# Getting Started

## Prerequisites

Before using the SDK, you'll need:

1. **API Credentials** - Client ID and Client Secret from the Partner Dashboard (for your backend)
2. **A backend endpoint** - To generate checkout tokens for your frontend
3. **Invoice ID** - The invoice the customer will be paying
4. **A container element** - An HTML element where the SDK will render

   <div data-gb-custom-block data-tag="hint" data-style="warning" class="hint hint-warning"><p><strong>Important:</strong> API credentials (Client ID and Secret) should only be used on your backend server. The frontend SDK uses access tokens generated by your backend to keep credentials secure.</p></div>

   \*\*\*

## Step-by-Step Setup### Install the SDK

````bash
npm install @getalternative/partner-sdk
```</div><div data-gb-custom-block data-tag="step">### Create a Backend Token Endpoint

Your backend generates checkout tokens using your API credentials:

```typescript
// backend/routes/checkout.ts (example with Express)
import express from 'express';

const router = express.Router();

router.post('/api/checkout-token', async (req, res) => {
  const { customerId, invoiceId } = req.body;

  // 1. Get OAuth token using client credentials
  const oauthResponse = await fetch('https://public-api.alternativepayments.io/oauth/token', {
    method: 'POST',
    headers: {
      'Content-Type': 'application/x-www-form-urlencoded',
      'Authorization': `Basic ${Buffer.from(`${CLIENT_ID}:${CLIENT_SECRET}`).toString('base64')}`,
    },
    body: 'grant_type=client_credentials',
  });
  const { access_token } = await oauthResponse.json();

  // 2. Generate checkout token
  const checkoutResponse = await fetch('https://public-api.alternativepayments.io/v1/checkout-auth/init', {
    method: 'POST',
    headers: {
      'Authorization': `Bearer ${access_token}`,
      'Content-Type': 'application/json',
    },
    body: JSON.stringify({ customer_id: customerId, invoice_id: invoiceId }),
  });
  const { token, expires_at } = await checkoutResponse.json();

  res.json({ token, expiresAt: expires_at });
});
```</div><div data-gb-custom-block data-tag="step">### Add a Container Element

```html
<div id="payment-container"></div>
```</div><div data-gb-custom-block data-tag="step">### Initialize the SDK

```typescript
import { AlternativeClient } from '@getalternative/partner-sdk';

// Fetch token from your backend
const { token } = await fetch('/api/checkout-token', {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({ customerId: 'cus_xxx', invoiceId: 'inv_xxx' }),
}).then(res => res.json());

// Initialize SDK
const client = await AlternativeClient.create({
  accessToken: token,
  environment: 'production',
  onAccessTokenExpired: async () => {
    // Re-fetch token when expired
    const response = await fetch('/api/checkout-token', {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ customerId: 'cus_xxx', invoiceId: 'inv_xxx' }),
    });
    const { token } = await response.json();
    return token;
  },
});
```</div><div data-gb-custom-block data-tag="step">### Create the Payment Flow

```typescript
const flow = client.createPaymentFlow({
  containerId: 'payment-container',
  onPaymentSuccess: (payment) => {
    console.log('Payment completed:', payment.id);
  },
  onPaymentError: (error) => {
    console.error('Payment failed:', error.message);
  },
});
```</div></div>***

## Configuration Options

### AlternativeClientConfig

| Property | Type | Required | Description |
|----------|------|----------|-------------|
| `accessToken` | `string` | Yes | JWT access token from your backend |
| `environment` | `'production' \| 'staging' \| 'demo'` | No | API environment (default: production) |
| `baseUrl` | `string` | No | Custom API base URL (overrides environment) |
| `timeout` | `number` | No | Request timeout in ms (default: 30000) |
| `retries` | `number` | No | Number of retry attempts (default: 3) |
| `onAccessTokenExpired` | `() => Promise<string>` | No | Callback to fetch new token when expired |
| `theme` | `ThemeConfig` | No | Default theme for all components |

***

## Environments

<table>
<thead>
<tr><th width="200">Environment</th><th>Description</th></tr>
</thead>
<tbody>
<tr><td><code>production</code></td><td>Live environment for real payments</td></tr>
<tr><td><code>staging</code></td><td>Test environment for development</td></tr>
<tr><td><code>demo</code></td><td>Demo environment for showcasing and testing</td></tr>
</tbody>
</table><div data-gb-custom-block data-tag="hint" data-style='danger'>**Important:** Use separate API credentials for each environment. Production credentials will not work in staging and vice versa.</div>***

## Full Example

```html
<!DOCTYPE html>
<html>
<head>
  <title>Payment Page</title>
</head>
<body>
  <h1>Complete Your Payment</h1>
  <div id="payment-container"></div>

  <script type="module">
    import { AlternativeClient } from '@getalternative/partner-sdk';

    // Fetch token from your backend
    const { token } = await fetch('/api/checkout-token', {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({
        customerId: 'cus_abc123',
        invoiceId: 'inv_abc123'
      }),
    }).then(res => res.json());

    const client = await AlternativeClient.create({
      accessToken: token,
      environment: 'staging',
      onAccessTokenExpired: async () => {
        const response = await fetch('/api/checkout-token', {
          method: 'POST',
          headers: { 'Content-Type': 'application/json' },
          body: JSON.stringify({
            customerId: 'cus_abc123',
            invoiceId: 'inv_abc123'
          }),
        });
        const { token } = await response.json();
        return token;
      },
    });

    const flow = client.createPaymentFlow({
      containerId: 'payment-container',
      onPaymentSuccess: (payment) => {
        alert('Payment successful!');
        window.location.href = '/thank-you';
      },
      onPaymentError: (error) => {
        alert('Payment failed: ' + error.message);
      },
      onClose: () => {
        console.log('Payment flow closed');
      },
    });

    // Cleanup when navigating away
    window.addEventListener('beforeunload', () => {
      flow.unmount();
    });
  </script>
</body>
</html>
````

***

## React Integration

```tsx
import { useEffect, useRef } from 'react';
import { AlternativeClient } from '@getalternative/partner-sdk';

interface PaymentWidgetProps {
  customerId: string;
  invoiceId: string;
}

function PaymentWidget({ customerId, invoiceId }: PaymentWidgetProps) {
  const flowRef = useRef<ReturnType<typeof AlternativeClient.prototype.createPaymentFlow> | null>(null);

  useEffect(() => {
    let mounted = true;

    async function initPayment() {
      // Fetch token from your backend
      const { token } = await fetch('/api/checkout-token', {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ customerId, invoiceId }),
      }).then(res => res.json());

      if (!mounted) return;

      const client = await AlternativeClient.create({
        accessToken: token,
        environment: 'staging',
        onAccessTokenExpired: async () => {
          const response = await fetch('/api/checkout-token', {
            method: 'POST',
            headers: { 'Content-Type': 'application/json' },
            body: JSON.stringify({ customerId, invoiceId }),
          });
          const { token } = await response.json();
          return token;
        },
      });

      if (!mounted) return;

      flowRef.current = client.createPaymentFlow({
        containerId: 'payment-container',
        onPaymentSuccess: (payment) => {
          console.log('Success:', payment);
        },
      });
    }

    initPayment();

    return () => {
      mounted = false;
      flowRef.current?.unmount();
    };
  }, [customerId, invoiceId]);

  return <div id="payment-container" />;
}
```

***

## Next Steps


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.alternativepayments.io/web-sdk/getting-started.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.