feat(coverage): per-provider coverage breakdowns (V1) replace placeholder stub

[cristim]

Summary

Inventory & Coverage > Coverage sub-tab previously showed a placeholder:

Per-provider coverage breakdowns are coming soon. Your overall coverage rate is on the Home dashboard.

V1 replaces the stub with real per-provider, per-service breakdowns.

What V1 ships

• New endpoint GET /api/inventory/coverage returning CoverageBreakdownResponse (per-provider sections, each with a list of service rows: covered, on-demand, coverage_pct).
• Frontend section in inventory.ts renders each provider that has data; per-provider empty state when a provider has no usage.
• Bar visualisation per row showing covered vs on-demand.
• Refresh button + period selector wired.

Data sources

No new cloud-provider SDK calls. Coverage % derived from data already in the system:

• Covered = MonthlyCost on active commitments (from purchase history)
• On-demand = Savings on current recommendations (the gap the user could be covering)

coverage_pct is *float64 (Go) / number|null (TS) -- null when both sides are 0, NOT coerced to 0. Matches the feedback_nullable_not_zero pattern.

Files changed (11)

Backend:

• internal/api/types.go -- new types CoverageServiceRow, ProviderCoverageSection, CoverageBreakdownResponse
• internal/api/handler_inventory.go -- getCoverageBreakdown, buildCoverageBreakdown, coveragePct, splitProviderService
• internal/api/router.go -- route + handler wrapper
• internal/api/handler_inventory_test.go -- 5 new tests

Frontend:

• frontend/src/api/types.ts, frontend/src/api/inventory.ts, frontend/src/api/index.ts -- typed API client
• frontend/src/inventory.ts -- loadCoverageBreakdown + render
• frontend/src/index.html -- container structure (#coverage-providers, #coverage-refresh-btn)
• frontend/src/__tests__/inventory.test.ts -- 6 new render tests (full, empty providers, null coverage, error, refresh)
• frontend/src/__tests__/api-inventory.test.ts -- 2 new API tests

Test plan

• 1332 backend tests pass (10 new)
• 21 frontend tests pass (8 new)
• Manual post-deploy: open Coverage tab with multi-provider data; confirm per-provider sections render and empty providers show their own empty state.

Deferred to follow-up

• Per-account drilldown within each provider.
• Real-time coverage from CE GetReservationCoverage / Azure Consumption / GCP equivalent (current V1 derives from purchase history + open recommendations; good first cut but real-time API would refine).
• Forecasting / what-if simulations.
• Cross-cloud unified view.

Closes #754.

Summary by CodeRabbit

Release Notes

• New Features

  • Inventory Coverage tab now displays per-provider coverage breakdown showing covered and on-demand metrics by service.
  • Added coverage percentage calculations and visual indicators for each provider.
  • Implemented refresh functionality to update coverage data on demand.

• Tests

  • Added comprehensive test coverage for the new coverage breakdown feature.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 38ea107d-afeb-4431-8e53-53afb6b20acd

📥 Commits

Reviewing files that changed from the base of the PR and between ab6dccf and d96bfc9.

📒 Files selected for processing (4)

• frontend/src/__tests__/inventory.test.ts
• frontend/src/inventory.ts
• internal/api/handler_inventory.go
• internal/api/handler_per_account_perms_test.go

📝 Walkthrough

Walkthrough

This PR implements the coverage breakdown feature for the inventory & coverage sub-tab. It adds a new backend endpoint (GET /api/inventory/coverage) that aggregates committed and on-demand usage by provider and service, computes per-service and per-provider coverage percentages, and exposes the data via TypeScript client adapters to a fully interactive frontend UI with provider cards, service rows, and a refresh button.

Changes

Coverage Breakdown Feature

Layer / File(s)	Summary
API Response Types frontend/src/api/types.ts, internal/api/types.go, frontend/src/api/index.ts	CoverageServiceRow, ProviderCoverageSection, and CoverageBreakdownResponse types establish the contract for per-provider breakdown responses, with nullable coverage percentages to represent "no data" vs. "0%" states. Both frontend and backend define these interfaces; barrel re-exports add them to the public API surface.
Backend Coverage Handler internal/api/handler_inventory.go, internal/api/router.go, internal/api/handler_inventory_test.go	New getCoverageBreakdown() handler aggregates committed usage from purchase history (filtered by view:purchases permission) and on-demand gaps from scheduler recommendations (best-effort fallback on error). buildCoverageBreakdown() merges the aggregated data, computes per-service and per-provider coverage %, sorts services alphabetically for stability, and emits nil coverage/services for providers with no data. GET /api/inventory/coverage route wires the endpoint. Unit tests cover single-provider, empty-provider, nil-vs-zero, and on-demand-only cases; integration test validates auth and the full response shape.
Frontend API Client frontend/src/api/inventory.ts, frontend/src/__tests__/api-inventory.test.ts	getCoverageBreakdown() function calls apiRequest for /inventory/coverage and returns the typed response. Tests verify the request path and response envelope structure including the providers array.
Frontend UI and End-to-End Tests frontend/src/index.html, frontend/src/inventory.ts, frontend/src/__tests__/inventory.test.ts	HTML markup replaces the "coming soon" placeholder with a Coverage card, Refresh button, and coverage-providers container. loadCoverageBreakdown() fetches data, renders per-provider cards with service rows showing covered/on-demand amounts and coverage %, handles skeleton loading, error states, empty-provider messages ("No usage detected"), and idempotent refresh. Sub-tab router maps the coverage tab to the new loader. E2E tests build the full DOM, mock the API, verify provider card rendering, test null-service and null-coverage-pct edge cases, assert error display, and confirm refresh re-fetches and updates in place.

Sequence Diagram

sequenceDiagram
  participant User
  participant Frontend as Frontend UI
  participant API as /api/inventory/coverage
  participant Store as PurchaseStore
  participant Scheduler as RecommendationScheduler
  
  User->>Frontend: Switch to Coverage sub-tab
  Frontend->>Frontend: loadCoverageBreakdown()
  Frontend->>API: GET /api/inventory/coverage
  API->>Store: Fetch active commitments (view:purchases)
  Store-->>API: Commitment data by provider/service
  API->>Scheduler: Fetch recommendations
  Scheduler-->>API: On-demand gaps (best-effort)
  API->>API: buildCoverageBreakdown() aggregates & computes %
  API-->>Frontend: CoverageBreakdownResponse
  Frontend->>Frontend: Render provider cards with services
  Frontend->>Frontend: Display coverage % per service & provider
  User->>Frontend: Click refresh button
  Frontend->>API: GET /api/inventory/coverage (reload)
  API-->>Frontend: Updated response
  Frontend->>Frontend: Update provider sections in-place

Loading

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Poem

A rabbit hops through cloud data with glee,
Counting commitments and gaps, coverage to see—
Per-provider breakdowns now bloom on the screen,
With refresh buttons gleaming, a UI so clean!
Service by service, the percentages shine,
No more "coming soon," the coverage is mine. 🐰☁️

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 72.73% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: replacing the coverage placeholder stub with a V1 implementation of per-provider coverage breakdowns.
Linked Issues check	✅ Passed	The PR implements all coding-related acceptance criteria from issue #754: per-provider breakdowns, empty-state handling, refresh functionality, and service-level drilldown.
Out of Scope Changes check	✅ Passed	All changes are directly aligned with issue #754 objectives. No unrelated modifications to other features, performance optimizations, refactorings, or deferred items are present in the changeset.

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✨ Finishing Touches

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• Create PR with unit tests
• Commit unit tests in branch feat/754-coverage-per-provider-breakdowns

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Actionable comments posted: 2

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@frontend/src/inventory.ts`:
- Around line 319-323: The last table header is created as an empty string which
is inaccessible; update the header creation loop in inventory.ts (the block that
builds headerRow) to use a meaningful label such as "Coverage" or "Coverage bar"
instead of '' and/or add an explicit aria-label (e.g.,
th.setAttribute('aria-label', 'Coverage bar')) on the created <th> so screen
readers can identify the coverage bar column; locate the header generation loop
that iterates over ['Service', 'Covered/mo', 'On-demand gap/mo', 'Coverage %',
''] and replace the empty entry with the chosen non-empty label and optional
aria-label on the <th>.

In `@internal/api/handler_inventory.go`:
- Around line 154-164: Recommendations returned by
h.scheduler.ListRecommendations are aggregated into onDemandByKey without
applying the same account-access scope used for commitments; restrict
aggregation to only recommendations that match the allowed-account scope (the
same filter applied to commitments) by either passing the allowed-accounts into
ListRecommendations (instead of config.RecommendationFilter{}), or
post-filtering recs by account before the loop (e.g., skip recs whose account is
not in the allowed-account set), then sum onDemandByKey using
rec.Provider+":"+rec.Service and rec.Savings only for those allowed recs.

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Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: afb41bee-1981-4414-8662-edf2a3409fbe

📥 Commits

Reviewing files that changed from the base of the PR and between f5b76eb and ab6dccf.

📒 Files selected for processing (11)

• frontend/src/__tests__/api-inventory.test.ts
• frontend/src/__tests__/inventory.test.ts
• frontend/src/api/index.ts
• frontend/src/api/inventory.ts
• frontend/src/api/types.ts
• frontend/src/index.html
• frontend/src/inventory.ts
• internal/api/handler_inventory.go
• internal/api/handler_inventory_test.go
• internal/api/router.go
• internal/api/types.go

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