@stillkinetic/web-sdk

Behavioral tracking + threshold-triggered Stripe billing for web apps and JS desktop apps (Electron, Tauri).

npm install @stillkinetic/web-sdk @stripe/stripe-js

@stripe/stripe-js is a peer dependency — install it alongside.

import { StillKinetic } from '@stillkinetic/web-sdk';

const tp = new TrackPay({
  appId: 'app_123',
  apiKey: 'pk_app_abc',              // issued by the platform dashboard
  apiBaseUrl: 'https://api.yourplatform.com',
  stripePublishableKey: 'pk_live_...',
  endUserId: currentUser.id,
  trackedMetrics: ['stay_duration', 'scroll_length'], // pick any subset of the 5
});

tp.start();

// ... later, e.g. when a "you're nearing your free usage" banner shows:
const result = await tp.setupBilling('#card-container', {
  amountCents: 5000,   // $50.00
  period: 'monthly',
});

if (!result.success) {
  console.error(result.error);
}

// On unmount / route change:
tp.stop();

setupBilling must be called once per end user before the backend will fire any charge for them — this is the single consent screen in the whole flow. It mounts a Stripe Card Element into the DOM node matching containerSelector, so make sure that element exists first, e.g.:

<div id="card-container"></div>

• All five metrics (press_count, scroll_length, scroll_speed, type_speed, stay_duration) are tracked passively; only the ones listed in trackedMetrics are enabled.
• The backend re-validates trackedMetrics against the app's subscription tier and will ignore any metric the tier doesn't allow — the SDK does not enforce this client-side.
• Charges never fire from this package directly. It only reports metrics and handles the one-time card bind; the threshold engine and all Stripe charge calls live server-side (see the platform app).
• Each start() creates a fresh visit identifier. Cumulative usage resets between visits, so 2.5 minutes before leaving plus 2 minutes after returning does not reach a 3-minute threshold. Call getAccessStatus(metric) before rendering protected content, or handle onAccessDecision; when it reports cap_reached, hide/lock the content and show its message.