Update PiStableCoin.sol

Author: KOSASIH

contracts/PiStableCoin.sol

@@ -3,32 +3,31 @@ pragma solidity ^0.8.0;
 
 import "@openzeppelin/contracts/access/Ownable.sol";
 import "@openzeppelin/contracts/security/Pausable.sol";
-import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
-import "@openzeppelin/contracts/proxy/utils/Initializable.sol";
 
-contract PiStableCoin is Ownable, Pausable, Initializable {
+contract PiStableCoin is Ownable, Pausable {
     uint256 public constant GCV_VALUE = 314159 * 10**18; // $314,159 in wei
     uint256 public totalSupply;
     mapping(address => uint256) public balances;
     mapping(address => mapping(address => uint256)) public allowances;
 
-    uint256 public transactionFee; // Fee percentage (in basis points)
-    address public feeRecipient; // Address to receive fees
+    uint256 public transactionFee; // Fee percentage in basis points (10000 = 100%)
+    address public feeRecipient;
 
     event Mint(address indexed to, uint256 amount);
     event Burn(address indexed from, uint256 amount);
     event Transfer(address indexed from, address indexed to, uint256 amount);
     event FeeUpdated(uint256 newFee);
     event FeeRecipientUpdated(address newRecipient);
+    event SupplyAdjusted(uint256 oldSupply, uint256 newSupply, int256 supplyChange, uint256 marketPrice);
 
     modifier onlyFeeRecipient() {
         require(msg.sender == feeRecipient, "Caller is not the fee recipient");
         _;
     }
 
-    function initialize(address _feeRecipient, uint256 _transactionFee) public initializer {
+    constructor(address _feeRecipient, uint256 _transactionFee) {
         require(_feeRecipient != address(0), "Invalid fee recipient");
-        require(_transactionFee <= 10000, "Fee exceeds maximum limit"); // 100% in basis points
+        require(_transactionFee <= 10000, "Fee exceeds maximum limit");
         feeRecipient = _feeRecipient;
         transactionFee = _transactionFee;
     }
@@ -43,7 +42,7 @@ contract PiStableCoin is Ownable, Pausable, Initializable {
     function mint(address to, uint256 amount) public onlyOwner whenNotPaused {
         require(to != address(0), "Cannot mint to the zero address");
         require(amount > 0, "Amount must be greater than 0");
-        
+
         totalSupply += amount;
         balances[to] += amount;
         emit Mint(to, amount);
@@ -74,7 +73,7 @@ contract PiStableCoin is Ownable, Pausable, Initializable {
         return true;
     }
 
-    function approve(address spender, uint256 amount) public returns (bool) {
+    function approve(address spender, uint256 amount) public whenNotPaused returns (bool) {
         allowances[msg.sender][spender] = amount;
         return true;
     }
@@ -126,4 +125,49 @@ contract PiStableCoin is Ownable, Pausable, Initializable {
     function allowance(address owner, address spender) public view returns (uint256) {
         return allowances[owner][spender];
     }
+
+    /**
+     * @notice Adjust supply based on the market price compared to the GCV_VALUE.
+     *         If market price is below GCV_VALUE, burn tokens from owner to reduce supply.
+     *         If market price is above GCV_VALUE, mint new tokens to owner to increase supply.
+     * @param marketPrice The current market price in wei
+     */
+    function adjustSupply(uint256 marketPrice) public onlyOwner whenNotPaused {
+        require(marketPrice > 0, "Market price must be positive");
+
+        uint256 oldSupply = totalSupply;
+        int256 supplyChange = 0;
+
+        if (marketPrice < GCV_VALUE) {
+            // Calculate difference scaled by token decimals
+            uint256 diff = (GCV_VALUE - marketPrice);
+            uint256 burnAmount = diff; // Already in 18-decimals wei
+
+            // Limit burn to owner's balance to prevent underflow
+            uint256 ownerBalance = balances[msg.sender];
+            if (burnAmount > ownerBalance) {
+                burnAmount = ownerBalance;
+            }
+
+            require(burnAmount > 0, "No tokens available to burn for supply adjustment");
+
+            totalSupply -= burnAmount;
+            balances[msg.sender] -= burnAmount;
+            supplyChange = -int256(burnAmount);
+
+            emit Burn(msg.sender, burnAmount);
+
+        } else if (marketPrice > GCV_VALUE) {
+            uint256 diff = (marketPrice - GCV_VALUE);
+            uint256 mintAmount = diff; // Already in 18-decimals wei
+
+            totalSupply += mintAmount;
+            balances[msg.sender] += mintAmount;
+            supplyChange = int256(mintAmount);
+
+            emit Mint(msg.sender, mintAmount);
+        }
+
+        emit SupplyAdjusted(oldSupply, totalSupply, supplyChange, marketPrice);
+    }
 }