This repo contains a simple ERC-20 faucet dApp that will distribute a ERC-20 token called TestToken to whomever interacts with the dApp.

The intention of this dApp is to showcase how to build a simple dApp on Harmony.

This repo contains two implementation contracts: TestToken.sol and Faucet.sol.

Solidity 0.6.12 is used as the compiler for these contracts, primarily due to @openzeppelin's dependency on pragma solidity ^0.6.0;.

Deployment of these contracts can be done using either Truffle or @harmony-js/core (more on this later).

TestToken.sol is a simple ERC-20 token that is implemented using @openzeppelin's smart contract suite. The token contract will automatically mint 100,000,000 tokens when deployed.

Faucet.sol is the actual faucet contract. It's a configurable contract that can be deployed for any ERC-20 token and the amount as well as the frequency for requesting funds from the faucet can be configured.

As previously mentioned smart contracts can be deployed using Truffle or @harmony-js/core. If you're used to Truffle deployments you can continue to use that for deploying smart contracts on Harmony as well.

@harmony-js/core can be used to perform more advanced and custom deployments.

This repository contains examples for deploying contracts using both methods. Harmony also has a fork of the Remix IDE which is available here.

Both deployment methods in this repository depend on a .env file being populated with a correct private key for a deployer wallet on each respective network. If you intend to use the same deployer wallet for all networks (localnet, testnet & mainnet), you can use the same private key for all these three separate networks.

A .env-example file is included in this repository by default, copy it to .env and add the private keys you intend to use to perform smart contract deployments on Harmony.

In order to deploy the smart contracts you need to add a custom provider in truffle-config.js:

require('dotenv').config()
const { TruffleProvider } = require('@harmony-js/core')

module.exports = {
  networks: {
    testnet: {
      network_id: '2',
      provider: () => {
        const truffleProvider = new TruffleProvider(
          process.env.TESTNET_URL,
          { },
          { shardID: 0, chainId: 2 },
          { gasLimit: process.env.GAS_LIMIT, gasPrice: process.env.GAS_PRICE},
        );
        const newAcc = truffleProvider.addByPrivateKey(process.env.TESTNET_PRIVATE_KEY);
        truffleProvider.setSigner(newAcc);
        return truffleProvider;
      },
    },
    mainnet: {
      network_id: '1',
      provider: () => {
        const truffleProvider = new TruffleProvider(
          process.env.MAINNET_URL,
          { },
          { shardID: 0, chainId: 1 },
          { gasLimit: process.env.GAS_LIMIT, gasPrice: process.env.GAS_PRICE },
        );
        const newAcc = truffleProvider.addByPrivateKey(process.env.MAINNET_PRIVATE_KEY);
        truffleProvider.setSigner(newAcc);
        return truffleProvider;
      },
    }
  },

  ...
};

The above will configure Truffle to deploy smart contracts to Harmony's testnet and mainnet.

You can now go ahead and deploy these contracts to Harmony:

truffle compile
truffle migrate --network testnet --reset --skip-dry-run

This repository has also been configured to support smart contract compilation using Waffle

You can compile the smart contracts using Waffle optimizations by running the command yarn compile.

yarn compile will also run a separate ABI extractor script in a postcompile step that will be exported to build/abi.

@harmony-js/core is Harmony's own JavaScript/TypeScript SDK.

It can be used for both smart contract deployment as well as smart contract interactions (which we'll look into a bit more later).

In order to deploy smart contracts using @harmony-js/core you need to implement your own custom deployment tool. You'll find an example of such a tool in tools/deployment/deploy.js.

To deploy smart contracts using this tool you'd do the following:

yarn compile
node tools/deployment/deploy.js --network testnet

This tool will output something similar to the following:

$ node tools/deployment/deploy.js --network testnet
    Deployed TestToken contract to address 0xd801333222bffa78df2663f91f76a91dc0dea408 (one1mqqnxv3zhla83hexv0u37a4frhqdafqg6c92ty)
    Deployed Faucet contract to address 0xbca23ecd4de7067e715119bd274904fea2e53526 (one1hj3ran2duur8uu23rx7jwjgyl63w2dfxz6hp4m)

To interact with the smart contracts in this repository there are also three separate CLI tools:

• tools/faucet/init.js: This tool initializes the faucet and transfers tokens to it so that dApp users can request funds from it. This step is mandatory, otherwise users can't request funds from the faucet.
• tools/faucet/request.js: This tool requests funds from the faucet for a given user.
• tools/tokens/mint.js: This tool mints new TestToken tokens.

The purpose of these tools is to showcase how to interact with smart contracts on the CLI level.

tools/faucet/init.js is the only mandatory CLI tool you have to execute for this demo dApp in order to properly initialize the system.

Usage:

$ node tools/faucet/init.js --network NETWORK --token TEST_TOKEN_CONTRACT_ADDRESS --faucet FAUCET_CONTRACT_ADDRESS --amount AMOUNT

Example - sending 1,000,000 tokens to the faucet on the testnet:

$ node tools/faucet/init.js --network testnet --token 0xd801333222bffa78df2663f91f76a91dc0dea408 --faucet 0xbca23ecd4de7067e715119bd274904fea2e53526 --amount 1000000

Usage:

$ node tools/faucet/request.js --network NETWORK --token TEST_TOKEN_CONTRACT_ADDRESS --faucet FAUCET_CONTRACT_ADDRESS

Example - requesting tokens from the faucet on the testnet:

$ node tools/faucet/request.js --network testnet --token 0xd801333222bffa78df2663f91f76a91dc0dea408 --faucet 0xbca23ecd4de7067e715119bd274904fea2e53526

Usage:

$ node tools/tokens/mint.js --network NETWORK --token TEST_TOKEN_CONTRACT_ADDRESS --amount AMOUNT

Example - minting 1,000,000 tokens on the testnet:

$ node tools/tokens/mint.js --network testnet --token 0xd801333222bffa78df2663f91f76a91dc0dea408 --amount 1000000

This demo dApp comes with a super minimal UI created in React.

The UI was originally forked from Yearn's UI but simplified to only showcase this dApp's functionality.

The UI also showcases wallet integration with Harmony's own OneWallet as well as MathWallet.

The respective wallet implementations/integrations can be found here:

• OneWallet
• MathWallet

The UI also showcases the interaction with the faucet smart contract and allows the user to request funds from the faucet every x blocks (depending on the smart contract deployment).

Harmony isn't currently compatible with MetaMask. There's also nothing similar to web3-react right now.

Harmony is looking into both MetaMask support as well as creating a web3-react component compatible with OneWallet and MathWallet.

Depending on when you read this, this tools might (or might not) have been implemented.

The UI resides in the ui folder, so cd ui before running the commands below.

To start the UI on http://localhost:3000, just run yarn start.

To create a production build, run yarn build.