feat(nwis): site + stats enrichment — named location + WaterWatch normalcy band (v0.8.0)

Opens the v0.8.x data-quality cleanup arc. Production code; central-gui AND
central-supervisor restart (adapter contract + enrichment behavior change).

NWIS events rendered as a bare "Water reading: 111 ft3/s" with an empty Location
column -- an operator couldn't tell where the gauge is or whether 111 ft3/s is
drought-low, normal, or near-flood. Coordinates were present but the reverse
geocoder returns null city/state/county for rural gauge points, and USGS site +
percentile data was never fetched. v0.8.0 fetches both.

Approach B (adapter-owned, per the proposal decision): the NWIS adapter -- which
already owns the USGS APIs -- fetches site metadata and daily stats itself and
writes two provenance bundles under event.data["_enriched"]:
- usgs_site {name, lat, lon, state, county} from the OGC monitoring-locations
  item-by-id (the API family the adapter already speaks; JSON, no RDB parser).
- usgs_stats {value, percentile, class_label, severity_band, p10..p90, record_max,
  count, period} from the legacy RDB daily-statistics service (the OGC API has no
  stats endpoint). USGS percentiles are % of days at-or-below, so higher = higher
  flow; classified to the WaterWatch bands -> severity 0-4 (record=4, much
  above/below=3, above/below=2, normal=1; None reserved for "no stats", distinct
  from a normal-flow gauge). Severity is set on the event, so it drives the v0.7.1
  severity chip-picker filter + v0.7.2 map-marker opacity.
- new nwis_enrich.py: pure parse/classify/percentile/band helpers + a sqlite
  SiteStatsCache (site TTL 365d, stats TTL 90d -- one fetch per site+param serves
  every reading for the window, so a warm cache makes zero USGS calls). USGS down
  -> cached-if-present else all-null bundle; the event still publishes.

Framework: the single agreed generic change -- supervisor apply_enrichment now
MERGES into _enriched instead of overwriting, so the still-global geocoder phase
doesn't clobber the adapter's bundles. No other adapter writes _enriched, so this
is inert for them.

GUI: _event_summaries/nwis.html -> "<site> -- <value> <units> (<band>, <Nth>
percentile)", with graceful fallback to "<site> -- <value>" then the bare
"Water reading:". _event_rows/nwis.html detail gains site/normalcy/typical/location
rows. _events_rows.html Location column falls back generically to any
_enriched.<source> carrying state/county when the geocoder is null (works for
future enrichers). events.json contract unchanged (additions under _enriched only).

conftest isolate_enrichment_cache also redirects NWIS_CACHE_DB_PATH off the prod
path (unprivileged-user test isolation). Adds tests/test_nwis_enrichment.py (28
tests: parse, band edges incl P0/P9/P10/P75/P90/record, percentile interpolation,
cache hit/miss/expire, adapter enrich + graceful-null + cache-hit-no-refetch,
summary rendering per band).

Full suite: 710 passed, 1 skipped (central and unprivileged zvx, 3x each).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/test_nwis_enrichment.py

@@ -0,0 +1,260 @@
+"""Tests for v0.8.0 NWIS site + stats enrichment.
+
+Covers the pure parse/classify/band logic, the SiteStatsCache (hit/miss/expire),
+the adapter's _enrich_event orchestration with mocked USGS responses (incl.
+graceful nulls when USGS is down and cache-hit avoiding a refetch), and the
+L-c summary template rendering per WaterWatch band. No live network, no live DB.
+"""
+
+from datetime import datetime, timezone
+from pathlib import Path
+
+import jinja2
+import pytest
+
+from central.adapters import nwis_enrich as ne
+from central.adapters.nwis import NWISAdapter
+from central.models import Event, Geo
+
+# ── canned USGS fixtures ────────────────────────────────────────────────────
+
+SITE_JSON = """
+{"type":"Feature",
+ "geometry":{"type":"Point","coordinates":[-93.1926861111111,40.8004444444444]},
+ "properties":{"monitoring_location_name":"South Fork Chariton River near Promise City, IA",
+               "state_name":"Iowa","county_name":"Wayne County",
+               "country_name":"United States of America"}}
+"""
+
+# header / RDB-format row / one data row for month 1 day 1 (p90 intentionally blank).
+STATS_RDB = (
+    "# canned\n"
+    "agency_cd\tsite_no\tparameter_cd\tts_id\tloc_web_ds\tmonth_nu\tday_nu\tbegin_yr\tend_yr\tcount_nu\tmax_va_yr\tmax_va\tp10_va\tp25_va\tp50_va\tp75_va\tp90_va\n"
+    "5s\t15s\t5s\t10n\t15s\t3n\t3n\t6n\t6n\t8n\t5n\t12s\t12s\t12s\t12s\t12s\t12s\n"
+    "USGS\t06903700\t00060\t43334\t\t1\t1\t1968\t2026\t59\t2019\t315\t10\t25\t50\t75\t90\n"
+)
+
+DAY = {"p10": 10.0, "p25": 25.0, "p50": 50.0, "p75": 75.0, "p90": 90.0, "max": 200.0}
+
+
+# ── parse_site_feature ──────────────────────────────────────────────────────
+
+def test_parse_site_feature_full():
+    import json
+    b = ne.parse_site_feature(json.loads(SITE_JSON))
+    assert b["name"] == "South Fork Chariton River near Promise City, IA"
+    assert b["state"] == "Iowa" and b["county"] == "Wayne County"
+    assert round(b["lat"], 3) == 40.800 and round(b["lon"], 3) == -93.193
+
+
+def test_parse_site_feature_bad_shape_is_all_null():
+    assert ne.parse_site_feature({}) == ne.site_null_bundle()
+    assert ne.parse_site_feature(None) == ne.site_null_bundle()
+
+
+# ── parse_stats_rdb ─────────────────────────────────────────────────────────
+
+def test_parse_stats_rdb_keys_and_values():
+    table = ne.parse_stats_rdb(STATS_RDB)
+    assert "1-1" in table
+    row = table["1-1"]
+    assert row["p10"] == 10.0 and row["p75"] == 75.0 and row["max"] == 315.0
+    assert row["count"] == 59 and row["begin_yr"] == 1968.0 and row["end_yr"] == 2026.0
+
+
+def test_parse_stats_rdb_garbage_is_empty():
+    assert ne.parse_stats_rdb("") == {}
+    assert ne.parse_stats_rdb("not\trdb\n") == {}
+
+
+# ── classify: WaterWatch band edges ─────────────────────────────────────────
+
+@pytest.mark.parametrize(
+    "value,label,severity",
+    [
+        (5.0, "much below normal", 3),     # < P10  (P0-P9 region)
+        (9.0, "much below normal", 3),     # P9
+        (10.0, "below normal", 2),         # == P10 boundary
+        (24.0, "below normal", 2),
+        (25.0, "normal", 1),               # == P25
+        (50.0, "normal", 1),
+        (75.0, "normal", 1),               # == P75 (not > P75)
+        (80.0, "above normal", 2),         # P75..P90
+        (90.0, "above normal", 2),         # == P90 (not > P90)
+        (120.0, "much above normal", 3),   # > P90, <= max
+        (250.0, "record high", 4),         # > historical max
+    ],
+)
+def test_classify_bands(value, label, severity):
+    lbl, pct, sev = ne.classify(value, DAY)
+    assert lbl == label
+    assert sev == severity
+    assert ne.SEVERITY_BY_BAND.get(label) == severity
+
+
+def test_classify_no_thresholds_is_none():
+    assert ne.classify(42.0, {}) == (None, None, None)
+
+
+def test_classify_none_value():
+    assert ne.classify(None, DAY) == (None, None, None)
+
+
+def test_percentile_interpolates_and_bounds():
+    assert ne.percentile_of(50.0, DAY) == 50      # on the P50 point
+    assert ne.percentile_of(0.0, DAY) == 0        # lower bound
+    assert ne.percentile_of(200.0, DAY) == 100    # at max
+    mid = ne.percentile_of(17.5, DAY)             # between P10(10) and P25(25)
+    assert 10 < mid < 25
+
+
+# ── build_stats_bundle ──────────────────────────────────────────────────────
+
+def test_build_stats_bundle_classifies_matching_day():
+    table = ne.parse_stats_rdb(STATS_RDB)
+    b = ne.build_stats_bundle(120.0, table, 1, 1)
+    assert b["value"] == 120.0
+    assert b["class_label"] == "much above normal"
+    assert b["severity_band"] == 3
+    assert b["p50"] == 50.0 and b["record_max"] == 315.0
+    assert b["period"] == "1968–2026" and b["count"] == 59
+
+
+def test_build_stats_bundle_no_matching_day_echoes_value_only():
+    table = ne.parse_stats_rdb(STATS_RDB)
+    b = ne.build_stats_bundle(120.0, table, 7, 4)  # no 7-4 row
+    assert b["value"] == 120.0
+    assert b["class_label"] is None and b["severity_band"] is None
+
+
+# ── SiteStatsCache: miss / hit / expire ─────────────────────────────────────
+
+@pytest.mark.asyncio
+async def test_cache_miss_then_hit(tmp_path):
+    cache = ne.SiteStatsCache(tmp_path / "nwis_cache.db")
+    assert await cache.get("site", "X", 100) is None
+    await cache.set("site", "X", {"name": "Gauge"})
+    assert (await cache.get("site", "X", 100))["name"] == "Gauge"
+
+
+@pytest.mark.asyncio
+async def test_cache_expired(tmp_path):
+    cache = ne.SiteStatsCache(tmp_path / "nwis_cache.db")
+    await cache.set("stats", "X:00060", {"p10": 1})
+    assert await cache.get("stats", "X:00060", -1) is None  # ttl already elapsed
+
+
+# ── adapter _enrich_event orchestration ─────────────────────────────────────
+
+def _make_event():
+    return Event(
+        id="USGS-06903700:00060:2026-01-01T00:00:00+00:00",
+        adapter="nwis",
+        category="hydro.00060.usgs.06903700",
+        time=datetime(2026, 1, 1, tzinfo=timezone.utc),
+        severity=0,
+        geo=Geo(centroid=(-93.19, 40.80)),
+        data={
+            "monitoring_location_id": "USGS-06903700",
+            "parameter_code": "00060",
+            "value": 120.0,
+        },
+    )
+
+
+def _adapter_with_fetch(fetch, cache=None):
+    a = object.__new__(NWISAdapter)
+    a._enrich_cache = cache
+    a._fetch = fetch  # shadows the @retry method
+    return a
+
+
+@pytest.mark.asyncio
+async def test_enrich_event_populates_bundles_and_severity(tmp_path):
+    async def fetch(url):
+        if "monitoring-locations" in url:
+            return SITE_JSON
+        if "/stat/" in url or "statReportType" in url:
+            return STATS_RDB
+        raise AssertionError(url)
+
+    a = _adapter_with_fetch(fetch, cache=ne.SiteStatsCache(tmp_path / "c.db"))
+    ev = _make_event()
+    sev = await a._enrich_event(ev)
+    enr = ev.data["_enriched"]
+    assert enr["usgs_site"]["name"].startswith("South Fork Chariton")
+    assert enr["usgs_site"]["state"] == "Iowa"
+    assert enr["usgs_stats"]["class_label"] == "much above normal"
+    assert enr["usgs_stats"]["severity_band"] == 3
+    assert sev == 3
+
+
+@pytest.mark.asyncio
+async def test_enrich_event_graceful_nulls_when_usgs_down(tmp_path):
+    async def fetch(url):
+        raise TimeoutError("USGS down")
+
+    a = _adapter_with_fetch(fetch, cache=ne.SiteStatsCache(tmp_path / "c.db"))
+    ev = _make_event()
+    sev = await a._enrich_event(ev)
+    enr = ev.data["_enriched"]
+    assert enr["usgs_site"] == ne.site_null_bundle()
+    assert enr["usgs_stats"]["value"] == 120.0  # value still echoed
+    assert enr["usgs_stats"]["class_label"] is None
+    assert sev is None  # no stats -> unknown severity
+
+
+@pytest.mark.asyncio
+async def test_enrich_event_cache_hit_avoids_refetch(tmp_path):
+    calls = {"n": 0}
+
+    async def fetch(url):
+        calls["n"] += 1
+        return SITE_JSON if "monitoring-locations" in url else STATS_RDB
+
+    cache = ne.SiteStatsCache(tmp_path / "c.db")
+    a = _adapter_with_fetch(fetch, cache=cache)
+    await a._enrich_event(_make_event())
+    first = calls["n"]
+    assert first == 2  # one site + one stats fetch
+    await a._enrich_event(_make_event())  # same site+param -> both cached
+    assert calls["n"] == first  # no additional USGS calls
+
+
+# ── L-c summary template rendering per band ─────────────────────────────────
+
+_TEMPLATES_DIR = Path(__file__).resolve().parents[1] / "src/central/gui/templates"
+
+
+def _render_summary(stats=None, site=None, value=120.0, unit="ft3/s"):
+    src = (_TEMPLATES_DIR / "_event_summaries/nwis.html").read_text()
+    tmpl = jinja2.Environment(autoescape=True).from_string(src)
+    inner = {"value": value, "unit_of_measure": unit}
+    enriched = {}
+    if site is not None:
+        enriched["usgs_site"] = site
+    if stats is not None:
+        enriched["usgs_stats"] = stats
+    if enriched:
+        inner["_enriched"] = enriched
+    event = type("E", (), {"data": {"data": {"data": inner}}})()
+    return tmpl.render(event=event).strip()
+
+
+def test_summary_full_band_and_percentile():
+    out = _render_summary(
+        site={"name": "South Fork Grand River near Gallatin, MO"},
+        stats={"class_label": "below normal", "percentile": 18},
+    )
+    assert "South Fork Grand River near Gallatin, MO — 120.0 ft3/s" in out
+    assert "(below normal, 18th percentile)" in out
+
+
+def test_summary_site_no_stats():
+    out = _render_summary(site={"name": "Some Creek near Town, IA"}, stats=None)
+    assert out == "Some Creek near Town, IA — 120.0 ft3/s"
+
+
+def test_summary_no_enrichment_falls_back():
+    out = _render_summary(site=None, stats=None)
+    assert out == "Water reading: 120.0 ft3/s"