import logging
from contextlib import contextmanager
from datetime import datetime, timezone
from typing import Iterator

from sqlalchemy import create_engine, or_, select
from sqlalchemy.orm import Session, sessionmaker

from ..core.config import Settings
from .models import Base, Car, Image, SyncRun
from .schemas import CarRecord

logger = logging.getLogger("iaai_scraper.db")


CAR_DB_FIELDS = {
	col.key for col in Car.__table__.columns
	if col.key not in ("id",)
}


class PersistenceService:

	def __init__(self, settings: Settings) -> None:
		self.settings = settings
		engine_kwargs = {
			"echo": settings.database.echo,
			"future": True,
		}
		if "postgresql" in settings.database.url:
			engine_kwargs["pool_size"] = settings.database.pool_size
			engine_kwargs["max_overflow"] = settings.database.max_overflow
			engine_kwargs["pool_pre_ping"] = True
			engine_kwargs["pool_recycle"] = settings.database.pool_recycle_seconds
		self.engine = create_engine(settings.database.url, **engine_kwargs)
		self.session_factory = sessionmaker(bind=self.engine, expire_on_commit=False, future=True)

	def create_tables(self) -> None:
		# В тестах/локально на SQLite разрешаем create_all; для non-SQLite в проде — только через миграции.
		is_sqlite = self.settings.database.url.startswith("sqlite")
		if not is_sqlite and not self.settings.database.auto_create_tables:
			return
		try:
			Base.metadata.create_all(self.engine)
		except Exception:
			logger.debug("create_tables skipped (schema already exists)")

	@contextmanager
	def session_scope(self) -> Iterator[Session]:
		session = self.session_factory()
		try:
			yield session
			session.commit()
		except Exception:
			session.rollback()
			raise
		finally:
			session.close()

	def start_sync_run(self, lane: str) -> int:
		with self.session_scope() as session:
			now = datetime.now(timezone.utc)
			stale_runs = session.execute(select(SyncRun).where(SyncRun.status == "running")).scalars().all()
			for stale in stale_runs:
				stale.status = "failed"
				stale.finished_at = now
				if not stale.error_summary:
					stale.error_summary = "Recovered stale running sync run before starting a new run"

			run = SyncRun(status="running", lane=lane, ids_fetched=0, cars_upserted=0, cars_failed=0, images_upserted=0)
			session.add(run)
			session.flush()
			return int(run.id)

	def finish_sync_run(self, run_id: int, *, status: str, ids_fetched: int, cars_upserted: int, cars_failed: int, images_upserted: int, error_summary: str | None = None) -> None:
		with self.session_scope() as session:
			run = session.get(SyncRun, run_id)
			if run is None:
				return
			run.finished_at = datetime.now(timezone.utc)
			run.status = status
			run.ids_fetched = ids_fetched
			run.cars_upserted = cars_upserted
			run.cars_failed = cars_failed
			run.images_upserted = images_upserted
			run.error_summary = error_summary

	def get_existing_origin_urls(self, origin_urls: list[str]) -> set[str]:
		if not origin_urls:
			return set()
		with self.session_scope() as session:
			rows = session.execute(select(Car.origin_url).where(Car.origin_url.in_(origin_urls))).all()
			return {str(row[0]) for row in rows if row and row[0]}

	def get_existing_origin_ids(self, origin_ids: list[str]) -> set[str]:
		if not origin_ids:
			return set()
		with self.session_scope() as session:
			rows = session.execute(select(Car.origin_id).where(Car.origin_id.in_(origin_ids))).all()
			return {str(row[0]) for row in rows if row and row[0]}

	@staticmethod
	def _add_images(session: Session, car_id: int, images: list[dict[str, object]]) -> None:
		for image_payload in images:
			session.add(Image(fullres_image=str(image_payload["fullres_image"]), preview_image=str(image_payload["preview_image"]), order_index=int(image_payload.get("order_index", 0)), car_id=car_id))

	@staticmethod
	def _car_payload(record: CarRecord) -> dict[str, object]:
		payload = record.model_dump(mode="python")
		return {key: value for key, value in payload.items() if key in CAR_DB_FIELDS}

	def upsert_car(self, record: CarRecord):
		# Insert/update автомобиля по origin_id/origin_url.
		payload = self._car_payload(record)
		images = [image.model_dump(mode="python") for image in record.images]
		with self.session_scope() as session:
			car = session.execute(
				select(Car).where(or_(Car.origin_id == record.origin_id, Car.origin_url == record.origin_url))
			).scalar_one_or_none()
			action = "inserted"
			if car is None:
				car = Car(**payload)
				session.add(car)
				session.flush()
			else:
				action = "updated"
				for key, value in payload.items():
					setattr(car, key, value)
				car.last_seen_at = record.last_seen_at
				session.flush()
				nested = session.begin_nested()
				try:
					for image in list(car.images):
						session.delete(image)
					session.flush()
					self._add_images(session, int(car.id), images)
					session.flush()
					nested.commit()
				except Exception:
					nested.rollback()
					logger.warning("Image replacement failed for car %s, keeping old images", record.origin_id)
					images = []
				return {"car_id": int(car.id), "images_upserted": len(images), "action": action}
			self._add_images(session, int(car.id), images)
			session.flush()
			return {"car_id": int(car.id), "images_upserted": len(images), "action": action}