> ## Documentation Index
> Fetch the complete documentation index at: https://docs.qu.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Deploy with Solidity

> A guide to deploying a simple single-chain smart contract on Quai Network.

## Introduction

This article shows how to deploy a Solidity smart contract using Hardhat on any of Quai Network's chains.

## Prerequisites

To deploy single chain smart contracts on Quai, we'll need a few tool-kits and dependencies. Here's an overview of all of the dependencies we'll be using:

|                                                                               |                                                                              |
| ----------------------------------------------------------------------------- | ---------------------------------------------------------------------------- |
| [**NodeJS**](https://nodejs.org/en/download/)                                 | Javascript runtime environment. Use the LTS version.                         |
| [**hardhat-example**](https://github.com/dominant-strategies/hardhat-example) | A Hardhat project with sample contracts and deploy scripts for Quai Network. |
| [**Quais.js**](https://www.npmjs.com/package/quais)                           | A JavaScript library for interacting with Quai Network.                      |

## Environment Setup

### Install Example Repository

Start by cloning the `hardhat-example` repository, navigating to the `Solidity` directory we'll be using for this tutorial, and installing the dependencies via `npm`.

```bash theme={null}
git clone https://github.com/dominant-strategies/hardhat-example.git
cd hardhat-example/Solidity
npm install
```

### Smart Contracts

The `Solidity/` directory comes with 2 sample contracts: `ERC20.sol` and `ERC721.sol` inside of the `contracts/` directory. Both contracts are implementations derived from the [Open Zeppelin library](https://www.openzeppelin.com/contracts).

We'll be using the `ERC20.sol` sample contract for this tutorial, but you can also add your own contracts or use contracts from other libraries.

<Warning>
  The Quai Network EVM supports Solidity versions up to 0.8.20. Using a newer
  version of Solidity may result in errors when deploying smart contracts.
</Warning>

### Environment Variables

We've included a sample environment file, `.env.dist`, file at the root of the `hardhat-example` repo to manage token details, private keys, and your RPC URL in a secure fashion.

<Note>
  The `.env.dist` file is a template file and should not be used as is. You should copy the `.env.dist` file to a new `.env` file.

  This file lives at the root of the `hardhat-example` repository and serves as the config file for the `Solidity/` directory.
</Note>

Copy the `.env.dist` file in the root to a new `.env` file in the repository root using the following command:

```bash theme={null}
cp ../.env.dist ../.env
```

Open the `.env` file and add your private keys, RPC URLs, and token args for the contract you'd like to deploy. The `.env` file should look like this:

```bash .env theme={null}
# Unique Privkey for each deployment address
CYPRUS1_PK="0x3700000000000000000000000000000000000000000000000000000000000000" # pubkey starting with 0x00
CYPRUS2_PK="0x9400000000000000000000000000000000000000000000000000000000000000" # pubkey starting with 0x01
...more priv keys

# Chain ID (local: 1337, testnet and devnet: 9000)
CHAIN_ID="9000"

# RPC endpoint
RPC_URL="https://rpc.quai.network"

# Token Arguments
...more token args
```

<Note>
  The `PK` values must all be for unique addresses and correspond to the zone
  name, i.e. your `CYPRUS1_PK` should be the private key of your Cyprus1
  address.
</Note>

Further information on RPC endpoints can be found in the [local network specifications](/build/networks#local-network) section for **local nodes** and the [devnet specifications](/build/networks#devnet) section for **remote nodes**.

The `hardhat-example` repository uses the [Quais SDK](/sdk/introduction) to configure network connections using only a single RPC URL. To learn more about how the SDK configures network providers, visit the [SDK provider examples](/sdk/static/provider) section.

After filling in your private keys, RPC URL, we're now ready to securely consume them inside of `hardhat.config.js`.

### Hardhat Configuration

Hardhat uses a `hardhat.config.js` file to configure smart contract deployments. The config file allows you to define deployment networks, tasks, compilers, etc.

`hardhat-example` contains a prebuilt `hardhat.config.js` file with configurations for deploying and verifying smart contracts on any shard in the network.

<Accordion title="Sample hardhat configuration file" icon="file" iconType="solid">
  This sample configuration file is provided as part of the `hardhat-example` repository.

  ```javascript hardhat.config.js theme={null}
  /**
   * @type import('hardhat/config').HardhatUserConfig
   */

  require("@nomicfoundation/hardhat-toolbox");
  require("@quai/hardhat-deploy-metadata");
  const dotenv = require("dotenv");
  dotenv.config({ path: "../.env" });

  const rpcUrl = process.env.RPC_URL;
  const chainId = Number(process.env.CHAIN_ID);

  module.exports = {
    defaultNetwork: "cyprus1",
    networks: {
      cyprus1: {
        url: rpcUrl,
        accounts: [process.env.CYPRUS1_PK],
        chainId: chainId,
      },
      cyprus2: {
        url: rpcUrl,
        accounts: [process.env.CYPRUS2_PK],
        chainId: chainId,
      },
      ...more networks
    },

    solidity: {
      version: "0.8.20",
      settings: {
        optimizer: {
          enabled: true,
          runs: 1000,
        },
      },
    },
  };
  ```

  <Warning>
    The Golden Age devnet currently supports Cyprus 1 and 2. All other shards are not running in the current network configuration.
  </Warning>

  Inside the config file you can find deployment and verification definitions for:

  * `cyprus1`
  * `cyprus2`
  * `cyprus3`
  * `paxos1`
  * `paxos2`
  * `paxos3`
  * `hydra1`
  * `hydra2`
  * `hydra3`
</Accordion>

When deploying or verifying a contract, `hardhat.config.js` will pull your private keys and RPC URL from the `.env` file and use them to deploy and verify your contracts. You can also specify the Solidity version and compiler settings in the `solidity` object.

## Deploy and Interact

<Steps>
  <Step title="Compile with Hardhat">
    Smart contract compilation with Hardhat is simple and can be done using `npx` in the CLI.

    Compile all of the contracts inside the `contracts/` directory with:

    ```bash theme={null}
    npx hardhat compile
    ```

    Which should output:

    ```bash theme={null}
    Downloading compiler 0.8.20

    Compiled 2 Solidity files successfully
    ```
  </Step>

  <Step title="Configure deployment scripts">
    Inside the `scripts/` directory, you'll find a deploy script for both the ERC20 and ERC721 contracts: `deployERC20.js` and `deployERC721.js`. For this tutorial, we'll be deploying an ERC20 contract.

    The `deployERC20.js` script pulls your network configuration from `hardhat.config.js` and your token arguments from the `.env` file at the root of the repository and uses them to deploy your contract.

    Token arguments are consumed via the `tokenArgs` array:

    ```js theme={null}
    const tokenArgs = [process.env.ERC20_NAME, process.env.ERC20_SYMBOL, quais.parseUnits(process.env.ERC20_INITIALSUPPLY)]
    ```

    Your specified network configuration and deployment account is consumed inside of the `provider` and `wallet` variables in tandem with the compiled contract ABI and bytecode to create a new contract instance:

    ```js theme={null}
    const provider = new quais.JsonRpcProvider(hre.network.config.url, undefined, { usePathing: true })
    const wallet = new quais.Wallet(hre.network.config.accounts[0], provider)
    const ERC20 = new quais.ContractFactory(ERC20Json.abi, ERC20Json.bytecode, wallet)
    ```

    We'll use these ideas to properly modify the token args and network specification to deploy our contract in the next step.

    <Tip>
      The `deployERC721.js` script functions in a similar manner, but with different contract arguments and a different contract ABI and
      bytecode. You can replicate this configuration for any contract you'd like to deploy.
    </Tip>
  </Step>

  <Step title="Deploy your contract">
    The deploy script takes in a `--network` flag to specify the network you'd like to deploy to (available options can be found [here](#hardhat-configuration)). For this tutorial, we'll be deploying to `cyprus1`.

    ```bash theme={null}
    npx hardhat run scripts/deployERC20.js --network cyprus1
    ```

    Which should output:

    ```bash theme={null}
    Transaction broadcasted: 0x235fdeb85db5b6cee8da9780e2246907e8342751849f5ce3514847a5dffd916f
    Contract deployed to:  0x00735E9B2c731Fd3eCC8129a3653ACb99dF969cC
    ```

    Congratulations, you've now deployed a ERC20 token to Quai Network!

    <Warning>
      The `ERC20.sol` and `ERC721.sol` sample contracts are basic implementations of each token for example purposes. It is highly recommended
      to modify these contracts to fit your specific use case before deploying them for any production use.
    </Warning>
  </Step>

  <Step title="Interact with the contract">
    Hardhat console does not currently offer support for interaction with smart contracts on Quai Network.

    To interact with the contract, you can configure a simple script using the [Quais SDK](/sdk/static/contract). The script below configures a [Contract](/sdk/content/classes/Contract) instance for the ERC20 token we deployed to `0x00735E9B2c731Fd3eCC8129a3653ACb99dF969cC` to get the name, symbol, and total supply of the token.

    ```javascript getContractDetails.js theme={null}
    const quais = require('quais')
    const ERC20Json = require('../artifacts/contracts/ERC20.sol/TestERC20.json')

    async function getContractDetails() {
      // Config provider, wallet, and contract factory
      const provider = new quais.JsonRpcProvider(hre.network.config.url, undefined, { usePathing: true })
      const wallet = new quais.Wallet(hre.network.config.accounts[0], provider)
      const ERC20 = new quais.Contract("0x00735E9B2c731Fd3eCC8129a3653ACb99dF969cC", ERC20Json.abi, wallet)

      const tokenName = await ERC20.name()
      const tokenSymbol = await ERC20.symbol()
      const tokenDecimals = await ERC20.decimals()
      const tokenTotalSupply = await ERC20.totalSupply()
    }

    getContractDetails()
      .then(() => process.exit(0))
      .catch((error) => {
        console.error(error)
        process.exit(1)
      })
    ```
  </Step>
</Steps>

## Summary

Now you have all the tools you need to create a simple Hardhat project, deploy, and interact with your own smart contracts.