Universal Coupon Finder Plugin

I’m looking to have a plugin built that mirrors the core experience of Coupert: when a shopper reaches checkout, the tool should automatically hunt down every available coupon, test them in real time, and apply the single best code to maximise savings.

The solution has to work across all online stores, not just a curated set, so the detection logic must be flexible enough to recognise varied cart and checkout structures. Whether a user is on a small boutique site or a major retailer, the plugin should seamlessly surface discounts without manual input.

Key points I need you to address:
• Robust coupon-code discovery, validation, and ranking so only the most valuable offer is applied
• Lightweight architecture that won’t slow page loads or break storefront scripts
• Clean, intuitive user interface that signals progress (searching, testing, success) and final savings
• Scalable rules engine to keep adding new coupon sources or parsing methods with minimal code rewrites

On delivery I’ll want the compiled plugin plus well-documented source, a short setup guide, and a quick demo video showing it in action from product page through checkout. Provide any framework recommendations you have up front so we can align early.