Model/tests/domain/modelling/test_optimiser_goal_objective.py

"""Behaviour of the Optimiser under a goal-aligned objective (ADR-0062): a
Scenario whose goal is Reducing CO2 emissions / Energy Savings optimises its
own metric, not SAP. The caller supplies group signals already measured in the
objective's currency; the optimiser must price everything *it* computes — the
forced Measure Dependency signals — in the same currency, so a ventilation
that costs SAP but is carbon-neutral cannot sink a carbon-improving wall.
"""

from __future__ import annotations

from typing import Sequence

from datatypes.epc.domain.epc_property_data import (
    BuildingPartIdentifier,
    EpcPropertyData,
)
from domain.modelling.measure_type import MeasureType
from domain.modelling.optimisation.optimiser import (
    OptimisedPackage,
    ScoredOption,
    optimise_package,
    optimise_package_fabric_first,
)
from domain.modelling.scoring.package_scorer import Score
from domain.modelling.simulation import BuildingPartOverlay, EpcSimulation
from tests.domain.modelling._optimiser_fixtures import (
    ASHP_OVERLAY,
    BOILER_OVERLAY,
    WALL_OVERLAY,
    scored_option,
    selected_types,
    ventilation_dependency,
)
from tests.domain.sap10_calculator.worksheet._elmhurst_worksheet_000490 import (
    build_epc,
)


class _CarbonScorer:
    """A stub where the wall is a small carbon win (−20 kg/yr) and a large SAP
    win (+6), while its forced ventilation is carbon-neutral but SAP-ruinous
    (−30): SAP-priced dependency signals sink the wall; carbon-priced ones
    keep it."""

    def score(
        self, baseline: EpcPropertyData, simulations: Sequence[EpcSimulation]
    ) -> Score:
        sap, co2 = 60.0, 500.0
        for sim in simulations:
            if sim.ventilation is not None:
                sap -= 30.0
            for part in sim.building_parts.values():
                if part.wall_insulation_type is not None:
                    sap += 6.0
                    co2 -= 20.0
        return Score(
            sap_continuous=sap, co2_kg_per_yr=co2, primary_energy_kwh_per_yr=0.0
        )


def _carbon_reduction(score: Score) -> float:
    return -score.co2_kg_per_yr


def test_dependency_signals_are_priced_in_the_objective_currency() -> None:
    # Arrange — the wall's signal (supplied by the caller, +20 kg CO2 saved)
    # and the ventilation it forces in (carbon-neutral). Under legacy SAP
    # pricing the ventilation's −30 SAP would outweigh the wall's +20 signal
    # and the package would collapse to nothing.
    groups: list[list[ScoredOption]] = [
        [scored_option("cavity_wall_insulation", gain=20.0, cost=1000.0, overlay=WALL_OVERLAY)],
    ]
    dependency = ventilation_dependency(
        cost=300.0, triggers=frozenset({MeasureType.CAVITY_WALL_INSULATION})
    )

    # Act — a Reducing-CO2 brief: maximise carbon reduction within budget.
    package: OptimisedPackage = optimise_package(
        groups=groups,
        scorer=_CarbonScorer(),
        baseline_epc=build_epc(),
        budget=5000.0,
        target_sap=None,
        dependencies=[dependency],
        objective=_carbon_reduction,
    )

    # Assert — the wall survives with its ventilation: the dependency is worth
    # 0 kg CO2, not −30 SAP, so the package is a net +20 kg saving.
    assert selected_types(package.selected) == {
        "cavity_wall_insulation",
        "mechanical_ventilation",
    }
    assert abs(package.score.co2_kg_per_yr - 480.0) <= 1e-9


# Internal wall insulation — a distinct fabric overlay so the fabric-first
# phase-1 pick is unambiguous. No shared fixture (the shared WALL_OVERLAY is a
# cavity fill, type 2); this is a solid-wall internal treatment, type 3.
_IWI_OVERLAY = EpcSimulation(
    building_parts={
        BuildingPartIdentifier.MAIN: BuildingPartOverlay(wall_insulation_type=3)
    }
)


class _CarbonHeatingScorer:
    """A stub where the boiler wins on SAP (+10 vs +2) but the heat pump wins
    on carbon (−50 vs −5 kg/yr): a fabric-first phase 2 that re-scores its
    candidates in SAP picks the wrong heating for a Reducing-CO2 brief."""

    def score(
        self, baseline: EpcPropertyData, simulations: Sequence[EpcSimulation]
    ) -> Score:
        sap, co2 = 60.0, 500.0
        for sim in simulations:
            for part in sim.building_parts.values():
                if part.wall_insulation_type is not None:
                    sap += 5.0
                    co2 -= 10.0
            if sim.heating is None:
                continue
            if sim.heating.sap_main_heating_code is not None:
                sap += 10.0
                co2 -= 5.0
            if sim.heating.main_heating_index_number is not None:
                sap += 2.0
                co2 -= 50.0
        return Score(
            sap_continuous=sap, co2_kg_per_yr=co2, primary_energy_kwh_per_yr=0.0
        )


def test_fabric_first_phase_two_rescores_in_the_objective_currency() -> None:
    # Arrange — a fabric-first Reducing-CO2 brief. Phase 1 commits the wall;
    # phase 2 must choose the heating on its post-fabric *carbon* worth, not
    # its SAP worth. Signals are supplied in kg CO2 saved (the caller's job).
    groups: list[list[ScoredOption]] = [
        [scored_option("internal_wall_insulation", gain=10.0, cost=1000.0, overlay=_IWI_OVERLAY)],
        [
            scored_option("gas_boiler_upgrade", gain=5.0, cost=2000.0, overlay=BOILER_OVERLAY),
            scored_option("air_source_heat_pump", gain=50.0, cost=6000.0, overlay=ASHP_OVERLAY),
        ],
    ]

    # Act — no target (goal-aligned briefs have none), generous budget.
    package: OptimisedPackage = optimise_package_fabric_first(
        groups=groups,
        scorer=_CarbonHeatingScorer(),
        baseline_epc=build_epc(),
        budget=10000.0,
        target_sap=None,
        objective=_carbon_reduction,
    )

    # Assert — the wall plus the heat pump (−50 kg), not the SAP-favoured
    # boiler; the truthful package carbon is 500 − 10 − 50 = 440.
    assert selected_types(package.selected) == {
        "internal_wall_insulation",
        "air_source_heat_pump",
    }
    assert abs(package.score.co2_kg_per_yr - 440.0) <= 1e-9