Colin/liquid exchange

contracts/arbiter_token.sol

@@ -1,12 +1,25 @@
 pragma solidity ^0.8.10;
 import "../../openzeppelin-contracts/contracts/token/ERC20/ERC20.sol";
+
 contract ArbiterToken is ERC20 {
+    address public admin;
+
     constructor(string memory name, string memory symbol) 
         ERC20(name, symbol) {
-
+            admin = msg.sender; // Set the contract deployer as the initial admin
+    }
+
+    // Our admin lock
+    modifier onlyAdmin() {
+        require(msg.sender == admin, "Only admin can call this function");
+        _;
     }
 
-    function mint(address receiver, uint256 amount) public {
+    function mint(address receiver, uint256 amount) public onlyAdmin {
         _mint(receiver, amount);
     }
+
+    function mintMax(address receiver) public onlyAdmin {
+        _mint(receiver, type(uint256).max);
+    }
 }

contracts/liquid_exchange.sol

@@ -0,0 +1,75 @@
+// SPDX-License-Identifier: MIT
+// compiler version must be greater than or equal to 0.8.17 and less than 0.9.0
+pragma solidity ^0.8.17;
+// import "solmate/utils/FixedPointMathLib.sol"; // This import is correct given Arbiter's foundry.toml
+import "../../portfolio/lib/solmate/src/utils/FixedPointMathLib.sol"; // This import goes directly to the contract
+import "../../openzeppelin-contracts/contracts/token/ERC20/ERC20.sol";
+
+/**
+ * @dev Implementation of the test interface for Arbiter writing contracts.
+ */
+contract LiquidExchange {
+    using FixedPointMathLib for int256;
+    using FixedPointMathLib for uint256;
+    address public admin;
+    ERC20 public arbiter_token_x;
+    address public arbiter_token_x_address;
+    ERC20 public arbiter_token_y;
+    address public arbiter_token_y_address;
+    uint256 public price;
+    uint256 public constant WAD = 10**18;
+
+    // Each LiquidExchange contract will be deployed with a pair of token addresses and an initial price
+    constructor(address _arbiter_token_x, address _arbiter_token_y, uint256 _price) {
+        admin = msg.sender; // Set the contract deployer as the initial admin
+        arbiter_token_x = ERC20(_arbiter_token_x);
+        arbiter_token_x_address = _arbiter_token_x;
+        arbiter_token_y = ERC20(_arbiter_token_y);
+        arbiter_token_y_address = _arbiter_token_x;
+        price = _price;
+    }
+
+    // Our admin lock
+    modifier onlyAdmin() {
+        require(msg.sender == admin, "Only admin can call this function");
+        _;
+    }
+
+    event PriceChange(uint256 price);
+    event Swap(address token_in, address token_out, uint256 amount_in, uint256 amount_out, address to);
+
+    // Admin only function to set the price of x in terms of y
+    function setPrice(uint256 _price) public onlyAdmin {
+        price = _price;
+        emit PriceChange(price);
+    }
+
+    // Returns the price of x in terms of y (i.e., y is the numeraire)
+    function getPrice() public view returns (uint256) {
+        return price;
+    }
+
+    // TODO: This function is NOT completed yet. It is just a placeholder for now.
+    function swap(address _token_in_address, uint256 _amount_in) public {
+        uint256 amount_out;
+        address token_out_address;
+        if (_token_in_address == arbiter_token_x_address) {
+            // amount_out = FixedPointMathLib.mulWadDown(_amount_in, price);
+            amount_out = _amount_in * price;
+            // Set allowances
+            // arbiter_token_x.increaseAllowance(msg.sender, _amount_in);
+            // arbiter_token_y.increaseAllowance(admin, amount_out); //might not be necessary if we increase the allowance for the manager outside of this
+            // Transfer amount in and amount out
+            arbiter_token_x.transferFrom(msg.sender, admin, _amount_in);
+            arbiter_token_y.transferFrom(admin, msg.sender, amount_out);
+        } else if (_token_in_address == arbiter_token_y_address) {
+            amount_out = FixedPointMathLib.divWadDown(_amount_in, price);
+            // Transfer amount in and amount out
+            arbiter_token_y.transferFrom(msg.sender, admin, _amount_in);
+            arbiter_token_x.transferFrom(admin, msg.sender, amount_out);
+        } else {
+            revert("Invalid token");
+        }
+        emit Swap(_token_in_address, token_out_address, _amount_in, amount_out, msg.sender);    
+    }
+}