OPT-11 P4: solar forecast and day plan

A Home Assistant solar forecast (Forecast.Solar, Solcast or Open-Meteo
shapes) and the add-on's own hourly house use decide, before each cheap
run, whether the sun will fill each battery before the expensive hours.
Leftover solar then buys from the grid only the shortfall; Cheap hours only
skips the part the sun covers; Solar first never grid-charges. No, stale or
failed forecast: P3 option A exactly (12 digests pinned from 5a4cdc2).

Replay (16 recorded days, forecast errors from Elia's day-ahead BE solar):
year-earlier prices P4 19.15 vs P2 19.33 / option A 19.44 / old trade 18.14;
real 2026 prices P4 29.19 vs 32.26 / 32.01 / 31.40 EUR net.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

goodwe_controller/app/homeview.py

@@ -345,7 +345,10 @@ def mode_runs(c, day0, day1, now, shadow):
                                    else (soc - floor)) / 100.0 * cap)
             return kwh
         blocks = []
-        if rp.charge_useful() and pm.mode in GRID_CHARGE_MODES:
+        # P4: with a day plan, the grid block is the planned shortfall.
+        need = plan_need(c, inv.name)
+        if rp.charge_useful() and (need > 0.0 if need is not None
+                                   else pm.mode in GRID_CHARGE_MODES):
             blocks.append(("grid", rp.cheap))
         sell = rp.sell if pm.sell and pm.can_sell else None
         for g in rp.give:
@@ -358,6 +361,8 @@ def mode_runs(c, day0, day1, now, shadow):
                 continue
             hrs = (run.end - run.start).total_seconds() / 3600.0
             kwh = room(kind, hrs)
+            if kind == "grid" and need is not None:
+                kwh = min(kwh, need)
             if kwh < MIN_KWH:
                 continue
             price = run.mean_eur_kwh
@@ -382,6 +387,56 @@ def mode_runs(c, day0, day1, now, shadow):
     return out, None
 
 
+def plan_need(c, name):
+    """P4: kWh this battery buys from the grid by the day plan, or None when
+    there is no plan for it (then P3 option A applies)."""
+    targets = c.plan_targets() if hasattr(c, "plan_targets") else None
+    if not targets or name not in targets:
+        return None
+    inv = next((i for i in c.inverters if i.name == name), None)
+    if inv is None or inv.soc is None or not inv.capacity_kwh:
+        return None
+    return max(0.0, targets[name] - float(inv.soc)) / 100.0 * float(
+        inv.capacity_kwh)
+
+
+def plan_state(c):
+    """P4: `"plan"` (a day plan is made), `"learning"` (no house profile
+    yet), `"no_forecast"` (set but missing or stale), or None (not set, or
+    battery modes off)."""
+    if not getattr(c, "modes_on", False) or \
+            getattr(c, "fc_entity", None) is None:
+        return None
+    if getattr(c, "solar_fc", None) is None:
+        return "no_forecast"
+    hp = getattr(c, "house_profile", None)
+    if hp is not None and not hp.ready():
+        return "learning"
+    return "plan" if getattr(c, "day_plan", None) is not None else None
+
+
+def solar_block(c, now):
+    """P4: the solar forecast line for the Batteries screen and the Simple
+    settings view: `{state, fc_kwh, count_kwh, updated, line}`."""
+    st = plan_state(c)
+    out = {"state": st, "fc_kwh": None, "count_kwh": None, "updated": None,
+           "line": ""}
+    if st is None and getattr(c, "solar_fc", None) is None:
+        return out
+    fc = getattr(c, "solar_fc", None)
+    if fc is not None:
+        trust = float(getattr(c, "solar_trust_pct", 70)) / 100.0
+        out.update(fc_kwh=round(fc.today.kwh, 1),
+                   count_kwh=round(fc.today.kwh * trust, 1),
+                   updated=hhmm(fc.at))
+    if st in ("no_forecast", "learning"):
+        out["line"] = _t("solar." + st)
+    elif fc is not None:
+        out["line"] = line_solar(fc.today.kwh, out["count_kwh"],
+                                 out["updated"])
+    return out
+
+
 def maintenance_runs(c, day0, day1, now, shadow):
     """The monthly battery cycle: under way now, or starting later today.
     The cycle starts in the hour `maintenance_start_hour` names, read as the
@@ -655,7 +710,9 @@ def battery_rows(c, shadow, running, held=False):
             phase=phase, shadow=shadow, running=running, held=held,
             refused=refusing(c, inv), peak=peak,
             giving=flow(inv.batt) == "giving", other_refuses=other,
-            sf_ahead=sf_ahead, role=role, plan=plan, has_at=bool(at))
+            sf_ahead=sf_ahead, role=role, plan=plan, has_at=bool(at),
+            day=None if pm is None or pm.mode not in PRICE_MODES
+            else day_key(c, inv.name))
         rows.append({
             "name": inv.name,
             "level_pct": None if inv.soc is None else float(inv.soc),
@@ -689,10 +746,25 @@ def battery_rows(c, shadow, running, held=False):
     return rows
 
 
+def day_key(c, name):
+    """P4: the day plan's word for one Leftover solar or Cheap hours
+    battery: `sun_fills`, `tops_up`, `no_forecast`, or None."""
+    st = plan_state(c)
+    if st == "no_forecast":
+        mode = c.pack_mode(next(i for i in c.inverters if i.name == name))
+        return "no_forecast" if mode.mode == LEFTOVER_SOLAR else None
+    if st != "plan":
+        return None
+    need = plan_need(c, name)
+    if need is None:
+        return None
+    return "tops_up" if need >= MIN_KWH else "sun_fills"
+
+
 def battery_why(*, modes_on, mode, off, reading, phase, shadow, running,
                 held, refused, peak, sf_ahead, giving=False,
                 other_refuses=None, role=None, plan=None,
-                has_at=False) -> str:
+                has_at=False, day=None) -> str:
     """The key of one battery's "why" line (`home_words.why`), most urgent
     first. Pure, so every branch is tested without a controller."""
     if not reading:
@@ -717,6 +789,8 @@ def battery_why(*, modes_on, mode, off, reading, phase, shadow, running,
     if not modes_on:
         return "modes_off"
     # OPT-11 P3: the battery's role in the price runs this cycle.
+    if role == "hold" and day is not None:
+        return day              # P4: what the day plan decided
     if role in ROLE_WHY:
         if role == "hold" and not has_at:
             return "saves_later"
@@ -864,6 +938,7 @@ def _build(c, *, level, checks, now):
                  modes_on=bool(getattr(c, "modes_on", False)),
                  running=running, held=held, shadow=shadow)
     return {
+        "solar": solar_block(c, now),
         "state": {"kind": kind, "pill": pill(kind),
                   "ran": ctl.get("text", "") if ctl else "",
                   "sub": banner_sub(kind)},
@@ -1160,6 +1235,10 @@ def run_house_amount() -> str:
     return _t("run.house_amount")
 
 
+def line_solar(fc_kwh, count_kwh, at) -> str:
+    return _t("solar.line", kwh=_kwh(fc_kwh), count=_kwh(count_kwh), at=at)
+
+
 def line_no_trade(key) -> str:
     return "" if key == "off" else _t("no_trade." + key)
 
@@ -1302,6 +1381,8 @@ def _samples() -> list:
                                                 off=off, peak=peak)))
     out += [("plan", why_words(k, name="Battery A")) for k in words["why"]]
     out += [("plan", today_words(k)) for k in words["today"]]
+    out += [("plan", line_solar(9.2, 6.4, "10:15")),
+            ("plan", _t("solar.no_forecast")), ("plan", _t("solar.learning"))]
     out += [("plan", line_no_trade(k)) for k in
             ("not_covered", "no_prices", "peak", "not_firm", "not_worth",
              "no_level")]