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// Copyright 2021 ChainSafe Systems
// SPDX-License-Identifier: LGPL-3.0-only

use frame_support::dispatch::DispatchResult;
use orml_traits::GetByKey;

/// The trait that provides balances related info about the parachain's various
/// sovereign accounts.
///
/// Definitions:
///  - *Sovereign Account* is an account controlled by a particular Consensus System, within some
///    other Consensus System: The account on the relay chain controlled by the PINT parachain.
///  - *Stash Account* holds funds bonded for staking. If a remote asset (DOT) supports staking then
///    PINT can bond funds that it holds in the sovereign account on the remote chain.
///   Meaning as soon as remote assets are bonded from PINT's sovereign account
///   on a target chain this sovereign account becomes a *stash account*. Both
///   terms now describe one and the same account and are therefore used in the
///   following interchangeably for the same account, even if the remote asset
///   does not support staking.
///
/// Staking rewards are not tracked since it is intended that the generated
/// staking rewards are routinely exchanged via an AMM for PINT. Some of the
/// resulting PINT will be allocated to the Treasury, with the
/// remainder being burned. This does not affect the staked funds itself, so we
/// only consider two states the funds can have: either free (not bonded), or
/// not free (bonded or unbonded but not withdrawn yet.)
pub trait BalanceMeter<Balance, AssetId> {
	/// The assumed balance of the PINT's parachain sovereign account on the
	/// asset's native chain that is currently not bonded or otherwise locked.
	fn free_stash_balance(asset: AssetId) -> Balance;

	/// Ensures that the given amount can be removed from the parachain's
	/// sovereign account without falling below the configured
	/// `minimum_stash_balance`
	fn ensure_free_stash(asset: AssetId, amount: Balance) -> DispatchResult;

	/// Returns the configured minimum stash balance below which the parachain's
	/// sovereign account balance must not fall.
	fn minimum_free_stash_balance(asset: &AssetId) -> Balance;
}

/// A type to abstract several staking related thresholds
pub trait StakingCap<AssetId, Balance> {
	/// The minimum amount that should be held in stash (must remain
	/// unbonded).
	/// Withdrawals are only authorized if the updated stash balance does
	/// exceeds this.
	///
	/// This must be at least the `ExistentialDeposit` as configured on the
	/// asset's native chain (e.g. DOT/Polkadot)
	fn minimum_reserve_balance(asset: AssetId) -> Balance;

	/// The minimum required amount to justify an additional `bond_extra` XCM call to stake
	/// additional funds.
	fn minimum_bond_extra(asset: AssetId) -> Balance;
}

// Convenience impl for orml `parameter_type_with_key!` impls
impl<AssetId, Balance, ReserveMinimum, BondExtra> StakingCap<AssetId, Balance> for (ReserveMinimum, BondExtra)
where
	ReserveMinimum: GetByKey<AssetId, Balance>,
	BondExtra: GetByKey<AssetId, Balance>,
{
	fn minimum_reserve_balance(asset: AssetId) -> Balance {
		ReserveMinimum::get(&asset)
	}

	fn minimum_bond_extra(asset: AssetId) -> Balance {
		BondExtra::get(&asset)
	}
}