Withdraw and Burn

@view
@external
def admin_balances(i: uint256) -> uint256:
    return ERC20(self.coins[i]).balanceOf(self) - self.balances[i]

interface Curve:
    def withdraw_admin_fees(): nonpayable

@external
@nonreentrant('lock')
def withdraw_admin_fees(_pool: address):
    """
    @notice Withdraw admin fees from `_pool`
    @param _pool Pool address to withdraw admin fees from
    """
    Curve(_pool).withdraw_admin_fees()

interface Curve:
    def withdraw_admin_fees(): nonpayable

@external
@nonreentrant('lock')
def withdraw_many(_pools: address[20]):
    """
    @notice Withdraw admin fees from multiple pools
    @param _pools List of pool address to withdraw admin fees from
    """
    for pool in _pools:
        if pool == ZERO_ADDRESS:
            break
        Curve(pool).withdraw_admin_fees()

event ClaimAdminFee:
    admin: indexed(address)
    tokens: uint256

@external
@nonreentrant("lock")
def claim_admin_fees():
    """
    @notice Claim admin fees. Callable by anyone.
    """
    self._claim_admin_fees()

@internal
def _claim_admin_fees():
    """
    @notice Claims admin fees and sends it to fee_receiver set in the factory.
    """
    A_gamma: uint256[2] = self._A_gamma()

    xcp_profit: uint256 = self.xcp_profit  # <---------- Current pool profits.
    xcp_profit_a: uint256 = self.xcp_profit_a  # <- Profits at previous claim.
    total_supply: uint256 = self.totalSupply

    # Do not claim admin fees if:
    # 1. insufficient profits accrued since last claim, and
    # 2. there are less than 10**18 (or 1 unit of) lp tokens, else it can lead
    #    to manipulated virtual prices.
    if xcp_profit <= xcp_profit_a or total_supply < 10**18:
        return

    #      Claim tokens belonging to the admin here. This is done by 'gulping'
    #       pool tokens that have accrued as fees, but not accounted in pool's
    #         `self.balances` yet: pool balances only account for incoming and
    #                  outgoing tokens excluding fees. Following 'gulps' fees:

    for i in range(N_COINS):
        if coins[i] == WETH20:
            self.balances[i] = self.balance
        else:
            self.balances[i] = ERC20(coins[i]).balanceOf(self)

    #            If the pool has made no profits, `xcp_profit == xcp_profit_a`
    #                         and the pool gulps nothing in the previous step.

    vprice: uint256 = self.virtual_price

    #  Admin fees are calculated as follows.
    #      1. Calculate accrued profit since last claim. `xcp_profit`
    #         is the current profits. `xcp_profit_a` is the profits
    #         at the previous claim.
    #      2. Take out admin's share, which is hardcoded at 5 * 10**9.
    #         (50% => half of 100% => 10**10 / 2 => 5 * 10**9).
    #      3. Since half of the profits go to rebalancing the pool, we
    #         are left with half; so divide by 2.

    fees: uint256 = unsafe_div(
        unsafe_sub(xcp_profit, xcp_profit_a) * ADMIN_FEE, 2 * 10**10
    )

    # ------------------------------ Claim admin fees by minting admin's share
    #                                                of the pool in LP tokens.
    receiver: address = Factory(self.factory).fee_receiver()
    if receiver != empty(address) and fees > 0:

        frac: uint256 = vprice * 10**18 / (vprice - fees) - 10**18
        claimed: uint256 = self.mint_relative(receiver, frac)

        xcp_profit -= fees * 2

        self.xcp_profit = xcp_profit

        log ClaimAdminFee(receiver, claimed)

    # ------------------------------------------- Recalculate D b/c we gulped.
    D: uint256 = MATH.newton_D(A_gamma[0], A_gamma[1], self.xp(), 0)
    self.D = D

    # ------------------- Recalculate virtual_price following admin fee claim.
    #     In this instance we do not check if current virtual price is greater
    #               than old virtual price, since the claim process can result
    #                                     in a small decrease in pool's value.

    self.virtual_price = 10**18 * self.get_xcp(D) / self.totalSupply
    self.xcp_profit_a = xcp_profit  # <------------ Cache last claimed profit.

@external
@view
def admin_fees() -> uint256:
    """
    @notice Calculate the amount of fees obtained from the interest
    """
    rate_mul: uint256 = AMM.get_rate_mul()
    loan: Loan = self._total_debt
    loan.initial_debt = loan.initial_debt * rate_mul / loan.rate_mul
    loan.initial_debt += self.redeemed
    minted: uint256 = self.minted
    return unsafe_sub(max(loan.initial_debt, minted), minted)

@external
@nonreentrant('lock')
def collect_fees() -> uint256:
    """
    @notice Collect the fees charged as interest
    """
    _to: address = FACTORY.fee_receiver()
    # AMM-based fees
    borrowed_fees: uint256 = AMM.admin_fees_x()
    collateral_fees: uint256 = AMM.admin_fees_y()
    if borrowed_fees > 0:
        STABLECOIN.transferFrom(AMM.address, _to, borrowed_fees)
    if collateral_fees > 0:
        assert COLLATERAL_TOKEN.transferFrom(AMM.address, _to, collateral_fees, default_return_value=True)
    AMM.reset_admin_fees()

    # Borrowing-based fees
    rate_mul: uint256 = self._rate_mul_w()
    loan: Loan = self._total_debt
    loan.initial_debt = loan.initial_debt * rate_mul / loan.rate_mul
    loan.rate_mul = rate_mul
    self._total_debt = loan

    # Amount which would have been redeemed if all the debt was repaid now
    to_be_redeemed: uint256 = loan.initial_debt + self.redeemed
    # Amount which was minted when borrowing + all previously claimed admin fees
    minted: uint256 = self.minted
    # Difference between to_be_redeemed and minted amount is exactly due to interest charged
    if to_be_redeemed > minted:
        self.minted = to_be_redeemed
        to_be_redeemed = unsafe_sub(to_be_redeemed, minted)  # Now this is the fees to charge
        STABLECOIN.transfer(_to, to_be_redeemed)
        log CollectFees(to_be_redeemed, loan.initial_debt)
        return to_be_redeemed
    else:
        log CollectFees(0, loan.initial_debt)
        return 0

interface Burner:
    def burn(_coin: address) -> bool: payable

@external
@nonreentrant('burn')
def burn(_coin: address):
    """
    @notice Burn accrued `_coin` via a preset burner
    @dev Only callable by an EOA to prevent flashloan exploits
    @param _coin Coin address
    """
    assert tx.origin == msg.sender
    assert not self.burner_kill

    _value: uint256 = 0
    if _coin == 0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE:
        _value = self.balance

    Burner(self.burners[_coin]).burn(_coin, value=_value)  # dev: should implement burn()

@external
@nonreentrant('burn')
def burn_many(_coins: address[20]):
    """
    @notice Burn accrued admin fees from multiple coins
    @dev Only callable by an EOA to prevent flashloan exploits
    @param _coins List of coin addresses
    """
    assert tx.origin == msg.sender
    assert not self.burner_kill

    for coin in _coins:
        if coin == ZERO_ADDRESS:
            break

        _value: uint256 = 0
        if coin == 0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE:
            _value = self.balance

        Burner(self.burners[coin]).burn(coin, value=_value)  # dev: should implement burn()

interface Curve:
    def donate_admin_fees(): nonpayable

@external
@nonreentrant('lock')
def donate_admin_fees(_pool: address):
    """
    @notice Donate admin fees of `_pool` pool
    @param _pool Pool address
    """
    if msg.sender != self.ownership_admin:
        assert self.donate_approval[_pool][msg.sender], "Access denied"

    Curve(_pool).donate_admin_fees()  # dev: if implemented by the pool

# pool -> caller -> can call `donate_admin_fees`
donate_approval: public(HashMap[address, HashMap[address, bool]])

@external
def set_donate_approval(_pool: address, _caller: address, _is_approved: bool):
    """
    @notice Set approval of `_caller` to donate admin fees for `_pool`
    @param _pool Pool address
    @param _caller Adddress to set approval for
    @param _is_approved Approval status
    """
    assert msg.sender == self.ownership_admin, "Access denied"

    self.donate_approval[_pool][_caller] = _is_approved