The unfortunate short answer is that you cannot process it automatically directly through MiGS.
When using the 3rd party version ( Migs_ThreeParty ), you rely on the returning end user and click this completePurchase() method. You can configure cron jobs to detect βabandonedβ sales (which may or may not actually be left) for manual approval in the Mastercard control panel, but MiGS does not provide an option for notifyUrl , as well as no implementation of acceptNotification() for notifications based on the gateway, like IPN PayPal. Unfortunately, it also does not have a simple request URL for βthis transaction yetβ, which you could attach to a cron job with a refusal check.
The best thing you can hope for is to talk to Mastercard and see if you can shorten the redirection time by automatically redirecting or if your return URL is a super fast "Do not close this window" download, which then loads completePurchase into background mode.
Redirection / 3-way gateways have this problem. This is one of the reasons most merchants prefer double-sided gateways (if they can be bothered with PCI compliance), and have seen the growth of gateways on tokens (so that they can avoid the burden of matching PCI without redirection headaches).
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