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// This file is part of Substrate.

// Copyright (C) 2019-2021 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.

//! The lockable currency trait and some associated types.

use super::{super::misc::WithdrawReasons, Currency};
use crate::{dispatch::DispatchResult, traits::misc::Get};

/// An identifier for a lock. Used for disambiguating different locks so that
/// they can be individually replaced or removed.
pub type LockIdentifier = [u8; 8];

/// A currency whose accounts can have liquidity restrictions.
pub trait LockableCurrency<AccountId>: Currency<AccountId> {
	/// The quantity used to denote time; usually just a `BlockNumber`.
	type Moment;

	/// The maximum number of locks a user should have on their account.
	type MaxLocks: Get<u32>;

	/// Create a new balance lock on account `who`.
	///
	/// If the new lock is valid (i.e. not already expired), it will push the struct to
	/// the `Locks` vec in storage. Note that you can lock more funds than a user has.
	///
	/// If the lock `id` already exists, this will update it.
	fn set_lock(
		id: LockIdentifier,
		who: &AccountId,
		amount: Self::Balance,
		reasons: WithdrawReasons,
	);

	/// Changes a balance lock (selected by `id`) so that it becomes less liquid in all
	/// parameters or creates a new one if it does not exist.
	///
	/// Calling `extend_lock` on an existing lock `id` differs from `set_lock` in that it
	/// applies the most severe constraints of the two, while `set_lock` replaces the lock
	/// with the new parameters. As in, `extend_lock` will set:
	/// - maximum `amount`
	/// - bitwise mask of all `reasons`
	fn extend_lock(
		id: LockIdentifier,
		who: &AccountId,
		amount: Self::Balance,
		reasons: WithdrawReasons,
	);

	/// Remove an existing lock.
	fn remove_lock(id: LockIdentifier, who: &AccountId);
}

/// A vesting schedule over a currency. This allows a particular currency to have vesting limits
/// applied to it.
pub trait VestingSchedule<AccountId> {
	/// The quantity used to denote time; usually just a `BlockNumber`.
	type Moment;

	/// The currency that this schedule applies to.
	type Currency: Currency<AccountId>;

	/// Get the amount that is currently being vested and cannot be transferred out of this account.
	/// Returns `None` if the account has no vesting schedule.
	fn vesting_balance(who: &AccountId)
		-> Option<<Self::Currency as Currency<AccountId>>::Balance>;

	/// Adds a vesting schedule to a given account.
	///
	/// If the account has `MaxVestingSchedules`, an Error is returned and nothing
	/// is updated.
	///
	/// Is a no-op if the amount to be vested is zero.
	///
	/// NOTE: This doesn't alter the free balance of the account.
	fn add_vesting_schedule(
		who: &AccountId,
		locked: <Self::Currency as Currency<AccountId>>::Balance,
		per_block: <Self::Currency as Currency<AccountId>>::Balance,
		starting_block: Self::Moment,
	) -> DispatchResult;

	/// Checks if `add_vesting_schedule` would work against `who`.
	fn can_add_vesting_schedule(
		who: &AccountId,
		locked: <Self::Currency as Currency<AccountId>>::Balance,
		per_block: <Self::Currency as Currency<AccountId>>::Balance,
		starting_block: Self::Moment,
	) -> DispatchResult;

	/// Remove a vesting schedule for a given account.
	///
	/// NOTE: This doesn't alter the free balance of the account.
	fn remove_vesting_schedule(who: &AccountId, schedule_index: u32) -> DispatchResult;
}