Skip to main content

IC-POS

IC-POS is an experimental app to demonstrate a real-world use case for ckBTC on the Internet Computer. It is a simple Point of Sale app that allows users to accept ckBTC payments.

The Internet Computer integrates directly with the Bitcoin network. This allows canisters on the Internet Computer to receive, hold, and send Bitcoin, all directly with transactions on the Bitcoin network. Chain-key Bitcoin (ckBTC) is an ICRC-1-compliant token that is backed 1:1 by Bitcoin and held 100% on the ICP mainnet.

For deeper understanding of the ICP < > BTC integration, see the IC wiki article on Bitcoin integration.

Features​

  • Create store: Users log in with their Internet Identity and configure the store with a name and other settings.
  • Charge customer: Users can charge a customer by entering an amount. This will generate and display a QR code for the customer to scan and pay. QR code follows the ICRC-22 standard.
  • Send tokens: Users can send ckBTC tokens to other users.
  • Receive notifications: Users can choose to receive notifications by email or SMS when a payment is received. This uses the HTTP Outcall feature of the Internet Computer.
  • Transaction history: Users can view a list of transactions made to the store.

Try it!​

IC-POS is deployed on the Internet Computer. You can try it out here:

https://hngac-6aaaa-aaaal-qb6tq-cai.icp0.io

Note: The live version of IC-POS uses real ckBTC tokens. To test, use only fractions of a token to avoid losing funds.

Architecture​

Backend​

The backend is written in Motoko and consists of one canister, icpos. It exposes five public methods:

  • getMerchant - returns the store configuration for a given principal.
  • updateMerchant - updates the store configuration for a given principal.
  • setCourierApiKey - sets the Courier API key used to send email and SMS notifications. Only the canister controller can call this method.
  • setLedgerId - xsets the ledger ID to monitor for transactions. Only the canister controller can call this method.
  • getLogs - The canister maintains a debug log that can be fetched using this method.

In addition to the public methods, the canister uses a timer to monitor ledger transactions. When a new transaction is found that matches a configured store – depending on the store settings – the canister will send a notification either by email or SMS.

Frontend​

The frontend is written in Typescript/Vite/React/TailwindCSS. Users authenticate using the Internet Identity to access their store. The first time a user logs in, a store is created for them.

The frontend interacts with the following IC canisters:

  • icpos - to fetch and update store configuration.
  • ckbtc ledger - to send ckBTC to other users.
  • ckbtc index - to fetch transaction history.
  • internet identity - to authenticate users.

Setup, dev environment​

Pre-requisites:

Deploy using script​

To get started quickly and deploy the IC-POS app locally, you can run a deploy script. This script will start a local replica, deploy the necessary canisters, and build and deploy the frontend.

bash ./scripts/deploy.sh

Once the script has finished, you should proceed to step 10 to create a store and mint yourself some test tokens.

Deploy manually​

1. Clone the examples repository and navigate to the IC-POS project:​

git clone https://github.com/dfinity/examples
cd examples/motoko/ic-pos

2. Start a local instance of the replica:​

dfx start --clean --background

3. Deploy the Internet Identity canister:​

Integration with the Internet Identity allows store owners to securely setup and manage their store. The Internet Identity canister is already deployed on the IC mainnet. For local development, you need to deploy it to your local instance of the IC.

dfx deploy internet_identity

4. Save the current principal as a variable:​

The principal will be used when deploying the ledger canister.

export OWNER=$(dfx identity get-principal)

5. Deploy the ckBTC ledger canister:​

The responsibilities of the ledger canister is to keep track of token balances and handle token transfers.

The ckBTC ledger canister is already deployed on the IC mainnet. ckBTC implements the ICRC-1 token standard. For local development, we deploy the ledger for an ICRC-1 token mimicking the mainnet setup.

Take a moment to read the details of the call we are making below. Not only are we deploying the ledger canister, we are also:

  • Deploying the canister to the same canister ID as the mainnet ledger canister. This is to make it easier to switch between local and mainnet deployments.
  • Naming the token Local ckBTC / LCKBTC
  • Setting the owner principal to the principal we saved in the previous step.
  • Minting 100_000_000_000 tokens to the owner principal.
  • Setting the transfer fee to 10 LCKBTC.
dfx deploy icrc1_ledger --argument '
  (variant {
    Init = record {
      token_name = "Local ckBTC";
      token_symbol = "LCKBTC";
      minting_account = record {
        owner = principal "'${OWNER}'";
      };
      initial_balances = vec {
        record {
          record {
            owner = principal "'${OWNER}'";
          };
          100_000_000_000;
        };
      };
      metadata = vec {};
      transfer_fee = 10;
      archive_options = record {
        trigger_threshold = 2000;
        num_blocks_to_archive = 1000;
        controller_id = principal "'${OWNER}'";
      }
    }
  })
'

6. Deploy the index canister​

The index canister syncs the ledger transactions and indexes them by account.

dfx deploy icrc1_index --argument '
  record {
   ledger_id = (principal "mxzaz-hqaaa-aaaar-qaada-cai");
  }
'

7. Deploy the icpos canister​

The icpos canister manages the store configuration and sends notifications when a payment is received.

The --argument '(0)' argument is used to initialize the canister with startBlock set to 0. This is used to tell the canister to start monitoring the ledger from block 0. When deploying to the IC mainnet, this should be set to the current block height to prevent the canister from processing old transactions.

dfx deploy icpos --argument '(0)'

8. Configure the icpos canister​

IC-POS uses Courier to send email and SMS notifications. If you want to enable notifications, you need to sign up for a Courier account and and create and API key. Then issue the following command:

dfx canister call icpos setCourierApiKey "pk_prod_..."

9. Build and run the frontend​

Run npm to install dependencies and start a development version of the frontend. 

pnpm install
pnpm run dev

The app should now be accessible at a local url, typically http://localhost:5173.

10. Make a transfer!​

Now that everything is up and running, you can make a transfer to your newly created store.

The easiest way to do this is to create two stores using two different Internet Identity accounts, using two different web browsers. Then, transfer some tokens from one store to the other.

10.1 Create the first store and supply it with some tokens​

Log in to the frontend using the Internet Identity. Configure the store with a name and then, on the main store page, click on the principal pill to copy the address to your clipboard. Using the dfx command, now mint some tokens from your owner principal to the store principal.

dfx canister call icrc1_ledger icrc1_transfer '
  (record {
    to=(record {
      owner=(principal "[STORE PRINCIPAL 1 HERE]")
    });
    amount=100_000
  })
'

10.2 Create the second store​

Log in to the frontend using a new Internet Identity using another web browser. Give this store a name as well and copy the store principal like in the previous step.

Now, go back to the first browser/store, navigate to the Send page, and transfer some tokens to the second store.

If everything is working, you should see a notification in the second store.

🎉

Possible improvements​

  • Show more information about transactions.
    • A transaction detail page.
    • Pagination, currently only the first 5 transactions are shown.
  • Show a confirmation dialog after the user clicks on the Send button.

Contributing​

Contributions are welcome! Please open an issue or submit a pull request.

Author​

License​

MIT