"""Assemble an EPC-less Property's PredictionTarget, with the eligibility gate
(ADR-0031 slice-5d).

A `PredictionTarget` needs the target's own known inputs: its postcode (to find
the cohort), coordinates (to distance-weight it), and the Landlord-Override
attributes that condition selection — `property_type` (the HARD cohort filter),
plus optional `built_form` / `wall_construction`. `property_type` is required: a
Property whose type is unknown is gated out (never sized from a mixed-type
cohort), so the builder returns None and the caller skips prediction.
"""

from __future__ import annotations

from dataclasses import dataclass
from typing import Optional, Union

from domain.geospatial.coordinates import Coordinates
from domain.property.property import PropertyIdentity


@dataclass(frozen=True)
class PredictionTarget:
    """The known inputs for the Property whose EPC we are predicting — the fields
    guaranteed at ingestion (plus any Landlord Overrides, added as they're used).
    `built_form` is often but not always known.
    """

    postcode: str
    property_type: str
    built_form: Optional[str] = None
    # A known Landlord Override (e.g. solid brick) conditions cohort selection —
    # matching comparables are emphasised while enough remain (ADR-0029).
    wall_construction: Optional[Union[int, str]] = None
    # The target Property's own coordinates (resolved from its UPRN), against
    # which neighbours are distance-weighted. None disables geo-weighting.
    coordinates: Optional[Coordinates] = None


@dataclass(frozen=True)
class PredictionTargetAttributes:
    """The target Property's own attributes resolved from Landlord Overrides,
    needed to find and condition its cohort. `property_type` is the code-space
    value the cohort EPCs carry (e.g. "2"); None means it could not be resolved,
    which gates the Property out of prediction."""

    property_type: Optional[str]
    built_form: Optional[str] = None
    wall_construction: Optional[Union[int, str]] = None


def build_prediction_target(
    identity: PropertyIdentity,
    coordinates: Optional[Coordinates],
    attributes: PredictionTargetAttributes,
) -> Optional[PredictionTarget]:
    """The PredictionTarget for an EPC-less Property, or None when ineligible —
    `property_type` is the hard cohort filter, so a Property whose type is unknown
    is gated out of prediction (ADR-0031) rather than sized from a mixed-type
    cohort."""
    if attributes.property_type is None:
        return None
    return PredictionTarget(
        postcode=identity.postcode,
        property_type=attributes.property_type,
        built_form=attributes.built_form,
        wall_construction=attributes.wall_construction,
        coordinates=coordinates,
    )