OTC Bridge: Peer-to-peer RTC trading with RIP-302 escrow (Bounty #695)

[mtarcure]

Bounty Claim: #695 — Tier 2 (150 RTC)

Full Tier 2 OTC Bridge implementation with RIP-302 escrow and HTLC smart contract.

Deliverables

Backend (otc_bridge.py — Flask, 9 API endpoints):

• POST /api/orders — Create buy/sell order (sell orders auto-lock RTC in escrow)
• GET /api/orders — List open orders with pair/side filters
• GET /api/orderbook — Aggregated bids/asks with spread calculation
• POST /api/orders/{id}/match — Match an order (counterparty)
• POST /api/orders/{id}/confirm — Confirm settlement (reveals HTLC secret, releases escrow)
• POST /api/orders/{id}/cancel — Cancel with escrow refund
• GET /api/trades — Trade history with audit trail
• GET /api/stats — Market stats (volume, open orders, prices)
• SQLite persistence (shared order book — fixes the localStorage gap from Tier 1)
• Rate limiting (10 req/min per IP), self-match prevention, auto-expiry

Frontend (static/index.html — single-file SPA):

• Dark theme matching RustChain branding (#0d1117 bg, #f39c12 gold accents)
• Live order book with depth bars, spread display
• Buy/sell order form with escrow cost preview
• Match modal for counterparty matching
• Trade history table
• Wallet balance check against live node
• 15-second auto-refresh

HTLC Smart Contract (contracts/HTLC.sol):

• Hash Time-Locked Contract for ETH/USDC side on Base
• Supports both native ETH and ERC20 (USDC) swaps
• createSwapETH() / createSwapERC20() — Lock funds with hashlock + timelock
• claim() — Seller reveals preimage to claim
• refund() — Buyer reclaims after timeout
• OpenZeppelin ReentrancyGuard + SafeERC20
• Cross-referenced with OTC Bridge order IDs

Settlement Flow:

Seller posts sell order → RTC locked in RIP-302 escrow
Buyer matches → locks ETH/USDC in HTLC (hashlock = seller's hash)
Seller confirms → HTLC secret revealed, RTC escrow releases to buyer
Buyer claims ETH/USDC from HTLC using revealed secret

Tests: 23 unit tests, all passing — covers order CRUD, escrow locking/refund, matching, settlement, rate limiting, auth checks.

Docker: Production-ready with gunicorn.

Tier 2 Checklist

• Everything in Tier 1 (order book, create/list/match orders, hosted)
• RTC side uses RIP-302 escrow (/agent/jobs with escrow lock)
• ETH/USDC side has HTLC escrow (Solidity smart contract)
• Near-atomic settlement (HTLC secret reveal links both sides)
• Transaction history / audit trail
• Rate limiting and abuse prevention

Supported Pairs

RTC/USDC, RTC/ETH, RTC/ERG

Wallet: wirework