from __future__ import annotations

from datetime import datetime
from typing import ClassVar, Optional

from sqlalchemy import BigInteger, Column, ForeignKey, TIMESTAMP
from sqlalchemy import Enum as SAEnum
from sqlalchemy.sql import func
from sqlmodel import Field, SQLModel

from datatypes.enums import QuantityUnits
from domain.modelling.plan import PlanMeasure

# Calculator metrics are in kg CO₂/yr; the live ``recommendation`` column is
# tonnes (legacy ``emissions_kg / 1000``). Convert on the way in.
_KG_PER_TONNE = 1000.0


class RecommendationModel(SQLModel, table=True):
    """The single SQLModel definition of the live ``recommendation`` table
    (ADR-0017 amendment) — one row per persisted Plan Measure.

    Carries full legacy column parity (the readers iterate the columns / sum
    them) **plus** ``plan_id``, the FK that links a measure to its Plan and
    replaces the retired ``plan_recommendations`` m2m. Out-of-cluster columns
    (``property_id``) are plain indexed ints, not FK constraints, matching the
    mirror convention so ``SQLModel.metadata.create_all`` needs no foreign
    table to exist (the live FKs are owned by the Drizzle schema).
    """

    __tablename__: ClassVar[str] = "recommendation"  # pyright: ignore[reportIncompatibleVariableOverride]

    id: Optional[int] = Field(default=None, primary_key=True)
    property_id: int = Field(index=True)
    plan_id: Optional[int] = Field(
        default=None,
        sa_column=Column(
            BigInteger,
            ForeignKey("plan.id", ondelete="CASCADE"),
            nullable=True,
            index=True,
        ),
    )
    created_at: Optional[datetime] = Field(
        default=None,
        sa_column=Column(TIMESTAMP, nullable=False, server_default=func.now()),
    )

    type: str
    measure_type: Optional[str] = Field(default=None)
    description: str
    # The single Product this measure installs — the live ``material_id`` column
    # that replaces the retired ``recommendation_materials`` BOM (one material
    # per Plan Measure). Plain int, out-of-cluster (mirror convention).
    material_id: Optional[int] = Field(default=None, index=True)
    estimated_cost: Optional[float] = Field(default=None)
    starting_u_value: Optional[float] = Field(default=None)
    new_u_value: Optional[float] = Field(default=None)
    sap_points: Optional[float] = Field(default=None)
    heat_demand: Optional[float] = Field(default=None)
    kwh_savings: Optional[float] = Field(default=None)  # delivered kWh/yr
    co2_equivalent_savings: Optional[float] = Field(default=None)  # tonnes/yr
    energy_savings: Optional[float] = Field(default=None)
    energy_cost_savings: Optional[float] = Field(default=None)  # £/yr
    property_valuation_increase: Optional[float] = Field(default=None)
    rental_yield_increase: Optional[float] = Field(default=None)
    total_work_hours: Optional[float] = Field(default=None)
    labour_days: Optional[float] = Field(default=None)
    default: bool = True
    already_installed: bool = False

    @classmethod
    def from_domain(
        cls, measure: PlanMeasure, *, property_id: int, plan_id: int
    ) -> "RecommendationModel":
        return cls(
            property_id=property_id,
            plan_id=plan_id,
            type=measure.measure_type,
            measure_type=measure.measure_type,
            description=measure.description,
            material_id=measure.material_id,
            estimated_cost=measure.cost.total,
            sap_points=measure.impact.sap_points,
            co2_equivalent_savings=(
                measure.impact.co2_savings_kg_per_yr / _KG_PER_TONNE
            ),
            kwh_savings=measure.kwh_savings,
            energy_cost_savings=measure.energy_cost_savings,
            default=True,
            already_installed=False,
        )


class RecommendationMaterialModel(SQLModel, table=True):
    """The live ``recommendation_materials`` table — one row per material used
    by a Recommendation. ``recommendation_id`` is an intra-cluster FK;
    ``material_id`` is a plain int (out-of-cluster, mirror convention)."""

    __tablename__: ClassVar[str] = "recommendation_materials"  # pyright: ignore[reportIncompatibleVariableOverride]

    id: Optional[int] = Field(default=None, primary_key=True)
    recommendation_id: int = Field(
        sa_column=Column(
            BigInteger, ForeignKey("recommendation.id"), nullable=False
        )
    )
    material_id: int = Field(index=True)
    created_at: Optional[datetime] = Field(
        default=None,
        sa_column=Column(TIMESTAMP, nullable=False, server_default=func.now()),
    )
    depth: Optional[float] = Field(default=None)
    quantity: Optional[float] = Field(default=None)
    quantity_unit: Optional[QuantityUnits] = Field(
        default=None,
        sa_column=Column(
            SAEnum(
                QuantityUnits,
                values_callable=lambda cls: [m.value for m in cls],  # pyright: ignore[reportUnknownLambdaType, reportUnknownMemberType, reportUnknownVariableType]
            ),
            nullable=True,
        ),
    )
    estimated_cost: Optional[float] = Field(default=None)