PRICE-01: price_service provider, fallback chain, and the gate read from it

A new price source, `price_provider: price_service`: the owner's price server,
one fixed HTTPS host, a bearer token (new password option
`price_service_token`), wholesale energy only so markup and taxes are added as
for generic_dayahead.

The chain is server, then energy-charts, then the prices the history store
kept. A step counts only if it has a price for now. Each step down and back up
is one log line. With every source down a site plans from what it saved.

No price for now: one status row, one Home plan line and one notification, in
English and Dutch, cleared when a price returns. With this provider the
maintenance charge gate reads the provider's prices and keeps the Home
Assistant rule: the current 15-minute price is at or below today's average.

The token is hidden on the settings page, refused when missing, and taken out
of any error text. Other providers, `off` and the Home Assistant pair take the
road they always took (scripted-day probe against 0ce7d35: one line differs,
the refusal that lists the known providers). See
DECISIONS/PRICE-01-own-price-server.md.

Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Bdqr7PiaHcBnzPituu2yTC

goodwe_controller/app/static_tariff.py

@@ -204,12 +204,13 @@ import math
 from dataclasses import dataclass
 from datetime import datetime, timedelta, timezone
 
-from . import messages
+from . import messages, price_chain
 from .price import (
     MAX_PLAUSIBLE_EUR_KWH, Absence, PricePoint, PriceProduct, PriceRead,
     Uncertainty, _Outcome, brussels, load_prices, price_option,
     provider_configured, required_spread, uncertainty_of, widen_factor,
 )
+from .price_chain import uses_chain
 
 _LOG = logging.getLogger("goodwe.tariff.static")
 
@@ -793,6 +794,13 @@ class TariffPlan:
         self.read = read
         self.profile = profile
         self.origin = origin
+        # PRICE-01. The series the price chain found, BEFORE the yesterday fill
+        # cut it to the hours ahead: the maintenance gate needs the whole of
+        # today to know its average. None for every plan that did not come
+        # through the chain, which is every plan of every other provider.
+        self.published = None
+        self.step = None
+        self.reasons = ()
 
     # -- derived facts -------------------------------------------------------
     @property
@@ -1274,7 +1282,8 @@ def static_status(opts: dict, now: datetime):
 
 
 async def resolve_tariff(opts: dict, since: datetime, until: datetime,
-                         transport=None, now=None, *, history) -> TariffPlan:
+                         transport=None, now=None, *, history,
+                         watch=None) -> TariffPlan:
     """The full §9.2 + §11.4 resolution. MAY PERFORM I/O - see `static_plan`.
 
     ⚠️ NOT ON THE 30 s TICK, and that is a deliberate boundary rather than an
@@ -1330,13 +1339,30 @@ async def resolve_tariff(opts: dict, since: datetime, until: datetime,
     if not provider_configured(opts):
         return static_plan(opts, since, until, provisional=False, now=stamp)
 
+    if uses_chain(opts):
+        # PRICE-01. The provider names fallbacks, so its prices come from the
+        # first step of the chain that has one for now. Nothing else does.
+        found = await price_chain.resolve(
+            opts, since, until, transport, history, stamp,
+            watch if watch is not None else price_chain.PriceWatch(),
+            load=load_prices)
+        plan = found.read.match(
+            series=lambda r: _provider_plan(
+                opts, r, since, until, stamp, history,
+                remember=found.step != price_chain.STEP_STORED),
+            no_data=lambda r: _degrade(opts, r, since, until, stamp))
+        plan.published, plan.step = found.published, found.step
+        plan.reasons = found.reasons
+        return plan
+
     read = await load_prices(opts, since, until, transport)
     return read.match(
         series=lambda r: _provider_plan(opts, r, since, until, stamp, history),
         no_data=lambda r: _degrade(opts, r, since, until, stamp))
 
 
-def _provider_plan(opts, read, since, until, stamp, history) -> TariffPlan:
+def _provider_plan(opts, read, since, until, stamp, history, *,
+                   remember=True) -> TariffPlan:
     """§8.3: record what the feed published, carry yesterday into the gaps.
 
     The fill can itself return `no_data` - a feed whose points all fall outside
@@ -1344,7 +1370,12 @@ def _provider_plan(opts, read, since, until, stamp, history) -> TariffPlan:
     §11.4 row arrived at one step later, so it degrades exactly as a failed
     fetch does rather than being special-cased here.
     """
-    filled = history.carry(read, since=since, until=until, stamp=stamp)
+    if remember:
+        filled = history.carry(read, since=since, until=until, stamp=stamp)
+    else:
+        # PRICE-01: a read that came out of the store is not filed again.
+        filled = history.carry(read, since=since, until=until, stamp=stamp,
+                               remember=False)
     return filled.match(
         series=lambda r: TariffPlan(r, _quiet_profile(opts), "provider"),
         no_data=lambda r: _degrade(opts, r, since, until, stamp))