From db0b95aba14c0240ab5d96fdf42863abf99d42b7 Mon Sep 17 00:00:00 2001
From: Nicholas Addison <nick@addisonbrown.com.au>
Date: Wed, 9 Oct 2024 15:59:49 +1100
Subject: [PATCH] Allow the cross price to be 20 basis points below 1

---
 src/contracts/AbstractARM.sol                   | 17 +++++++++++++----
 .../fork/LidoFixedPriceMultiLpARM/Setters.t.sol | 10 +++++-----
 2 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/src/contracts/AbstractARM.sol b/src/contracts/AbstractARM.sol
index 90987d4..d6ca721 100644
--- a/src/contracts/AbstractARM.sol
+++ b/src/contracts/AbstractARM.sol
@@ -12,9 +12,9 @@ abstract contract AbstractARM is OwnableOperable, ERC20Upgradeable {
     ///                 Constants
     ////////////////////////////////////////////////////
 
-    /// @notice Maximum amount the Operator can set the price from 1 scaled to 36 decimals.
-    /// 2e33 is a 0.02% deviation, or 2 basis points.
-    uint256 public constant MAX_PRICE_DEVIATION = 2e32;
+    /// @notice Maximum amount the Owner can set the cross price below 1 scaled to 36 decimals.
+    /// 20e32 is a 0.2% deviation, or 20 basis points.
+    uint256 public constant MAX_CROSS_PRICE_DEVIATION = 20e32;
     /// @notice Scale of the prices.
     uint256 public constant PRICE_SCALE = 1e36;
     /// @dev The amount of shares that are minted to a dead address on initalization
@@ -391,8 +391,17 @@ abstract contract AbstractARM is OwnableOperable, ERC20Upgradeable {
         emit TraderateChanged(_baseToTokenRate, _tokenToBaseRate);
     }
 
+    /**
+     * @notice set the price that buy and sell prices can not cross.
+     * That is, the buy prices must be below the cross price
+     * and the sell prices must be above the cross price.
+     * If the cross price is being lowered, there can not be any base assets in the ARM. eg stETH.
+     * The base assets should be sent to the withdrawal queue before the cross price can be lowered.
+     * The cross price can be increased with assets in the ARM.
+     * @param newCrossPrice The new cross price scaled to 36 decimals.
+     */
     function setCrossPrice(uint256 newCrossPrice) external onlyOwner {
-        require(newCrossPrice >= PRICE_SCALE - MAX_PRICE_DEVIATION, "ARM: cross price too low");
+        require(newCrossPrice >= PRICE_SCALE - MAX_CROSS_PRICE_DEVIATION, "ARM: cross price too low");
         require(newCrossPrice <= PRICE_SCALE, "ARM: cross price too high");
 
         // If the new cross price is lower than the current cross price
diff --git a/test/fork/LidoFixedPriceMultiLpARM/Setters.t.sol b/test/fork/LidoFixedPriceMultiLpARM/Setters.t.sol
index 55e3456..20964a3 100644
--- a/test/fork/LidoFixedPriceMultiLpARM/Setters.t.sol
+++ b/test/fork/LidoFixedPriceMultiLpARM/Setters.t.sol
@@ -173,9 +173,9 @@ contract Fork_Concrete_lidoARM_Setters_Test_ is Fork_Shared_Test_ {
     }
 
     function test_RevertWhen_SetCrossPrice_Because_PriceRange() public asLidoARMOwner {
-        // 3 basis points lower than 1.0
+        // 21 basis points lower than 1.0
         vm.expectRevert("ARM: cross price too low");
-        lidoARM.setCrossPrice(0.9997e36);
+        lidoARM.setCrossPrice(0.9979e36);
 
         // 1 basis points higher than 1.0
         vm.expectRevert("ARM: cross price too high");
@@ -201,10 +201,10 @@ contract Fork_Concrete_lidoARM_Setters_Test_ is Fork_Shared_Test_ {
         emit AbstractARM.CrossPriceUpdated(1e36);
         lidoARM.setCrossPrice(1e36);
 
-        // 2 basis points lower than 1.0
+        // 20 basis points lower than 1.0
         vm.expectEmit({emitter: address(lidoARM)});
-        emit AbstractARM.CrossPriceUpdated(0.9998e36);
-        lidoARM.setCrossPrice(0.9998e36);
+        emit AbstractARM.CrossPriceUpdated(0.9980e36);
+        lidoARM.setCrossPrice(0.9980e36);
     }
 
     function test_SetCrossPrice_With_StETH_PriceUp_Owner() public {