from __future__ import annotations

from dataclasses import dataclass
from typing import Optional

from domain.billing.bill import Bill
from domain.property_baseline.performance import Performance
from domain.property_baseline.rebaseliner import RebaselineReason


@dataclass(frozen=True)
class PropertyBaselinePerformance:
    """A Property's current performance aggregate (CONTEXT.md, ADR-0004).

    Holds both halves — ``lodged`` (what the gov register says) and
    ``effective`` (what the modelling pipeline scored against) — plus the
    ``rebaseline_reason`` recording *why* they differ (``"none"`` when equal).
    Both halves are populated for a Property with a real record of itself; the
    ``lodged`` half is ``None`` for a predicted Property, which has no lodged cert
    to read a Lodged Performance off — only the Effective half is established then
    (ADR-0004 amendment, #1361).

    Carries the part of the energy block that needs no derivation: annual
    ``space_heating_kwh`` / ``water_heating_kwh`` read off the EPC's RHI.

    Carries the derived ``bill`` (ADR-0014): the calculator's delivered kWh per
    end use priced at current Fuel Rates. It is ``None`` only when no calculator
    ran (the stub path produced no ``SapResult`` to price).
    """

    lodged: Optional[Performance]
    effective: Performance
    rebaseline_reason: RebaselineReason
    space_heating_kwh: float
    water_heating_kwh: float
    bill: Optional[Bill] = None