feat(frontend/recs): default-seed payment/term from GlobalConfig (closes #223)

[cristim]

Summary

Closes #223. After PR #231 merged `pickBestVariantPerCell`, this PR replaces its effective-savings tiebreaker with config-match, and fixes the two adjacent surfaces that hardcoded `'all-upfront'`.

Three surfaces changed:

• `pickBestVariantPerCell` (select-all tiebreaker) — now prefers the variant matching `(GlobalConfig.DefaultTerm, GlobalConfig.DefaultPayment)` over highest effective savings. Falls back to highest-effective when no variant matches.
• `defaultBulkPurchaseState.payment` (bulk toolbar init) — seeded from `GlobalConfig.DefaultPayment` after page-load bootstrap; no longer hardcodes `'all-upfront'`.
• `resolvePerRecPaymentSeed` fallback — prefers `GlobalConfig.DefaultPayment` when the service supports it, before falling back to `paymentOptionsFor[0]`.

Bootstrap approach: `loadRecommendations()` adds `api.getConfig()` as a siloed third leg of its `Promise.all` (`.catch(() => null)` — a missing config endpoint cannot block rec load). Resolved values populate module-level `cachedGlobalDefaultTerm / Payment`.

Exported for testing: `pickBestVariantPerCell` (pure function, no DOM side effects) and `seedGlobalDefaults(term, payment)` (test injection hook).

Test plan

• `npx jest --testPathPatterns=recommendations` passes (1420 tests)
• `npx tsc --noEmit` clean (pre-existing `styles.css` TS2882 is unrelated, present on base branch)
• `npm run build` succeeds
• New describe block `'issue feat(frontend/recs): default-select per-cell variant matching configured term + payment #223: pickBestVariantPerCell config-match tiebreaker'` — 4 tests covering: config-match preference, highest-effective fallback, multi-cell independence, and 3yr/partial-upfront as configured default

Summary by CodeRabbit

• Bug Fixes
  • Improved consistency of default payment and term option selections across the application.
  • Enhanced fallback behavior for configuration defaults when stored user preferences are unavailable.
  • Optimized selection logic to prefer configured defaults with improved fallback mechanisms.

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Run ID: 9403f58e-f325-4f33-a1f4-e8beb6ded82d

📥 Commits

Reviewing files that changed from the base of the PR and between c8a78cb and d95194a.

📒 Files selected for processing (2)

• frontend/src/__tests__/recommendations.test.ts
• frontend/src/recommendations.ts

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📝 Walkthrough

Walkthrough

This PR implements default-variant selection for recommendations based on GlobalConfig settings. The change fetches GlobalConfig on page load, caches the default term and payment, and uses those values to pre-select matching variants across the recommendation list, bulk purchase toolbar, and purchase modal, with fallback to the highest-effective variant when no config-matching option exists.

Changes

GlobalConfig-Driven Default Variant Selection

Layer / File(s)	Summary
Caching Setup frontend/src/recommendations.ts:29-43	Module-level cachedGlobalDefaultTerm and cachedGlobalDefaultPayment are introduced with historical fallback values; exported seedGlobalDefaults() function enables test-time overrides.
API Integration frontend/src/recommendations.ts:92-119	loadRecommendations() fetches api.getConfig() in parallel with recommendations and account lists; on success, the cached defaults are updated with validated values from cfgResponse.global.
Variant Selection Logic frontend/src/recommendations.ts:198-247	pickBestVariantPerCell() is exported and refactored to prefer, per cell, the variant matching both cachedGlobalDefaultTerm and cachedGlobalDefaultPayment; if no match exists, it falls back to the highest-effective-savings tie-breaker.
UI Integration frontend/src/recommendations.ts:1342-1344, 2160-2166	loadBulkPurchaseState() and resolvePerRecPaymentSeed() fallback logic updated to use cachedGlobalDefaultPayment instead of hardcoded 'all-upfront'.
Test Coverage frontend/src/__tests__/recommendations.test.ts:4-14, 2238-2320	API mock extended to resolve getConfig({ global: {} }); new test block validates config-match preference, highest-effective fallback, multi-cell independence, and correctness under different seedGlobalDefaults() scenarios.

Sequence Diagram

sequenceDiagram
    participant App as Page Load
    participant API as API Layer
    participant Cache as GlobalConfig Cache
    participant Selector as Variant Selector
    participant UI as UI Components
    
    App->>API: loadRecommendations()
    par
        API->>API: getRecommendations()
        API->>API: listAccounts()
        API->>API: getConfig()
    end
    
    API->>Cache: Update cached defaults<br/>(term, payment)
    API->>Selector: pickBestVariantPerCell(recs)
    Selector->>Cache: Read cachedGlobalDefaultTerm<br/>cachedGlobalDefaultPayment
    Selector->>Selector: Match variant per cell
    alt Variant match found
        Selector->>Selector: Select config-matching variant
    else No match
        Selector->>Selector: Fall back to highest-effective
    end
    
    Selector->>UI: Return pre-selected variants
    
    par
        API->>Cache: loadBulkPurchaseState() reads<br/>cachedGlobalDefaultPayment
        API->>Cache: resolvePerRecPaymentSeed() reads<br/>cachedGlobalDefaultPayment
    end
    
    UI->>UI: Render with consistent defaults

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Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• fix(frontend/recs): enforce one-variant-per-cell radio selection (closes #224) #231: Both PRs modify pickBestVariantPerCell and per-cell selection logic — PR #231 adds the cellKey and highest-effective tie-breaker infrastructure that this PR leverages for the fallback when no GlobalConfig-matching variant is found.

Poem

🐰 A rabbit hops through config trees,
Pre-picking variants with ease and grace,
No more re-clicks on each fresh load—
The defaults remember, the UI knows its place! 🌟

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The PR title clearly summarizes the main change: default-seeding payment/term from GlobalConfig to address issue #223.
Linked Issues check	✅ Passed	The PR fully implements all coding requirements from issue #223: config-match variant pre-selection with fallback, GlobalConfig payment seeding in bulk toolbar and modal, exports for testing, and comprehensive test coverage.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to issue #223 objectives: variant pre-selection logic, GlobalConfig seeding, and necessary test infrastructure; no unrelated modifications detected.
Docstring Coverage	✅ Passed	Docstring coverage is 83.33% which is sufficient. The required threshold is 80.00%.

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• Commit unit tests in branch feat/issue-223-default-seed-per-cell

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[cristim]

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