Hello World Smart Contract

2025-02-21: Missing steps for lock and unlock

Requirements

• A Cup of Coffee

• The Aiken Hello World Example (You need to update the smart contract name to avoid getting the already exists message from Anvil API.)

  • The Smart Contract name should be in this format: your_org/hello-world

  • See the official documentation: Aiken Hello World

• An Anvil API Key (you can use the one provided in this document to access preprod)

• customer.json with 100ADA, you can use the CLI tool to generate the wallet, then send funds from the faucet to it. (Wallet CLI)

---

Objectives

Interact with any Smart Contracts using Anvil API

Objectives

• Upload Blueprint

• Deploy Smart Contract On-Chain

• Update/Delete Blueprint

• Hello World Lock & Unlock ADA

• Get a jsonSchema from your blueprint to get types for the language you use.

• See below for the code in one file (full.ts)

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Aiken Smart Contract

Smart Contract - Update Name

aiken.toml

name = "your-org/your-sc-name"
version = "0.0.0"
compiler = "v1.1.10"
plutus = "v3"
license = "Apache-2.0"
description = "Aiken contracts for project 'your-org/your-sc-name'"

[repository]
user = "your-org"
project = "your-sc-name"
platform = "github"

[[dependencies]]
name = "aiken-lang/stdlib"
version = "v2.2.0"
source = "github"

[config]

Helper Functions

Function to extract validator hashes from a blueprint

function getValidators(validators: typeof blueprint.validators) {
  return [...validators.reduce((a, b) => a.set(b.hash, b) && a, new Map<string, typeof blueprint.validators[number]>()).values()];
}

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Prerequisites

You need to load your Blueprint like this:

import blueprint from "./hello-world/plutus.json" with {type: "json"};

The wallet used in this guide is loaded like this:

You also need the CSL imports and Buffer for that to work, it is only the case when you are using the wallet in the backend.

import { Buffer } from "node:buffer";
import { FixedTransaction, PrivateKey } from "npm:@emurgo/[email protected]"; // only required due to signing in the backend.

import customer from "./customer.json" with {type: "json"}; // Optional, this guide is using this approach.

You can use any wallet, like the one in your browser or with weld, but to limit the external steps and streamline the flow. This guide uses the wallet directly in the backend. You can take a look at the signing transaction document to see how to use the browser wallet.

The api key used is this one:

const X_API_KEY = "testnet_EyrkvCWDZqjkfLSe1pxaF0hXxUcByHEhHuXIBjt9";

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Payload

To upload your validator on Anvil Backend

Benefit of doing so, will reduce the complexity and steps to interact with your smart contract. as it will be store directly in the backend. Your API Key is link with your Blueprint and will let you update and delete it if needed.

Deploy the Smart Contract On-Chain

const payload = {
  changeAddress: "addr_test...",
  message: "Smart contract deployed using anvil API",
  outputs: getValidators(blueprint.validators).map(validator => ({
    address: scriptAddresses[validator.hash],
    datum: {
      type: "script",
      hash: validator.hash
    }
  }))
}

• scriptAddresses:

  • Key = Validator Hash

  • Value = Address of the Smart Contract (Enterprise Address)

---

Steps

Step 1 - Upload Blueprint

Upload your blueprint (plutus.json) to Anvil Backend

Create Blueprint

const blueprintRegistration = await fetch("https://preprod.api.ada-anvil.app/v2/services/blueprints",
  {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      "x-api-key": X_API_KEY
    },
    body: JSON.stringify({
      blueprint
    })
  });

const uploadedBlueprint = await blueprintRegistration.json();
console.debug(JSON.stringify(uploadedBlueprint, null, 2))

const { scriptAddresses } = uploadedBlueprint;

• scriptAddresses: Needed for Step #2

This API Call is an upsert, so if you forget the scriptAddresses or need to update your blueprint, you can reuse the same call.

Tip: Once registered, if you need to update the name without changing the smart contract code or logic, you can safely delete the blueprint using the former name and then re-upload it.

Step 2 - Deploy Smart Contract

You need a valid Cardano wallet with some ADA on it (100ADA should be more than enough) Wallet CLI

Deploy the smart contract on-chain in order to get the reference UTXO

Payload to build the transaction:

const contract = {
  changeAddress: customer.base_address_preprod,
  message: "Smart contract deployed using anvil API",
  outputs: getValidators(blueprint.validators).map(validator => ({
    address: scriptAddresses[validator.hash],
    datum: {
      type: "script",
      hash: validator.hash,
    }
  })),
};

Create the transaction

const contractDeployed = await fetch(
  `https://preprod.api.ada-anvil.app/v2/services/transactions/build`,
  {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      "x-api-key": X_API_KEY
    },
    body: JSON.stringify(contract),
  }
);

const contractToDeployTransaction = await contractDeployed.json();
console.log(JSON.stringify(contractToDeployTransaction));

Sign and Submit the transaction

The signature process uses CSL for simplicity. For more information, see the Signing a Transaction guide.

// Sign the transaction using CSL.
const txToSubmitOnChain = FixedTransaction.from_bytes(
  Buffer.from(contractToDeployTransaction.complete, "hex")
);
txToSubmitOnChain.sign_and_add_vkey_signature(
  PrivateKey.from_bech32(customer.skey)
);

const urlSubmit = "https://preprod.api.ada-anvil.app/v2/services/transactions/submit";
const submitted = await fetch(urlSubmit, {
  method: "POST",
  body: JSON.stringify({
    signatures: [], // no signature required as it is part of the `txToSubmitOnChain`.
    transaction: txToSubmitOnChain.to_hex(),
  }),
  headers: {
    "Content-Type": "application/json",
    "X-Api-Key": X_API_KEY,
  },
});

const response = await submitted.json();
console.debug(response);

const { txHash } = response;

Step 3 - Link Blueprint and UTXO

Update blueprint to link references to deployed validators.

const response = await fetch(`https://preprod.api.ada-anvil.app/v2/services/blueprints`,
  {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      "x-api-key": X_API_KEY
    },
    body: JSON.stringify({
      blueprint,
      refs: getValidators(blueprint.validators).reduce((a, b, index) => {
        a[b.hash] = { txHash, index };
        return a;
      }, {} as Record<string, { txHash: string, index: number }>),
    })
  });

const updatedBlueprint = await response.json()
console.log(updatedBlueprint);

Conclusion

From here you have uploaded your blueprint and linked the reference UTXO on-chain and in Anvil Backend.

The next step is to interact with the hello-world Smart Contract (Lock & Unlock ADA)

---

Full Example

full.ts

import { Buffer } from "node:buffer";
import { FixedTransaction, PrivateKey } from "npm:@emurgo/[email protected]"; // only required due to signing in the backend.

import blueprint from "./plutus.json" with {type: "json"};
import customer from "./customer.json" with {type: "json"};

const X_API_KEY = "testnet_EyrkvCWDZqjkfLSe1pxaF0hXxUcByHEhHuXIBjt9";
const API_ENDPOINT = "https://preprod.api.ada-anvil.app/v2/services"

const headers = {
  "x-api-key": X_API_KEY,
  "Content-Type": "application/json",
};

function getValidators(validators: typeof blueprint.validators) {
  return [...validators.reduce((a, b) => a.set(b.hash, b) && a, new Map<string, typeof blueprint.validators[number]>()).values()];
}

const blueprintRegistration = await fetch(`${API_ENDPOINT}/blueprints`,
  {
    method: "POST",
    headers,
    body: JSON.stringify({ blueprint })
  });

const uploadedBlueprint = await blueprintRegistration.json();
console.debug("uploadedBlueprint", JSON.stringify(uploadedBlueprint, null, 2))

const { scriptAddresses } = uploadedBlueprint;

const contract = {
  changeAddress: customer.base_address_preprod,
  message: "Smart contract deployed using anvil API",
  outputs: getValidators(blueprint.validators).map(validator => ({
    address: scriptAddresses[validator.hash],
    datum: {
      type: "script",
      hash: validator.hash,
    }
  })),
};

const contractDeployed = await fetch(
  `${API_ENDPOINT}/transactions/build`,
  {
    method: "POST",
    headers,
    body: JSON.stringify(contract),
  }
);

const contractToDeployTransaction = await contractDeployed.json();
console.log("contractToDeployTransaction", JSON.stringify(contractToDeployTransaction));

// Sign the transaction using CSL.
const txToSubmitOnChain = FixedTransaction.from_bytes(
  Buffer.from(contractToDeployTransaction.complete, "hex")
);
txToSubmitOnChain.sign_and_add_vkey_signature(
  PrivateKey.from_bech32(customer.skey)
);

console.log(txToSubmitOnChain.transaction_hash().to_hex());

const urlSubmit = `${API_ENDPOINT}/transactions/submit`;
const submitted = await fetch(urlSubmit, {
  method: "POST",
  body: JSON.stringify({
    signatures: [], // no signature required as it is part of the `txToSubmitOnChain`.
    transaction: txToSubmitOnChain.to_hex(),
  }),
  headers,
});

const response = await submitted.json();
console.debug("response", response);

const { txHash } = response;

const linkBlueprintAndTxHash = await fetch(`${API_ENDPOINT}/blueprints`,
  {
    method: "POST",
    headers,
    body: JSON.stringify({
      blueprint,
      refs: getValidators(blueprint.validators).reduce((a, b, index) => {
        a[b.hash] = { txHash, index };
        return a;
      }, {} as Record<string, { txHash: string, index: number }>),
    })
  });

const updatedBlueprint = await linkBlueprintAndTxHash.json()
console.log("updatedBlueprint", updatedBlueprint);

---

Usage (Hello World Lock/Unlock)

Lock Funds

Payload

TODO: Explain the JSON below

const input = {
  changeAddress: customer.base_address_preprod,
  message: "Locking my fortune using anvil API",
  outputs: [
    {
      address: await getScriptAddr(hash), // script address of the first validator
      lovelace: 2_000_000, // 1 ADA = 1_000_000 Lovelace
      datum: {
        type: "inline",
        value: {
          owner: customer.key_hash // Only the Customer will be able to unlock the funds
        },
        shape: {
          validatorHash: hash,
          purpose: "spend"
        }
      }
    }
  ],
};

Unlock Funds

Payload

TODO: Explain the JSON below

const input = {
  changeAddress: customer.base_address_preprod,
  message: "Unlock my fortune using anvil API",
  scriptInteractions: [
    {
      hash,
      purpose: "spend",
      // This Output ref and index is the UTXO locked at the previous step.
      outputRef: {
        txHash: "7ac8f6922d51ffe2980e73c57c985b3906795440b5a565cc8806899dc88b110e", // ACTION: Replace with your txHash
        index: 0, // ACTION: Replace with you index
      },
      redeemer: { // Aka. Smart contract Parameters
        type: "json",
        value: {
          msg: Buffer.from("Bonjour Monde!!", "utf8").toString("hex") // ACTION: Replace with your String
        }
      }
    }
  ],
  requiredSigners: [customer.key_hash], // Aka. extra_signatories
};

Full Example - Lock Fund

lock.ts

import { Buffer } from "node:buffer";
import {
  FixedTransaction,
  PrivateKey
} from "npm:@emurgo/[email protected]";

import blueprint from "./hello-world/plutus.json" with {type: "json"}; // NOTE: You only need the hash.
import customer from "./customer.json" with {type: "json"};

const X_API_KEY = "testnet_EyrkvCWDZqjkfLSe1pxaF0hXxUcByHEhHuXIBjt9";

// Save the hash in your database or backend.
// You are gonna need this hash everytime you need to interact with the smart contract.
// In this example we are loading it from the blueprint, but you do not need the blueprint.
const hash = blueprint.validators[0].hash;

async function getScriptAddr(hash: string): Promise<string> {
  const response = await fetch(`https://preprod.api.ada-anvil.app/v2/services/validators/${hash}/address`, {
    method: "GET",
    headers: {
      "x-api-key": X_API_KEY
    },
  });

  const scriptAddress = await response.json();
  console.debug("scriptAddress", scriptAddress)
  return scriptAddress.hex as string;
}

// Send 2 ADA to the Smart Contract (Lock ADA)
const input = {
  changeAddress: customer.base_address_preprod,
  message: "Locking my fortune using anvil API",
  outputs: [
    {
      address: await getScriptAddr(hash), // script address of the first validator
      lovelace: 2_000_000, // 1 ADA = 1_000_000 Lovelace
      datum: {
        type: "inline",
        value: {
          owner: customer.key_hash // Only the Customer will be able to unlock the funds
        },
        shape: {
          validatorHash: hash,
          purpose: "spend"
        }
      }
    }
  ],
};

const response = await fetch(
  `https://preprod.api.ada-anvil.app/v2/services/transactions/build`,
  {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      "x-api-key": X_API_KEY
    },
    body: JSON.stringify(input),
  }
);

const result = await response.json()
console.log("result", result);
const txToSign = result.complete;

// Sign transaction directly in the backend
const txToSubmitOnChain = FixedTransaction.from_bytes(
  Buffer.from(txToSign, "hex")
);
// This sign the tx and add vkeys to the txToSubmitOnChain, so in submit we don't need to provide signatures
txToSubmitOnChain.sign_and_add_vkey_signature(
  PrivateKey.from_bech32(customer.skey)
);


const urlSubmit = "https://preprod.api.ada-anvil.app/v2/services/transactions/submit";
const submitted = await fetch(urlSubmit, {
  method: "POST",
  body: JSON.stringify({
    signatures: [],
    transaction: txToSubmitOnChain.to_hex(),
  }),
  headers: {
    "Content-Type": "application/json",
    "X-Api-Key": X_API_KEY,
  },
});

const submittedResponse = await submitted.json();
console.debug("submittedResponse", submittedResponse);

Full Example - Unlock Fund

unlock.ts

import { Buffer } from "node:buffer";
import { FixedTransaction, PrivateKey } from "npm:@emurgo/[email protected]"; // update utilities doc.

import blueprint from "./hello-world/plutus.json" with {type: "json"}; // NOTE: You only need the hash.
import customer from "./customer.json" with {type: "json"};

const X_API_KEY = "testnet_EyrkvCWDZqjkfLSe1pxaF0hXxUcByHEhHuXIBjt9";

// Save the hash in your database or backend.
// You are gonna need this hash everytime you need to interact with the smart contract.
// In this example we are loading it from the blueprint, but you do not need the blueprint.
const hash = blueprint.validators[0].hash;

const input = {
  changeAddress: customer.base_address_preprod,
  message: "Unlock my fortune using anvil API",
  scriptInteractions: [
    {
      hash,
      purpose: "spend",
      // This Output ref and index is the UTXO locked at the previous step.
      outputRef: {
        txHash: "7ac8f6922d51ffe2980e73c57c985b3906795440b5a565cc8806899dc88b110e", // ACTION: Replace with your txHash
        index: 0, // ACTION: Replace with you index
      },
      redeemer: { // Aka. Smart contract Parameters
        type: "json",
        value: {
          msg: Buffer.from("Bonjour Monde!!", "utf8").toString("hex") // ACTION: Replace with your String
        }
      }
    }
  ],
  requiredSigners: [customer.key_hash], // Aka. extra_signatories
};

const response = await fetch(
  `https://preprod.api.ada-anvil.app/v2/services/transactions/build`,
  {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      "x-api-key": X_API_KEY
    },
    body: JSON.stringify(input),
  }
);


const result = await response.json()
console.log("result", result);
const txToSign = result.complete;

// Sign transaction directly in the backend
const txToSubmitOnChain = FixedTransaction.from_bytes(
  Buffer.from(txToSign, "hex")
);
// This sign the tx and add vkeys to the txToSubmitOnChain, so in submit we don't need to provide signautres
txToSubmitOnChain.sign_and_add_vkey_signature(
  PrivateKey.from_bech32(customer.skey)
);

const urlSubmit = "https://preprod.api.ada-anvil.app/v2/services/transactions/submit";
const submitted = await fetch(urlSubmit, {
  method: "POST",
  body: JSON.stringify({
    signatures: [], // no signature required as it is part of the `txToSubmitOnChain`.
    transaction: txToSubmitOnChain.to_hex(),
  }),
  headers: {
    "Content-Type": "application/json",
    "X-Api-Key": X_API_KEY,
  },
})

const submittedResponse = await submitted.json();
console.debug("submittedResponse", submittedResponse);

---