"""The wall Recommendation Generator.

Detects a treatable main wall on an EpcPropertyData and emits a Recommendation
whose Measure Option carries the Simulation Overlay for the intervention. No
scoring, no persistence — impact is produced later by scoring (ADR-0016).
"""

from typing import Optional

from datatypes.epc.domain.epc_property_data import (
    BuildingPartIdentifier,
    EpcPropertyData,
)
from domain.building_geometry import gross_heat_loss_wall_area
from domain.modelling.measure_type import MeasureType
from domain.modelling.recommendation import Cost, MeasureOption, Recommendation
from domain.modelling.simulation import BuildingPartOverlay, EpcSimulation
from repositories.product.product_repository import ProductRepository

_CAVITY_MEASURE_TYPE = MeasureType.CAVITY_WALL_INSULATION

# RdSAP 10 Table 5 wall_construction: 4 = "Cavity". Table 6
# wall_insulation_type: 4 = "as-built / assumed" (uninsulated), 2 = "Filled
# cavity" (the calculator's dedicated filled-cavity U row — see
# domain/sap10_ml/rdsap_uvalues.py u_wall).
_CAVITY_WALL_CONSTRUCTION = 4
_WALL_UNINSULATED = 4
_FILLED_CAVITY = 2


def recommend_cavity_wall(
    epc: EpcPropertyData, products: ProductRepository
) -> Optional[Recommendation]:
    """Return a cavity-fill Recommendation for the main wall when it is an
    uninsulated cavity wall, else None. The Option's cost is the heat-loss wall
    area priced at the Product's fully-loaded unit cost, with its contingency."""
    main = next(
        part
        for part in epc.sap_building_parts
        if part.identifier is BuildingPartIdentifier.MAIN
    )

    if (
        main.wall_construction != _CAVITY_WALL_CONSTRUCTION
        or main.wall_insulation_type != _WALL_UNINSULATED
    ):
        return None

    product = products.get(_CAVITY_MEASURE_TYPE)
    wall_area: float = gross_heat_loss_wall_area(epc, BuildingPartIdentifier.MAIN)
    cost = Cost(
        total=wall_area * product.unit_cost_per_m2,
        contingency_rate=product.contingency_rate,
    )

    option = MeasureOption(
        measure_type=_CAVITY_MEASURE_TYPE,
        description="Cavity wall insulation (fill the existing cavity)",
        overlay=EpcSimulation(
            building_parts={
                BuildingPartIdentifier.MAIN: BuildingPartOverlay(
                    wall_insulation_type=_FILLED_CAVITY
                )
            }
        ),
        cost=cost,
        material_id=product.id,
    )
    return Recommendation(surface="Main wall", options=(option,))