Zer0 Token

This repository contains the Zer0 Token and other utility contracts for airdropping and vesting ERC20 tokens.

Check out the docs folder for more information on what they do.

Building and Development

Follow this guide to learn how to get started with building and developing locally.

This guide will assume you are using Visual Studio Code as an IDE, however you can use whatever IDE you would like.

Required Tools

This project requires yarn to be installed on your system, as well as node.js. Please ensure those are installed on your system before continuing.

Getting Started

In the command line terminal, run the following:

yarn

This will:

• Install required node packages (this may take awhile)
• Compile the smart contracts
• Generate typechain helper types

This step should complete without any errors. If you encounter errors there may be something wrong with your node or yarn installation, ensure you have node version 14 or higher.

If you are still encountering errors please file a GitHub issue with as much detail as possible.

Running Tests

To run the tests for the smart contracts simply run

yarn test

You can check test coverage by running

yarn coverage

You may get a warning about contract code size exceeding 24576 bytes, you can ignore this.

Compiling Contracts

If you ever need to recompile the smart contracts you can run

yarn compile

To recompile the smart contracts.

Running yarn compile will also re-generate the typechain helpers

In some cases you may need to clean previously built artifacts, if you run into errors you can try running yarn build which will clean and re-compile the smart contracts

Linting

You can lint any Solidity and TypeScript files in the project by running:

yarn lint

Many linting issues can be solved automatically by running:

yarn fix

Ensure you run both yarn fix and yarn lint before creating a pull request.

You may get some line-ending errors, this project expects that line-endings are LF and not CRLF.

Generating Merkle Trees

Both the MerkleTokenAirdrop and MerkleTokenVesting contracts require a valid Merkle Tree to run properly.

Merkle Tree Concept

If you aren't familiar with Merkle Tree's as a concept, check out these resources:

• Wikipedia: https://en.wikipedia.org/wiki/Merkle_tree
• ERC20 Snapshot with Merkle Trees: https://medium.com/coinmonks/erc20-snapshot-using-merkle-trees-aeeac48ce925
• Merkling in Ethereum: https://medium.com/coinmonks/erc20-snapshot-using-merkle-trees-aeeac48ce925

Without explaining how the concept works, and instead what it enables, consider this statement:

We can use a Merkle Tree to distribute tokens to thousands of addresses with minimal gas costs.

We create a Merkle Tree out of a list of all the addresses we need to send tokens to, each address is a node in this tree. A Merkle Root is also created when we make this tree, we must store this root in our smart contract.

Using the smart contract, a user an make a call, with the data from their node on the Merkle Tree we created. Through a mathematical operation, we can verify that the data from the node is valid (part of the tree) by using the Merkle Root in the smart contract.

After verifying the data, we can distribute tokens.

In short:

• We make a Merkle Tree which has a root key, and child keys
• We deploy a smart contract which only stores the root key
• Users can call the smart contract with a child key
• The child key is verified against the root key using 'math'
• If verification is successful, we distribute tokens
  • We also store a flag indicating that a child key has been used so it can't be used twice

One important feature of a Merkle Tree is that any data can be stored in the tree on a child key. This allows us to store a user address and an owed amount inside of a child key.

Generating Merkle Trees

There are two different types of Merkle Trees used in this project, Airdrop and Vesting.

The MerkleTokenAirdrop uses Airdrop trees and MerkleTokenVesting uses Vesting trees. You can find examples of these trees in the ./merkle/airdrop/example-merkleTree.json and ./merkle/vesting/example-merkleTree.json files.

There are scripts to generate both of these types of Merkle Trees in this project.

Create Input file

To create a Merkle Tree you must create an input json file:

It is recommended you create this file in the ./merkle/<type>/ directory where <type> is the type of tree you are making.

For Vesting Trees

The json file should follow this schema:

{
  "<account address>": {
    "amount": number,
    "revocable": boolean
  }
}

Where:

• <account address> is the string of the account address (ie: 0x70997970C51812dc3A010C7d01b50e0d17dc79C8)
• amount is the number of tokens to be vested (ie: 5000)
  • Note: You most likely will need to pad zeros to account for the decimal places in ERC20 tokens more info here
• revocable whether this vesting award is revocable

You can have as many addresses as you want in this file.

For Airdrop Trees

The json file should follow this schema:

{
  "<account address>": {
    "amount": number
  }
}

Where:

• <account address> is the string of the account address (ie: 0x70997970C51812dc3A010C7d01b50e0d17dc79C8)
• amount is the number of tokens to be air dropped (ie: 5000)
  • Note: You most likely will need to pad zeros to account for the decimal places in ERC20 tokens more info here

You can have as many addresses as you want in this file.

Generate Tree

To generate a merkle tree you can run the following command:

yarn merkle generate <type> <input file>

Where:

• <type> is the type of merkle tree (vesting or airdrop)
• <input file> is the path to the input file (ie: "./merkle/vesting/example.json")

This will generate and output a json file in the same directory and name as the input file but with -merkleTree appended on the end of the filename.

Given the input "./merkle/vesting/example.json" the generate command will output "./merkle/vesting/example-merkleTree.json"

Verifying Merkle Tree Files

In case you wish to verify that a Merkle Tree has been properly generated, you can use the following command to verify the tree:

yarn merkle verify <type> <merkle tree file>

Where:

• <type> is the type of merkle tree (vesting or airdrop)
• <merkle tree file> is the path to the merkle tree file (ie: "./merkle/vesting/example-merkleTree.json")

Use the XXX-merkleTree.json file here instead of the input file

Deployment

You can use the yarn hardhat deploy task to deploy contracts.

Information about deployments are stored in the deployments/ folder where the name of the file is the network you deployed to.

Deploying Token Contract

Run the this command to deploy a token contract:

yarn hardhat deploy token --tag "<tag>" --name "<name>" --symbol "<symbol>" --network <network>

Where:

• <tag> is a user friendly tag (used in the deployment file)
• <name> is the token name to be used
• <symbol> is the token symbol to be used
• <network> is the network to deploy to

Deploying Merkle Token Airdrop Contract

Run the this command to deploy a Merkle Token Airdrop contract:

yarn hardhat deploy airdrop --tag "<tag>" --merkle "<merkle file>" --token "<token>"

Where:

• <tag> is a user friendly tag (used in the deployment file)
• <merkle file> is the path to the merkle file to use
• <token> is the address of the token that is being airdropped

You will need to transfer the proper quantity of tokens to the contract once it has been deployed so users can claim their tokens.

Make sure that <merkle_file> is a path to a JSON file which is the proper type (airdrop, not vesting)
You can find <token> (the address) in the deployment file if you deployed a token wih the deployment scripts

Deploying Merkle Token Vesting Contract

Run the this command to deploy a Merkle Token Airdrop contract:

yarn hardhat deploy vesting --tag "<tag>" --merkle "<merkle file>" --token "<token>" --start <start> --duration <duration> --cliff <cliff>

Where:

• <tag> is a user friendly tag (used in the deployment file)
• <merkle file> is the path to the merkle file to use
• <token> is the address of the token that is being airdropped
• <start> is what block number vesting should start on
• <duration> is how many blocks until all tokens are vested (linearly)
• <cliff> is how many blocks until the vesting cliff is reached

You will need to transfer the proper quantity of tokens to the contract once it has been deployed so users can claim their tokens.

Make sure that <merkle_file> is a path to a JSON file which is the proper type (vesting, not airdrop)
You can find <token> (the address) in the deployment file if you deployed a token wih the deployment scripts

Open Zeppelin Modifications

A slightly modified version of the ERC20 Open Zeppelin Contracts are used in this project. For more information check this file.

These modifications have been deemed minor, so no additional tests have been written for the contracts in the ./contracts/oz folder.