Model/tests/domain/epc/test_main_fuel_overlay.py

"""The Landlord-Override main-fuel → heating Simulation Overlay mapping.

A main-fuel value resolves to the RdSAP `main_fuel_type` int code the calculator
reads from the dwelling's primary heating system; the overlay is whole-dwelling.
"""

from __future__ import annotations

import pytest

from domain.epc.property_overrides.main_fuel_type import MainFuelType
from domain.epc.property_overlays.main_fuel_overlay import fuel_overlay_for
from domain.modelling.scoring.overlay_applicator import apply_simulations
from tests.domain.sap10_calculator.worksheet._elmhurst_worksheet_000490 import (
    build_epc,
)


def test_mains_gas_overlays_the_primary_fuel() -> None:
    # Act
    simulation = fuel_overlay_for("mains gas", 0)

    # Assert — mains gas (not community) is RdSAP main_fuel code 26.
    assert simulation is not None
    assert simulation.heating is not None
    assert simulation.heating.main_fuel_type == 26


@pytest.mark.parametrize(
    ("main_fuel_value", "code"),
    [
        ("electricity", 29),
        ("LPG (bulk)", 27),
        ("oil", 28),
        ("house coal", 33),
    ],
)
def test_fuels_decode_to_their_modern_not_community_codes(
    main_fuel_value: str, code: int
) -> None:
    # Act
    simulation = fuel_overlay_for(main_fuel_value, 0)

    # Assert
    assert simulation is not None
    assert simulation.heating is not None
    assert simulation.heating.main_fuel_type == code


@pytest.mark.parametrize(
    ("main_fuel_value", "code"),
    [
        ("bottled LPG", 3),
        ("LPG special condition", 17),
        ("electricity (community)", 25),
        ("biomass (community)", 31),
        ("dual fuel (mineral and wood)", 10),
        ("smokeless coal", 15),
    ],
)
def test_more_fuels_decode_to_their_codes(main_fuel_value: str, code: int) -> None:
    # Act
    simulation = fuel_overlay_for(main_fuel_value, 0)

    # Assert
    assert simulation is not None
    assert simulation.heating is not None
    assert simulation.heating.main_fuel_type == code


def test_community_mains_gas_is_a_distinct_fuel_code() -> None:
    # Act
    simulation = fuel_overlay_for("mains gas (community)", 0)

    # Assert — community mains gas is code 20, distinct from 26 (not community).
    assert simulation is not None
    assert simulation.heating is not None
    assert simulation.heating.main_fuel_type == 20


def test_mains_gas_fuel_sets_the_mains_gas_connection_flag() -> None:
    # A "mains gas" fuel means the dwelling has a mains-gas connection, so the
    # overlay must set sap_energy_source.mains_gas too — not only the fuel code.
    # Without it the effective EPC says "fuel = mains gas" yet mains_gas=False,
    # which suppresses the gas-boiler-upgrade path and wrongly offers HHRSH
    # storage (the off-gas path). (Property 728513.)
    simulation = fuel_overlay_for("mains gas", 0)
    assert simulation is not None
    assert simulation.heating is not None
    assert simulation.heating.mains_gas is True


@pytest.mark.parametrize(
    "main_fuel_value",
    ["electricity", "LPG (bulk)", "bottled LPG", "oil", "house coal"],
)
def test_non_mains_gas_fuel_leaves_the_mains_gas_flag_unchanged(
    main_fuel_value: str,
) -> None:
    # Only an explicit "mains gas" fuel asserts a mains-gas connection. An
    # electric (or LPG/oil) main fuel does NOT tell us there is no gas supply
    # (the dwelling could still have a gas hob), so the flag is left None
    # ("leave the baseline unchanged") rather than cleared to False.
    simulation = fuel_overlay_for(main_fuel_value, 0)
    assert simulation is not None
    assert simulation.heating is not None
    assert simulation.heating.mains_gas is None


@pytest.mark.parametrize("main_fuel_value", ["Unknown", "", "no heating or hot water"])
def test_unresolvable_fuel_produces_no_overlay(main_fuel_value: str) -> None:
    # Act
    simulation = fuel_overlay_for(main_fuel_value, 0)

    # Assert
    assert simulation is None


def test_fuel_override_remaps_the_primary_systems_fuel_on_the_epc() -> None:
    # Arrange — a landlord correction that the dwelling runs on electricity.
    baseline = build_epc()
    overlay = fuel_overlay_for("electricity", 0)
    assert overlay is not None

    # Act
    result = apply_simulations(baseline, [overlay])

    # Assert — the calculator reads the primary fuel from main_heating_details[0].
    assert result.sap_heating.main_heating_details[0].main_fuel_type == 29


@pytest.mark.parametrize(
    "member", [m for m in MainFuelType if m is not MainFuelType.UNKNOWN]
)
def test_every_resolvable_fuel_value_decodes_to_a_code(member: MainFuelType) -> None:
    # A classifier emits a MainFuelType value; if the overlay can't decode it the
    # override silently no-ops. Every non-UNKNOWN member must resolve.

    # Act
    simulation = fuel_overlay_for(member.value, 0)

    # Assert
    assert simulation is not None