Refactored hasActiveOffer and _getActiveDiscount to share common logic

[mike182uk]

ref https://linear.app/ghost/issue/BER-3338

Both functions independently computed discount windows using the same three data paths (trial periods, Stripe coupon data, and legacy offer duration fallback). This extracts the shared computation into a single getDiscountWindow utility so the two callers stay in sync as the discount model evolves.

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📥 Commits

Reviewing files that changed from the base of the PR and between 519483f and 01dfb7a.

📒 Files selected for processing (5)

• ghost/core/core/server/services/members/members-api/services/next-payment-calculator.js
• ghost/core/core/server/services/members/members-api/utils/get-discount-window.js
• ghost/core/core/server/services/members/members-api/utils/has-active-offer.js
• ghost/core/test/unit/server/services/members/members-api/utils/get-discount-window.test.js
• ghost/core/test/unit/server/services/members/members-api/utils/has-active-offer.test.js

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Walkthrough

This change introduces a new utility function getDiscountWindow that consolidates discount window calculation logic across multiple files. The function handles three offer types: free_months (trial-based), Stripe coupon discounts with explicit start/end dates, and legacy offers with duration specifications. The next-payment-calculator.js and has-active-offer.js files were refactored to delegate discount window computation to this new utility. Corresponding unit tests were added to validate discount scenarios across all three offer handling paths, and existing test helpers were expanded to support trial_start_at field mapping.

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main refactoring objective: extracting common logic from hasActiveOffer and _getActiveDiscount into a shared utility.
Description check	✅ Passed	The description clearly explains the rationale for the refactoring and identifies the specific shared computation patterns being consolidated.

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[sagzy]

Nice! Refactoring makes sense. Naming: getActiveDiscount instead of getDiscountWindow?