from __future__ import annotations

from datetime import datetime, timezone

from sqlalchemy import DateTime, Float, Integer, String, UniqueConstraint
from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column
from sqlalchemy.types import TypeDecorator


class UTCDateTime(TypeDecorator):
    """SQLite has no real timezone-aware datetime type: SQLAlchemy's
    `DateTime(timezone=True)` silently stores and returns *naive* datetimes
    on this backend, which then get misinterpreted as system-local time by
    `.astimezone()` anywhere they're read back (e.g. every time-of-use
    match in the costing engine) -- a correctness bug that only shows up
    when the host's local timezone isn't UTC. This type makes the
    round-trip explicit: always stores naive-UTC, always returns
    timezone-aware UTC.
    """

    impl = DateTime
    cache_ok = True

    def process_bind_param(self, value: datetime | None, dialect):
        if value is None:
            return None
        if value.tzinfo is None:
            raise ValueError("UTCDateTime requires a timezone-aware datetime")
        return value.astimezone(timezone.utc).replace(tzinfo=None)

    def process_result_value(self, value: datetime | None, dialect):
        if value is None:
            return None
        return value.replace(tzinfo=timezone.utc)


class Base(DeclarativeBase):
    pass


class IntervalReadingRow(Base):
    __tablename__ = "interval_reading"
    __table_args__ = (UniqueConstraint("ts", "source", name="uq_interval_reading_ts_source"),)

    id: Mapped[int] = mapped_column(Integer, primary_key=True)
    ts: Mapped[datetime] = mapped_column(UTCDateTime, index=True)
    source: Mapped[str] = mapped_column(String)  # 'isolarcloud' | 'mock'
    generation_kwh: Mapped[float] = mapped_column(Float)
    load_kwh: Mapped[float] = mapped_column(Float)
    import_kwh: Mapped[float] = mapped_column(Float)
    export_kwh: Mapped[float] = mapped_column(Float)
    resolution_minutes: Mapped[int] = mapped_column(Integer)


class PlanCacheRow(Base):
    __tablename__ = "plan_cache"

    plan_id: Mapped[str] = mapped_column(String, primary_key=True)
    retailer: Mapped[str] = mapped_column(String)
    plan_name: Mapped[str] = mapped_column(String)
    fuel_type: Mapped[str] = mapped_column(String)
    distributors_json: Mapped[str] = mapped_column(String)  # JSON list
    last_refreshed: Mapped[datetime] = mapped_column(UTCDateTime)
    raw_detail_json: Mapped[str] = mapped_column(String)
    parsed_tariff_json: Mapped[str] = mapped_column(String)


class CurrentPlanConfigRow(Base):
    __tablename__ = "current_plan_config"

    id: Mapped[int] = mapped_column(Integer, primary_key=True, default=1)
    retailer_name: Mapped[str] = mapped_column(String)
    plan_name: Mapped[str] = mapped_column(String)
    tariff_json: Mapped[str] = mapped_column(String)


class HouseholdConfigRow(Base):
    __tablename__ = "household_config"

    id: Mapped[int] = mapped_column(Integer, primary_key=True, default=1)
    distributor: Mapped[str] = mapped_column(String, default="Energex")
    postcode: Mapped[str] = mapped_column(String, default="")
    isolarcloud_ps_id: Mapped[str] = mapped_column(String, default="")


class SyncStateRow(Base):
    __tablename__ = "sync_state"

    key: Mapped[str] = mapped_column(String, primary_key=True)
    value: Mapped[str] = mapped_column(String)