Add Login Feature

Features in this step

In this step, we'll add the following features in to the first "hello-world" boilerplate:

  • Login using Metamask.

  • Look up account balance.

  • Use faucet to get some TEA tokens for testing.

These features are the most common features for almost every TApp (the faucet only works in the local development environment, not on testnet or production). You may want to use the login branch as the boilerplate instead of the master branch because he master branch only has the "hello-world" example.

Switch to the login branch and test run

Run git checkout login to switch to the login branch.

Now you'll use what you've learned in previous steps to build and run the code on top of "dev-runner" and see how it works.

Build the actor in the sample-actor folder by running ./

Go to your local dev-runner folder and check that the local/b-node/sample-actor.wasm file is the most recent version.

total 9224
-rw-r--r--@ 1 kevinzhang  staff       85 Mar 10 12:29
-rwxr-xr-x@ 1 kevinzhang  staff  4118177 Mar 11 13:51 sample_actor.wasm

If the sample_actor.wasm file isn't recent, check if your build failed.

From the dev-runner repo root directory, run docker compose up. Make sure you wait about 2 minutes untill all actors are successfully activated.

In a different terminal window, go to the tutorial-v1 repo and cd sample-front-end. From this directory you can start the frontend:

npm install
npm start

Then start your browser go to http://localhost:3200/

You should see a page that looks like the following:

When you click the login button the Metamask popup opens prompting you to connect with Metamask:

Q: Why do I need to connect Metamask?

Answer: In Web3, there's no centralized account management system. That means you're the only person to control your account. No one else can disable, remove, or alter your account. Metamask is an Ethereum browser wallet. When you login, the Metamask is used to sign a txn (short for transaction) using your own private key. This signed txn will be verified by the backend then the code will know it's you who's logging in. As long as you do not leak your private key, there is no way for anyone else impersonating you to login. In the future steps, all layer1 (blockchain) related txn will need Metamask to sign.

After connecting Metamask to this URL, you can see your account and a login button showing in the right top corner. Clicking the login button will bring up the login box:

This is the login authorization box. It lists all the rights that the TApp wants you to authorize.

  • Move would allow this app to transfer your funds to other users.

  • In-app purchases allows the app to spend your funds in relation to in-app functions and assets.

  • Manage investments allows the app to buy / sell / transfer your token investments (i.e. those issued on a bonding curve).

  • Withdraw would allow to move your layer-2 TEA to layer-1 (Ethereum).

Click login again to bring up the Metamask login again. Please double check the message in the box and make sure it's what you selected to authorize in the login box. In our case, it's sig_consume.

Please pay attention on the message you're going to sign. In this case it's "sig". It's a placeholder for such a sample login. In other cases, this message has some real meaning, such as the authorization you give to the TApp. We'll get into more details in future steps.

After login, the UI jumps to the account profile page and shows your balance.

You can see you have a zero balance in your account. That's because everytime you start the dev-runner, the state will be reset to the init state.

You can click the Faucet button to get 1000 free test tokens in your account.

These are all the features we added to the login branch.

What happened under the hood?

After we built the sample-actor, a new sample-actor.wasm is copied to the dev-runner local/b-node folder. When we launch the dev-runner, the actor will be loaded into he TEA-runtime and activated. You should see something like the following in the log:

client-bob | [enclave] INFO host_main{enabled_clients=["adapter", "libp2p", "third-api", "http"] app_id=0 tea_id="0000000000000000000000000000000000000000000000000000000000000000" conn_id="12D3KooWPLns5y2qhcLFb6WCYhTiT7gXnx9ubfUhcgNV8rdjCfee"}: INFO activate sample actor successfully

This means the sample-actor is loaded and active. It's waiting for a request from the client.

Then we start the frontend and click the login button on the web page. The frontend generates a login message asking you to sign-in using Metamask. The signed message and login request is sent to the backend sample-actor to complete the login process. Once logged in, the frontend will receive an auth_key similar to a session key in web2. It's the proof that the user has logged in and will be attached for almost every future request. Once the login is completed, the frontend jumps to the account profile page.

The account profile page sends a query request to sample-actor for the account balance. After a few seconds, the response of the balance information is received by the frontend and shown in the UI. You should see 0 in the balance because it's a new test state.

When you click the "Faucet" button, a transfer request is sent to the backend. In the local dev-runner mode, a special logic allows anyone to transfer 1000 TEA from the DAO_RESERVE account for testing purposes. That's why you can get 1000 FREE TEA. Note that this won't happen in a non local dev-runner configuration. So you won't have such free gifts in Testnet or Production for sure.

Once the Faucet transfer has completed, you'll see your new 1000 TEA balance after the follow up balance query completes.

That's a recap of the steps that just happened. For more detailed information please see the code walkthrough articles in the sidebar.

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