add: PriceIndexQuote.sol

PriceIndexQuote.sol

@@ -0,0 +1,117 @@
+/**
+ *Submitted for verification at celoscan.io on 2023-12-12
+*/
+
+pragma solidity ^0.8.0;
+
+// Author: Louis Holbrook <dev@holbrook.no> 0826EDA1702D1E87C6E2875121D2E7BB88C2A746
+// Author: Mohamed Sohail <sohail@grassecon.org>
+// SPDX-License-Identifier: AGPL-3.0-or-later
+// File-Version: 1
+// Description: ACL-enabled ERC20 token swap quoter that queries a price index for the latest exchange rates.
+
+contract PriceIndexQuote {
+    // Implements EIP173
+    address public owner;
+    // consts
+    uint256 constant EXCHANGE_RATE_PRECISION = 10 ** 4;
+
+    mapping(address => uint256) public priceIndex;
+
+    event PriceIndexUpdated(address _tokenAddress, uint256 _exchangeRate);
+    // Implements ERC173
+    event OwnershipTransferred(
+        address indexed previousOwner,
+        address indexed newOwner
+    );
+
+    constructor() {
+        owner = msg.sender;
+    }
+
+    function setPriceIndexValue(
+        address _tokenAddress,
+        uint256 _exchangeRate
+    ) public returns (uint256) {
+        require(owner == msg.sender, "ERR_NOT_OWNER");
+        priceIndex[_tokenAddress] = _exchangeRate;
+        emit PriceIndexUpdated(_tokenAddress, _exchangeRate);
+        return _exchangeRate;
+    }
+
+    // Implements TokenQuote
+    function valueFor(
+        address _outToken,
+        address _inToken,
+        uint256 _value
+    ) public returns (uint256) {
+        uint8 dout;
+        uint8 din;
+        bool r;
+        bytes memory v;
+
+        uint256 exchangeRate = priceIndex[_inToken] > 0
+            ? priceIndex[_inToken]
+            : priceIndex[_outToken];
+
+        (r, v) = _outToken.call(abi.encodeWithSignature("decimals()"));
+        require(r, "ERR_TOKEN_OUT");
+        dout = abi.decode(v, (uint8));
+
+        (r, v) = _inToken.call(abi.encodeWithSignature("decimals()"));
+        require(r, "ERR_TOKEN_IN");
+        din = abi.decode(v, (uint8));
+
+        if (din == dout) {
+            uint256 x = _value;
+            if (exchangeRate > 0) {
+                x = (x * exchangeRate) / EXCHANGE_RATE_PRECISION;
+            }
+            return x;
+        }
+
+        uint256 d = din > dout ? 10 ** ((din - dout)) : 10 ** ((dout - din));
+        if (din > dout) {
+            uint256 x = _value / d;
+            if (exchangeRate > 0) {
+                x = (x * exchangeRate) / EXCHANGE_RATE_PRECISION;
+            }
+            return x;
+        } else {
+            uint256 x = _value * d;
+            if (exchangeRate > 0) {
+                x = (x / exchangeRate) * EXCHANGE_RATE_PRECISION;
+            }
+            return x;
+        }
+    }
+
+    // Implements EIP173
+    function transferOwnership(address _newOwner) public returns (bool) {
+        address oldOwner;
+        require(msg.sender == owner, "ERR_AXX");
+
+        oldOwner = owner;
+        owner = _newOwner;
+
+        emit OwnershipTransferred(oldOwner, owner);
+        return true;
+    }
+
+    // Implements EIP165
+    function supportsInterface(bytes4 _sum) public pure returns (bool) {
+        if (_sum == 0x01ffc9a7) {
+            // ERC165
+            return true;
+        }
+        if (_sum == 0x9493f8b2) {
+            // ERC173
+            return true;
+        }
+        if (_sum == 0xdbb21d40) {
+            // TokenQuote
+            return true;
+        }
+        return false;
+    }
+}