from __future__ import annotations

import logging
from typing import TYPE_CHECKING, Optional

from domain.property_baseline.performance import Performance
from domain.property_baseline.rebaseliner import (
    Rebaseliner,
    RebaselineReason,
    RebaselineResult,
)

if TYPE_CHECKING:
    from datatypes.epc.domain.epc_property_data import EpcPropertyData
    from domain.sap10_calculator.calculator import SapCalculator, SapResult

logger = logging.getLogger(__name__)

# Lodged figures are trusted from SAP 10.2 (14-03-2025) onward — the version the
# calculator targets. A cert lodged below this carries a superseded methodology,
# so the calculator's output replaces it; at or above it the lodged figures are
# kept and the calculator only validates against them.
_MIN_TRUSTED_SAP_VERSION = 10.2

# Divergence thresholds for that validation log. The calculator emits a
# *continuous* SAP score whereas the lodged score is rounded to an integer, so a
# gap up to half a point is just rounding — beyond it the calculator and the
# register genuinely disagree and we record it. CO2 and Primary Energy Intensity
# are not rounded that way, so they get a 1% relative band instead.
_MAX_SAP_SCORE_DIVERGENCE = 0.5
_MAX_RELATIVE_DIVERGENCE = 0.01
_KG_PER_TONNE = 1000.0


def _relative_diff(calculated: float, lodged: float) -> float:
    if lodged == 0:
        return 0.0 if calculated == 0 else float("inf")
    return abs(calculated - lodged) / abs(lodged)


class CalculatorRebaseliner(Rebaseliner):
    """Produces Effective Performance from the deterministic `Sap10Calculator`
    (ADR-0013 amendment — the calculator is load-bearing).

    Runs the calculator on every Property. For a cert lodged under a superseded
    methodology (``sap_version < 10.2``) the calculator's output **is** Effective
    Performance. At or above 10.2 the API's lodged figures are kept and the
    calculator only **logs divergence** (a validation signal). A calculator
    strict-raise propagates — the batch aborts (ADR-0012) and the un-mapped cert
    is fixed immediately.
    """

    def __init__(self, calculator: "SapCalculator") -> None:
        self._calculator = calculator

    def rebaseline(
        self,
        property_id: int,
        effective_epc: "EpcPropertyData",
        lodged: Performance,
        *,
        physical_state_changed: bool = False,
    ) -> RebaselineResult:
        # A raise (UnmappedSapCode, etc.) propagates: the calculator is
        # load-bearing, so the batch aborts and the cert is fixed at once. The
        # SapResult rides on the result either way — Bill Derivation prices it
        # regardless of whether lodged or calculated figures win (ADR-0013/0014).
        result: SapResult = self._calculator.calculate(effective_epc)
        sap_version: Optional[float] = effective_epc.sap_version
        pre_sap10 = sap_version is not None and sap_version < _MIN_TRUSTED_SAP_VERSION
        # The calculator output IS Effective Performance whenever a Rebaselining
        # trigger fired: (a) a superseded methodology (pre-SAP10), or (b)/(c) the
        # physical state was changed by Landlord Overrides / Prediction. Only a
        # pristine lodged SAP >= 10.2 cert keeps its accredited figure — that is
        # the *only* case where the calculator runs purely to validate (and where
        # its known divergence from the accredited register would mislead).
        if pre_sap10 or physical_state_changed:
            reason: RebaselineReason = (
                "both"
                if pre_sap10 and physical_state_changed
                else "pre_sap10"
                if pre_sap10
                else "physical_state_changed"
            )
            return RebaselineResult(
                effective=Performance.from_sap_result(result),
                reason=reason,
                sap_result=result,
            )
        self._log_divergence(
            property_id=property_id, sap_version=sap_version, result=result, lodged=lodged
        )
        return RebaselineResult(effective=lodged, reason="none", sap_result=result)

    def _log_divergence(
        self,
        *,
        property_id: int,
        sap_version: Optional[float],
        result: "SapResult",
        lodged: Performance,
    ) -> None:
        if abs(result.sap_score_continuous - lodged.sap_score) > _MAX_SAP_SCORE_DIVERGENCE:
            self._warn(property_id, sap_version, "sap_score", lodged.sap_score, result.sap_score_continuous)
        if _relative_diff(result.primary_energy_kwh_per_m2, lodged.primary_energy_intensity) > _MAX_RELATIVE_DIVERGENCE:
            self._warn(
                property_id, sap_version, "primary_energy_intensity",
                lodged.primary_energy_intensity, result.primary_energy_kwh_per_m2,
            )
        calculated_co2_t = result.co2_kg_per_yr / _KG_PER_TONNE
        if _relative_diff(calculated_co2_t, lodged.co2_emissions) > _MAX_RELATIVE_DIVERGENCE:
            self._warn(property_id, sap_version, "co2_emissions", lodged.co2_emissions, calculated_co2_t)

    def _warn(
        self,
        property_id: int,
        sap_version: Optional[float],
        quantity: str,
        lodged: float,
        calculated: float,
    ) -> None:
        logger.warning(
            "SAP10 calculator divergence on %s for property_id=%s sap_version=%s: "
            "lodged=%s calculated=%s",
            quantity,
            property_id,
            sap_version,
            lodged,
            calculated,
        )