		/// -------------------
		/// - DB Weight:
		///    - Reads: Indices Accounts, System Account (original owner)
		///    - Writes: Indices Accounts, System Account (original owner)
		/// # </weight>
		#[pallet::weight(T::WeightInfo::force_transfer())]
		pub fn force_transfer(
			origin: OriginFor<T>,
			new: T::AccountId,
			index: T::AccountIndex,
			freeze: bool,
		) -> DispatchResult {
			ensure_root(origin)?;

			Accounts::<T>::mutate(index, |maybe_value| {
				if let Some((account, amount, _)) = maybe_value.take() {
					T::Currency::unreserve(&account, amount);
				}
				*maybe_value = Some((new.clone(), Zero::zero(), freeze));
			});
			Self::deposit_event(Event::IndexAssigned(new, index));
			Ok(())
		}

		/// Freeze an index so it will always point to the sender account. This consumes the deposit.
		///
		/// The dispatch origin for this call must be _Signed_ and the signing account must have a
		/// non-frozen account `index`.
		///
		/// - `index`: the index to be frozen in place.
		///
		/// Emits `IndexFrozen` if successful.
		///
		/// # <weight>
		/// - `O(1)`.
		/// - One storage mutation (codec `O(1)`).
		/// - Up to one slash operation.
		/// - One event.
		/// -------------------
		/// - DB Weight: 1 Read/Write (Accounts)
		/// # </weight>
		#[pallet::weight(T::WeightInfo::freeze())]
		pub fn freeze(origin: OriginFor<T>, index: T::AccountIndex) -> DispatchResult {
			let who = ensure_signed(origin)?;

			Accounts::<T>::try_mutate(index, |maybe_value| -> DispatchResult {
				let (account, amount, perm) = maybe_value.take().ok_or(Error::<T>::NotAssigned)?;
				ensure!(!perm, Error::<T>::Permanent);
				ensure!(&account == &who, Error::<T>::NotOwner);
				T::Currency::slash_reserved(&who, amount);
				*maybe_value = Some((account, Zero::zero(), true));
				Ok(())
			})?;
			Self::deposit_event(Event::IndexFrozen(index, who));
			Ok(())
		}
	}

	#[pallet::event]
	#[pallet::generate_deposit(pub(super) fn deposit_event)]
	#[pallet::metadata(T::AccountId = "AccountId", T::AccountIndex = "AccountIndex")]
	pub enum Event<T: Config> {
		/// A account index was assigned. \[index, who\]
		IndexAssigned(T::AccountId, T::AccountIndex),
		/// A account index has been freed up (unassigned). \[index\]
		IndexFreed(T::AccountIndex),
		/// A account index has been frozen to its current account ID. \[index, who\]
		IndexFrozen(T::AccountIndex, T::AccountId),
	}

	/// Old name generated by `decl_event`.
	#[deprecated(note="use `Event` instead")]
	pub type RawEvent<T> = Event<T>;

	#[pallet::error]
	pub enum Error<T> {
		/// The index was not already assigned.
		NotAssigned,
		/// The index is assigned to another account.
		NotOwner,
		/// The index was not available.
		InUse,
		/// The source and destination accounts are identical.
		NotTransfer,
		/// The index is permanent and may not be freed/changed.
		Permanent,
	}

	/// The lookup from index to account.
	#[pallet::storage]
	pub type Accounts<T: Config> = StorageMap<
		_, Blake2_128Concat,
		T::AccountIndex,
		(T::AccountId, BalanceOf<T>, bool)
	>;

	#[pallet::genesis_config]
	pub struct GenesisConfig<T: Config> {
		pub indices: Vec<(T::AccountIndex, T::AccountId)>,
	}

	#[cfg(feature = "std")]
	impl<T: Config> Default for GenesisConfig<T> {
		fn default() -> Self {
			Self {
				indices: Default::default(),
			}
		}
	}

	#[pallet::genesis_build]
	impl<T: Config> GenesisBuild<T> for GenesisConfig<T> {
		fn build(&self) {
			for (a, b) in &self.indices {
				<Accounts<T>>::insert(a, (b, <BalanceOf<T>>::zero(), false))
			}
		}
	}
}

impl<T: Config> Pallet<T> {
	// PUBLIC IMMUTABLES

	/// Lookup an T::AccountIndex to get an Id, if there's one there.
	pub fn lookup_index(index: T::AccountIndex) -> Option<T::AccountId> {
		Accounts::<T>::get(index).map(|x| x.0)
	}

	/// Lookup an address to get an Id, if there's one there.
	pub fn lookup_address(
		a: MultiAddress<T::AccountId, T::AccountIndex>
	) -> Option<T::AccountId> {
		match a {
			MultiAddress::Id(i) => Some(i),
			MultiAddress::Index(i) => Self::lookup_index(i),
			_ => None,
		}
	}
}

impl<T: Config> StaticLookup for Pallet<T> {
	type Source = MultiAddress<T::AccountId, T::AccountIndex>;
	type Target = T::AccountId;

	fn lookup(a: Self::Source) -> Result<Self::Target, LookupError> {
		Self::lookup_address(a).ok_or(LookupError)
	}

	fn unlookup(a: Self::Target) -> Self::Source {
		MultiAddress::Id(a)
	}
}