National Alert Browser: browse active weather alerts by service/country

[kellylford]

Closes #87.

Adds a National Alert Browser to the iOS app: browse active government weather alerts independent of any saved city, by service/country, with a VoiceOver-first digest. Behind the alertBrowserEnabled feature flag (default on), reached from a new Weather Alerts section in the Browse tab.

What's included

Sources (all free, keyless — none touch the paid Open-Meteo account):

• United States — NWS api.weather.gov
• Canada — Environment Canada api.weather.gc.ca
• Europe — MeteoAlarm, 36 countries, with per-country active-alert counts

Digest UI (NationalAlertDigestView):

• Alerts collapsed by event type, grouped under severity headers with counts.
• Exclusive severity buttons (Extreme / Severe / Moderate / All) — each shows only that severity; counts announced per VoiceOver segment.
• Hazard-type "Type" menu (Storms, Tropical, Flooding, Rain, Heat, Winter, Wind, Fire, Fog, Marine & Coastal, Air Quality, Other) — only present families shown, each with a count.
• Tap a category → affected areas → existing AlertDetailView.

Design: each provider normalizes into the existing WeatherAlert model, so AlertDetailView + severity coloring + a11y labels are reused. New AlertSource cases .eccc / .meteoalarm. No new dependencies.

New / changed files

• New: Services/AlertBrowserService.swift (providers, fetch, digest grouping, hazard classifier), Views/AlertBrowserView.swift (region picker, Europe country list, digest, group detail)
• Edited: Models/WeatherAlert.swift (source cases), Views/AlertDetailView.swift (generalized source link), Services/FeatureFlags.swift + Views/DeveloperSettingsView.swift (flag + toggle), Views/BrowseCitiesView.swift (entry point)

Notable fixes surfaced during development

• NWS /alerts/active rejects a limit param (HTTP 400) — removed.
• Air Quality (NWS "Unknown" severity) remapped to Moderate.
• Dropped the land/marine toggle — Small Craft Advisories are Minor, so severity buttons already handle them.
• Repaired feed data-quality issues: Austria's glued "Heatwarning" names, and raw awareness_type=… event dumps decoded via the structured awareness code.
• Broadened the hazard classifier for non-US vocabulary — "Other" fell from 35% to 0.7% across live Canada + Europe data.

Testing

• Builds clean for simulator and device (Xcode 26.6); installed and exercised on a physical iPhone throughout.
• Cross-checked digest counts against raw API (e.g. the single US Severe Thunderstorm Warning matched the feed).
• Hazard classifier validated against live CA + 18 EU feeds.

Follow-ups (not in this PR)

• Full VoiceOver walkthrough of every new screen before merge.
• Greece's generic "Yellow Warning" stays in "Other."
• Possible additional sources (Australia BOM, Japan JMA, NZ MetService).

🤖 Generated with Claude Code

[kellylford]

Code review — National Alert Browser

Reviewed the diff (NWS/ECCC/MeteoAlarm alert browser behind alertBrowserEnabled). Overall this is clean, well-factored work: each provider normalizes into the shared WeatherAlert model so AlertDetailView, severity coloring, and a11y labels are all reused, and the a11y labeling on the new screens is thorough. No correctness bugs that produce a crash or clearly-wrong output survived verification. Findings below are cleanup/efficiency plus two minor correctness notes, most-actionable first.

1. Dead land/marine filter machinery (cleanup)

Services/AlertBrowserService.swift

• AlertRegion.supportsLandMarineFilter (line 38) is never referenced anywhere in the tree.
• fetchAlerts(for:landOnly:) defaults landOnly: true, but both callers pass false (AlertBrowserService.swift:192 and AlertBrowserView.swift:312), so the if landOnly { region_type=land } branch (:293) is unreachable.

The PR description notes the land/marine toggle was dropped — this is its leftover skeleton. Suggest removing supportsLandMarineFilter, the landOnly parameter, and the branch so the fetch path has one behavior.

2. Dead selectedAlert state + sheet in NationalAlertDigestView (cleanup)

Views/AlertBrowserView.swift:128 declares @State private var selectedAlert and :145 attaches .sheet(item: $selectedAlert), but nothing in that view ever assigns selectedAlert (rows use NavigationLink to AlertGroupDetailView, which has its own selectedAlert/sheet at :326/:362). The digest view's state + sheet are dead and can be deleted.

3. parseISO re-allocates ISO8601 formatters on every call (efficiency)

Services/AlertBrowserService.swift:266-272 — each parseISO call constructs two ISO8601DateFormatter instances (fractional + plain). It's called ~3× per alert (ends/expires/onset), and a US NWS /alerts/active fetch can be hundreds of alerts → ~600–900 formatter allocations per load. ISO8601DateFormatter construction is notably expensive. Hoist the two formatters into static let singletons (the codebase already caches formatters this way in SettingsManager.swift).

4. HazardType.classify recomputed repeatedly per render (efficiency/simplification)

Views/AlertBrowserView.swift — the scoped array (alerts.filter { … classify($0.event) … }) is computed in both loadedContent and filterControls, and classify is called again in the presentFamilies filter and both picker loops. Every SwiftUI re-render re-runs all of it (lowercasing + substring scans per alert). Compute the classification/scoped set once and reuse.

5. MeteoAlarm id fallback uses array index — unstable (minor correctness)

Services/AlertBrowserService.swift:431 — id: warning.alert.identifier ?? "meteoalarm-\(slug)-\(index)". When a feed omits an identifier, the id is the position in the decoded array, so the same alert can get a different id across refetches if the feed reorders/adds entries, churning SwiftUI ForEach identity (flicker/re-render). A content-derived key (e.g. hash of event+area+onset) would be stable. Low impact since most CAP alerts carry an identifier.

6. "Special Weather Statement" always classified as Storms (minor, judgment call)

Services/AlertBrowserService.swift:128 folds "special weather statement" into .storms, but NWS issues SPS products for fog, wind, etc. as well. Not wrong enough to block, but it will mis-bucket non-storm statements under the Storms hazard filter.

Also minor: shortTime (AlertBrowserView.swift:302) allocates a DateFormatter per call — same static-caching fix as #3.

🤖 Review by Claude Code

[kellylford]

Review feedback addressed — resolved in 36a31b2

#	Finding	Resolution
1	Dead land/marine filter machinery	Removed supportsLandMarineFilter, the landOnly param, and the unreachable region_type=land branch; both callers updated.
2	Dead selectedAlert state + sheet in NationalAlertDigestView	Deleted — rows use NavigationLink; the group-detail view owns its own sheet.
3	parseISO re-allocating ISO8601 formatters	Hoisted both formatters into static let singletons.
4	HazardType.classify recomputed per render	Classified once in loadedContent, threaded through filterControls.
5	MeteoAlarm array-index id fallback	Now derives a stable content-based id (slug + event + area + onset + expires) when the feed omits an identifier.
—	shortTime allocating a DateFormatter per call	Cached as a static let singleton.
6	"Special Weather Statement" → Storms	Left as-is by design — correctly re-bucketing needs the alert description text; the storms default is the reasonable choice.

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