Esewa Integration

In this section, we will walk through the implementation of the eSewa payment gateway within a Django application. This integration will involve creating a product model, generating a signature for secure transactions, and managing the payment process.

1. Product Model

First, let's create a Product model to represent the items for sale. This model will include attributes for the product details such as name, price, and code.

from django.db import models

class Product(models.Model):
    name = models.CharField(max_length=100)
    price = models.DecimalField(max_digits=10, decimal_places=2)
    code = models.CharField(max_length=20, unique=True)  # eSewa product code

    def __str__(self):
        return self.name

2. Generating the Signature

Before processing a payment, we need to generate a signature using HMAC/SHA256 to ensure the transaction's integrity. The required parameters include total_amount, transaction_uuid, and product_code. For development Esewa has specified that we need to use the secret key's value as "8gBm/:&EnhH.1/q" Here's how to create the signature in Django:

import hmac
import hashlib
import base64

def generate_signature(key, message):
    key = key.encode('utf-8')
    message = message.encode('utf-8')

    hmac_sha256 = hmac.new(key, message, hashlib.sha256)
    digest = hmac_sha256.digest()

    #Convert the digest to a Base64-encoded string
    signature = base64.b64encode(digest).decode('utf-8')

    return signature

3. Payment View

We will create a view to handle the payment process. This view will generate the necessary parameters, including the signature, and render a checkout form for the user to submit the payment.

from django.shortcuts import render
from django.utils.crypto import get_random_string
from .models import Product

def checkout(request, product_id):


    product = Product.objects.get(id=product_id)
    transaction_uuid = uuid.uuid4()
    tax_amount = 10  
    total_amount = product.price + tax_amount
    secret_key = '8gBm/:&EnhH.1/q'
    data_to_sign = f"total_amount={total_amount},transaction_uuid={transaction_uuid},product_code=EPAYTEST"
    result = generate_signature(secret_key, data_to_sign)

    context = {
        'product': product,
        'tax_amount': tax_amount,
        'total_amount': total_amount,
        'transaction_uuid': transaction_uuid,
        'product_delivery_charge': 0,
        'product_service_charge': 0,
        'signature': result,
    }

    return render(request, 'checkout.html', context)

4. Checkout Template

Next, we will create a simple HTML template for the checkout process. This form will send the payment details to eSewa.

<!-- templates/checkout.html -->
<form action="https://rc-epay.esewa.com.np/api/epay/main/v2/form" method="POST">
    <input type="hidden" name="amount" value="{{ product.price }}" required>
    <input type="hidden" name="tax_amount" value="{{ tax_amount }}" required>
    <input type="hidden" name="total_amount" value="{{ total_amount }}" required>
    <input type="hidden" name="transaction_uuid" value="{{ transaction_uuid }}" required>
    <input type="hidden" name="product_code" value="{{ product.code }}" required>
    <input type="hidden" name="product_service_charge" value="0" required>
    <input type="hidden" name="product_delivery_charge" value="0" required>
    <input type="hidden" name="success_url" value="http://localhost:8000/success" required>
    <input type="hidden" name="failure_url" value="http://localhost:8000/failure" required>
    <input type="hidden" name="signed_field_names" value="total_amount,transaction_uuid,product_code" required>
    <input type="hidden" name="signature" value="{{ signature }}" required>
    <input type="submit" value="Pay with eSewa">
</form>

5. URLs Configuration

Lastly, let's add a URL pattern to route requests to the checkout view.

from django.urls import path
from .views import checkout

urlpatterns = [
    path('checkout/<int:product_id>/', checkout, name='checkout'),
    path('failure', failure, name='failure'),
    path('success', success, name='success'),
]

Conclusion

In this implementation guide, we created a Product model, generated a secure signature using HMAC/SHA256, and set up a checkout process that integrates with eSewa's payment gateway. By following these steps, you can effectively handle transactions and ensure the integrity of the payment process.

Integration