CryptoFlowCheck

A crypto market-intelligence dashboard built around public exchange data, deterministic portfolio math, guarded AI features, and a security-conscious Stripe subscription flow.

Portfolio status: lint, 35 automated tests, the Next.js production build, and the dependency audit are verified locally and repeated by public CI. Live Stripe settlement, OpenAI generation, and external exchange availability require owner-managed credentials or services and are documented as deployment gates.

Product evidence

Current default-branch UI running against the public market-data adapter. Prices in the capture are a point-in-time snapshot, not a performance or availability claim.

What it demonstrates

• Public market data: Binance REST/WebSocket price paths, historical candles, 24-hour change, volume, comparisons, heatmaps, and fear/greed context.
• Local portfolio tools: holdings, cost basis, live P&L, drawdown alerts, threshold watches, and analysis history stay in browser storage.
• Fail-closed admin auth: HMAC-signed, expiring, HTTP-only session cookies; both the signing secret and password hash are required.
• Verified subscription identity: Stripe Checkout returns are verified server-side before an HTTP-only, HMAC-signed identity token is issued.
• Independent entitlement check: a verified identity is still looked up in the subscription store; neither a client cookie nor UI state grants Pro access by itself.
• Export hardening: CSV formula-injection neutralization covers =, +, -, @, tab, carriage return, and quoting edge cases.
• Optional AI: model-backed analysis and brief generation disable cleanly when no OpenAI key is configured.

Architecture

flowchart LR
    Binance[Binance public APIs] --> UI[Next.js market UI]
    UI --> Local[Browser portfolio + alerts]
    UI --> AI[Server-side AI routes]
    Checkout[Stripe Checkout] --> Verify[Server session verification]
    StripeWebhook[Signed Stripe webhook] --> Store[Subscription store]
    Verify --> Identity[HTTP-only signed identity]
    Identity --> Entitlement[Server entitlement lookup]
    Store --> Entitlement
    Proxy[Next.js proxy] --> Admin[Signed admin session]

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The animated terminal scanner is deliberately labeled SIMULATED. It is a presentation component, not an on-chain transaction feed. Market prices and candles come from the public data adapters described above.

Security work captured in this repository

• Upgraded from a vulnerable Next.js 15 release candidate stack to Next.js 16.3 and stable React 19.
• Removed the built-in admin password fallback; missing configuration now returns 503.
• Migrated deprecated middleware to the Next.js 16 proxy convention.
• Added signed subscription identity with tamper and expiry tests.
• Changed Checkout success handling so typing or forging a paid email cannot directly create a Pro identity.
• Kept Stripe webhook signature verification on the raw request body and rejected missing configuration.
• Rate-limit identity prefers proxy-derived addresses and validates IP shape before keying counters.
• Assistant-generated comparison links are reconstructed from allowlisted exchange IDs; unsafe destinations render as plain text.
• Checkout email validation is bounded and linear-time rather than dependent on a backtracking regular expression.

Test coverage

The 35-case suite covers:

• portfolio P&L, aggregate totals, missing prices, drawdown alerts, and zero-cost edge cases;
• CSV formula injection and RFC-compatible quoting;
• Stripe-style signature tampering, wrong secrets, timestamps, and malformed headers;
• subscription identity signing, tampering, expiry, and missing-secret failure;
• tier resolution, normalization, cancellation, anonymous access, and forged values.
• bounded email validation and fail-closed handling of script, external, unknown, and malformed comparison links.

Run locally

Requirements: Node.js 24+ and npm.

git clone https://github.com/yigiterturk-dev/cryptoflowcheck.git
cd cryptoflowcheck
npm ci
cp .env.example .env.local
npm run dev

Quality gates:

npm run lint
npm test
npm run build
npm audit

Public market screens can run without private credentials. Stripe, admin, cron, and OpenAI routes fail closed or disable their optional behavior when their corresponding server-only values are absent.

Honest scope

• The current subscription store is JSON-file-backed and suitable only for a single persistent instance. Production/serverless deployment needs PostgreSQL, Redis, or another durable shared store.
• Rate-limit counters are process-local; multi-instance deployments need a shared limiter.
• Portfolio, watch, and analysis-history records are browser-local, not synchronized user accounts.
• Checkout and webhook code paths are unit/audit reviewed but were not exercised against an owner Stripe test account in this audit.
• The app provides informational tooling, not investment advice or trading guarantees.

See .env.example, SECURITY.md, and docs/showcase-audit.md.

Stack

Next.js 16 · React 19 · TypeScript · Tailwind CSS · Framer Motion · Lightweight Charts · Binance APIs · Stripe · OpenAI (optional)

License

MIT