Normalize PasHub main-heating Mains gas to SAP fuel code 26 🟩

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

datatypes/epc/domain/mapper.py

@@ -6027,7 +6027,7 @@ def _map_sap_heating(
         main_heating_details=[
             MainHeatingDetail(
                 has_fghrs=main.flue_gas_heat_recovery_system,
-                main_fuel_type=fuel_type,
+                main_fuel_type=_pashub_main_fuel_code(fuel_type),
                 heat_emitter_type=main.emitter,
                 emitter_temperature=main.emitter_temperature,
                 fan_flue_present=main.fan_assist,
@@ -7030,6 +7030,28 @@ def _elmhurst_main_fuel_int(fuel_type: str) -> Optional[int]:
     return _ELMHURST_MAIN_FUEL_TO_SAP10.get(fuel_type)
 
 
+# PasHub Site-Notes surveyed main-heating "Fuel" labels mapped to SAP10 fuel
+# codes (the epc-codes `main_fuel` enum the calculator's resolver routes via
+# its API→Table-12/32 translation). Seeded only with labels confirmed from
+# live PasHub fixtures; a dedicated lookup rather than reuse of the Elmhurst
+# map, which carries legacy label oddities PasHub must not inherit. New labels
+# are a one-line addition — until then they strict-raise at the boundary
+# (ADR-0015) rather than being silently mis-billed downstream.
+_PASHUB_MAIN_FUEL_TO_SAP10: Dict[str, int] = {
+    "Mains gas": 26,  # matches the Elmhurst mapper's mains-gas code
+    "Electricity": 30,  # the standard-electricity fuel code
+}
+
+
+def _pashub_main_fuel_code(fuel_label: str) -> Union[int, str]:
+    """Resolve a PasHub surveyed main-heating Fuel label to a SAP10 fuel code
+    at the mapper boundary (ADR-0015). A genuinely blank label is the "no main
+    heating" shape and passes through unchanged."""
+    if not fuel_label:
+        return fuel_label
+    return _PASHUB_MAIN_FUEL_TO_SAP10.get(fuel_label, fuel_label)
+
+
 def _resolve_elmhurst_underfloor_subtype(
     main_floor: ElmhurstFloorDetails,
     main_age_band: str,

datatypes/epc/domain/tests/test_from_site_notes.py

@@ -379,7 +379,7 @@ class TestFromSiteNotesExample1:
                 main_heating_details=[
                     MainHeatingDetail(
                         has_fghrs=False,
-                        main_fuel_type="Mains gas",
+                        main_fuel_type=26,
                         heat_emitter_type="Radiators",
                         emitter_temperature="Unknown",
                         fan_flue_present=True,