Feature/bridge

[Bakobiibizo]

🚀 Bridge Relayer Integration Summary

📋 Overview

Adds a node-integrated bridge relayer that listens for BridgeOut::BridgeToL1Locked events and calls the L1 BridgeMinter on Ethereum (Sepolia) to mint and deposit to Base L2 via the canonical bridge.

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🔑 Key Changes

• subspace/node/src/relayer.rs:65
  Enables relayer when BRIDGE_ENABLE is true; merges env config.
• subspace/node/src/relayer.rs:80
  Reads System::Events from storage each imported block.
• subspace/node/src/relayer.rs:93
  Matches RuntimeEvent::BridgeOut(BridgeToL1Locked { … }).
• subspace/node/src/relayer.rs:118
  Scales native amount → ERC20 using BRIDGE_SUBSTRATE_DECIMALS and BRIDGE_ERC20_DECIMALS.
• subspace/node/src/relayer.rs:121
  Builds eventId and invokes BridgeMinter.mintAndBridge via Foundry cast.
• subspace/node/Cargo.toml:93
  Adds pallet-bridge-out dependency for event type matching.

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⚙️ Configuration

Environment Variables:

• BRIDGE_ENABLE=true
• BRIDGE_L1_RPC
• BRIDGE_MINTER
• BRIDGE_PK
• BRIDGE_L1_TOKEN
• BRIDGE_L2_GAS
• BRIDGE_SUBSTRATE_DECIMALS
• BRIDGE_ERC20_DECIMALS

Dependencies:

• Requires Foundry cast in PATH on the node host.

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🛠️ How It Works

1. On BridgeOut.lock_for_base(amount, l2_recipient), the relayer:
   • Derives eventId = keccak256(block_hash || nonce_le || l2_recipient).
   • Converts amount to ERC20 units.
   • Calls mintAndBridge(eventId, to, amountWei, l2Gas).
2. Idempotent by design using BridgeMinter.consumed(eventId).

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🧪 Testing

1. Start node with:

   --chain <main.json|test.json> --bridge-enable

   (with env vars set).
2. Submit BridgeOut.lock_for_base from Polkadot.js Apps.
3. Observe logs:
   • “mintAndBridge …”
   • “L1 tx sent …”
4. Verify:
   • Sepolia logs (Consumed / Bridged).
   • Base Sepolia balance updated.

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🔮 Follow-ups

• Optionally switch from cast to ethers-rs.
• Add retry/backoff + a persisted cursor (finalized only).
• Governance-controlled runtime upgrade path for live networks.

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📚 Quick Reviewer References

• subspace/node/src/relayer.rs
• cargo.toml