🚩 Challenge 1: 🥩 Decentralized Staking App

🦸 A superpower of Ethereum is allowing you, the builder, to create a simple set of rules that an adversarial group of players can use to work together. In this challenge, you create a decentralized application where users can coordinate a group funding effort. If the users cooperate, the money is collected in a second smart contract. If they defect, the worst that can happen is everyone gets their money back. The users only have to trust the code.

🏦 Build a Staker.sol contract that collects ETH from numerous addresses using a payable stake() function and keeps track of balances. After some deadline if it has at least some threshold of ETH, it sends it to an ExampleExternalContract and triggers the complete() action sending the full balance. If not enough ETH is collected, allow users to withdraw().

🎛 Building the frontend to display the information and UI is just as important as writing the contract. The goal is to deploy the contract and the app to allow anyone to stake using your app. Use a Stake(address,uint256) event to list all stakes.

🌟 The final deliverable is deploying a Dapp that lets users send ether to a contract and stake if the conditions are met, then yarn vercel your app to a public webserver. Submit the url on SpeedRunEthereum.com!

💬 Meet other builders working on this challenge and get help in the Challenge 1 Telegram!

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Checkpoint 0: 📦 Environment 📚

Before you begin, you need to install the following tools:

• Node (v18 LTS)
• Yarn (v1 or v2+)
• Git

Then download the challenge to your computer and install dependencies by running:

git clone https://github.com/scaffold-eth/se-2-challenges.git challenge-1-decentralized-staking
cd challenge-1-decentralized-staking
git checkout challenge-1-decentralized-staking
yarn install

in the same terminal, start your local network (a blockchain emulator in your computer):

yarn chain

in a second terminal window, 🛰 deploy your contract (locally):

cd challenge-1-decentralized-staking
yarn deploy

in a third terminal window, start your 📱 frontend:

cd challenge-1-decentralized-staking
yarn start

📱 Open http://localhost:3000 to see the app.

👩‍💻 Rerun yarn deploy --reset whenever you want to deploy new contracts to the frontend, update your current contracts with changes, or re-deploy it to get a fresh contract address.

🔏 Now you are ready to edit your smart contract Staker.sol in packages/hardhat/contracts

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Checkpoint 1: 🥩 Staking 💵

You'll need to track individual balances using a mapping:

mapping ( address => uint256 ) public balances;

And also track a constant threshold at 1 ether

uint256 public constant threshold = 1 ether;

👩‍💻 Write your stake() function and test it with the Debug Contracts tab in the frontend.

💸 Need more funds from the faucet? Click on "Grab funds from faucet", or use the Faucet feature at the bottom left of the page to get as much as you need!

✏ Need to troubleshoot your code? If you import hardhat/console.sol to your contract, you can call console.log() right in your Solidity code. The output will appear in your yarn chain terminal.

🥅 Goals

• Do you see the balance of the Staker contract go up when you stake()?

• Is your balance correctly tracked?

• Do you see the events in the Stake Events tab?

  

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Checkpoint 2: 🔬 State Machine / Timing ⏱

State Machine

⚙️ Think of your smart contract like a state machine. First, there is a stake period. Then, if you have gathered the threshold worth of ETH, there is a success state. Or, we go into a withdraw state to let users withdraw their funds.

Set a deadline of block.timestamp + 30 seconds

uint256 public deadline = block.timestamp + 30 seconds;

👨‍🏫 Smart contracts can't execute automatically, you always need to have a transaction execute to change state. Because of this, you will need to have an execute() function that anyone can call, just once, after the deadline has expired.

👩‍💻 Write your execute() function and test it with the Debug Contracts tab

Check the ExampleExternalContract.sol for the bool you can use to test if it has been completed or not. But do not edit the ExampleExternalContract.sol as it can slow the auto grading.

If the address(this).balance of the contract is over the threshold by the deadline, you will want to call: exampleExternalContract.complete{value: address(this).balance}()

If the balance is less than the threshold, you want to set a openForWithdraw bool to true which will allow users to withdraw() their funds.

Timing

You'll have 30 seconds after deploying until the deadline is reached, you can adjust this in the contract.

👩‍💻 Create a timeLeft() function including public view returns (uint256) that returns how much time is left.

⚠️ Be careful! If block.timestamp >= deadline you want to return 0;

⏳ "Time Left" will only update if a transaction occurs. You can see the time update by getting funds from the faucet button in navbar just to trigger a new block.

👩‍💻 You can call yarn deploy --reset any time you want a fresh contract, it will get re-deployed even if there are no changes on it.
You may need it when you want to reload the "Time Left" of your tests.

Your Staker UI tab should be almost done and working at this point.

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🥅 Goals

• Can you see timeLeft counting down in the Staker UI tab when you trigger a transaction with the faucet button?
• If enough ETH is staked by the deadline, does your execute() function correctly call complete() and stake the ETH?
• If the threshold isn't met by the deadline, are you able to withdraw() your funds?

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Checkpoint 3: 💵 Receive Function / UX 🙎

🎀 To improve the user experience, set your contract up so it accepts ETH sent to it and calls stake(). You will use what is called the receive() function.

Use the receive() function in solidity to "catch" ETH sent to the contract and call stake() to update balances.

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🥅 Goals

• If you send ETH directly to the contract address does it update your balance and the balance of the contract?

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⚔️ Side Quests

• Can execute() get called more than once, and is that okay?
• Can you stake and withdraw freely after the deadline, and is that okay?
• What are other implications of anyone being able to withdraw for someone?

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🐸 It's a trap!

• Make sure funds can't get trapped in the contract! Try sending funds after you have executed! What happens?
• Try to create a modifier called notCompleted. It will check that ExampleExternalContract is not completed yet. Use it to protect your execute and withdraw functions.

⚠️ Test it!

• Now is a good time to run yarn test to run the automated testing function. It will test that you hit the core checkpoints. You are looking for all green checkmarks and passing tests!

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Checkpoint 4: 💾 Deploy your contract! 🛰

📡 Edit the defaultNetwork to your choice of public EVM networks in packages/hardhat/hardhat.config.ts

🔐 You will need to generate a deployer address using yarn generate This creates a mnemonic and saves it locally.

👩‍🚀 Use yarn account to view your deployer account balances.

⛽️ You will need to send ETH to your deployer address with your wallet, or get it from a public faucet of your chosen network.

📝 If you plan on submitting this challenge, be sure to set your deadline to at least block.timestamp + 72 hours

🚀 Run yarn deploy to deploy your smart contract to a public network (selected in hardhat.config.ts)

💬 Hint: You can set the defaultNetwork in hardhat.config.ts to sepolia OR you can yarn deploy --network sepolia.

💬 Hint: For faster loading of your "Stake Events" page, consider updating the fromBlock passed to useScaffoldEventHistory in packages/nextjs/pages/stakings.tsx to blocknumber - 10 at which your contract was deployed. Example: fromBlock: 3750241.

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Checkpoint 5: 🚢 Ship your frontend! 🚁

✏️ Edit your frontend config in packages/nextjs/scaffold.config.ts to change the targetNetwork to chains.sepolia or any other public network.

💻 View your frontend at http://localhost:3000/stakerUI and verify you see the correct network.

📡 When you are ready to ship the frontend app...

📦 Run yarn vercel to package up your frontend and deploy.

Follow the steps to deploy to Vercel. Once you log in (email, github, etc), the default options should work. It'll give you a public URL.

If you want to redeploy to the same production URL you can run yarn vercel --prod. If you omit the --prod flag it will deploy it to a preview/test URL.

🦊 Since we have deployed to a public testnet, you will now need to connect using a wallet you own or a burner wallet. By default 🔥 burner wallets are only available on hardhat . You can enable them on every chain by setting onlyLocal : false inside burnerWallet in your frontend config (scaffold.config.ts in packages/nextjs/scaffold.config.ts)

Configuration of Third-Party Services for Production-Grade Apps.

By default, 🏗 Scaffold-ETH 2 provides predefined API keys for popular services such as Alchemy and Etherscan. This allows you to begin developing and testing your applications more easily, avoiding the need to register for these services.
This is great to complete your SpeedRunEthereum.

For production-grade applications, it's recommended to obtain your own API keys (to prevent rate limiting issues). You can configure these at:

• 🔷ALCHEMY_API_KEY variable in packages/hardhat/.env and packages/nextjs/.env.local. You can create API keys from the Alchemy dashboard.

• 📃ETHERSCAN_API_KEY variable in packages/hardhat/.env with your generated API key. You can get your key here.

💬 Hint: It's recommended to store env's for nextjs in Vercel/system env config for live apps and use .env.local for local testing.

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Checkpoint 6: 📜 Contract Verification

Run the yarn verify --network your_network command to verify your contracts on etherscan 🛰

👉 Search this address on Etherscan to get the URL you submit to 🏃‍♀️SpeedRunEthereum.com.

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🏃 Head to your next challenge here.

💬 Problems, questions, comments on the stack? Post them to the 🏗 scaffold-eth developers chat