Final Project - EVM Token Bridge

0. Overview

This final project is part of the requirements to fulfil in order graduate from LimeAcademy. Specifically, the project aims to build a EVM token bridge which allows users to swap ERC-20 tokens between two chains.

1. User Stories

• As a user, I want to select a token (from my wallet or by address):
  • There should be a separate “Transfer” view (can be a page, tab or other)
  • List ERC-20 tokens (names) from the wallet (in a dropdown for example)
  • The selected ERC-20 contract address is shown in a text field
  • Give option to manually paste a token contract address
• As a user, I can select a target chain:
  • List target chains in a dropdown
  • The current active chain should be grayed out in the dropdown
• As a user, I want to be able to lock tokens in the bridge contract:
  • Should happen in “Transfer” view
  • When the Send button is clicked, three things should happen:
    • Approve the bridge contract as a token spender for the user’s wallet
    • Send a transaction that initiates the bridge operation
    • Emit blockchain event about the operation
• As a user, I can connect to the target chain:
  • Provide a button that will initiate the change of the network
• As a user, I want to be able to claim the locked tokens:
  • There should be a separate “Claim” view (can be a page, tab or other)
  • The “Claim” button should be active only if there are tokens to be claimed
  • The button action should match the type of the operation
• As a user, I can bridge the tokens (previously claimed) back to their native chain:
  • Should happen in “Transfer” view
  • The “Send” button should detect if this is a previously claimed token or a native one
  • When the Send button is clicked, three things should happen:
    • Approve the bridge contract as a token spender for the user’s wallet
    • Send a transaction that initiates the bridge operation
    • Emit blockchain event about the operation
• As a user, I can claim the tokens on the native chain and receive the original ones:
  • Should happen in the “Claim” view
  • The “Claim” button should be active only if there are tokens to be claimed
  • The button action should match the type of the operation

2. Overall Architecture

Design for V1

Bonus feature 1

Bonus feature 2

3. Run application

To run local nodes, run npx hardhat node.

To deploy contracts locally, run npx hardhat run --network localhost scripts/deploy-local-EthBridge.ts. Note that this step is necessary for tests to run locally.

To deploy contracts to goerli testnet, run npx hardhat run --network goerli scripts/deploy-local-EthBridge.ts.

• EthBridge.sol is deployed to 0xaac8e2a85454222ad0407Ce1580cdEBC86eC5ccC.
• PolygonBridge.sol is deployed to 0xfF97997A860BcD0E79E3889aaca6fA5Dd071a4a3.
• WERC20.sol is deployed to 0x204448ff00888A6b11D7216985DDeAED91dae0e2.
• WToken.sol is deployed to 0xE2E96cBCE11AD1A2557C2aa03Dff9e73c3d812F8.