feat: add swap contract

packages/hardhat/contracts/MockSwap.sol

@@ -0,0 +1,52 @@
+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.19;
+
+contract MockSwap {
+    event Swap(address indexed user, uint256 amount);
+    event Mint(address indexed user, uint256 amount);
+    event ReverseSwap(address indexed user, uint256 amount);
+
+    mapping(address => uint256) public balances;
+    mapping(address => uint256) public tokenBalances;
+    address[] public users;
+
+    function deposit() external payable {
+        if (balances[msg.sender] == 0 && tokenBalances[msg.sender] == 0) {
+            users.push(msg.sender);
+        }
+        balances[msg.sender] += msg.value;
+        tokenBalances[msg.sender] += msg.value; // 1:1 ratio for simplicity
+        emit Mint(msg.sender, msg.value);
+    }
+
+    function swap(uint256 amount) external {
+        require(tokenBalances[msg.sender] >= amount, "Insufficient token balance");
+        tokenBalances[msg.sender] -= amount;
+        emit Swap(msg.sender, amount);
+    }
+
+    function reverseSwap(uint256 amount) external {
+        require(balances[msg.sender] >= amount, "Insufficient ether balance");
+        balances[msg.sender] -= amount;
+        tokenBalances[msg.sender] += amount; // Mint back the tokens
+        payable(msg.sender).transfer(amount);
+        emit ReverseSwap(msg.sender, amount);
+    }
+
+    function getBalance(address user) external view returns (uint256) {
+        return balances[user];
+    }
+
+    function getTokenBalance(address user) external view returns (uint256) {
+        return tokenBalances[user];
+    }
+
+    function resetBalances() external {
+        // Only for demonstration purposes; in a real scenario, proper access control is needed.
+        for (uint256 i = 0; i < users.length; i++) {
+            balances[users[i]] = 0;
+            tokenBalances[users[i]] = 0;
+        }
+        delete users;
+    }
+}