feat: fill up challenge

packages/hardhat/contracts/CrowdFund.sol

@@ -10,18 +10,27 @@ contract CrowdFund {
     /////////////////
 
     // Errors go here...
+    error NotOpenToWithdraw();
+    error WithdrawTransferFailed(address to, uint256 amount);
+    error TooEarly(uint256 deadline, uint256 currentTimestamp);
+    error AlreadyCompleted();
 
     //////////////////////
     /// State Variables //
     //////////////////////
 
     FundingRecipient public fundingRecipient;
+    mapping(address => uint256) public balances;
+    bool public openToWithdraw;
+    uint256 public deadline = block.timestamp + 2 hours;
+    uint256 public constant threshold = 1 ether;
 
     ////////////////
     /// Events /////
     ////////////////
 
     // Events go here...
+    event Contribution(address, uint256);
 
     ///////////////////
     /// Modifiers /////
@@ -29,6 +38,7 @@ contract CrowdFund {
 
     modifier notCompleted() {
         _;
+	if (block.timestamp >= deadline) revert AlreadyCompleted();
     }
 
     ///////////////////
@@ -43,19 +53,42 @@ contract CrowdFund {
     /// Functions /////
     ///////////////////
 
-    function contribute() public payable {}
+    function contribute() public payable {
+      balances[msg.sender] += msg.value;
+      emit Contribution(msg.sender, msg.value);
+    }
 
-    function withdraw() public {}
+    function withdraw() public {
+      if (!openToWithdraw) revert NotOpenToWithdraw();
 
-    function execute() public {}
+      uint256 amount = balances[msg.sender];
+      balances[msg.sender] = 0;
 
-    receive() external payable {}
+      (bool success,) = msg.sender.call{value: amount}("");
+      if (!success) revert WithdrawTransferFailed(msg.sender, amount);
+    }
+
+    function execute() public {
+      if (block.timestamp < deadline) revert TooEarly(deadline, block.timestamp);
+
+      uint256 balance = address(this).balance;
+      if (balance >= threshold) {
+        fundingRecipient.complete{value: balance}();
+      } else {
+        openToWithdraw = true;
+      }
+    }
+
+    receive() external payable {
+      contribute();
+    }
 
     ////////////////////////
     /// View Functions /////
     ////////////////////////
 
     function timeLeft() public view returns (uint256) {
-        return 0;
+	if (block.timestamp >= deadline) return 0;
+        return deadline - block.timestamp;
     }
 }