add fundingRate update with zk

src/FundingRateUpdateZk.sol

@@ -0,0 +1,87 @@
+/*
+    Copyright 2022 JOJO Exchange
+    SPDX-License-Identifier: BUSL-1.1
+*/
+
+pragma solidity ^0.8.19;
+
+import "@openzeppelin/contracts/access/Ownable.sol";
+import "@brevis/sdk/interface/IBrevisProof.sol";
+import "@brevis/sdk/apps/framework/BrevisApp.sol";
+import "./interfaces/internal/IPriceSource.sol";
+import "./interfaces/IDealer.sol";
+import "./interfaces/IPerpetual.sol";
+import "./libraries/Types.sol";
+import "./libraries/SignedDecimalMath.sol";
+
+/// @notice Limiting funding rate change speed
+/// Mainly for preventing JOJO's backend errors
+/// and to prevent mischief
+contract FundingRateUpdateZk is Ownable, BrevisApp {
+    using SignedDecimalMath for int256;
+
+    // dealer
+    address immutable dealer;
+    // max speed multiplier, should be 1/2/3/4/5..., no decimal
+    // funding rate max daily change will be limited to
+    // speedMultiplier*liquidationThreshold
+    // e.d 3 * 3% = 9%
+    uint8 immutable speedMultiplier;
+    // The timestamp of the last funding rate update
+    // used to limit the change rate of fundingRate
+    mapping(address => uint256) public fundingRateUpdateTimestamp;
+
+    int248 public btcRateLimit;
+
+    bytes32 public vkHash;
+
+    constructor(address _dealer, uint8 _speedMultiplier, address brevisProof) BrevisApp(IBrevisProof(brevisProof)) {
+        dealer = _dealer;
+        speedMultiplier = _speedMultiplier;
+    }
+
+    function setVkHash(bytes32 _vkHash) external onlyOwner {
+        vkHash = _vkHash;
+    }
+
+    // BrevisQuery contract will call our callback once Brevis backend submits the proof.
+    function handleProofResult(bytes32, bytes32 _vkHash, bytes calldata _circuitOutput) internal override {
+        require(vkHash == _vkHash, "invalid vk");
+        (uint64 symbol, uint248 limitRate) = decodeOutput(_circuitOutput);
+        if(symbol == 0){
+            btcRateLimit = int248(limitRate);
+        } else {
+            btcRateLimit = -int248(limitRate);
+        }
+    }
+
+    function decodeOutput(bytes calldata output) internal pure returns (uint64, uint248) {
+        uint64 symbol = uint64(bytes8(output[0:8]));
+        uint248 limitRate = uint248(bytes31(output[8:8 + 31]));
+        return (symbol, limitRate);
+    }
+
+    function updateFundingRate(address perp, int256 rate) external onlyOwner {
+        int256 oldRate = IPerpetual(perp).getFundingRate();
+        uint256 maxChange = getMaxChange(perp);
+        require((rate - oldRate).abs() <= maxChange, "FUNDING_RATE_CHANGE_TOO_MUCH");
+        fundingRateUpdateTimestamp[perp] = block.timestamp;
+        address[] memory perpList = new address[](1);
+        perpList[0] = perp;
+        int256[] memory rateList = new int256[](1);
+        rateList[0] = rate;
+
+        IDealer(dealer).updateFundingRate(perpList, rateList);
+    }
+
+    // limit funding rate change speed
+    // can not exceed speedMultiplier*liquidationThreshold
+    function getMaxChange(address perp) public view returns (uint256) {
+        Types.RiskParams memory params = IDealer(dealer).getRiskParams(perp);
+        uint256 markPrice = IPriceSource(params.markPriceSource).getMarkPrice();
+        uint256 timeInterval = block.timestamp - fundingRateUpdateTimestamp[perp];
+        uint256 maxChangeRate = (speedMultiplier * timeInterval * params.liquidationThreshold) / (1 days);
+        uint256 maxChange = (maxChangeRate * markPrice) / Types.ONE;
+        return maxChange;
+    }
+}