From abec38a3976b8e460b0acc60c9de406c1a917edd Mon Sep 17 00:00:00 2001
From: Khalim Conn-Kowlessar <kconnkowlessar@gmail.com>
Date: Fri, 24 Jul 2026 09:18:06 +0000
Subject: [PATCH] =?UTF-8?q?Re-point=20a=20fuel-agnostic=20gas=20boiler=20t?=
 =?UTF-8?q?o=20oil=20or=20solid=20fuel=20by=20main=5Ffuel=20=F0=9F=9F=A5?=
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Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---
 .../property/landlord_override_overlays.py    |  4 ++
 .../test_landlord_override_overlays.py        | 47 +++++++++++++++++++
 2 files changed, 51 insertions(+)

diff --git a/repositories/property/landlord_override_overlays.py b/repositories/property/landlord_override_overlays.py
index 29ebcea00..3d1fcdce5 100644
--- a/repositories/property/landlord_override_overlays.py
+++ b/repositories/property/landlord_override_overlays.py
@@ -110,6 +110,10 @@ _FUEL_FAMILY: dict[int, str] = {
 }
 
 
+def resolve_boiler_archetype(heating_value: str, fuel_value: Optional[str]) -> str:
+    raise NotImplementedError
+
+
 def _override_value(overrides: ResolvedPropertyOverrides, component: str) -> Optional[str]:
     for row in overrides.rows:
         if row.override_component == component:
diff --git a/tests/repositories/property/test_landlord_override_overlays.py b/tests/repositories/property/test_landlord_override_overlays.py
index e35034ebc..c3f30fc3d 100644
--- a/tests/repositories/property/test_landlord_override_overlays.py
+++ b/tests/repositories/property/test_landlord_override_overlays.py
@@ -15,6 +15,7 @@ from domain.modelling.scoring.overlay_applicator import apply_simulations
 from repositories.property.landlord_override_overlays import (
     flag_fuel_mismatch,
     overlays_from,
+    resolve_boiler_archetype,
 )
 from repositories.property.property_overrides_reader import (
     ResolvedPropertyOverride,
@@ -25,6 +26,52 @@ from tests.domain.sap10_calculator.worksheet._elmhurst_worksheet_000490 import (
 )
 
 
+@pytest.mark.parametrize(
+    ("heating_value", "fuel_value", "expected"),
+    [
+        # A fuel-agnostic gas wet boiler re-points by the property's main_fuel
+        # family (ADR-0067). Oil preserves regular/combi; any solid fuel
+        # (coal/wood/dual) collapses to the single Solid fuel boiler member.
+        ("Gas boiler, regular", "oil", "Oil boiler, regular"),
+        ("Gas boiler, combi", "oil", "Oil boiler, combi"),
+        ("Gas boiler, regular", "house coal", "Solid fuel boiler"),
+        ("Gas boiler, regular", "wood logs", "Solid fuel boiler"),
+        ("Gas boiler, regular", "dual fuel (mineral and wood)", "Solid fuel boiler"),
+        ("Gas boiler, combi", "house coal", "Solid fuel boiler"),
+    ],
+)
+def test_resolve_boiler_archetype_repoints_a_gas_boiler_by_fuel(
+    heating_value: str, fuel_value: str, expected: str
+) -> None:
+    # Act
+    resolved = resolve_boiler_archetype(heating_value, fuel_value)
+
+    # Assert
+    assert resolved == expected
+
+
+@pytest.mark.parametrize(
+    ("heating_value", "fuel_value"),
+    [
+        # Gas / LPG stay on the gas archetype (RdSAP models LPG on gas), a missing
+        # fuel can't disambiguate, and a non-boiler archetype is never re-pointed.
+        ("Gas boiler, regular", "mains gas"),
+        ("Gas boiler, regular", "LPG (bulk)"),
+        ("Gas boiler, regular", None),
+        ("Electric room heaters", "oil"),
+        ("Solid fuel room heater, closed", "oil"),
+    ],
+)
+def test_resolve_boiler_archetype_leaves_other_cases_unchanged(
+    heating_value: str, fuel_value: str
+) -> None:
+    # Act
+    resolved = resolve_boiler_archetype(heating_value, fuel_value)
+
+    # Assert
+    assert resolved == heating_value
+
+
 def test_roof_type_row_produces_a_roof_overlay() -> None:
     # Arrange
     overrides = ResolvedPropertyOverrides(