🌉 Cross-Chain Token Bridge

Welcome to the cross_chain_bridge project! This repository contains a functional implementation of a cross-chain token bridge between Ethereum Holesky and Sepolia testnets. It includes smart contracts, deployment scripts, and an automated event indexer.

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🚀 Features

• 🔒 Secure token deposits with ownership and pause control
• 📦 Token distribution across chains
• 🔁 Bidirectional bridging (Holesky ↔ Sepolia)
• 🧠 Finality-aware indexer using confirmation thresholds
• 🪙 Multi-token support
• 💱 Swap functionality via token mappings (implemented in code, not deployed)

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🧱 Project Structure

/cross_chain_bridge    
├── /scripts         # Deployment and indexer scripts
├── /src             # contracts
├── /test            #testing files
├── foundry.toml     # Forge config
├── tsconfig.json    # TypeScript config
├── package.json
├── package-lock.json 
├── .env             # Runtime variables (private key, RPC URLs, etc.)

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📜 Workshop Objectives (Completed ✅)

• Deploy bridge contracts to Holesky and Sepolia
• Handle deposits and distributions
• Build a resilient event indexer (listens on both chains)
• Verify transaction finality before triggering actions
• Process tokens in both directions
• Add support for multiple tokens

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🧪 Optional (Implemented in Code, Not Deployed)

• setTokenMapping(fromToken, toToken) to link ERC20s across chains
• depositAndSwap() to swap TokenA for TokenB cross-chain
• Final deployment of the swap-ready contract (skipped for simplicity)

🔎 The contract logic is complete and tested locally — only deployment was skipped.

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🧪 How to Test Locally

1. Install dependencies:

npm install
forge install

2. Compile contracts:

forge build

3. Deploy bridge (if needed):

forge script script/DeployTokenBridge.s.sol:DeployTokenBridge \
  --rpc-url $HOLESKY_RPC_URL \
  --private-key $PRIVATE_KEY \
  --broadcast --verify

4. Run indexer:

npm run indexer

5. Use cast to interact:

cast send <token> "approve(address,uint256)" <bridge> <amount> --rpc-url $RPC --private-key $KEY
cast send <bridge> "deposit(address,uint256,address)" ...

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🔐 Security Considerations

This project is for educational purposes only.

In production, you should:

• Use multi-sig or access control for critical functions
• Verify tokens via checksums or allowlists
• Limit deposits / add rate limiting
• Integrate Chainlink oracles for dynamic swaps

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Holesky Addresses

• Bridge : 0x38b4B2602bb087df7fa4508344837775d51e3261
• Token TST : 0xbC4cAe667fbA05a1206742581E6908bfB224f505

Sepolia

• Bridge : 0x48F1A795B903eE7b705009C0AAc8d56BAa359705
• Token TST : 0xacB0399DE3c433bF0b7aaF2B844cB642D89105Ae