Translate full-SAP electricity tariff into the RdSAP meter type 🟥

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

datatypes/epc/domain/mapper.py

@@ -2932,6 +2932,20 @@ def _sap_dwelling_on_mains_gas(schema: SapSchema17_1) -> bool:
     )
 
 
+def _sap_17_1_meter_type(electricity_tariff: Optional[int]) -> str:
+    """Translate a full-SAP ``energy_tariff`` code into the RdSAP ``meter_type``
+    value the calculator's Table 12a tariff resolver consumes.
+
+    The two code spaces *differ* (epc_codes.csv `energy_tariff` vs
+    `_METER_INT_TO_TARIFF`): full-SAP 1=standard / 2=off-peak-7hr / 3=off-peak-
+    10hr / 4=24-hour, whereas RdSAP meter 1=dual-7hr / 2=single / 3=unknown /
+    4=24-hour. Passing the full-SAP code straight through (the prior bug) read a
+    standard-tariff cert as Economy 7 (over-rated) and an Economy-7 cert as
+    single (under-rated). Map onto the RdSAP word aliases so the resolved tariff
+    is correct; absent/ND → "" (the unknown→standard sentinel)."""
+    raise NotImplementedError(electricity_tariff)
+
+
 def _sap_17_1_heating(schema: SapSchema17_1) -> SapHeating:
     """D6: map full-SAP `sap_heating` onto the domain `SapHeating`. Field names
     differ from RdSAP — `is_flue_fan_present`→`fan_flue_present`,

datatypes/epc/domain/tests/test_from_sap_schema.py

@@ -137,6 +137,26 @@ class TestFromSapSchema17_1RebaselineFields:
         assert result.assessment_type == "SAP"
 
 
+class TestFullSapElectricityTariffTranslation:
+    """The full-SAP `energy_tariff` code space differs from the RdSAP
+    `meter_type` one the calculator reads, so the mapper must translate it."""
+
+    def test_economy7_tariff_is_not_read_as_single_rate(self) -> None:
+        # full-SAP energy_tariff 2 = "off-peak 7 hour" (Economy 7). Passing the
+        # code straight through read it as RdSAP meter 2 = Single → no off-peak
+        # split (under-rated). It must resolve to the SEVEN_HOUR off-peak tariff.
+        from domain.sap10_calculator.tables.table_12a import (
+            Tariff,
+            tariff_from_meter_type,
+        )
+
+        from datatypes.epc.domain.mapper import _sap_17_1_meter_type
+
+        meter_type = _sap_17_1_meter_type(2)
+
+        assert tariff_from_meter_type(meter_type) is Tariff.SEVEN_HOUR
+
+
 class TestFromSapSchema17_1DisplayElements:
     """Display EnergyElements the WIP mapper dropped, leaving the FE
     property-details panel "Unknown" for full-SAP certs (ADR-0037). Brings