from __future__ import annotations

from collections.abc import Callable
from typing import Final, Optional

from datatypes.epc.domain.epc import Epc
from datatypes.epc.domain.epc_property_data import EpcPropertyData
from domain.billing.bill import Bill, EnergyBreakdown
from domain.billing.bill_derivation import BillDerivation
from domain.modelling.considered_measures import (
    combine_considered_measures,
    restrict_to_considered_measures,
)
from domain.modelling.generators.floor_recommendation import recommend_floor_insulation
from domain.modelling.measure_type import MeasureType
from domain.modelling.optimisation.measure_dependency import ventilation_dependency
from domain.modelling.optimisation.optimiser import (
    MeasureDependency,
    OptimisedPackage,
    ScoredOption,
    optimise_package,
)
from domain.modelling.scoring.package_scorer import PackageScorer, Score
from domain.modelling.plan import Plan, PlanMeasure
from domain.modelling.recommendation import MeasureOption, Recommendation
from domain.modelling.generators.roof_recommendation import recommend_roof_insulation
from domain.modelling.scenario import Scenario
from domain.modelling.scoring.scoring import (
    MeasureImpact,
    cascade_scores,
    independent_option_impacts,
    marginals_from_scores,
)
from domain.modelling.generators.wall_recommendation import recommend_cavity_wall
from domain.modelling.generators.solid_wall_recommendation import recommend_solid_wall
from domain.modelling.generators.glazing_recommendation import recommend_glazing
from domain.modelling.generators.lighting_recommendation import recommend_lighting
from domain.modelling.generators.heating_recommendation import recommend_heating
from domain.modelling.generators.secondary_heating_recommendation import (
    recommend_secondary_heating_removal,
)
from domain.modelling.generators.solar_recommendation import recommend_solar
from domain.modelling.solar_potential import SolarPotential
from domain.geospatial.planning_restrictions import PlanningRestrictions
from domain.sap10_calculator.calculator import SapCalculator
from repositories.fuel_rates.fuel_rates_repository import FuelRatesRepository
from repositories.product.product_repository import ProductRepository
from repositories.solar.solar_repository import SolarRepository
from repositories.unit_of_work import UnitOfWork

# The PortfolioGoal value that targets a SAP band (cf.
# backend.app.db.models.portfolio.PortfolioGoal.INCREASING_EPC). Other goals
# (Energy Savings, Reducing CO2 emissions) don't yet set a SAP repair target —
# the optimiser just maximises SAP gain within budget for them (later slice).
_INCREASING_EPC_GOAL: Final[str] = "Increasing EPC"

# Best-practice install sequence for the role-3 attribution cascade (ADR-0016):
# walls → roof → ventilation → floor, per the legacy `Recommendations` class.
# Ventilation sits after the fabric that triggers it so its (negative) marginal
# is attributed against the insulated envelope.
_BEST_PRACTICE_ORDER: Final[tuple[str, ...]] = (
    "cavity_wall_insulation",
    "external_wall_insulation",
    "internal_wall_insulation",
    "loft_insulation",
    "mechanical_ventilation",
    "suspended_floor_insulation",
    "solid_floor_insulation",
)


class ModellingOrchestrator:
    """Stage 3 — scores each baselined Property against its Scenarios into Plans
    and persists them (CONTEXT.md: Modelling; ADR-0011 / ADR-0012 / ADR-0016 /
    ADR-0017).

    Runs the whole batch in **one** Unit of Work and commits once. For each
    (Property × Scenario) it reads the Property's Effective EPC and the Scenario
    through repos, generates the candidate Recommendations (wall / roof /
    floor), scores each Option independently (role 1), runs the grouped-knapsack
    Optimiser + whole-package re-score + greedy repair toward the Scenario's SAP
    target (role 2, ADR-0016), attributes each selected measure via the
    best-practice marginal cascade (role 3), and persists a **Plan** with its
    **Plan Measures**. Single-phase — multi-phase is deferred (ADR-0005).

    Reads only through repos and threads only IDs (`property_ids`,
    `scenario_ids`, `portfolio_id`) — never an in-memory hand-off from Baseline
    (ADR-0011). The injected `SapCalculator` is the scoring-engine seam.
    """

    def __init__(
        self,
        *,
        unit_of_work: Callable[[], UnitOfWork],
        calculator: SapCalculator,
        fuel_rates: FuelRatesRepository,
    ) -> None:
        self._unit_of_work = unit_of_work
        self._calculator = calculator
        self._fuel_rates = fuel_rates

    def run(
        self,
        property_ids: list[int],
        scenario_ids: list[int],
        portfolio_id: int,
        *,
        considered_measures: Optional[frozenset[MeasureType]] = None,
    ) -> None:
        """Model the batch. ``considered_measures`` restricts the run to those
        measure types (mirroring the legacy `inclusions`); None considers every
        modelled measure."""
        scorer = PackageScorer(self._calculator)
        # Resolve Fuel Rates once and reuse the BillDerivation across the batch,
        # so every baseline/post bill is priced at the same snapshot (ADR-0014).
        bill_derivation = BillDerivation(self._fuel_rates.get_current())
        with self._unit_of_work() as uow:
            properties = uow.property.get_many(property_ids)
            scenarios: list[Scenario] = uow.scenario.get_many(scenario_ids)
            for property_id, prop in zip(property_ids, properties, strict=True):
                effective_epc: EpcPropertyData = prop.effective_epc
                # The Property's Google Solar potential (raw buildingInsights
                # JSON persisted by Ingestion), projected once per Property and
                # threaded into the solar Generator (ADR-0026). None when no
                # solar data was fetched — the Generator then offers nothing.
                solar_potential: Optional[SolarPotential] = _solar_potential_for(
                    uow.solar, prop.identity.uprn
                )
                for scenario in scenarios:
                    plan = self._plan_for(
                        scorer,
                        bill_derivation,
                        effective_epc,
                        uow.product,
                        scenario,
                        current_market_value=prop.current_market_value,
                        planning_restrictions=prop.planning_restrictions,
                        solar_potential=solar_potential,
                        considered_measures=considered_measures,
                    )
                    uow.plan.save(
                        plan,
                        property_id=property_id,
                        scenario_id=scenario.id,
                        portfolio_id=portfolio_id,
                        is_default=scenario.is_default,
                    )
            uow.commit()

    def _plan_for(
        self,
        scorer: PackageScorer,
        bill_derivation: BillDerivation,
        effective_epc: EpcPropertyData,
        products: ProductRepository,
        scenario: Scenario,
        *,
        current_market_value: Optional[float],
        planning_restrictions: PlanningRestrictions,
        solar_potential: Optional[SolarPotential],
        considered_measures: Optional[frozenset[MeasureType]],
    ) -> Plan:
        """Generate → score → optimise → re-score/repair → attribute → bill →
        assemble the Plan for one Property + Scenario."""
        # The Scenario's own exclusions scope the run; an explicit
        # ``considered_measures`` (e.g. from a harness) narrows it further.
        considered: Optional[frozenset[MeasureType]] = combine_considered_measures(
            scenario.considered_measures(), considered_measures
        )
        groups: list[list[ScoredOption]] = _scored_candidate_groups(
            scorer,
            effective_epc,
            products,
            planning_restrictions,
            solar_potential,
            considered,
        )
        # Forced Measure Dependencies (ventilation) are excluded from the pool
        # but injected into the package before the re-score (ADR-0016).
        dependencies: list[MeasureDependency] = _measure_dependencies(
            effective_epc, products, considered
        )
        package: OptimisedPackage = optimise_package(
            groups=groups,
            scorer=scorer,
            baseline_epc=effective_epc,
            budget=scenario.budget,
            target_sap=_target_sap(scenario),
            dependencies=dependencies,
        )

        # Role-3 attribution: re-apply the *selected* set in best-practice order
        # so each measure's marginal telescopes to the truthful package total.
        ordered: list[MeasureOption] = sorted(
            (scored.option for scored in package.selected), key=_best_practice_key
        )
        # Score the baseline + every cumulative prefix once (cascade[0] is the
        # baseline, cascade[-1] the whole package), then reuse those Scores for
        # both the marginal attribution and the per-measure bill cascade.
        cascade: list[Score] = cascade_scores(
            scorer, effective_epc, [option.overlay for option in ordered]
        )
        impacts: list[MeasureImpact] = marginals_from_scores(cascade)
        # Bill every prefix at one Fuel Rates snapshot; consecutive Bill deltas
        # are each measure's marginal energy/cost saving — negative for
        # ventilation — telescoping exactly to the Plan totals (ADR-0014). The
        # Plan's baseline/post Bills are the cascade endpoints, so the
        # per-measure savings and the headline savings share one source.
        bills: list[Bill] = [_bill_for(bill_derivation, score) for score in cascade]
        measures: tuple[PlanMeasure, ...] = tuple(
            _plan_measure(option, impact, before, after)
            for option, impact, before, after in zip(
                ordered, impacts, bills[:-1], bills[1:], strict=True
            )
        )
        return Plan(
            measures=measures,
            baseline=cascade[0],
            post_retrofit=package.score,
            baseline_bill=bills[0],
            post_bill=bills[-1],
            current_market_value=current_market_value,
        )


def _bill_for(bill_derivation: BillDerivation, score: Score) -> Bill:
    """Derive the annual Bill for a scored end-state, pricing the delivered
    energy off the Score's SapResult. The real PackageScorer always attaches the
    SapResult; a missing one is a wiring error, so raise rather than bill at a
    default (ADR-0014)."""
    if score.sap_result is None:
        raise ValueError(
            "cannot derive a bill: the Score carries no SapResult to price"
        )
    return bill_derivation.derive(EnergyBreakdown.from_sap_result(score.sap_result))


def _solar_potential_for(
    solar_repo: SolarRepository, uprn: Optional[int]
) -> Optional[SolarPotential]:
    """Project the UPRN's persisted Google Solar `buildingInsights` JSON
    into a typed `SolarPotential` (ADR-0026), or None when there is no UPRN /
    none was fetched / the lookup returned an error payload (no `solarPotential`
    block). Solar is keyed by UPRN to match the live ``solar`` table."""
    if uprn is None:
        return None
    insights = solar_repo.get(uprn)
    if not insights or "solarPotential" not in insights:
        return None
    return SolarPotential.from_building_insights(insights)


def _candidate_recommendations(
    effective_epc: EpcPropertyData,
    products: ProductRepository,
    planning_restrictions: PlanningRestrictions,
    solar_potential: Optional[SolarPotential],
    considered_measures: Optional[frozenset[MeasureType]],
) -> list[Recommendation]:
    """Run the applicable Recommendation Generators; keep the ones that apply.
    Solid-wall insulation, glazing, heating and solar are additionally gated by
    the Property's planning protections (ADR-0019 / ADR-0022 / ADR-0024 /
    ADR-0026); solar also needs the Property's Google solar potential.

    ``considered_measures`` gates generation *up front*: a generator runs only
    when the allowlist admits at least one of the measure types it can emit
    (None = every measure), so an excluded measure never reaches the catalogue —
    which matters when the live ``material.type`` enum cannot even represent it
    (e.g. ``secondary_heating_removal``). ``restrict_to_considered_measures``
    then trims any disallowed Options off the multi-Option survivors."""

    def admitted(*emits: MeasureType) -> bool:
        return considered_measures is None or any(
            measure in considered_measures for measure in emits
        )

    # Each generator paired with the measure types it can emit, so the allowlist
    # can skip a generator whose every type is excluded before it is invoked.
    generators: tuple[
        tuple[bool, Callable[[], Optional[Recommendation]]], ...
    ] = (
        (
            admitted(MeasureType.CAVITY_WALL_INSULATION),
            lambda: recommend_cavity_wall(effective_epc, products),
        ),
        (
            admitted(
                MeasureType.INTERNAL_WALL_INSULATION,
                MeasureType.EXTERNAL_WALL_INSULATION,
            ),
            lambda: recommend_solid_wall(
                effective_epc, products, planning_restrictions
            ),
        ),
        (
            admitted(
                MeasureType.LOFT_INSULATION,
                MeasureType.SLOPING_CEILING_INSULATION,
                MeasureType.FLAT_ROOF_INSULATION,
            ),
            lambda: recommend_roof_insulation(effective_epc, products),
        ),
        (
            admitted(
                MeasureType.SUSPENDED_FLOOR_INSULATION,
                MeasureType.SOLID_FLOOR_INSULATION,
            ),
            lambda: recommend_floor_insulation(effective_epc, products),
        ),
        (
            admitted(MeasureType.DOUBLE_GLAZING, MeasureType.SECONDARY_GLAZING),
            lambda: recommend_glazing(effective_epc, products, planning_restrictions),
        ),
        (
            admitted(MeasureType.LOW_ENERGY_LIGHTING),
            lambda: recommend_lighting(effective_epc, products),
        ),
        (
            admitted(
                MeasureType.HIGH_HEAT_RETENTION_STORAGE_HEATERS,
                MeasureType.AIR_SOURCE_HEAT_PUMP,
                MeasureType.GAS_BOILER_UPGRADE,
                MeasureType.SYSTEM_TUNE_UP,
                MeasureType.SYSTEM_TUNE_UP_ZONED,
            ),
            lambda: recommend_heating(effective_epc, products, planning_restrictions),
        ),
        (
            admitted(MeasureType.SECONDARY_HEATING_REMOVAL),
            lambda: recommend_secondary_heating_removal(effective_epc, products),
        ),
        (
            admitted(MeasureType.SOLAR_PV),
            lambda: recommend_solar(
                effective_epc, products, solar_potential, planning_restrictions
            ),
        ),
    )
    found = [thunk() for is_admitted, thunk in generators if is_admitted]
    applicable = [
        recommendation for recommendation in found if recommendation is not None
    ]
    return restrict_to_considered_measures(applicable, considered_measures)


def _measure_dependencies(
    effective_epc: EpcPropertyData,
    products: ProductRepository,
    considered_measures: Optional[frozenset[MeasureType]],
) -> list[MeasureDependency]:
    """The forced Measure Dependencies for this Property — currently just
    ventilation, suppressed when the dwelling is already mechanically
    ventilated (ADR-0016). A dependency whose required measure is outside the
    run's allowlist is also suppressed, so a restricted run forces nothing it is
    not considering."""
    dependency: Optional[MeasureDependency] = ventilation_dependency(
        effective_epc, products
    )
    if dependency is None:
        return []
    if (
        considered_measures is not None
        and dependency.required.option.measure_type not in considered_measures
    ):
        return []
    return [dependency]


def _scored_candidate_groups(
    scorer: PackageScorer,
    effective_epc: EpcPropertyData,
    products: ProductRepository,
    planning_restrictions: PlanningRestrictions,
    solar_potential: Optional[SolarPotential],
    considered_measures: Optional[frozenset[MeasureType]],
) -> list[list[ScoredOption]]:
    """One group per Recommendation: each Option scored independently against
    the baseline (role-1 warm-start signal, ADR-0016)."""
    groups: list[list[ScoredOption]] = []
    for recommendation in _candidate_recommendations(
        effective_epc, products, planning_restrictions, solar_potential, considered_measures
    ):
        options = list(recommendation.options)
        impacts: list[MeasureImpact] = independent_option_impacts(
            scorer, effective_epc, options
        )
        groups.append(
            [
                ScoredOption(option=option, sap_gain=impact.sap_points)
                for option, impact in zip(options, impacts, strict=True)
            ]
        )
    return groups


def _target_sap(scenario: Scenario) -> Optional[float]:
    """The SAP rating the Optimiser repairs toward — the floor of the goal
    band for an INCREASING_EPC goal, else None (no SAP target)."""
    if scenario.goal != _INCREASING_EPC_GOAL:
        return None
    return float(Epc(scenario.goal_value).sap_lower_bound())


def _best_practice_key(option: MeasureOption) -> int:
    try:
        return _BEST_PRACTICE_ORDER.index(option.measure_type)
    except ValueError:
        return len(_BEST_PRACTICE_ORDER)


def _plan_measure(
    option: MeasureOption, impact: MeasureImpact, before: Bill, after: Bill
) -> PlanMeasure:
    """Assemble a Plan Measure, attributing this measure's marginal bill saving
    as the delta between the running package Bill before and after it (delivered
    kWh and £). Signed so positive is a saving; ventilation is negative."""
    if option.cost is None:
        raise ValueError(
            f"measure option {option.measure_type!r} has no cost; cannot persist"
        )
    return PlanMeasure(
        measure_type=option.measure_type,
        description=option.description,
        cost=option.cost,
        impact=impact,
        kwh_savings=before.total_consumption_kwh - after.total_consumption_kwh,
        energy_cost_savings=before.total_gbp - after.total_gbp,
        material_id=option.material_id,
    )