rock-paper-scissors

This a blockchain based rock paper scissors game. Enjoy it.

Intructions of the exercise

Write a Smart Contract in Solidity to model the Rock, Paper, Scissors game. The requirements are:

1. A game is played by two participants in which one challenges the other.
2. An event must be logged when one player wins the game.
3. Appropriate tests must be implemented (if some tests are not included, at least specify which cases would be covered).
4. Include a README.md file with instructions on how to set up the environment and run the tests.
5. (Optional) Allow players to bet on the native token of the network (ETH, RBTC, ETC). How would this be implemented if you wanted to bet on compatible ERC-20 tokens?
6. (Optional) Implement a super simple interface that allows people to play using Metamask.
7. (Help) Keep in mind that transactions are executed in sequence. How could a move be made without the other player knowing the chosen element(rock, paper or Scissors)? Consider that the game can be played in several turns.

Intructions to run the tests

1 - Clone the repository

git clone git@github.com:hanzel98/rock-paper-scissors.git

2 - Go to the cloned repository in the local machine and inside the /client folder run npm install

3 - Make sure to have truffle installed.

4 - Download and install Ganache. Configure a new workspace with this values:

• Host: 127.0.0.1
• Port: 7545
• Network id: 5777
• Create at least 3 different unlockced accounts with funds

5 - Open a terminal inside the root of the project /rock-paper-scissors and run truffle test. After that the tests should start running. If all tests were marked as correct then the application is working as it should

Intructions to play

1 - The above instructions for testing must be followed before beginning these instructions.

2 - Download Firefox and Google Chrome. (Two browsers are needed)

3 - Install the Metamask extension in each browser and follow the next steps to configure it:

• Open and create you metamask wallet, once you are inside create a new network in the option Networks/Custom RPC and insert these values New RPC URL: HTTP://127.0.0.1:7545 Chain Id: 1337 then change to this network.
• Open the gananche instance that is running and copy the private key of the first account.
• Go to one of the metamask extensions in one of the browsers and inside My Accounts/Import Account paste the first private key.
• Repeat the process to configure the second account, but this time with a different private key and a different browser.
• If everything went well in these steps you will have two browsers connected to the local ganache, and you will be using two different accounts that will have ethers.

4 - Open a terminal and go to the project root folder then run truffle console, after that type migrate and hit enter, this will compile and migrate the smart contracts.

5 - Open a terminal and move to the /rock-paper-scissors/client folder then run npm run start, this will start the server that will open the UI here http://localhost:3000

Demo in video

Check out these demo videos to get more familiar with the user interface:

Application: https://youtu.be/TQrwd7zdorU

Tests: https://youtu.be/ob-42PSaQr8

Proposal for missing features

How could a move be made without the other player knowing the chosen element (rock, paper or scissors)?

• Currently if someone listens to the smart contract that person will be able to know the input that the opponent chose. One possible solution for this is that both players hash their answers with a random string and initially send just the hash as the answer to the smart contract, the opponnt will not be able to know what was the answer, even if he can see the input that was used in the smart contract. The hash is saved in the smart contract for both players. Once both of them sent the hash they can now send the real answer without the hash but they will also include the random string that they used to hash it iniatially. With those two values the smart contract can replicate the hash and validate that the initial choice was not changed. In each round the hash saved in the smart contract will be reset and also the random string will be generated again for the next round.

Allow players to bet on the native token of the network (ETH, RBTC, ETC). How would this be implemented if you wanted to bet on compatible ERC-20 tokens?

• For this exercise I started an implementation that due to lack of time I could not complete. You can take a look at the smart contract proposal inside contracts/RockPaperScissorsERC20Proposal, I took into consideration several things, for example:
• Locking the fungible tokens once that the player accepts the bet. The idea here was that players would not be able to bet tokens that we do not know if they will be available to pay the bet when the winner is announced. So a smart contract will own them and release them when needed. This part of the ERC20 token contract manager is failing since I tried to send the tokens to the a RockPaperScissors smart contract and that works fine but then I could not get the tokens out the smart contract since it does not allow to transfer and throws this error "ERC20: transfer amount exceeds allowance".. The ideal approach in this case would be to integrate a scrow contract which would act like a middle man, that contract would hold the tokens meanwhile the winner is chosen and then it would transfer the tokens only to the winner.
• There is another consideration related to the bet tokens, here the idea was that since the tokens would be kept in the smart contract at the moment that the first player accepts the bet and there is no guarantee that the second player will accept the bet too or even that it will play again, I implemented a deadline, after 15 minutes without getting any response from the opponent, the saved tokens would be released by the smart contract to the original owner. This lock was done using the current epoch time plus 600 seconds. The tokens would be released the next time that the player check his balance but it could be a different function made just for this.
• Another consideration was to include the ability to decline the bet, that would mean that all the variables related to the bet would be reset. This would allow to propose a new bet.