2. PayPal REST API

This section provides comprehensive API documentation for integrating LeadsCalendar with PayPal REST API.

Integration Purpose: Process secure payments of 1 USD (or equivalent in cryptocurrency) through PayPal upon event creation in LeadsCalendar.

Authentication:

Obtain PayPal REST API credentials from your PayPal Developer account. These include Client ID and Secret.

API Calls:

Create Payment (POST): Initiates a payment using the /payments endpoint. You'll need to specify payment details in the request body.

Parameters:

intent (string) - Required: Set to sale for a one-time payment.
payer (object) - Required: Defines the payment source.
- payment_method (string): Set to paypal for payments using user's PayPal account.
transactions (list of objects) - Required: Specifies the transaction details.
- amount (object):
  - total (number): Required. Total amount to be paid.
  - currency (string): Required. Currency code (e.g., USD).
- description (string): Required. Brief description of the payment purpose (e.g., "LeadsCalendar Event Fee").

Code Sample (using Python and requests library):

import requests

def create_paypal_payment(access_token, amount, description):
  headers = {"Authorization": f"Bearer {access_token}"}
  data = {
      "intent": "sale",
      "payer": {
          "payment_method": "paypal"
      },
      "transactions": [
          {
              "amount": {
                  "total": amount,
                  "currency": "USD"
              },
              "description": description
          }
      ]
  }

  response = requests.post("https://api.paypal.com/v1/payments/payment", headers=headers, json=data)
  response.raise_for_status()  # Raise exception for non-200 status codes

  return response.json()

Error Handling:

PayPal REST API uses standard HTTP status codes and provides detailed error messages in the JSON response body. Here are some common codes and recommendations:

Code	Meaning	Recommendation
400 (Bad Request)	The request is invalid due to missing or malformed parameters.	- Parse the error message to identify the specific parameter causing the issue. - Correct the parameter value and retry the API call.
401 (Unauthorized)	Invalid or expired client credentials.	- Verify your PayPal REST API credentials are correct.
403 (Forbidden)	Insufficient permissions for the requested operation.	- Ensure your account has permission to create payments.
404 (Not Found)	The requested resource (e.g., specific payment) doesn't exist.	- Double-check the payment ID used in the request (if applicable).
429 (Too Many Requests)	Rate limit exceeded for API calls.	- Implement exponential backoff to retry the request after a delay.

A code snippet (Python with requests library) demonstrating error handling based on status code and parsing the error response:

  try:
    response = requests.post("https://api.paypal.com/v1/payments/payment", headers=headers, json=data)
    response.raise_for_status()  # Raise exception for non-200 status codes
    return response.json()
  except requests.exceptions.HTTPError as error:
    # Check the status code
    if error.response.status_code in (400, 401, 403):
      # Parse the error JSON for details
      error_data = error.response.json()
      error_code = error_data.get('error_code')
      error_message = error_data.get('message')
      print(f"Error creating payment: {error_code} - {error_message}")
      # Handle the error based on the specific code (e.g., refresh token, inform user)
    else:
      raise  # Re-raise unexpected errors

Important Notes:

Ensure secure storage and transmission of access tokens.
Refer to PayPal REST API documentation for a complete list of parameters and response structures: https://developer.paypal.com/api/rest/