_Follow along with this video:_ --- ### Business Logic Edge Case By now we've identified fairly clearly how the `enterRaffle` function works. Our finding looks great. Let's next move onto the `refund` function, this one was mentioned explicitly in our documentation. ``` Users are allowed to get a refund of their ticket & value if they call the refund function ``` This is what the function looks like. ```js /// @param playerIndex the index of the player to refund. You can find it externally by calling `getActivePlayerIndex` /// @dev This function will allow there to be blank spots in the array function refund(uint256 playerIndex) public { address playerAddress = players[playerIndex]; require(playerAddress == msg.sender, "PuppyRaffle: Only the player can refund"); require(playerAddress != address(0), "PuppyRaffle: Player already refunded, or is not active"); payable(msg.sender).sendValue(entranceFee); players[playerIndex] = address(0); emit RaffleRefunded(playerAddress); } ``` Remember to start with the documentation so that we understand what's supposed to happen. In order to call this function a player needs to provide their `playerIndex`, and this is acquired through the `getActivePlayerIndex` function. Let's jump over there quickly. ```js /// @notice a way to get the index in the array /// @param player the address of a player in the raffle /// @return the index of the player in the array, if they are not active, it returns 0 function getActivePlayerIndex(address player) external view returns (uint256) { for (uint256 i = 0; i < players.length; i++) { if (players[i] == player) { return i; } } return 0; } ``` I think we may have stumbled upon our next bug. The logic here has a problem. Can you spot it? <details> <summary>The Problem</summary> :br When looking at this function, we have to ask _"Why is this returning zero?"_ Arrays begin at index 0, were the player at this index to call this function it would be very unclear whether or not they were in the raffle or not! </details> ### Wrap Up We're not going to go through writing this finding report together, but I absolutely challenge you to write one yourself before moving forward! **\*Hint:** It's informational severity\* Up next we're going back to the `refund` function!