// 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 traits for dealing with a single fungible token class and any associated types.

use super::{
	misc::{Balance, DepositConsequence, WithdrawConsequence},
	*,
};
use crate::{
	dispatch::{DispatchError, DispatchResult},
	traits::misc::Get,
};
use sp_runtime::traits::Saturating;

mod balanced;
mod imbalance;
pub use balanced::{Balanced, Unbalanced};
pub use imbalance::{CreditOf, DebtOf, HandleImbalanceDrop, Imbalance};

/// Trait for providing balance-inspection access to a fungible asset.
pub trait Inspect<AccountId> {
	/// Scalar type for representing balance of an account.
	type Balance: Balance;

	/// The total amount of issuance in the system.
	fn total_issuance() -> Self::Balance;

	/// The minimum balance any single account may have.
	fn minimum_balance() -> Self::Balance;

	/// Get the balance of `who`.
	fn balance(who: &AccountId) -> Self::Balance;

	/// Get the maximum amount that `who` can withdraw/transfer successfully.
	fn reducible_balance(who: &AccountId, keep_alive: bool) -> Self::Balance;

	/// Returns `true` if the balance of `who` may be increased by `amount`.
	fn can_deposit(who: &AccountId, amount: Self::Balance) -> DepositConsequence;

	/// Returns `Failed` if the balance of `who` may not be decreased by `amount`, otherwise
	/// the consequence.
	fn can_withdraw(who: &AccountId, amount: Self::Balance) -> WithdrawConsequence<Self::Balance>;
}

/// Trait for providing an ERC-20 style fungible asset.
pub trait Mutate<AccountId>: Inspect<AccountId> {
	/// Increase the balance of `who` by exactly `amount`, minting new tokens. If that isn't
	/// possible then an `Err` is returned and nothing is changed.
	fn mint_into(who: &AccountId, amount: Self::Balance) -> DispatchResult;

	/// Decrease the balance of `who` by at least `amount`, possibly slightly more in the case of
	/// minimum_balance requirements, burning the tokens. If that isn't possible then an `Err` is
	/// returned and nothing is changed. If successful, the amount of tokens reduced is returned.
	fn burn_from(who: &AccountId, amount: Self::Balance) -> Result<Self::Balance, DispatchError>;

	/// Attempt to reduce the balance of `who` by as much as possible up to `amount`, and possibly
	/// slightly more due to minimum_balance requirements. If no decrease is possible then an `Err`
	/// is returned and nothing is changed. If successful, the amount of tokens reduced is returned.
	///
	/// The default implementation just uses `withdraw` along with `reducible_balance` to ensure
	/// that is doesn't fail.
	fn slash(who: &AccountId, amount: Self::Balance) -> Result<Self::Balance, DispatchError> {
		Self::burn_from(who, Self::reducible_balance(who, false).min(amount))
	}

	/// Transfer funds from one account into another. The default implementation uses `mint_into`
	/// and `burn_from` and may generate unwanted events.
	fn teleport(
		source: &AccountId,
		dest: &AccountId,
		amount: Self::Balance,
	) -> Result<Self::Balance, DispatchError> {
		let extra = Self::can_withdraw(&source, amount).into_result()?;
		Self::can_deposit(&dest, amount.saturating_add(extra)).into_result()?;
		let actual = Self::burn_from(source, amount)?;
		debug_assert!(
			actual == amount.saturating_add(extra),
			"can_withdraw must agree with withdraw; qed"
		);
		match Self::mint_into(dest, actual) {
			Ok(_) => Ok(actual),
			Err(err) => {
				debug_assert!(false, "can_deposit returned true previously; qed");
				// attempt to return the funds back to source
				let revert = Self::mint_into(source, actual);
				debug_assert!(revert.is_ok(), "withdrew funds previously; qed");
				Err(err)
			},
		}
	}
}

/// Trait for providing a fungible asset which can only be transferred.
pub trait Transfer<AccountId>: Inspect<AccountId> {
	/// Transfer funds from one account into another.
	fn transfer(
		source: &AccountId,
		dest: &AccountId,
		amount: Self::Balance,
		keep_alive: bool,
	) -> Result<Self::Balance, DispatchError>;
}

/// Trait for inspecting a fungible asset which can be reserved.
pub trait InspectHold<AccountId>: Inspect<AccountId> {
	/// Amount of funds held in reserve by `who`.
	fn balance_on_hold(who: &AccountId) -> Self::Balance;

	/// Check to see if some `amount` of funds of `who` may be placed on hold.
	fn can_hold(who: &AccountId, amount: Self::Balance) -> bool;
}

/// Trait for mutating a fungible asset which can be reserved.
pub trait MutateHold<AccountId>: InspectHold<AccountId> + Transfer<AccountId> {
	/// Hold some funds in an account.
	fn hold(who: &AccountId, amount: Self::Balance) -> DispatchResult;

	/// Release up to `amount` held funds in an account.
	///
	/// The actual amount released is returned with `Ok`.
	///
	/// If `best_effort` is `true`, then the amount actually unreserved and returned as the inner
	/// value of `Ok` may be smaller than the `amount` passed.
	fn release(
		who: &AccountId,
		amount: Self::Balance,
		best_effort: bool,
	) -> Result<Self::Balance, DispatchError>;

	/// Transfer held funds into a destination account.
	///
	/// If `on_hold` is `true`, then the destination account must already exist and the assets
	/// transferred will still be on hold in the destination account. If not, then the destination
	/// account need not already exist, but must be creatable.
	///
	/// If `best_effort` is `true`, then an amount less than `amount` may be transferred without
	/// error.
	///
	/// The actual amount transferred is returned, or `Err` in the case of error and nothing is
	/// changed.
	fn transfer_held(
		source: &AccountId,
		dest: &AccountId,
		amount: Self::Balance,
		best_effort: bool,
		on_held: bool,
	) -> Result<Self::Balance, DispatchError>;
}

/// Trait for slashing a fungible asset which can be reserved.
pub trait BalancedHold<AccountId>: Balanced<AccountId> + MutateHold<AccountId> {
	/// Reduce the balance of some funds on hold in an account.
	///
	/// The resulting imbalance is the first item of the tuple returned.
	///
	/// As much funds that are on hold up to `amount` will be deducted as possible. If this is less
	/// than `amount`, then a non-zero second item will be returned.
	fn slash_held(
		who: &AccountId,
		amount: Self::Balance,
	) -> (CreditOf<AccountId, Self>, Self::Balance);
}

impl<AccountId, T: Balanced<AccountId> + MutateHold<AccountId>> BalancedHold<AccountId> for T {
	fn slash_held(
		who: &AccountId,
		amount: Self::Balance,
	) -> (CreditOf<AccountId, Self>, Self::Balance) {
		let actual = match Self::release(who, amount, true) {
			Ok(x) => x,
			Err(_) => return (Imbalance::default(), amount),
		};
		<Self as fungible::Balanced<AccountId>>::slash(who, actual)
	}
}

/// Convert a `fungibles` trait implementation into a `fungible` trait implementation by identifying
/// a single item.
pub struct ItemOf<
	F: fungibles::Inspect<AccountId>,
	A: Get<<F as fungibles::Inspect<AccountId>>::AssetId>,
	AccountId,
>(sp_std::marker::PhantomData<(F, A, AccountId)>);

impl<
		F: fungibles::Inspect<AccountId>,
		A: Get<<F as fungibles::Inspect<AccountId>>::AssetId>,
		AccountId,
	> Inspect<AccountId> for ItemOf<F, A, AccountId>
{
	type Balance = <F as fungibles::Inspect<AccountId>>::Balance;
	fn total_issuance() -> Self::Balance {
		<F as fungibles::Inspect<AccountId>>::total_issuance(A::get())
	}
	fn minimum_balance() -> Self::Balance {
		<F as fungibles::Inspect<AccountId>>::minimum_balance(A::get())
	}
	fn balance(who: &AccountId) -> Self::Balance {
		<F as fungibles::Inspect<AccountId>>::balance(A::get(), who)
	}
	fn reducible_balance(who: &AccountId, keep_alive: bool) -> Self::Balance {
		<F as fungibles::Inspect<AccountId>>::reducible_balance(A::get(), who, keep_alive)
	}
	fn can_deposit(who: &AccountId, amount: Self::Balance) -> DepositConsequence {
		<F as fungibles::Inspect<AccountId>>::can_deposit(A::get(), who, amount)
	}
	fn can_withdraw(who: &AccountId, amount: Self::Balance) -> WithdrawConsequence<Self::Balance> {
		<F as fungibles::Inspect<AccountId>>::can_withdraw(A::get(), who, amount)
	}
}

impl<
		F: fungibles::Mutate<AccountId>,
		A: Get<<F as fungibles::Inspect<AccountId>>::AssetId>,
		AccountId,
	> Mutate<AccountId> for ItemOf<F, A, AccountId>
{
	fn mint_into(who: &AccountId, amount: Self::Balance) -> DispatchResult {
		<F as fungibles::Mutate<AccountId>>::mint_into(A::get(), who, amount)
	}
	fn burn_from(who: &AccountId, amount: Self::Balance) -> Result<Self::Balance, DispatchError> {
		<F as fungibles::Mutate<AccountId>>::burn_from(A::get(), who, amount)
	}
}

impl<
		F: fungibles::Transfer<AccountId>,
		A: Get<<F as fungibles::Inspect<AccountId>>::AssetId>,
		AccountId,
	> Transfer<AccountId> for ItemOf<F, A, AccountId>
{
	fn transfer(
		source: &AccountId,
		dest: &AccountId,
		amount: Self::Balance,
		keep_alive: bool,
	) -> Result<Self::Balance, DispatchError> {
		<F as fungibles::Transfer<AccountId>>::transfer(A::get(), source, dest, amount, keep_alive)
	}
}

impl<
		F: fungibles::InspectHold<AccountId>,
		A: Get<<F as fungibles::Inspect<AccountId>>::AssetId>,
		AccountId,
	> InspectHold<AccountId> for ItemOf<F, A, AccountId>
{
	fn balance_on_hold(who: &AccountId) -> Self::Balance {
		<F as fungibles::InspectHold<AccountId>>::balance_on_hold(A::get(), who)
	}
	fn can_hold(who: &AccountId, amount: Self::Balance) -> bool {
		<F as fungibles::InspectHold<AccountId>>::can_hold(A::get(), who, amount)
	}
}

impl<
		F: fungibles::MutateHold<AccountId>,
		A: Get<<F as fungibles::Inspect<AccountId>>::AssetId>,
		AccountId,
	> MutateHold<AccountId> for ItemOf<F, A, AccountId>
{
	fn hold(who: &AccountId, amount: Self::Balance) -> DispatchResult {
		<F as fungibles::MutateHold<AccountId>>::hold(A::get(), who, amount)
	}
	fn release(
		who: &AccountId,
		amount: Self::Balance,
		best_effort: bool,
	) -> Result<Self::Balance, DispatchError> {
		<F as fungibles::MutateHold<AccountId>>::release(A::get(), who, amount, best_effort)
	}
	fn transfer_held(
		source: &AccountId,
		dest: &AccountId,
		amount: Self::Balance,
		best_effort: bool,
		on_hold: bool,
	) -> Result<Self::Balance, DispatchError> {
		<F as fungibles::MutateHold<AccountId>>::transfer_held(
			A::get(),
			source,
			dest,
			amount,
			best_effort,
			on_hold,
		)
	}
}

impl<
		F: fungibles::Unbalanced<AccountId>,
		A: Get<<F as fungibles::Inspect<AccountId>>::AssetId>,
		AccountId,
	> Unbalanced<AccountId> for ItemOf<F, A, AccountId>
{
	fn set_balance(who: &AccountId, amount: Self::Balance) -> DispatchResult {
		<F as fungibles::Unbalanced<AccountId>>::set_balance(A::get(), who, amount)
	}
	fn set_total_issuance(amount: Self::Balance) -> () {
		<F as fungibles::Unbalanced<AccountId>>::set_total_issuance(A::get(), amount)
	}
	fn decrease_balance(
		who: &AccountId,
		amount: Self::Balance,
	) -> Result<Self::Balance, DispatchError> {
		<F as fungibles::Unbalanced<AccountId>>::decrease_balance(A::get(), who, amount)
	}
	fn decrease_balance_at_most(who: &AccountId, amount: Self::Balance) -> Self::Balance {
		<F as fungibles::Unbalanced<AccountId>>::decrease_balance_at_most(A::get(), who, amount)
	}
	fn increase_balance(
		who: &AccountId,
		amount: Self::Balance,
	) -> Result<Self::Balance, DispatchError> {
		<F as fungibles::Unbalanced<AccountId>>::increase_balance(A::get(), who, amount)
	}
	fn increase_balance_at_most(who: &AccountId, amount: Self::Balance) -> Self::Balance {
		<F as fungibles::Unbalanced<AccountId>>::increase_balance_at_most(A::get(), who, amount)
	}
}