Enhanced 1inch Fusion+ with Etherlink Integration

Enhanced cross-chain swap resolver for 1inch Fusion+ with integrated 3Route DEX aggregator support on Etherlink. Extends the hackathon resolver example to handle token swaps when exact tokens are not available in the resolver's inventory.

Problem Statement

Standard 1inch Fusion+ resolvers must maintain exact token inventories for cross-chain swaps. This implementation enhances the resolver example provided for the hackathon by integrating with 3Route DEX aggregator on Etherlink, enabling automatic token swaps during escrow operations.

Solution Architecture

Core Components

1. Enhanced Resolver Contract - Extends the hackathon resolver example with arbitrary call support for pre/post operation token swaps
2. EtherlinkResolver Service - TypeScript service integrating with 3Route DEX aggregator API
3. 3Route API Client - HTTP client for quote fetching and swap execution
4. Test Framework - Comprehensive multi-chain testing environment

Integration Scenarios

Scenario 1: Direct Transfer

ETH USDC → Etherlink USDC (no swap needed)

Scenario 2: Swap on Destination

ETH USDC → Etherlink WXTZ (swap USDC→WXTZ via 3Route during deployDst)

Scenario 3: Reverse Swap on Withdrawal

Resolver swaps received tokens back to preferred inventory tokens

Installation

Install Dependencies

pnpm install

Install Foundry

curl -L https://foundry.paradigm.xyz | bash

Install Contract Dependencies

forge install

Configuration

Environment Setup

cp .env.example .env

Required Environment Variables

# Ethereum (required)
ETH_CHAIN_RPC=https://eth.merkle.io
ETH_CHAIN_CREATE_FORK=true

# Etherlink Testnet (default)
TEST_ETHERLINK_CHAIN_RPC=https://node.ghostnet.etherlink.com
TEST_ETHERLINK_CHAIN_CREATE_FORK=false
TEST_ETHERLINK_API_URL=https://api.3route.io
TEST_ETHERLINK_API_KEY=your-3route-api-key

# Etherlink Mainnet (optional)
ETHERLINK_MAINNET_RPC=https://node.mainnet.etherlink.com
ETHERLINK_MAINNET_CREATE_FORK=false
ETHERLINK_MAINNET_API_URL=https://api.3route.io
ETHERLINK_MAINNET_API_KEY=your-3route-api-key

Running Tests

Build Contracts First

forge build

Fork Testing (Default)

# Run all tests
forge build && node --experimental-vm-modules ./node_modules/jest/bin/jest.js --runInBand

# Run specific test
node --experimental-vm-modules ./node_modules/jest/bin/jest.js -t 'should swap USDC to WXTZ using API integration and complete withdraw'

# Run scenario tests only
node --experimental-vm-modules ./node_modules/jest/bin/jest.js -t 'Scenario'

Mainnet Testing

For real mainnet testing, set these environment variables:

#ETHERLINK_MAINNET_CREATE_FORK=false
ETHERLINK_MAINNET_OWNER_PK=your-owner-private-key
ETHERLINK_MAINNET_RESOLVER_PK=your-resolver-private-key  
ETHERLINK_MAINNET_USER_PK=your-user-private-key

Then modify the test file:

// Change in your test file
const dstChainId = 42793 // Etherlink Mainnet instead of 128123 (testnet)

// Replace time manipulation calls
await increaseTime(env.getProviders(), 15) 
// with real delays for mainnet
await delay(15) // 15 seconds real delay

Run Specific Scenarios

# All scenarios with 3Route integration
node --experimental-vm-modules ./node_modules/jest/bin/jest.js -t 'should swap USDC to WXTZ using API integration and complete withdraw'

# Main scenario (no swap)
node --experimental-vm-modules ./node_modules/jest/bin/jest.js -t 'should transfer USDC to USDC without API calls'

Live Demo Results

Real Mainnet Transactions

Swap + Escrow Creation: https://explorer.etherlink.com/tx/0xc8fbe25c94f5d9c0ac98932dfda0fc537ed17a750f033a2e19fbb78f30e9df3f

This transaction shows:

• USDC approval to 3Route router
• USDC → WXTZ swap via 3Route DEX aggregator
• WXTZ approval to escrow factory
• Destination escrow creation with swapped tokens

User Withdrawal: https://explorer.etherlink.com/tx/0x24254ccb995689909881df55e53f11adde14cab4cef9cd95a8853271d59a5326

This transaction shows the user receiving exactly 0.6 WXTZ as specified in the test order.

Implementation Details

Enhanced Resolver Contract

Building on the hackathon resolver example:

contract Resolver is Ownable {
    // Original example methods
    function deploySrc(...) external payable onlyOwner;

// Enhanced methods with arbitrary calls
function deployDst(
address[] calldata targets,
bytes[] calldata callsData,
IBaseEscrow.Immutables calldata dstImmutables,
uint256 srcCancellationTimestamp
) external onlyOwner payable;

function withdraw(
IEscrow escrow,
bytes32 secret,
IBaseEscrow.Immutables calldata immutables,
address[] calldata targets,
bytes[] calldata callsData
) external;

// Fund management
function withdrawFunds(address token, address to, uint256 amount) external onlyOwner;
}

EtherlinkResolver API

class EtherlinkResolver {
  deployDstWithSwap(escrowFactory, order, immutables, srcToken, slippage)
  withdrawWithSwap(chainId, escrow, secret, immutables, src, dst, amount, slippage)
  cancelWithSwap(chainId, escrow, immutables, src, dst, amount, slippage)
}

Test Results

Test Coverage

• Scenario 1: USDC→USDC transfer without swaps
• Scenario 2: USDC→WXTZ with 3Route DEX aggregator integration
• Integration Tests: Token support and swap detection

Supported Networks

Ethereum Mainnet

• Chain ID: 1
• Role: Source chain for cross-chain swaps
• RPC: https://eth.merkle.io

Etherlink Testnet (Ghostnet)

• Chain ID: 128123
• Role: Destination chain with DEX aggregator integration
• RPC: https://node.ghostnet.etherlink.com

Etherlink Mainnet

• Chain ID: 42793
• Role: Production destination chain
• RPC: https://node.mainnet.etherlink.com

Token Configuration

Etherlink Testnet:

{
  USDC: '0x4C2AA252BEe766D3399850569713b55178934849',
    WXTZ: '0xB1Ea698633d57705e93b0E40c1077d46CD6A51d8',
    XTZ: '0x0000000000000000000000000000000000000000' // Native
}

Etherlink Mainnet:

{
  USDC: '0x796Ea11Fa2dD751eD01b53C372fFDB4AAa8f00F9',
    WXTZ: '0xc9b53ab2679f573e480d01e0f49e2b5cfb7a3eab',
    WETH: '0xfc24f770F94edBca6D6f885E12d4317320BcB401',
    WBTC: '0xbFc94CD2B1E55999Cfc7347a9313e88702B83d0F',
    XTZ: '0x0000000000000000000000000000000000000000' // Native
}

Technical Innovation

1. Arbitrary Call Support: Enhanced resolver contract enables complex multi-step operations beyond the base example
2. 3Route Integration: Seamless DEX aggregator integration for optimal routing

Results

• Successfully enhances the hackathon resolver example with 3Route DEX aggregator capabilities
• Reduces resolver inventory requirements

This implementation demonstrates how cross-chain protocols can be enhanced with 3Route DeFi integrations while maintaining security and compatibility with existing infrastructure.