⚡ Agnostic Checkout SDK

A provider-agnostic, embeddable React checkout component with dynamic theming, plugin architecture, and full TypeScript support.

Features

• 🛒 Embeddable checkout component — drop into any React app
• 🎨 Theme system — 5 built-in presets (light, dark, minimal, corporate, neon)
• 🎯 Brand Auto Theme — generate a full theme from a single brand color
• 🔌 Plugin architecture — extend checkout behavior without modifying core code
• 🏷️ Discount Plugin — coupon input, apply/remove with event-driven updates
• ✏️ Cart Edit Plugin — quantity stepper, item removal with configurable limits
• 🌍 i18n — built-in locales (en, es, pt-BR, auto)
• 💱 Multi-currency — 25+ currencies with automatic formatting
• 📱 Responsive — mobile-first layout with collapsible order summary
• 🔒 Provider-agnostic — works with any payment backend

Installation

npm install agnostic-checkout

Quick Start

import { Checkout } from "agnostic-checkout";

function App() {
  const items = [
    {
      id: "item_1",
      name: "Pro Plan",
      unitPrice: 49.00,
      quantity: 1,
      total: 49.00,
      image: "https://example.com/pro-plan.png",
    },
  ];

  const totals = {
    subtotal: 49.00,
    taxes: 4.90,
    total: 53.90,
  };

  const paymentMethods = [
    {
      id: "pm_card",
      label: "Credit Card",
      type: "card",
    },
  ];

  return (
    <Checkout
      items={items}
      totals={totals}
      paymentMethods={paymentMethods}
      provider={yourPaymentProvider}
      currency="USD"
      locale="en"
    />
  );
}

| Prop | Description | |---|---| | items | Array of cart items to display | | totals | Object with subtotal, taxes, shipping, discount, and total | | paymentMethods | Available payment methods | | provider | Your PaymentProvider implementation | | currency | Currency code for formatting ("USD", "EUR", etc.) | | locale | Language for UI text ("en", "es", "pt-BR", "auto") |

Theming

The checkout uses CSS variables internally and supports three theming strategies with the following priority chain:

customTheme (overrides)
       ↓
brandColor (auto-generated theme)
       ↓
theme preset ("light" | "dark" | ...)

Preset Themes

Choose from 5 built-in themes:

<Checkout theme="light" />
<Checkout theme="dark" />
<Checkout theme="minimal" />
<Checkout theme="corporate" />
<Checkout theme="neon" />

Brand Auto Theme

Generate a complete theme from a single brand color. The SDK automatically derives background, surface, text, border, and accent colors:

<Checkout brandColor="#6366F1" />

Custom Theme Overrides

Override specific tokens on top of any base theme:

<Checkout
  theme="light"
  customTheme={{
    colors: {
      primary: "#ff0055",
      success: "#00cc88",
    },
    radius: "1rem",
  }}
/>

Combine with brandColor:

<Checkout
  brandColor="#6366F1"
  customTheme={{
    radius: "20px",
    fontFamily: "'Poppins', sans-serif",
  }}
/>

Theme Tokens

| Token | CSS Variable | Description | |---|---|---| | colors.primary | --color-primary | Buttons, links, active states | | colors.background | --color-background | Page background | | colors.surface | --color-surface | Card/panel backgrounds | | colors.text | --color-text | Primary text color | | colors.border | --color-border | Borders and dividers | | colors.success | --color-success | Success states, discounts | | colors.error | --color-error | Error states, remove actions | | radius | --theme-radius | Border radius for cards/buttons | | fontFamily | --theme-font | Font family stack |

Plugin System

Plugins extend checkout functionality through a slot-based architecture. Plugins inject UI into predefined areas and communicate via events — they never modify state directly.

import { createDiscountPlugin, createCartEditPlugin } from "agnostic-checkout/plugins";

<Checkout
  plugins={[
    createDiscountPlugin(handleEvent),
    createCartEditPlugin(handleEvent, { allowRemove: true }),
  ]}
  onEvent={handleEvent}
/>

Plugins emit events. Your onEvent handler processes them and updates items/totals externally:

const handleEvent = (event) => {
  switch (event.type) {
    case "COUPON_APPLY_REQUESTED":
      // Validate event.code, update items/totals
      break;
    case "ITEM_REMOVE_REQUESTED":
      // Remove item by event.itemId
      break;
    case "ITEM_QUANTITY_UPDATE_REQUESTED":
      // Update quantity for event.itemId to event.quantity
      break;
  }
};

Discount Plugin

Adds a coupon input field to the order summary. Users can type a discount code, apply it, and remove it via a trash icon.

import { createDiscountPlugin } from "agnostic-checkout/plugins";

const plugins = [
  createDiscountPlugin(handleEvent),
];

Events emitted:

| Event | Payload | Description | |---|---|---| | COUPON_APPLY_REQUESTED | { code: string } | User submitted a coupon code | | COUPON_REMOVE_REQUESTED | — | User clicked the remove button |

The plugin does not calculate discounts. Your onEvent handler validates the code and updates items/totals with the new discount values.

Cart Edit Plugin

Allows users to modify item quantities and/or remove items from the cart.

import { createCartEditPlugin } from "agnostic-checkout/plugins";

const plugins = [
  createCartEditPlugin(handleEvent, {
    allowRemove: true,
    allowQuantityEdit: true,
    minQuantity: 1,
    maxQuantity: 10,
  }),
];

Options

| Option | Type | Default | Description | |---|---|---|---| | allowRemove | boolean | false | Show remove button per item | | allowQuantityEdit | boolean | false | Show quantity stepper per item | | minQuantity | number | 1 | Minimum allowed quantity | | maxQuantity | number | 99 | Maximum allowed quantity |

Events emitted:

| Event | Payload | Description | |---|---|---| | ITEM_QUANTITY_UPDATE_REQUESTED | { itemId, quantity } | User changed item quantity | | ITEM_REMOVE_REQUESTED | { itemId } | User clicked remove |

Payment Provider

The checkout is payment-agnostic. Implement the PaymentProvider interface to connect any backend:

interface PaymentProvider {
  initialize?(config: unknown): Promise<void>;
  createPayment(data: unknown): Promise<PaymentResult>;
  confirmPayment?(data: unknown): Promise<PaymentResult>;
}

class StripeProvider implements PaymentProvider {
  async createPayment(data) {
    const response = await fetch("/api/payments", {
      method: "POST",
      body: JSON.stringify(data),
    });
    return { status: "success" };
  }
}

<Checkout provider={new StripeProvider()} />

API Reference

<Checkout /> Props

| Prop | Type | Required | Default | Description | |---|---|---|---|---| | items | CheckoutItem[] | ✅ | — | Cart items | | totals | CheckoutTotals | ✅ | — | Order totals | | paymentMethods | PaymentMethod[] | ✅ | — | Available payment methods | | provider | PaymentProvider | ✅ | — | Payment provider implementation | | currency | SupportedCurrency | ✅ | — | Currency code | | locale | CheckoutLocale | — | "es" | UI language | | theme | CheckoutThemeName \| Partial<CheckoutTheme> | — | "light" | Theme preset or partial theme object | | brandColor | string | — | — | Auto-generate theme from hex color | | customTheme | Partial<CheckoutTheme> | — | — | Override specific theme tokens | | onEvent | EventHandler | — | — | Callback for checkout events | | plugins | CheckoutPlugin[] | — | [] | Plugins to extend functionality | | messages | Partial<CheckoutMessages> | — | — | Override default UI text | | formatters | CheckoutFormatters | — | — | Custom currency formatter | | devTools | boolean | — | false | Show dev tools panel | | initialState | PaymentResult | — | — | Start in a specific state |

CheckoutItem

interface CheckoutItem {
  id: string;
  name: string;
  quantity: number;
  unitPrice: number;
  total: number;
  image?: string;
  discount?: {
    type: "percentage" | "fixed";
    value: number;
    label?: string;
  };
}

CheckoutTotals

interface CheckoutTotals {
  subtotal: number;
  discount?: number;
  taxes?: number;
  shipping?: number;
  total: number;
}

Events

| Event | Description | |---|---| | CHECKOUT_VIEWED | Checkout component mounted | | STEP_CHANGED | User navigated to a new step | | PAYMENT_METHOD_SELECTED | User selected a payment method | | PAYMENT_SUBMITTED | Payment form submitted | | PAYMENT_SUCCESS | Payment completed successfully | | PAYMENT_ERROR | Payment failed | | COUPON_APPLY_REQUESTED | Coupon code submitted (Discount Plugin) | | COUPON_REMOVE_REQUESTED | Coupon removed (Discount Plugin) | | ITEM_QUANTITY_UPDATE_REQUESTED | Quantity changed (Cart Edit Plugin) | | ITEM_REMOVE_REQUESTED | Item removed (Cart Edit Plugin) |

Internationalization

Built-in support for three locales plus automatic detection:

<Checkout locale="en" />     // English
<Checkout locale="es" />     // Spanish
<Checkout locale="pt-BR" />  // Portuguese (Brazil)
<Checkout locale="auto" />   // Auto-detect from browser

Override specific messages:

<Checkout
  messages={{
    payNow: "Complete Purchase",
    continueToPay: "Proceed to Payment",
  }}
/>

Custom currency formatter:

<Checkout
  formatters={{
    currency: (amount) => `US$ ${amount.toFixed(2)}`,
  }}
/>

Demo

A built-in demo page is available with interactive controls:

npm run dev

The demo includes a Settings toolbar to test:

• Theme switching (5 presets + Brand Auto Theme)
• Locale and currency changes
• Item count adjustments
• Plugin enable/disable toggles
• Brand color picker with 12 presets

Development

# Install dependencies
npm install

# Start development server
npm run dev

# Type checking
npx tsc --noEmit

# Build
npm run build

Project Structure

src/
├── core/               # State machine, context, events, types
├── theme/              # Theme system, tokens, color utilities
├── locales/            # i18n messages (en, es, pt-BR)
├── plugins/            # Plugin system, discount & cart-edit plugins
├── ui/                 # React components (Checkout, Layout, Summary, etc.)
├── hooks/              # useCheckout hook
├── lib/                # Utilities (cn, formatNumber)
└── mock/               # Demo app, mock provider, toolbar

License

MIT