Added WorldPayExtension (#165)

* WorldPay Extension

code/extensions/WorldPayResponseExtension.php

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+<?php
+
+use SilverStripe\Omnipay\Service\ServiceResponse;
+
+/**
+ * Add specific response overwrites for WorldPay gateway responses.
+ * This allows us to provide a templated response to a WorldPay
+ * payment notification and auto redirect to the current site after
+ * payment.
+ * 
+ * If you need to accept payments via WorldPay and want to use the
+ * custom payment response page, then you need to enable this extension
+ * in your config.yml:
+ * 
+ * SilverStripe\Omnipay\Service\PaymentService:
+ *  extensions:
+ *    - WorldPayResponseExtension
+ * 
+ * If you would like to overwrite the default template (for example
+ * to use your own styling, WPDISPLAY tags, etc) then add a
+ * "WorldPayCallback.ss" file to the tempaltes directory in your
+ * theme.
+ * 
+ * @package silverstripe-omnipay
+ * @subpackage extensions
+ * @author Bummzack
+ * @author Mo <[email protected]>
+ */
+class WorldPayResponseExtension extends Extension
+{
+  public function updateServiceResponse($response)
+  {
+    $payment = $response->getPayment();
+
+    // We only want to respond to the notification if we are using WorldPay
+    if ($payment->Gateway !== 'WorldPay') {
+        return;
+    }
+
+    // Ignore payments that aren't in the PendingPurchase state
+    if ($payment->Status !== 'PendingPurchase') {
+        return;
+    }
+
+    $omnipayResponse = $response->getOmnipayResponse();
+
+    if ($omnipayResponse !== null && !$response->isError()) {
+
+        if ($omnipayResponse->isSuccessful()) {
+            $return_url = Director::absoluteURL($payment->SuccessUrl, true);
+        } else {
+            $return_url = Director::absoluteURL($payment->FailureUrl, true);
+        }
+
+        $viewer = new SSViewer("WorldPayCallback");
+        $html = $viewer->process(ArrayData::create(array(
+            "ReturnURL" => $return_url
+        )));
+
+        $response->setHttpResponse(new SS_HTTPResponse($html, 200));
+    }
+  }
+}

docs/en/WorldPaySetup.md

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+# Setting Up WorldPay payments
+
+In order to start taking payments with WorldPay you will need to
+create an account with [Worldpay](http://www.worldpay.com/).
+
+next you will need to install the Omnipay WorldPay libraries
+(ideally via composer):
+
+    # composer require "omnipay/worldpay:~2.0"
+
+## Setup WorldPay on your install
+
+Once you have the WorldPay module installed, add the following
+to `mysite/_config/payment.yml`
+
+````
+---
+Name: payment
+---
+Payment:
+  allowed_gateways:
+    - 'WorldPay'
+
+GatewayInfo:
+  WorldPay:
+    parameters:
+      installationId: '1010618'
+      callbackPassword: 'xyz'
+---
+Except:
+  environment: 'live'
+---
+GatewayInfo:
+  WorldPay:
+    parameters:
+      testMode: true
+---
+Only:
+  environment: 'live'
+---
+GatewayInfo:
+  WorldPay:
+    parameters:
+      callbackPassword: 'abc'
+````
+
+The `installationId` will be provided by WorldPay when your account is
+setup or can be retrieved from the "Installations" screen of the [WorldPay Admin](https://secure.worldpay.com/sso/public/auth/login.html).
+
+The `callbackPassword` can be set in the WorldPay admin > Installations > Installation Adminiatration (using the 'Payment Response password' field).
+**Note** You can add different passwords for test and live environments.
+
+Additional supported settings can be found at the [omnipay-worldpay github page](https://github.com/thephpleague/omnipay-worldpay/blob/master/src/Gateway.php#L21).
+
+## Using a custom callback response
+
+If you want a custom callback response (so the user sees a styled page at
+the end of the payment process and is returned back to your site) you
+will need to enable the `WorldPayResponseExtension`.
+
+You can add the following to your `config.yml` to achieve this:
+
+````
+SilverStripe\Omnipay\Service\PaymentService:
+  extensions:
+    - WorldPayResponseExtension
+````
+
+If you want to customise the apperance of the response page, just copy
+the `WorldPayCallback.ss` template from this module and add it to your
+`templates` folder.

templates/WorldPayCallback.ss

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+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
+<html lang="en">
+    <head>
+        <meta http-equiv="refresh" content="2;url={$ReturnURL}" />
+        <title><%t WorldPayExtension.Processing "Processing" %></title>
+    </head>
+
+    <body>
+        <div style="font-family:sans-serif;text-align:center;" class="payment-processing">
+            <h1><%t WorldPayExtension.Processing "Processing" %></h1>
+
+            <p>
+                <%t WorldPayExtension.RedirectingToStore "We are now redirecting you, if you are not redirected automatically then click the link below." %>
+            </p>
+
+            <p>
+                <a href="{$ReturnURL}"><%t WorldPayExtension.ReturnToStore "Return To Merchant's Store" %></a>
+            </p>
+
+            <WPDISPLAY ITEM="banner">
+        </div>
+    </body>
+</html>