"""Plan and Plan Measure — the Modelling stage's persisted output (ADR-0017).

A **Plan** is the per-Property output of one Scenario's modelling run: the
selected **Optimised Package** (its **Plan Measures**) plus the Property's
post-retrofit figures. It is single-phase — multi-phase is deferred
(ADR-0005) — so the headline figures are flat on the Plan.

A **Plan Measure** is the *output* counterpart of a Recommendation's candidate
Option: the one Option the Optimiser kept, frozen with its installed **Cost**
and its final-package (role-3) attributed **impact**. See CONTEXT.md.
"""

from dataclasses import dataclass
from typing import Optional

from datatypes.epc.domain.epc import Epc
from domain.billing.bill import Bill
from domain.modelling.scoring.package_scorer import Score
from domain.modelling.recommendation import Cost
from domain.modelling.scoring.scoring import MeasureImpact


def _total_consumption_kwh(bill: Bill) -> float:
    """A Bill's total delivered energy (kWh) — the sum of its section kWh
    (standing charges and the SEG credit are £, not energy)."""
    return sum((section.kwh for section in bill.sections.values()), 0.0)


@dataclass(frozen=True)
class PlanMeasure:
    """One selected Measure Option as it lands in a Plan: the measure, its
    installed Cost, and its role-3 (final-package cascade) attributed impact.

    `kwh_savings` (delivered energy) and `energy_cost_savings` (£) are this
    measure's slice of the telescoping bill cascade — its marginal Bill delta
    over the running package state. They can be negative (e.g. ventilation
    increases energy) and telescope exactly to the Plan totals; `None` until
    billing has run (persisted as NULL — ADR-0014 amendment). They are distinct
    from `impact.energy_savings_kwh_per_yr`, which is *primary* energy."""

    measure_type: str
    description: str
    cost: Cost
    impact: MeasureImpact
    kwh_savings: Optional[float] = None
    energy_cost_savings: Optional[float] = None


@dataclass(frozen=True)
class Plan:
    """A Property's Plan for one Scenario: the selected Plan Measures and the
    baseline / post-retrofit whole-package Scores. The persisted headline
    figures are derived from these (cost aggregates, CO₂ saving, post band).

    `baseline_bill` / `post_bill` are the Bills derived (at one Fuel Rates
    snapshot) for the unmodified and post-package end-states; the energy/bill
    headline figures derive from them, and are `None` until billing has run
    (persisted as NULL — ADR-0014 amendment)."""

    measures: tuple[PlanMeasure, ...]
    baseline: Score
    post_retrofit: Score
    baseline_bill: Optional[Bill] = None
    post_bill: Optional[Bill] = None

    @property
    def cost_of_works(self) -> float:
        """Sum of the Plan Measures' fully-loaded Costs."""
        return sum((measure.cost.total for measure in self.measures), 0.0)

    @property
    def contingency_cost(self) -> float:
        """Sum of each Plan Measure's contingency (its Cost total × its
        per-Measure-Type contingency rate)."""
        return sum(
            (
                measure.cost.total * measure.cost.contingency_rate
                for measure in self.measures
            ),
            0.0,
        )

    @property
    def post_sap_continuous(self) -> float:
        """The whole-package re-score's un-rounded SAP rating."""
        return self.post_retrofit.sap_continuous

    @property
    def post_epc_rating(self) -> Epc:
        """The post-retrofit EPC band, from the rounded SAP rating."""
        return Epc.from_sap_score(round(self.post_retrofit.sap_continuous))

    @property
    def co2_savings_kg_per_yr(self) -> float:
        """Whole-package CO₂ reduction (kg/yr) vs the baseline re-score. The
        persistence mapper converts to tonnes for the live column contract."""
        return self.baseline.co2_kg_per_yr - self.post_retrofit.co2_kg_per_yr

    @property
    def post_energy_bill(self) -> Optional[float]:
        """The post-package annual energy bill (£), or None if not billed."""
        return None if self.post_bill is None else self.post_bill.total_gbp

    @property
    def energy_bill_savings(self) -> Optional[float]:
        """Annual bill reduction (£) vs the baseline bill, both at the same Fuel
        Rates snapshot. None unless both bills were derived."""
        if self.baseline_bill is None or self.post_bill is None:
            return None
        return self.baseline_bill.total_gbp - self.post_bill.total_gbp

    @property
    def post_energy_consumption(self) -> Optional[float]:
        """The post-package total delivered energy (kWh), or None if not billed."""
        return None if self.post_bill is None else _total_consumption_kwh(self.post_bill)

    @property
    def energy_consumption_savings(self) -> Optional[float]:
        """Annual delivered-energy reduction (kWh) vs the baseline. None unless
        both bills were derived."""
        if self.baseline_bill is None or self.post_bill is None:
            return None
        return _total_consumption_kwh(self.baseline_bill) - _total_consumption_kwh(
            self.post_bill
        )