ChainWatch ASP

ChainWatch ASP is a production-style, off-chain evaluation backend that models how an Association Set Provider (ASP) processes on-chain events and produces compliance decisions.

It demonstrates how smart contract events can be ingested, evaluated against risk rules, and converted into enforceable eligibility decisions:

Smart Contract → Watcher → ASP Backend → Rule Engine → Decision Store → Eligibility Guard

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🔎 What This Project Shows

This project simulates the compliance and risk layer of a privacy-aware protocol.

It implements:

• On-chain event ingestion via watcher
• Asynchronous evaluation pipeline
• Deterministic rule engine (deny > flag > allow)
• Persistent decision storage
• Admin-managed policy layer
• Eligibility enforcement API

This is not just CRUD — it is an event-driven compliance backend.

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🏗 Architecture

1️⃣ Watcher (Worker Process)

• Listens to smart contract events via ethers.js
• Automatically forwards structured events to POST /events
• Runs independently from API server

2️⃣ Event Ingestion

POST /events

• Stores event in Postgres
• Enforces idempotency using (tx_hash, log_index)
• Dispatches asynchronous evaluation

3️⃣ Rule Engine

Each event is evaluated against modular rules:

• sanctionsRule → deny blocked senders
• amountRule → flag high-value deposits
• velocityRule → flag abnormal frequency

Priority resolution:

deny > flag > allow

All rules run; final decision is deterministic and auditable.

4️⃣ Decision Storage

Events and decisions are persisted:

• events
• decisions
• blocked_addresses

Schema managed via node-pg-migrate.

5️⃣ Eligibility Guard

GET /eligibility/:eventId

Used by relayers, frontends, or middleware before allowing sensitive actions.

Example response:

{
  "eligible": false,
  "status": "deny",
  "reason": "sender is blocked"
}

This simulates how compliance decisions are enforced off-chain.

6️⃣ Admin Policy Layer

POST /admin/block-address

Allows operators to manage blocked addresses.
Policy updates directly affect evaluation outcomes.

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🚀 How To Run

Start API server:

npm run dev

Start watcher worker:

npm run watcher

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🧠 Design Highlights

• Clean separation: controllers → services → repositories → rules
• Async evaluation via dispatcher
• Idempotent event ingestion
• Modular, extensible rule engine
• Clear enforcement boundary (eligibility API)
• Worker + API process separation
• Audit-ready decision storage

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🎯 Why This Matters

This project models real-world off-chain compliance systems used in:

• Privacy infrastructure
• Risk evaluation pipelines
• Relayer-based architectures
• Policy-driven transaction filtering

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