Can I vibe code PayPal?

Build a self-hosted Payment Gateway Router and Vault service in Node.js/TypeScript using Express and PostgreSQL.

DATA MODELS:
1. Merchant Account: id, business_name, api_key_hash, webhook_url, status.
2. Payment Intent: id, merchant_id, amount, currency, status (pending, authorized, captured, failed), risk_score, gateway_reference.
3. Vaulted Instrument: id, customer_id, tokenized_card_id, provider (Stripe, Adyen), last4, exp_month, exp_year.
4. Transaction Log: id, payment_intent_id, action, raw_gateway_response, latency_ms, created_at.

CORE INTEGRATIONS & APIs:
1. Stripe PaymentIntents API for fallback card processing.
2. Adyen Payments API for direct European local payment routing.
3. Modern Treasury or ACH/SEPA API interface for direct bank payout processing.

EXPECTED FLOW:
1. POST /v1/checkout/intents: Accept amount, currency, merchant_id, and payment method details.
2. Compute risk score based on IP geolocation, velocity checks, and card BIN pattern.
3. Route the transaction dynamically: if currency is EUR, route to Adyen API; if USD and high-risk, route to Stripe with 3DS enabled; if low-risk domestic, trigger direct card processing.
4. Tokenize payment method credentials securely via downstream provider tokens (never store raw PAN/CVV).
5. Expose POST /v1/checkout/intents/:id/capture and /refund endpoints.
6. Dispatch signed HMAC-SHA256 webhooks to the merchant on payment success or failure.

FAILURE MODES TO HANDLE:
1. Primary gateway timeout: failover to secondary provider automatically within 2 seconds.
2. Duplicate Webhooks: idempotency keys enforced on all inbound and outbound payment hooks.
3. Declined Cards: map raw gateway error codes into standardized decline categories (insufficient_funds, expired_card, suspected_fraud).

OUT OF SCOPE:
- Storing raw primary account numbers (PAN) or PCI audit scope features.
- P2P balance transfers or consumer wallet storage.
- Consumer-facing mobile application or login portals.

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