From 8a8d2e72c86538a6ec6d131f53f843f78bed399a Mon Sep 17 00:00:00 2001
From: bout3fiddy <11488427+bout3fiddy@users.noreply.github.com>
Date: Sat, 16 Sep 2023 09:37:03 +0200
Subject: [PATCH 1/3] update implementations

---
 .gitignore                                    |   1 +
 .../implementations/plain-2/Plain2Balances.vy | 339 ++++++++++++------
 .../implementations/plain-2/Plain2Price.vy    | 321 ++++++++++++-----
 3 files changed, 466 insertions(+), 195 deletions(-)

diff --git a/.gitignore b/.gitignore
index 9232552..eba381d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,6 +4,7 @@ __pycache__
 build/
 reports/
 node_modules
+.build/
 
 ### Python ###
 # Byte-compiled / optimized / DLL files
diff --git a/contracts/implementations/plain-2/Plain2Balances.vy b/contracts/implementations/plain-2/Plain2Balances.vy
index 61ee2c9..2296c65 100644
--- a/contracts/implementations/plain-2/Plain2Balances.vy
+++ b/contracts/implementations/plain-2/Plain2Balances.vy
@@ -1,6 +1,6 @@
-# @version 0.3.1
+# @version 0.3.9
 """
-@title StableSwap
+@title CurveStableSwap2Balances
 @author Curve.Fi
 @license Copyright (c) Curve.Fi, 2020-2021 - all rights reserved
 @notice 2 coin pool implementation with no lending
@@ -73,6 +73,7 @@ event StopRampA:
     t: uint256
 
 
+N_COINS_256: constant(uint256) = 2
 N_COINS: constant(int128) = 2
 PRECISION: constant(uint256) = 10 ** 18
 
@@ -105,6 +106,10 @@ future_A_time: public(uint256)
 
 rate_multipliers: uint256[N_COINS]
 
+last_prices_packed: uint256
+ma_exp_time: public(uint256)
+ma_last_time: public(uint256)
+
 name: public(String[64])
 symbol: public(String[32])
 
@@ -145,7 +150,7 @@ def initialize(
 
     for i in range(N_COINS):
         coin: address = _coins[i]
-        if coin == ZERO_ADDRESS:
+        if coin == empty(address):
             break
         self.coins[i] = coin
         self.rate_multipliers[i] = _rate_multipliers[i]
@@ -165,7 +170,7 @@ def initialize(
     )
 
     # fire a transfer event so block explorers identify the contract as an ERC20
-    log Transfer(ZERO_ADDRESS, self, 0)
+    log Transfer(empty(address), self, 0)
 
 
 ### ERC20 Functionality ###
@@ -213,7 +218,7 @@ def transferFrom(_from : address, _to : address, _value : uint256) -> bool:
     self._transfer(_from, _to, _value)
 
     _allowance: uint256 = self.allowance[_from][msg.sender]
-    if _allowance != MAX_UINT256:
+    if _allowance != max_value(uint256):
         self.allowance[_from][msg.sender] = _allowance - _value
 
     return True
@@ -262,7 +267,7 @@ def permit(
     @param _s The bytes[32:64] of the valid secp256k1 signature of permit by owner
     @return True, if transaction completes successfully
     """
-    assert _owner != ZERO_ADDRESS
+    assert _owner != empty(address)
     assert block.timestamp <= _deadline
 
     nonce: uint256 = self.nonces[_owner]
@@ -290,6 +295,27 @@ def permit(
 
 ### StableSwap Functionality ###
 
+
+@pure
+@internal
+def pack_prices(p1: uint256, p2: uint256) -> uint256:
+    assert p1 < 2**128
+    assert p2 < 2**128
+    return p1 | (p2 << 128)
+
+
+@view
+@external
+def last_price() -> uint256:
+    return self.last_prices_packed & (2**128 - 1)
+
+
+@view
+@external
+def ema_price() -> uint256:
+    return (self.last_prices_packed >> 128)
+
+
 @view
 @internal
 def _balances() -> uint256[N_COINS]:
@@ -385,11 +411,11 @@ def get_D(_xp: uint256[N_COINS], _amp: uint256) -> uint256:
         return 0
 
     D: uint256 = S
-    Ann: uint256 = _amp * N_COINS
+    Ann: uint256 = _amp * N_COINS_256
     for i in range(255):
         D_P: uint256 = D * D / _xp[0] * D / _xp[1] / (N_COINS)**2
         Dprev: uint256 = D
-        D = (Ann * S / A_PRECISION + D_P * N_COINS) * D / ((Ann - A_PRECISION) * D / A_PRECISION + (N_COINS + 1) * D_P)
+        D = (Ann * S / A_PRECISION + D_P * N_COINS_256) * D / ((Ann - A_PRECISION) * D / A_PRECISION + (N_COINS_256 + 1) * D_P)
         # Equality with the precision of 1
         if D > Dprev:
             if D - Dprev <= 1:
@@ -409,8 +435,144 @@ def get_D_mem(_rates: uint256[N_COINS], _balances: uint256[N_COINS], _amp: uint2
     return self.get_D(xp, _amp)
 
 
+@internal
+@view
+def _get_p(xp: uint256[N_COINS], amp: uint256, D: uint256) -> uint256:
+    # dx_0 / dx_1 only, however can have any number of coins in pool
+    ANN: uint256 = amp * N_COINS_256
+    Dr: uint256 = D / (N_COINS**N_COINS)
+    for i in range(N_COINS):
+        Dr = Dr * D / xp[i]
+    return 10**18 * (ANN * xp[0] / A_PRECISION + Dr * xp[0] / xp[1]) / (ANN * xp[0] / A_PRECISION + Dr)
+
+
+@external
+@view
+def get_p() -> uint256:
+    amp: uint256 = self._A()
+    xp: uint256[N_COINS] = self._xp_mem(self.rate_multipliers, self._balances())
+    D: uint256 = self.get_D(xp, amp)
+    return self._get_p(xp, amp, D)
+
+
+@internal
+@pure
+def exp(x: int256) -> uint256:
+
+    """
+    @dev Calculates the natural exponential function of a signed integer with
+         a precision of 1e18.
+    @notice Note that this function consumes about 810 gas units. The implementation
+            is inspired by Remco Bloemen's implementation under the MIT license here:
+            https://xn--2-umb.com/22/exp-ln.
+    @dev This implementation is derived from Snekmate, which is authored
+         by pcaversaccio (Snekmate), distributed under the AGPL-3.0 license.
+         https://github.com/pcaversaccio/snekmate
+    @param x The 32-byte variable.
+    @return int256 The 32-byte calculation result.
+    """
+    value: int256 = x
+
+    # If the result is `< 0.5`, we return zero. This happens when we have the following:
+    # "x <= floor(log(0.5e18) * 1e18) ~ -42e18".
+    if (x <= -42139678854452767551):
+        return empty(uint256)
+
+    # When the result is "> (2 ** 255 - 1) / 1e18" we cannot represent it as a signed integer.
+    # This happens when "x >= floor(log((2 ** 255 - 1) / 1e18) * 1e18) ~ 135".
+    assert x < 135305999368893231589, "wad_exp overflow"
+
+    # `x` is now in the range "(-42, 136) * 1e18". Convert to "(-42, 136) * 2 ** 96" for higher
+    # intermediate precision and a binary base. This base conversion is a multiplication with
+    # "1e18 / 2 ** 96 = 5 ** 18 / 2 ** 78".
+    value = unsafe_div(x << 78, 5 ** 18)
+
+    # Reduce the range of `x` to "(-½ ln 2, ½ ln 2) * 2 ** 96" by factoring out powers of two
+    # so that "exp(x) = exp(x') * 2 ** k", where `k` is a signer integer. Solving this gives
+    # "k = round(x / log(2))" and "x' = x - k * log(2)". Thus, `k` is in the range "[-61, 195]".
+    k: int256 = unsafe_add(unsafe_div(value << 96, 54916777467707473351141471128), 2 ** 95) >> 96
+    value = unsafe_sub(value, unsafe_mul(k, 54916777467707473351141471128))
+
+    # Evaluate using a "(6, 7)"-term rational approximation. Since `p` is monic,
+    # we will multiply by a scaling factor later.
+    y: int256 = unsafe_add(unsafe_mul(unsafe_add(value, 1346386616545796478920950773328), value) >> 96, 57155421227552351082224309758442)
+    p: int256 = unsafe_add(unsafe_mul(unsafe_add(unsafe_mul(unsafe_sub(unsafe_add(y, value), 94201549194550492254356042504812), y) >> 96,\
+                           28719021644029726153956944680412240), value), 4385272521454847904659076985693276 << 96)
+
+    # We leave `p` in the "2 ** 192" base so that we do not have to scale it up
+    # again for the division.
+    q: int256 = unsafe_add(unsafe_mul(unsafe_sub(value, 2855989394907223263936484059900), value) >> 96, 50020603652535783019961831881945)
+    q = unsafe_sub(unsafe_mul(q, value) >> 96, 533845033583426703283633433725380)
+    q = unsafe_add(unsafe_mul(q, value) >> 96, 3604857256930695427073651918091429)
+    q = unsafe_sub(unsafe_mul(q, value) >> 96, 14423608567350463180887372962807573)
+    q = unsafe_add(unsafe_mul(q, value) >> 96, 26449188498355588339934803723976023)
+
+    # The polynomial `q` has no zeros in the range because all its roots are complex.
+    # No scaling is required, as `p` is already "2 ** 96" too large. Also,
+    # `r` is in the range "(0.09, 0.25) * 2**96" after the division.
+    r: int256 = unsafe_div(p, q)
+
+    # To finalise the calculation, we have to multiply `r` by:
+    #   - the scale factor "s = ~6.031367120",
+    #   - the factor "2 ** k" from the range reduction, and
+    #   - the factor "1e18 / 2 ** 96" for the base conversion.
+    # We do this all at once, with an intermediate result in "2**213" base,
+    # so that the final right shift always gives a positive value.
+
+    # Note that to circumvent Vyper's safecast feature for the potentially
+    # negative parameter value `r`, we first convert `r` to `bytes32` and
+    # subsequently to `uint256`. Remember that the EVM default behaviour is
+    # to use two's complement representation to handle signed integers.
+    return unsafe_mul(convert(convert(r, bytes32), uint256), 3822833074963236453042738258902158003155416615667) >> convert(unsafe_sub(195, k), uint256)
+
+
+
+@internal
 @view
+def _ma_price() -> uint256:
+    ma_last_time: uint256 = self.ma_last_time
+
+    pp: uint256 = self.last_prices_packed
+    last_price: uint256 = pp & (2**128 - 1)
+    last_ema_price: uint256 = pp >> 128
+
+    if ma_last_time < block.timestamp:
+        alpha: uint256 = self.exp(- convert((block.timestamp - ma_last_time) * 10**18 / self.ma_exp_time, int256))
+        return (last_price * (10**18 - alpha) + last_ema_price * alpha) / 10**18
+
+    else:
+        return last_ema_price
+
+
 @external
+@view
+@nonreentrant('lock')
+def price_oracle() -> uint256:
+    return self._ma_price()
+
+
+@internal
+def save_p_from_price(last_price: uint256):
+    """
+    Saves current price and its EMA
+    """
+    if last_price != 0:
+        self.last_prices_packed = self.pack_prices(last_price, self._ma_price())
+        if self.ma_last_time < block.timestamp:
+            self.ma_last_time = block.timestamp
+
+
+@internal
+def save_p(xp: uint256[N_COINS], amp: uint256, D: uint256):
+    """
+    Saves current price and its EMA
+    """
+    self.save_p_from_price(self._get_p(xp, amp, D))
+
+
+@view
+@external
+@nonreentrant('lock')
 def get_virtual_price() -> uint256:
     """
     @notice The current virtual price of the pool LP token
@@ -482,20 +644,12 @@ def add_liquidity(
     for i in range(N_COINS):
         amount: uint256 = _amounts[i]
         if amount > 0:
+
             coin: address = self.coins[i]
             initial: uint256 = ERC20(coin).balanceOf(self)
-            response: Bytes[32] = raw_call(
-                coin,
-                concat(
-                    method_id("transferFrom(address,address,uint256)"),
-                    convert(msg.sender, bytes32),
-                    convert(self, bytes32),
-                    convert(amount, bytes32),
-                ),
-                max_outsize=32,
-            )
-            if len(response) > 0:
-                assert convert(response, bool)  # dev: failed transfer
+
+            assert ERC20(coin).transferFrom(msg.sender, self, amount, default_return_value=True)
+
             new_balances[i] += ERC20(coin).balanceOf(self) - initial
         else:
             assert total_supply != 0  # dev: initial deposit requires all coins
@@ -510,7 +664,7 @@ def add_liquidity(
     mint_amount: uint256 = 0
     if total_supply > 0:
         # Only account for fees if we are not the first to deposit
-        base_fee: uint256 = self.fee * N_COINS / (4 * (N_COINS - 1))
+        base_fee: uint256 = self.fee * N_COINS_256 / (4 * (N_COINS_256 - 1))
         for i in range(N_COINS):
             ideal_balance: uint256 = D1 * old_balances[i] / D0
             difference: uint256 = 0
@@ -522,8 +676,11 @@ def add_liquidity(
             fees[i] = base_fee * difference / FEE_DENOMINATOR
             self.admin_balances[i] += fees[i] * ADMIN_FEE / FEE_DENOMINATOR
             new_balances[i] -= fees[i]
+        
+        xp: uint256[N_COINS] = self._xp_mem(rates, new_balances)
         D2: uint256 = self.get_D_mem(rates, new_balances, amp)
         mint_amount = total_supply * (D2 - D0) / D0
+        self.save_p(xp, amp, D2)
     else:
         mint_amount = D1  # Take the dust if there was any
 
@@ -533,7 +690,7 @@ def add_liquidity(
     total_supply += mint_amount
     self.balanceOf[_receiver] += mint_amount
     self.totalSupply = total_supply
-    log Transfer(ZERO_ADDRESS, _receiver, mint_amount)
+    log Transfer(empty(address), _receiver, mint_amount)
 
     log AddLiquidity(msg.sender, _amounts, fees, D1, total_supply)
 
@@ -542,7 +699,14 @@ def add_liquidity(
 
 @view
 @internal
-def get_y(i: int128, j: int128, x: uint256, xp: uint256[N_COINS]) -> uint256:
+def get_y(
+    i: int128, 
+    j: int128,
+     x: uint256, 
+    xp: uint256[N_COINS],
+    amp: uint256,
+    D: uint256,
+) -> uint256:
     """
     Calculate x[j] if one makes x[i] = x
 
@@ -562,13 +726,11 @@ def get_y(i: int128, j: int128, x: uint256, xp: uint256[N_COINS]) -> uint256:
     assert i >= 0
     assert i < N_COINS
 
-    amp: uint256 = self._A()
-    D: uint256 = self.get_D(xp, amp)
     S_: uint256 = 0
     _x: uint256 = 0
     y_prev: uint256 = 0
     c: uint256 = D
-    Ann: uint256 = amp * N_COINS
+    Ann: uint256 = amp * N_COINS_256
 
     for _i in range(N_COINS):
         if _i == i:
@@ -578,9 +740,9 @@ def get_y(i: int128, j: int128, x: uint256, xp: uint256[N_COINS]) -> uint256:
         else:
             continue
         S_ += _x
-        c = c * D / (_x * N_COINS)
+        c = c * D / (_x * N_COINS_256)
 
-    c = c * D * A_PRECISION / (Ann * N_COINS)
+    c = c * D * A_PRECISION / (Ann * N_COINS_256)
     b: uint256 = S_ + D * A_PRECISION / Ann  # - D
     y: uint256 = D
 
@@ -612,7 +774,11 @@ def get_dy(i: int128, j: int128, dx: uint256) -> uint256:
     xp: uint256[N_COINS] = self._xp_mem(rates, self._balances())
 
     x: uint256 = xp[i] + (dx * rates[i] / PRECISION)
-    y: uint256 = self.get_y(i, j, x, xp)
+    
+    amp: uint256 = self._A()
+    D: uint256 = self.get_D(xp, amp)
+    y: uint256 = self.get_y(i, j, x, xp, amp, D)
+    
     dy: uint256 = xp[j] - y - 1
     fee: uint256 = self.fee * dy / FEE_DENOMINATOR
     return (dy - fee) * PRECISION / rates[j]
@@ -642,22 +808,16 @@ def exchange(
 
     coin: address = self.coins[i]
     dx: uint256 = ERC20(coin).balanceOf(self)
-    response: Bytes[32] = raw_call(
-        coin,
-        concat(
-            method_id("transferFrom(address,address,uint256)"),
-            convert(msg.sender, bytes32),
-            convert(self, bytes32),
-            convert(_dx, bytes32),
-        ),
-        max_outsize=32,
-    )
-    if len(response) > 0:
-        assert convert(response, bool)
+
+    assert ERC20(coin).transferFrom(msg.sender, self, _dx, default_return_value=True)
+
     dx = ERC20(coin).balanceOf(self) - dx
 
     x: uint256 = xp[i] + dx * rates[i] / PRECISION
-    y: uint256 = self.get_y(i, j, x, xp)
+
+    amp: uint256 = self._A()
+    D: uint256 = self.get_D(xp, amp)
+    y: uint256 = self.get_y(i, j, x, xp, amp, D)
 
     dy: uint256 = xp[j] - y - 1  # -1 just in case there were some rounding errors
     dy_fee: uint256 = dy * self.fee / FEE_DENOMINATOR
@@ -666,19 +826,15 @@ def exchange(
     dy = (dy - dy_fee) * PRECISION / rates[j]
     assert dy >= _min_dy, "Exchange resulted in fewer coins than expected"
 
+    # xp is not used anymore, so we reuse it for price calc
+    xp[i] = x
+    xp[j] = y
+    # D is not changed because we did not apply a fee
+    self.save_p(xp, amp, D)
+
     self.admin_balances[j] += (dy_fee * ADMIN_FEE / FEE_DENOMINATOR) * PRECISION / rates[j]
 
-    response = raw_call(
-        self.coins[j],
-        concat(
-            method_id("transfer(address,uint256)"),
-            convert(_receiver, bytes32),
-            convert(dy, bytes32),
-        ),
-        max_outsize=32,
-    )
-    if len(response) > 0:
-        assert convert(response, bool)
+    assert ERC20(self.coins[j]).transfer(_receiver, dy, default_return_value=True)
 
     log TokenExchange(msg.sender, i, _dx, j, dy)
 
@@ -709,22 +865,12 @@ def remove_liquidity(
         assert value >= _min_amounts[i], "Withdrawal resulted in fewer coins than expected"
         amounts[i] = value
 
-        response: Bytes[32] = raw_call(
-            self.coins[i],
-            concat(
-                method_id("transfer(address,uint256)"),
-                convert(_receiver, bytes32),
-                convert(value, bytes32),
-            ),
-            max_outsize=32,
-        )
-        if len(response) > 0:
-            assert convert(response, bool)
+        assert ERC20(self.coins[i]).transfer(_receiver, value, default_return_value=True)
 
     total_supply -= _burn_amount
     self.balanceOf[msg.sender] -= _burn_amount
     self.totalSupply = total_supply
-    log Transfer(msg.sender, ZERO_ADDRESS, _burn_amount)
+    log Transfer(msg.sender, empty(address), _burn_amount)
 
     log RemoveLiquidity(msg.sender, amounts, empty(uint256[N_COINS]), total_supply)
 
@@ -755,21 +901,12 @@ def remove_liquidity_imbalance(
         amount: uint256 = _amounts[i]
         if amount != 0:
             new_balances[i] -= amount
-            response: Bytes[32] = raw_call(
-                self.coins[i],
-                concat(
-                    method_id("transfer(address,uint256)"),
-                    convert(_receiver, bytes32),
-                    convert(amount, bytes32),
-                ),
-                max_outsize=32,
-            )
-            if len(response) > 0:
-                assert convert(response, bool)
+            assert ERC20(self.coins[i]).transfer(_receiver, amount, default_return_value=True)
+
     D1: uint256 = self.get_D_mem(rates, new_balances, amp)
 
     fees: uint256[N_COINS] = empty(uint256[N_COINS])
-    base_fee: uint256 = self.fee * N_COINS / (4 * (N_COINS - 1))
+    base_fee: uint256 = self.fee * N_COINS_256 / (4 * (N_COINS_256 - 1))
     for i in range(N_COINS):
         ideal_balance: uint256 = D1 * old_balances[i] / D0
         difference: uint256 = 0
@@ -783,6 +920,8 @@ def remove_liquidity_imbalance(
         new_balances[i] -= fees[i]
     D2: uint256 = self.get_D_mem(rates, new_balances, amp)
 
+    self.save_p(new_balances, amp, D2)
+
     total_supply: uint256 = self.totalSupply
     burn_amount: uint256 = ((D0 - D2) * total_supply / D0) + 1
     assert burn_amount > 1  # dev: zero tokens burned
@@ -791,7 +930,7 @@ def remove_liquidity_imbalance(
     total_supply -= burn_amount
     self.totalSupply = total_supply
     self.balanceOf[msg.sender] -= burn_amount
-    log Transfer(msg.sender, ZERO_ADDRESS, burn_amount)
+    log Transfer(msg.sender, empty(address), burn_amount)
     log RemoveLiquidityImbalance(msg.sender, _amounts, fees, D1, total_supply)
 
     return burn_amount
@@ -818,7 +957,7 @@ def get_y_D(A: uint256, i: int128, xp: uint256[N_COINS], D: uint256) -> uint256:
     _x: uint256 = 0
     y_prev: uint256 = 0
     c: uint256 = D
-    Ann: uint256 = A * N_COINS
+    Ann: uint256 = A * N_COINS_256
 
     for _i in range(N_COINS):
         if _i != i:
@@ -826,9 +965,9 @@ def get_y_D(A: uint256, i: int128, xp: uint256[N_COINS], D: uint256) -> uint256:
         else:
             continue
         S_ += _x
-        c = c * D / (_x * N_COINS)
+        c = c * D / (_x * N_COINS_256)
 
-    c = c * D * A_PRECISION / (Ann * N_COINS)
+    c = c * D * A_PRECISION / (Ann * N_COINS_256)
     b: uint256 = S_ + D * A_PRECISION / Ann
     y: uint256 = D
 
@@ -847,7 +986,7 @@ def get_y_D(A: uint256, i: int128, xp: uint256[N_COINS], D: uint256) -> uint256:
 
 @view
 @internal
-def _calc_withdraw_one_coin(_burn_amount: uint256, i: int128) -> uint256[2]:
+def _calc_withdraw_one_coin(_burn_amount: uint256, i: int128) -> uint256[3]:
     # First, need to calculate
     # * Get current D
     # * Solve Eqn against y_i for D - _token_amount
@@ -860,7 +999,7 @@ def _calc_withdraw_one_coin(_burn_amount: uint256, i: int128) -> uint256[2]:
     D1: uint256 = D0 - _burn_amount * D0 / total_supply
     new_y: uint256 = self.get_y_D(amp, i, xp, D1)
 
-    base_fee: uint256 = self.fee * N_COINS / (4 * (N_COINS - 1))
+    base_fee: uint256 = self.fee * N_COINS_256 / (4 * (N_COINS_256 - 1))
     xp_reduced: uint256[N_COINS] = empty(uint256[N_COINS])
 
     for j in range(N_COINS):
@@ -876,7 +1015,12 @@ def _calc_withdraw_one_coin(_burn_amount: uint256, i: int128) -> uint256[2]:
     dy_0: uint256 = (xp[i] - new_y) * PRECISION / rates[i]  # w/o fees
     dy = (dy - 1) * PRECISION / rates[i]  # Withdraw less to account for rounding errors
 
-    return [dy, dy_0 - dy]
+    xp[i] = new_y
+    last_p: uint256 = 0
+    if new_y > 0:
+        last_p = self._get_p(xp, amp, D1)
+
+    return [dy, dy_0 - dy, last_p]
 
 
 @view
@@ -907,29 +1051,21 @@ def remove_liquidity_one_coin(
     @param _receiver Address that receives the withdrawn coins
     @return Amount of coin received
     """
-    dy: uint256[2] = self._calc_withdraw_one_coin(_burn_amount, i)
+    dy: uint256[3] = self._calc_withdraw_one_coin(_burn_amount, i)
     assert dy[0] >= _min_received, "Not enough coins removed"
 
     self.admin_balances[i] += dy[1] * ADMIN_FEE / FEE_DENOMINATOR
     total_supply: uint256 = self.totalSupply - _burn_amount
     self.totalSupply = total_supply
     self.balanceOf[msg.sender] -= _burn_amount
-    log Transfer(msg.sender, ZERO_ADDRESS, _burn_amount)
+    log Transfer(msg.sender, empty(address), _burn_amount)
 
-    response: Bytes[32] = raw_call(
-        self.coins[i],
-        concat(
-            method_id("transfer(address,uint256)"),
-            convert(_receiver, bytes32),
-            convert(dy[0], bytes32),
-        ),
-        max_outsize=32,
-    )
-    if len(response) > 0:
-        assert convert(response, bool)
+    assert ERC20(self.coins[i]).transfer(_receiver, dy[0], default_return_value=True)
 
     log RemoveLiquidityOne(msg.sender, _burn_amount, dy[0], total_supply)
 
+    self.save_p_from_price(dy[2])
+
     return dy[0]
 
 
@@ -978,14 +1114,7 @@ def withdraw_admin_fees():
         amount: uint256 = self.admin_balances[i]
         if amount != 0:
             coin: address = self.coins[i]
-            raw_call(
-                coin,
-                concat(
-                    method_id("transfer(address,uint256)"),
-                    convert(receiver, bytes32),
-                    convert(amount, bytes32)
-                )
-            )
+            assert ERC20(coin).transfer(receiver, amount, default_return_value=True)
             self.admin_balances[i] = 0
 
 
diff --git a/contracts/implementations/plain-2/Plain2Price.vy b/contracts/implementations/plain-2/Plain2Price.vy
index 7bbc02c..c873130 100644
--- a/contracts/implementations/plain-2/Plain2Price.vy
+++ b/contracts/implementations/plain-2/Plain2Price.vy
@@ -1,4 +1,4 @@
-# @version 0.3.1
+# @version 0.3.9
 """
 @title StableSwap
 @author Curve.Fi
@@ -73,6 +73,7 @@ event StopRampA:
 
 
 N_COINS: constant(int128) = 2
+N_COINS_256: constant(uint256) = 2
 PRECISION: constant(uint256) = 10 ** 18
 
 FEE_DENOMINATOR: constant(uint256) = 10 ** 10
@@ -90,7 +91,7 @@ PERMIT_TYPEHASH: constant(bytes32) = keccak256("Permit(address owner,address spe
 ERC1271_MAGIC_VAL: constant(bytes32) = 0x1626ba7e00000000000000000000000000000000000000000000000000000000
 VERSION: constant(String[8]) = "v5.0.0"
 
-BIT_MASK: constant(uint256) = shift(2**32 - 1, 224)
+BIT_MASK: constant(uint256) = (2**32 - 1 << 224)
 
 
 factory: address
@@ -108,6 +109,9 @@ future_A_time: public(uint256)
 rate_multipliers: uint256[N_COINS]
 # [bytes4 method_id][bytes8 <empty>][bytes20 oracle]
 oracles: uint256[N_COINS]
+last_prices_packed: uint256
+ma_exp_time: public(uint256)
+ma_last_time: public(uint256)
 
 name: public(String[64])
 symbol: public(String[32])
@@ -152,7 +156,7 @@ def initialize(
 
     for i in range(N_COINS):
         coin: address = _coins[i]
-        if coin == ZERO_ADDRESS:
+        if coin == empty(address):
             break
         self.coins[i] = coin
         self.rate_multipliers[i] = _rate_multipliers[i]
@@ -172,7 +176,7 @@ def initialize(
     )
 
     # fire a transfer event so block explorers identify the contract as an ERC20
-    log Transfer(ZERO_ADDRESS, self, 0)
+    log Transfer(empty(address), self, 0)
 
 
 ### ERC20 Functionality ###
@@ -220,7 +224,7 @@ def transferFrom(_from : address, _to : address, _value : uint256) -> bool:
     self._transfer(_from, _to, _value)
 
     _allowance: uint256 = self.allowance[_from][msg.sender]
-    if _allowance != MAX_UINT256:
+    if _allowance != max_value(uint256):
         self.allowance[_from][msg.sender] = _allowance - _value
 
     return True
@@ -269,7 +273,7 @@ def permit(
     @param _s The bytes[32:64] of the valid secp256k1 signature of permit by owner
     @return True, if transaction completes successfully
     """
-    assert _owner != ZERO_ADDRESS
+    assert _owner != empty(address)
     assert block.timestamp <= _deadline
 
     nonce: uint256 = self.nonces[_owner]
@@ -297,10 +301,31 @@ def permit(
 
 ### StableSwap Functionality ###
 
+
+@pure
+@internal
+def pack_prices(p1: uint256, p2: uint256) -> uint256:
+    assert p1 < 2**128
+    assert p2 < 2**128
+    return p1 | (p2 << 128)
+
+
+@view
+@external
+def last_price() -> uint256:
+    return self.last_prices_packed & (2**128 - 1)
+
+
+@view
+@external
+def ema_price() -> uint256:
+    return (self.last_prices_packed >> 128)
+
+
 @view
 @internal
 def _stored_rates() -> uint256[N_COINS]:
-    assert self.originator == ZERO_ADDRESS
+    assert self.originator == empty(address)
     rates: uint256[N_COINS] = self.rate_multipliers
 
     for i in range(N_COINS):
@@ -311,7 +336,7 @@ def _stored_rates() -> uint256[N_COINS]:
         # NOTE: assumed that response is of precision 10**18
         response: Bytes[32] = raw_call(
             convert(oracle % 2**160, address),
-            _abi_encode(bitwise_and(oracle, BIT_MASK)),
+            _abi_encode(oracle & BIT_MASK),
             max_outsize=32,
             is_static_call=True,
         )
@@ -394,11 +419,11 @@ def get_D(_xp: uint256[N_COINS], _amp: uint256) -> uint256:
         return 0
 
     D: uint256 = S
-    Ann: uint256 = _amp * N_COINS
+    Ann: uint256 = _amp * N_COINS_256
     for i in range(255):
         D_P: uint256 = D * D / _xp[0] * D / _xp[1] / (N_COINS)**2
         Dprev: uint256 = D
-        D = (Ann * S / A_PRECISION + D_P * N_COINS) * D / ((Ann - A_PRECISION) * D / A_PRECISION + (N_COINS + 1) * D_P)
+        D = (Ann * S / A_PRECISION + D_P * N_COINS_256) * D / ((Ann - A_PRECISION) * D / A_PRECISION + (N_COINS_256 + 1) * D_P)
         # Equality with the precision of 1
         if D > Dprev:
             if D - Dprev <= 1:
@@ -418,8 +443,144 @@ def get_D_mem(_rates: uint256[N_COINS], _balances: uint256[N_COINS], _amp: uint2
     return self.get_D(xp, _amp)
 
 
+@internal
+@view
+def _get_p(xp: uint256[N_COINS], amp: uint256, D: uint256) -> uint256:
+    # dx_0 / dx_1 only, however can have any number of coins in pool
+    ANN: uint256 = amp * N_COINS_256
+    Dr: uint256 = D / (N_COINS**N_COINS)
+    for i in range(N_COINS):
+        Dr = Dr * D / xp[i]
+    return 10**18 * (ANN * xp[0] / A_PRECISION + Dr * xp[0] / xp[1]) / (ANN * xp[0] / A_PRECISION + Dr)
+
+
+@external
 @view
+def get_p() -> uint256:
+    amp: uint256 = self._A()
+    xp: uint256[N_COINS] = self._xp_mem(self.rate_multipliers, self.balances)
+    D: uint256 = self.get_D(xp, amp)
+    return self._get_p(xp, amp, D)
+
+
+@internal
+@pure
+def exp(x: int256) -> uint256:
+
+    """
+    @dev Calculates the natural exponential function of a signed integer with
+         a precision of 1e18.
+    @notice Note that this function consumes about 810 gas units. The implementation
+            is inspired by Remco Bloemen's implementation under the MIT license here:
+            https://xn--2-umb.com/22/exp-ln.
+    @dev This implementation is derived from Snekmate, which is authored
+         by pcaversaccio (Snekmate), distributed under the AGPL-3.0 license.
+         https://github.com/pcaversaccio/snekmate
+    @param x The 32-byte variable.
+    @return int256 The 32-byte calculation result.
+    """
+    value: int256 = x
+
+    # If the result is `< 0.5`, we return zero. This happens when we have the following:
+    # "x <= floor(log(0.5e18) * 1e18) ~ -42e18".
+    if (x <= -42139678854452767551):
+        return empty(uint256)
+
+    # When the result is "> (2 ** 255 - 1) / 1e18" we cannot represent it as a signed integer.
+    # This happens when "x >= floor(log((2 ** 255 - 1) / 1e18) * 1e18) ~ 135".
+    assert x < 135305999368893231589, "wad_exp overflow"
+
+    # `x` is now in the range "(-42, 136) * 1e18". Convert to "(-42, 136) * 2 ** 96" for higher
+    # intermediate precision and a binary base. This base conversion is a multiplication with
+    # "1e18 / 2 ** 96 = 5 ** 18 / 2 ** 78".
+    value = unsafe_div(x << 78, 5 ** 18)
+
+    # Reduce the range of `x` to "(-½ ln 2, ½ ln 2) * 2 ** 96" by factoring out powers of two
+    # so that "exp(x) = exp(x') * 2 ** k", where `k` is a signer integer. Solving this gives
+    # "k = round(x / log(2))" and "x' = x - k * log(2)". Thus, `k` is in the range "[-61, 195]".
+    k: int256 = unsafe_add(unsafe_div(value << 96, 54916777467707473351141471128), 2 ** 95) >> 96
+    value = unsafe_sub(value, unsafe_mul(k, 54916777467707473351141471128))
+
+    # Evaluate using a "(6, 7)"-term rational approximation. Since `p` is monic,
+    # we will multiply by a scaling factor later.
+    y: int256 = unsafe_add(unsafe_mul(unsafe_add(value, 1346386616545796478920950773328), value) >> 96, 57155421227552351082224309758442)
+    p: int256 = unsafe_add(unsafe_mul(unsafe_add(unsafe_mul(unsafe_sub(unsafe_add(y, value), 94201549194550492254356042504812), y) >> 96,\
+                           28719021644029726153956944680412240), value), 4385272521454847904659076985693276 << 96)
+
+    # We leave `p` in the "2 ** 192" base so that we do not have to scale it up
+    # again for the division.
+    q: int256 = unsafe_add(unsafe_mul(unsafe_sub(value, 2855989394907223263936484059900), value) >> 96, 50020603652535783019961831881945)
+    q = unsafe_sub(unsafe_mul(q, value) >> 96, 533845033583426703283633433725380)
+    q = unsafe_add(unsafe_mul(q, value) >> 96, 3604857256930695427073651918091429)
+    q = unsafe_sub(unsafe_mul(q, value) >> 96, 14423608567350463180887372962807573)
+    q = unsafe_add(unsafe_mul(q, value) >> 96, 26449188498355588339934803723976023)
+
+    # The polynomial `q` has no zeros in the range because all its roots are complex.
+    # No scaling is required, as `p` is already "2 ** 96" too large. Also,
+    # `r` is in the range "(0.09, 0.25) * 2**96" after the division.
+    r: int256 = unsafe_div(p, q)
+
+    # To finalise the calculation, we have to multiply `r` by:
+    #   - the scale factor "s = ~6.031367120",
+    #   - the factor "2 ** k" from the range reduction, and
+    #   - the factor "1e18 / 2 ** 96" for the base conversion.
+    # We do this all at once, with an intermediate result in "2**213" base,
+    # so that the final right shift always gives a positive value.
+
+    # Note that to circumvent Vyper's safecast feature for the potentially
+    # negative parameter value `r`, we first convert `r` to `bytes32` and
+    # subsequently to `uint256`. Remember that the EVM default behaviour is
+    # to use two's complement representation to handle signed integers.
+    return unsafe_mul(convert(convert(r, bytes32), uint256), 3822833074963236453042738258902158003155416615667) >> convert(unsafe_sub(195, k), uint256)
+
+
+
+@internal
+@view
+def _ma_price() -> uint256:
+    ma_last_time: uint256 = self.ma_last_time
+
+    pp: uint256 = self.last_prices_packed
+    last_price: uint256 = pp & (2**128 - 1)
+    last_ema_price: uint256 = pp >> 128
+
+    if ma_last_time < block.timestamp:
+        alpha: uint256 = self.exp(- convert((block.timestamp - ma_last_time) * 10**18 / self.ma_exp_time, int256))
+        return (last_price * (10**18 - alpha) + last_ema_price * alpha) / 10**18
+
+    else:
+        return last_ema_price
+
+
 @external
+@view
+@nonreentrant('lock')
+def price_oracle() -> uint256:
+    return self._ma_price()
+
+
+@internal
+def save_p_from_price(last_price: uint256):
+    """
+    Saves current price and its EMA
+    """
+    if last_price != 0:
+        self.last_prices_packed = self.pack_prices(last_price, self._ma_price())
+        if self.ma_last_time < block.timestamp:
+            self.ma_last_time = block.timestamp
+
+
+@internal
+def save_p(xp: uint256[N_COINS], amp: uint256, D: uint256):
+    """
+    Saves current price and its EMA
+    """
+    self.save_p_from_price(self._get_p(xp, amp, D))
+
+
+@view
+@external
+@nonreentrant('lock')
 def get_virtual_price() -> uint256:
     """
     @notice The current virtual price of the pool LP token
@@ -491,18 +652,7 @@ def add_liquidity(
     for i in range(N_COINS):
         amount: uint256 = _amounts[i]
         if amount > 0:
-            response: Bytes[32] = raw_call(
-                self.coins[i],
-                _abi_encode(
-                    msg.sender,
-                    self,
-                    amount,
-                    method_id=method_id("transferFrom(address,address,uint256)")
-                ),
-                max_outsize=32,
-            )
-            if len(response) > 0:
-                assert convert(response, bool)  # dev: failed transfer
+            assert ERC20(self.coins[i]).transferFrom(msg.sender, self, amount, default_return_value=True)
             new_balances[i] += amount
             # end "safeTransferFrom"
         else:
@@ -518,7 +668,7 @@ def add_liquidity(
     mint_amount: uint256 = 0
     if total_supply > 0:
         # Only account for fees if we are not the first to deposit
-        base_fee: uint256 = self.fee * N_COINS / (4 * (N_COINS - 1))
+        base_fee: uint256 = self.fee * N_COINS_256 / (4 * (N_COINS_256 - 1))
         for i in range(N_COINS):
             ideal_balance: uint256 = D1 * old_balances[i] / D0
             difference: uint256 = 0
@@ -530,8 +680,11 @@ def add_liquidity(
             fees[i] = base_fee * difference / FEE_DENOMINATOR
             self.balances[i] = new_balance - (fees[i] * ADMIN_FEE / FEE_DENOMINATOR)
             new_balances[i] -= fees[i]
+        
+        xp: uint256[N_COINS] = self._xp_mem(rates, new_balances)
         D2: uint256 = self.get_D_mem(rates, new_balances, amp)
         mint_amount = total_supply * (D2 - D0) / D0
+        self.save_p(xp, amp, D2)
     else:
         self.balances = new_balances
         mint_amount = D1  # Take the dust if there was any
@@ -542,7 +695,7 @@ def add_liquidity(
     total_supply += mint_amount
     self.balanceOf[_receiver] += mint_amount
     self.totalSupply = total_supply
-    log Transfer(ZERO_ADDRESS, _receiver, mint_amount)
+    log Transfer(empty(address), _receiver, mint_amount)
 
     log AddLiquidity(msg.sender, _amounts, fees, D1, total_supply)
 
@@ -551,7 +704,14 @@ def add_liquidity(
 
 @view
 @internal
-def get_y(i: int128, j: int128, x: uint256, xp: uint256[N_COINS]) -> uint256:
+def get_y(
+    i: int128, 
+    j: int128, 
+    x: uint256, 
+    xp: uint256[N_COINS],
+    amp: uint256,
+    D: uint256,
+) -> uint256:
     """
     Calculate x[j] if one makes x[i] = x
 
@@ -571,13 +731,11 @@ def get_y(i: int128, j: int128, x: uint256, xp: uint256[N_COINS]) -> uint256:
     assert i >= 0
     assert i < N_COINS
 
-    amp: uint256 = self._A()
-    D: uint256 = self.get_D(xp, amp)
     S_: uint256 = 0
     _x: uint256 = 0
     y_prev: uint256 = 0
     c: uint256 = D
-    Ann: uint256 = amp * N_COINS
+    Ann: uint256 = amp * N_COINS_256
 
     for _i in range(N_COINS):
         if _i == i:
@@ -587,9 +745,9 @@ def get_y(i: int128, j: int128, x: uint256, xp: uint256[N_COINS]) -> uint256:
         else:
             continue
         S_ += _x
-        c = c * D / (_x * N_COINS)
+        c = c * D / (_x * N_COINS_256)
 
-    c = c * D * A_PRECISION / (Ann * N_COINS)
+    c = c * D * A_PRECISION / (Ann * N_COINS_256)
     b: uint256 = S_ + D * A_PRECISION / Ann  # - D
     y: uint256 = D
 
@@ -621,7 +779,11 @@ def get_dy(i: int128, j: int128, dx: uint256) -> uint256:
     xp: uint256[N_COINS] = self._xp_mem(rates, self.balances)
 
     x: uint256 = xp[i] + (dx * rates[i] / PRECISION)
-    y: uint256 = self.get_y(i, j, x, xp)
+
+    amp: uint256 = self._A()
+    D: uint256 = self.get_D(xp, amp)
+    y: uint256 = self.get_y(i, j, x, xp, amp, D)
+
     dy: uint256 = xp[j] - y - 1
     fee: uint256 = self.fee * dy / FEE_DENOMINATOR
     return (dy - fee) * PRECISION / rates[j]
@@ -650,7 +812,10 @@ def exchange(
     xp: uint256[N_COINS] = self._xp_mem(rates, old_balances)
 
     x: uint256 = xp[i] + _dx * rates[i] / PRECISION
-    y: uint256 = self.get_y(i, j, x, xp)
+
+    amp: uint256 = self._A()
+    D: uint256 = self.get_D(xp, amp)
+    y: uint256 = self.get_y(i, j, x, xp, amp, D)
 
     dy: uint256 = xp[j] - y - 1  # -1 just in case there were some rounding errors
     dy_fee: uint256 = dy * self.fee / FEE_DENOMINATOR
@@ -667,26 +832,14 @@ def exchange(
     # When rounding errors happen, we undercharge admin fee in favor of LP
     self.balances[j] = old_balances[j] - dy - dy_admin_fee
 
-    response: Bytes[32] = raw_call(
-        self.coins[i],
-        _abi_encode(
-            msg.sender,
-            self,
-            _dx,
-            method_id=method_id("transferFrom(address,address,uint256)")
-        ),
-        max_outsize=32,
-    )
-    if len(response) > 0:
-        assert convert(response, bool)
+    # xp is not used anymore, so we reuse it for price calc
+    xp[i] = x
+    xp[j] = y
+    # D is not changed because we did not apply a fee
+    self.save_p(xp, amp, D)
 
-    response = raw_call(
-        self.coins[j],
-        _abi_encode(_receiver, dy, method_id=method_id("transfer(address,uint256)")),
-        max_outsize=32,
-    )
-    if len(response) > 0:
-        assert convert(response, bool)
+    assert ERC20(self.coins[i]).transferFrom(msg.sender, self, _dx, default_return_value=True)
+    assert ERC20(self.coins[j]).transfer(_receiver, dy, default_return_value=True)
 
     log TokenExchange(msg.sender, i, _dx, j, dy)
 
@@ -718,18 +871,12 @@ def remove_liquidity(
         self.balances[i] = old_balance - value
         amounts[i] = value
 
-        response: Bytes[32] = raw_call(
-            self.coins[i],
-            _abi_encode(_receiver, value, method_id=method_id("transfer(address,uint256)")),
-            max_outsize=32,
-        )
-        if len(response) > 0:
-            assert convert(response, bool)
+        assert ERC20(self.coins[i]).transfer(_receiver, value, default_return_value=True)
 
     total_supply -= _burn_amount
     self.balanceOf[msg.sender] -= _burn_amount
     self.totalSupply = total_supply
-    log Transfer(msg.sender, ZERO_ADDRESS, _burn_amount)
+    log Transfer(msg.sender, empty(address), _burn_amount)
 
     log RemoveLiquidity(msg.sender, amounts, empty(uint256[N_COINS]), total_supply)
 
@@ -760,17 +907,11 @@ def remove_liquidity_imbalance(
         amount: uint256 = _amounts[i]
         if amount != 0:
             new_balances[i] -= amount
-            response: Bytes[32] = raw_call(
-                self.coins[i],
-                _abi_encode(_receiver, amount, method_id=method_id("transfer(address,uint256)")),
-                max_outsize=32,
-            )
-            if len(response) > 0:
-                assert convert(response, bool)
+            assert ERC20(self.coins[i]).transfer(_receiver, amount, default_return_value=True)
     D1: uint256 = self.get_D_mem(rates, new_balances, amp)
 
     fees: uint256[N_COINS] = empty(uint256[N_COINS])
-    base_fee: uint256 = self.fee * N_COINS / (4 * (N_COINS - 1))
+    base_fee: uint256 = self.fee * N_COINS_256 / (4 * (N_COINS_256 - 1))
     for i in range(N_COINS):
         ideal_balance: uint256 = D1 * old_balances[i] / D0
         difference: uint256 = 0
@@ -784,6 +925,8 @@ def remove_liquidity_imbalance(
         new_balances[i] -= fees[i]
     D2: uint256 = self.get_D_mem(rates, new_balances, amp)
 
+    self.save_p(new_balances, amp, D2)
+
     total_supply: uint256 = self.totalSupply
     burn_amount: uint256 = ((D0 - D2) * total_supply / D0) + 1
     assert burn_amount > 1  # dev: zero tokens burned
@@ -792,7 +935,7 @@ def remove_liquidity_imbalance(
     total_supply -= burn_amount
     self.totalSupply = total_supply
     self.balanceOf[msg.sender] -= burn_amount
-    log Transfer(msg.sender, ZERO_ADDRESS, burn_amount)
+    log Transfer(msg.sender, empty(address), burn_amount)
     log RemoveLiquidityImbalance(msg.sender, _amounts, fees, D1, total_supply)
 
     return burn_amount
@@ -819,7 +962,7 @@ def get_y_D(A: uint256, i: int128, xp: uint256[N_COINS], D: uint256) -> uint256:
     _x: uint256 = 0
     y_prev: uint256 = 0
     c: uint256 = D
-    Ann: uint256 = A * N_COINS
+    Ann: uint256 = A * N_COINS_256
 
     for _i in range(N_COINS):
         if _i != i:
@@ -827,9 +970,9 @@ def get_y_D(A: uint256, i: int128, xp: uint256[N_COINS], D: uint256) -> uint256:
         else:
             continue
         S_ += _x
-        c = c * D / (_x * N_COINS)
+        c = c * D / (_x * N_COINS_256)
 
-    c = c * D * A_PRECISION / (Ann * N_COINS)
+    c = c * D * A_PRECISION / (Ann * N_COINS_256)
     b: uint256 = S_ + D * A_PRECISION / Ann
     y: uint256 = D
 
@@ -848,7 +991,7 @@ def get_y_D(A: uint256, i: int128, xp: uint256[N_COINS], D: uint256) -> uint256:
 
 @view
 @internal
-def _calc_withdraw_one_coin(_burn_amount: uint256, i: int128) -> uint256[2]:
+def _calc_withdraw_one_coin(_burn_amount: uint256, i: int128) -> uint256[3]:
     # First, need to calculate
     # * Get current D
     # * Solve Eqn against y_i for D - _token_amount
@@ -861,7 +1004,7 @@ def _calc_withdraw_one_coin(_burn_amount: uint256, i: int128) -> uint256[2]:
     D1: uint256 = D0 - _burn_amount * D0 / total_supply
     new_y: uint256 = self.get_y_D(amp, i, xp, D1)
 
-    base_fee: uint256 = self.fee * N_COINS / (4 * (N_COINS - 1))
+    base_fee: uint256 = self.fee * N_COINS_256 / (4 * (N_COINS_256 - 1))
     xp_reduced: uint256[N_COINS] = empty(uint256[N_COINS])
 
     for j in range(N_COINS):
@@ -877,7 +1020,12 @@ def _calc_withdraw_one_coin(_burn_amount: uint256, i: int128) -> uint256[2]:
     dy_0: uint256 = (xp[i] - new_y) * PRECISION / rates[i]  # w/o fees
     dy = (dy - 1) * PRECISION / rates[i]  # Withdraw less to account for rounding errors
 
-    return [dy, dy_0 - dy]
+    xp[i] = new_y
+    last_p: uint256 = 0
+    if new_y > 0:
+        last_p = self._get_p(xp, amp, D1)
+
+    return [dy, dy_0 - dy, last_p]
 
 
 @view
@@ -908,25 +1056,21 @@ def remove_liquidity_one_coin(
     @param _receiver Address that receives the withdrawn coins
     @return Amount of coin received
     """
-    dy: uint256[2] = self._calc_withdraw_one_coin(_burn_amount, i)
+    dy: uint256[3] = self._calc_withdraw_one_coin(_burn_amount, i)
     assert dy[0] >= _min_received, "Not enough coins removed"
 
     self.balances[i] -= (dy[0] + dy[1] * ADMIN_FEE / FEE_DENOMINATOR)
     total_supply: uint256 = self.totalSupply - _burn_amount
     self.totalSupply = total_supply
     self.balanceOf[msg.sender] -= _burn_amount
-    log Transfer(msg.sender, ZERO_ADDRESS, _burn_amount)
+    log Transfer(msg.sender, empty(address), _burn_amount)
 
-    response: Bytes[32] = raw_call(
-        self.coins[i],
-        _abi_encode(_receiver, dy[0], method_id=method_id("transfer(address,uint256)")),
-        max_outsize=32,
-    )
-    if len(response) > 0:
-        assert convert(response, bool)
+    assert ERC20(self.coins[i]).transfer(_receiver, dy[0], default_return_value=True)
 
     log RemoveLiquidityOne(msg.sender, _burn_amount, dy[0], total_supply)
 
+    self.save_p_from_price(dy[2])
+
     return dy[0]
 
 
@@ -980,10 +1124,7 @@ def withdraw_admin_fees():
     for i in range(N_COINS):
         coin: address = self.coins[i]
         fees: uint256 = ERC20(coin).balanceOf(self) - self.balances[i]
-        raw_call(
-            coin,
-            _abi_encode(receiver, fees, method_id=method_id("transfer(address,uint256)")),
-        )
+        assert ERC20(self.coins[i]).transfer(receiver, fees, default_return_value=True)
 
 
 @external
@@ -998,10 +1139,10 @@ def set_oracles(_method_ids: uint256[N_COINS], _oracles: address[N_COINS]):
     assert msg.sender == self.originator
 
     for i in range(N_COINS):
-        assert shift(_method_ids[i], 32) == 0
-        self.oracles[i] = bitwise_and(_method_ids[i], convert(_oracles[i], uint256))
+        assert (_method_ids[i] << 32) == 0
+        self.oracles[i] = (_method_ids[i] & convert(_oracles[i], uint256))
 
-    self.originator = ZERO_ADDRESS
+    self.originator = empty(address)
 
 
 @pure

From 34535cffc57d9c8416c4c938896db140b3d923e8 Mon Sep 17 00:00:00 2001
From: bout3fiddy <11488427+bout3fiddy@users.noreply.github.com>
Date: Sat, 16 Sep 2023 15:32:03 +0200
Subject: [PATCH 2/3] fix: use _stored_rates() in get_p()

---
 contracts/implementations/plain-2/Plain2Price.vy | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/contracts/implementations/plain-2/Plain2Price.vy b/contracts/implementations/plain-2/Plain2Price.vy
index c873130..2346258 100644
--- a/contracts/implementations/plain-2/Plain2Price.vy
+++ b/contracts/implementations/plain-2/Plain2Price.vy
@@ -458,7 +458,7 @@ def _get_p(xp: uint256[N_COINS], amp: uint256, D: uint256) -> uint256:
 @view
 def get_p() -> uint256:
     amp: uint256 = self._A()
-    xp: uint256[N_COINS] = self._xp_mem(self.rate_multipliers, self.balances)
+    xp: uint256[N_COINS] = self._xp_mem(self._stored_rates(), self.balances)
     D: uint256 = self.get_D(xp, amp)
     return self._get_p(xp, amp, D)
 

From d4012ab409b4a9a127ad5d1d0bc0f484700b7015 Mon Sep 17 00:00:00 2001
From: bout3fiddy <11488427+bout3fiddy@users.noreply.github.com>
Date: Mon, 18 Sep 2023 16:43:40 +0200
Subject: [PATCH 3/3] fix: add ma_exp_time setup and changing methods

---
 .../implementations/plain-2/Plain2Balances.vy | 10 ++++++++
 .../implementations/plain-2/Plain2Price.vy    | 23 +++++++++++++------
 2 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/contracts/implementations/plain-2/Plain2Balances.vy b/contracts/implementations/plain-2/Plain2Balances.vy
index 2296c65..a64d840 100644
--- a/contracts/implementations/plain-2/Plain2Balances.vy
+++ b/contracts/implementations/plain-2/Plain2Balances.vy
@@ -165,6 +165,8 @@ def initialize(
     self.name = name
     self.symbol = concat(_symbol, "-f")
 
+    self.ma_exp_time = 865  # set it to default = 10 mins
+
     self.DOMAIN_SEPARATOR = keccak256(
         _abi_encode(EIP712_TYPEHASH, keccak256(name), keccak256(VERSION), chain.id, self)
     )
@@ -1118,6 +1120,14 @@ def withdraw_admin_fees():
             self.admin_balances[i] = 0
 
 
+@external
+def set_ma_exp_time(_ma_exp_time: uint256):
+    assert msg.sender == Factory(self.factory).admin()  # dev: only owner
+    assert _ma_exp_time != 0
+
+    self.ma_exp_time = _ma_exp_time
+
+
 @pure
 @external
 def version() -> String[8]:
diff --git a/contracts/implementations/plain-2/Plain2Price.vy b/contracts/implementations/plain-2/Plain2Price.vy
index 2346258..b291a37 100644
--- a/contracts/implementations/plain-2/Plain2Price.vy
+++ b/contracts/implementations/plain-2/Plain2Price.vy
@@ -1,9 +1,9 @@
 # @version 0.3.9
 """
-@title StableSwap
+@title CurveStableSwap2Prices
 @author Curve.Fi
-@license Copyright (c) Curve.Fi, 2020-2021 - all rights reserved
-@notice 2 coin pool implementation with no lending
+@license Copyright (c) Curve.Fi, 2023 - all rights reserved
+@notice 2 coin pool implementation for tokens with rate oracles.
 @dev ERC20 support for return True/revert, return True/False, return None
 """
 
@@ -171,6 +171,8 @@ def initialize(
     self.name = name
     self.symbol = concat(_symbol, "-f")
 
+    self.ma_exp_time = 865  # set it to default = 10 mins
+
     self.DOMAIN_SEPARATOR = keccak256(
         _abi_encode(EIP712_TYPEHASH, keccak256(name), keccak256(VERSION), chain.id, self)
     )
@@ -1128,7 +1130,7 @@ def withdraw_admin_fees():
 
 
 @external
-def set_oracles(_method_ids: uint256[N_COINS], _oracles: address[N_COINS]):
+def set_oracles(_method_ids: bytes4[N_COINS], _oracles: address[N_COINS]):
     """
     @notice Set the oracles used for calculating rates
     @dev if any value is empty, rate will fallback to value provided on initialize, one time use.
@@ -1139,12 +1141,19 @@ def set_oracles(_method_ids: uint256[N_COINS], _oracles: address[N_COINS]):
     assert msg.sender == self.originator
 
     for i in range(N_COINS):
-        assert (_method_ids[i] << 32) == 0
-        self.oracles[i] = (_method_ids[i] & convert(_oracles[i], uint256))
+        self.oracles[i] = convert(_method_ids[i], uint256) * 2**224 | convert(_oracles[i], uint256)
 
     self.originator = empty(address)
 
 
+@external
+def set_ma_exp_time(_ma_exp_time: uint256):
+    assert msg.sender == Factory(self.factory).admin()  # dev: only owner
+    assert _ma_exp_time != 0
+
+    self.ma_exp_time = _ma_exp_time
+
+
 @pure
 @external
 def version() -> String[8]:
@@ -1157,4 +1166,4 @@ def version() -> String[8]:
 @view
 @external
 def oracle(_idx: uint256) -> address:
-    return convert(self.oracles[_idx] % 2**160, address)
\ No newline at end of file
+    return convert(self.oracles[_idx] % 2**160, address)