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

from sqlalchemy import create_engine, delete, or_, select, text, update
from sqlalchemy.dialects.postgresql import insert as pg_insert
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("dubizzle_scraper.db")


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

_IN_CHUNK_SIZE = 5000


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
			engine_kwargs["pool_timeout"] = 30
			# Таймауты запросов и блокировок.
			engine_kwargs["connect_args"] = {
				"options": "-c statement_timeout=120000 -c lock_timeout=30000"
			}
		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:
		# Для SQLite можно create_all.
		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]}

	def get_existing_urls_and_ids(
		self, origin_urls: list[str], origin_ids: list[str],
	) -> tuple[set[str], set[str]]:
		# Загрузка URL и origin_id.
		if not origin_urls and not origin_ids:
			return set(), set()
		urls: set[str] = set()
		ids: set[str] = set()
		with self.session_scope() as session:
			max_len = max(len(origin_urls), len(origin_ids), 1)
			for i in range(0, max_len, _IN_CHUNK_SIZE):
				url_chunk = origin_urls[i:i + _IN_CHUNK_SIZE]
				id_chunk = origin_ids[i:i + _IN_CHUNK_SIZE]
				conditions = []
				if url_chunk:
					conditions.append(Car.origin_url.in_(url_chunk))
				if id_chunk:
					conditions.append(Car.origin_id.in_(id_chunk))
				if not conditions:
					continue
				rows = session.execute(
					select(Car.origin_url, Car.origin_id).where(or_(*conditions))
				).all()
				for r in rows:
					if r[0]:
						urls.add(str(r[0]))
					if r[1]:
						ids.add(str(r[1]))
		return urls, ids

	@staticmethod
	def _add_images(session: Session, car_id: int, images: list[dict[str, object]]) -> None:
		if not images:
			return
		session.add_all([
			Image(
				fullres_image=str(img["fullres_image"]),
				preview_image=str(img["preview_image"]),
				order_index=int(img.get("order_index", 0)),
				car_id=car_id,
			)
			for img in images
		])

	@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 _is_postgres(self) -> bool:
		return self.engine.dialect.name == "postgresql"

	def _load_existing_cars(
		self,
		session: Session,
		origin_ids: list[str],
		origin_urls: list[str],
	) -> tuple[dict[str, Car], dict[str, Car]]:
		existing_by_id: dict[str, Car] = {}
		existing_by_url: dict[str, Car] = {}
		if not origin_ids and not origin_urls:
			return existing_by_id, existing_by_url

		existing_cars: list[Car] = []
		max_len = max(len(origin_ids), len(origin_urls), 1)
		for i in range(0, max_len, _IN_CHUNK_SIZE):
			id_chunk = origin_ids[i:i + _IN_CHUNK_SIZE]
			url_chunk = origin_urls[i:i + _IN_CHUNK_SIZE]
			conditions = []
			if id_chunk:
				conditions.append(Car.origin_id.in_(id_chunk))
			if url_chunk:
				conditions.append(Car.origin_url.in_(url_chunk))
			if not conditions:
				continue
			rows = session.execute(
				select(Car).where(or_(*conditions))
			).scalars().all()
			existing_cars.extend(rows)

		for car in existing_cars:
			if car.origin_id:
				existing_by_id[car.origin_id] = car
			if car.origin_url:
				existing_by_url[car.origin_url] = car
		return existing_by_id, existing_by_url

	def _load_existing_image_urls(self, session: Session, car_ids: set[int]) -> dict[int, set[str]]:
		existing_images_map: dict[int, set[str]] = {}
		if not car_ids:
			return existing_images_map

		car_id_list = list(car_ids)
		for i in range(0, len(car_id_list), _IN_CHUNK_SIZE):
			chunk = car_id_list[i:i + _IN_CHUNK_SIZE]
			img_rows = session.execute(
				select(Image.car_id, Image.fullres_image).where(Image.car_id.in_(chunk))
			).all()
			for cid, furl in img_rows:
				existing_images_map.setdefault(int(cid), set()).add(str(furl))
		return existing_images_map

	@staticmethod
	def _postgres_upsert_set_map(insert_stmt) -> dict[str, object]:
		return {
			key: getattr(insert_stmt.excluded, key)
			for key in CAR_DB_FIELDS
		}

	def _replace_images_for_car(
		self,
		session: Session,
		car_id: int,
		images: list[dict[str, object]],
		origin_id: str,
	) -> int:
		nested = session.begin_nested()
		try:
			session.execute(delete(Image).where(Image.car_id == car_id))
			self._add_images(session, car_id, images)
			session.flush()
			nested.commit()
			return len(images)
		except Exception:
			nested.rollback()
			logger.warning("Image replacement failed for car %s, keeping old images", origin_id, exc_info=True)
			return 0

	def _upsert_cars_batch_postgres(self, records: list[CarRecord]) -> dict[str, int]:
		inserted = 0
		updated = 0
		images_total = 0

		with self.session_scope() as session:
			origin_ids = [r.origin_id for r in records if r.origin_id]
			origin_urls = [r.origin_url for r in records if r.origin_url]
			existing_by_id, existing_by_url = self._load_existing_cars(session, origin_ids, origin_urls)

			entries: list[dict[str, object]] = []
			upsert_payloads: list[dict[str, object]] = []
			for record in records:
				payload = self._car_payload(record)
				images = [image.model_dump(mode="python") for image in record.images]
				car_by_id = existing_by_id.get(record.origin_id)
				car_by_url = existing_by_url.get(record.origin_url)
				entry: dict[str, object] = {"record": record, "images": images, "car_id": None}

				if car_by_url is not None and car_by_url.origin_id != record.origin_id and car_by_id is None:
					for key, value in payload.items():
						setattr(car_by_url, key, value)
					car_by_url.last_seen_at = record.last_seen_at
					entry["car_id"] = int(car_by_url.id)
					updated += 1
				else:
					upsert_payloads.append(payload)
					if car_by_id is not None:
						updated += 1
					else:
						inserted += 1
				entries.append(entry)

			session.flush()

			if upsert_payloads:
				insert_stmt = pg_insert(Car).values(upsert_payloads)
				upsert_stmt = insert_stmt.on_conflict_do_update(
					index_elements=[Car.origin_id],
					set_=self._postgres_upsert_set_map(insert_stmt),
				).returning(Car.id, Car.origin_id)
				rows = session.execute(upsert_stmt).all()
				car_ids_by_origin_id = {str(origin_id): int(car_id) for car_id, origin_id in rows}
				for entry in entries:
					if entry["car_id"] is not None:
						continue
					record = entry["record"]
					car_id = car_ids_by_origin_id.get(record.origin_id)
					if car_id is None:
						raise RuntimeError(f"PostgreSQL upsert did not return car_id for {record.origin_id}")
					entry["car_id"] = car_id

			car_ids = {int(entry["car_id"]) for entry in entries if entry["car_id"] is not None}
			existing_images_map = self._load_existing_image_urls(session, car_ids)
			images_by_car_id: dict[int, list[dict[str, object]]] = {}
			replace_ids: list[int] = []

			for entry in entries:
				car_id = int(entry["car_id"])
				images = entry["images"]
				new_image_urls = {
					str(img.get("fullres_image", ""))
					for img in images
					if img.get("fullres_image")
				}
				old_image_urls = existing_images_map.get(car_id, set())
				if new_image_urls != old_image_urls:
					replace_ids.append(car_id)
					images_by_car_id[car_id] = images
				else:
					images_total += len(old_image_urls)

			if replace_ids:
				for i in range(0, len(replace_ids), _IN_CHUNK_SIZE):
					chunk = replace_ids[i:i + _IN_CHUNK_SIZE]
					session.execute(delete(Image).where(Image.car_id.in_(chunk)))
				for car_id in replace_ids:
					images = images_by_car_id[car_id]
					self._add_images(session, car_id, images)
					images_total += len(images)

		return {"inserted": inserted, "updated": updated, "images_upserted": images_total}

	def upsert_car(self, record: CarRecord):
		# Вставка или обновление авто.
		payload = self._car_payload(record)
		images = [image.model_dump(mode="python") for image in record.images]
		with self.session_scope() as session:
			if self._is_postgres():
				car_by_url = session.execute(
					select(Car).where(Car.origin_url == record.origin_url)
				).scalar_one_or_none()
				if car_by_url is not None and car_by_url.origin_id != record.origin_id:
					for key, value in payload.items():
						setattr(car_by_url, key, value)
					car_by_url.last_seen_at = record.last_seen_at
					session.flush()
					car_id = int(car_by_url.id)
					action = "updated"
				else:
					existed = session.execute(
						select(Car.id).where(Car.origin_id == record.origin_id)
					).scalar_one_or_none() is not None
					insert_stmt = pg_insert(Car).values(**payload)
					upsert_stmt = insert_stmt.on_conflict_do_update(
						index_elements=[Car.origin_id],
						set_=self._postgres_upsert_set_map(insert_stmt),
					).returning(Car.id)
					car_id = int(session.execute(upsert_stmt).scalar_one())
					action = "updated" if existed or car_by_url is not None else "inserted"

				images_upserted = self._replace_images_for_car(
					session, car_id, images, record.origin_id,
				)
				return {"car_id": car_id, "images_upserted": images_upserted, "action": action}

			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()
				images_upserted = self._replace_images_for_car(session, int(car.id), images, record.origin_id)
				return {"car_id": int(car.id), "images_upserted": images_upserted, "action": action}
			self._add_images(session, int(car.id), images)
			session.flush()
			return {"car_id": int(car.id), "images_upserted": len(images), "action": action}
	def upsert_cars_batch(self, records: list[CarRecord]) -> dict[str, int]:
		"""Пакетный upsert нескольких автомобилей в одной транзакции.

		Оптимизации:
		- Дедупликация записей по origin_id перед вставкой.
		- Chunked IN-queries для больших списков (обход лимита PG параметров).
		- Пропуск перезаписи изображений, если набор URL не изменился.
		- Один DELETE по car_id IN (...) вместо удаления по одному.
		- Fallback на по-одному upsert если batch commit упал.
		"""
		# Дедупликация батча.
		seen_ids: dict[str, int] = {}
		unique_records: list[CarRecord] = []
		for idx, r in enumerate(records):
			key = r.origin_id or r.origin_url
			if key in seen_ids:
				logger.debug("Dedup: skipping duplicate record %s (idx %d vs %d)", key, idx, seen_ids[key])
				continue
			seen_ids[key] = idx
			unique_records.append(r)

		if len(unique_records) < len(records):
			logger.info("Deduped batch: %d → %d records", len(records), len(unique_records))
		records = unique_records

		try:
			return self._upsert_cars_batch_inner(records)
		except Exception as exc:
			logger.warning("Batch upsert failed (%s), falling back to individual upserts", exc)
			return self._upsert_cars_individually(records)

	def _upsert_cars_batch_inner(self, records: list[CarRecord]) -> dict[str, int]:
		"""Внутренняя реализация batched upsert (одна транзакция)."""
		if self._is_postgres():
			return self._upsert_cars_batch_postgres(records)

		inserted = 0
		updated = 0
		images_total = 0

		with self.session_scope() as session:
			# Загружаем существующие записи.
			origin_ids = [r.origin_id for r in records if r.origin_id]
			origin_urls = [r.origin_url for r in records if r.origin_url]

			existing_by_id, existing_by_url = self._load_existing_cars(session, origin_ids, origin_urls)

			# Предзагружаем изображения.
			existing_car_ids = set()
			for record in records:
				car = existing_by_id.get(record.origin_id) or existing_by_url.get(record.origin_url)
				if car is not None:
					existing_car_ids.add(int(car.id))

			# Готовим map car_id -> image_urls.
			existing_images_map = self._load_existing_image_urls(session, existing_car_ids)

			new_cars: list[tuple[Car, list[dict]]] = []
			update_cars_needing_images: list[tuple[Car, list[dict]]] = []

			for record in records:
				payload = self._car_payload(record)
				images = [image.model_dump(mode="python") for image in record.images]

				car = existing_by_id.get(record.origin_id) or existing_by_url.get(record.origin_url)
				if car is None:
					car = Car(**payload)
					session.add(car)
					inserted += 1
					new_cars.append((car, images))
				else:
					for key, value in payload.items():
						setattr(car, key, value)
					car.last_seen_at = record.last_seen_at
					updated += 1

					# Проверяем изменения картинок.
					new_image_urls = {img.get("fullres_image", "") for img in images}
					old_image_urls = existing_images_map.get(int(car.id), set())
					if new_image_urls != old_image_urls:
						update_cars_needing_images.append((car, images))
					else:
						images_total += len(old_image_urls)

			# Один flush.
			session.flush()

			# Добавляем картинки новым авто.
			for car, images in new_cars:
				self._add_images(session, int(car.id), images)
				images_total += len(images)

			# Обновляем только изменённые картинки.
			if update_cars_needing_images:
				update_ids = [int(car.id) for car, _ in update_cars_needing_images]
				for i in range(0, len(update_ids), _IN_CHUNK_SIZE):
					chunk = update_ids[i:i + _IN_CHUNK_SIZE]
					session.execute(delete(Image).where(Image.car_id.in_(chunk)))
				for car, images in update_cars_needing_images:
					self._add_images(session, int(car.id), images)
					images_total += len(images)

		return {"inserted": inserted, "updated": updated, "images_upserted": images_total}

	def _upsert_cars_individually(self, records: list[CarRecord]) -> dict[str, int]:
		# Запасной поштучный upsert.
		inserted = 0
		updated = 0
		images_total = 0
		for record in records:
			try:
				result = self.upsert_car(record)
				action = result.get("action", "inserted")
				if action == "inserted":
					inserted += 1
				else:
					updated += 1
				images_total += int(result.get("images_upserted", 0))
			except Exception as exc:
				logger.error("Individual upsert failed for %s: %s", record.origin_id, exc)
		return {"inserted": inserted, "updated": updated, "images_upserted": images_total}

	def mark_sold_not_in_listing(self, active_origin_ids: set[str], lane: str = "dubizzle") -> int:
		"""Помечает авто как проданные, если их нет в активном листинге (по origin_id)."""
		if not active_origin_ids:
			return 0
		with self.session_scope() as session:
			stmt = (
				update(Car)
				.where(Car.origin_id.notin_(active_origin_ids))
				.where(Car.is_sold == False)  # noqa: E712
				.where(Car.origin_id.like("dubizzle:%"))
				.values(is_sold=True)
			)
			result = session.execute(stmt)
			count = result.rowcount or 0
			if count:
				logger.info("Marked %d cars as sold (no longer in listing)", count)
			return count

	def mark_sold_not_in_listing_by_urls(self, active_origin_urls: set[str], lane: str = "dubizzle") -> int:
		"""Помечает авто как проданные, если их URL нет в активном листинге.

		Для PostgreSQL использует временную таблицу + LEFT JOIN вместо NOT IN,
		что кардинально быстрее при больших объёмах (100K+ URLs).
		Встроенная защита: нормализация URL (тильда/дефис) + safety-check на аномальный процент.
		"""
		if not active_origin_urls:
			return 0

		# Нормализация URL.
		def _norm(url: str) -> str:
			return url.replace("~", "-")

		normalized_urls = {_norm(u) for u in active_origin_urls}

		is_postgres = "postgresql" in self.settings.database.url

		with self.session_scope() as session:
			if is_postgres:
				# Считаем кандидатов на sold.
				total_active = session.execute(
					text("SELECT count(*) FROM cars WHERE is_sold = FALSE AND origin_id LIKE 'dubizzle:%%'")
				).scalar() or 0

				if total_active == 0:
					return 0

				# Временная таблица URL.
				session.execute(text("CREATE TEMP TABLE IF NOT EXISTS _active_urls (url TEXT NOT NULL) ON COMMIT DROP"))
				session.execute(text("TRUNCATE _active_urls"))

				# Вставляем URL чанками.
				url_list = list(normalized_urls)
				for i in range(0, len(url_list), _IN_CHUNK_SIZE):
					chunk = url_list[i:i + _IN_CHUNK_SIZE]
					values = ",".join(f"(:{f'u{j}'})" for j in range(len(chunk)))
					params = {f"u{j}": url for j, url in enumerate(chunk)}
					session.execute(text(f"INSERT INTO _active_urls (url) VALUES {values}"), params)

				# Индекс для JOIN.
				session.execute(text("CREATE INDEX IF NOT EXISTS _ix_active_urls ON _active_urls (url)"))

				# Считаем будущие sold.
				would_mark = session.execute(text("""
					SELECT count(*)
					FROM cars c
					LEFT JOIN _active_urls a ON replace(c.origin_url, '~', '-') = a.url
					WHERE a.url IS NULL
					AND c.is_sold = FALSE
					AND c.origin_id LIKE 'dubizzle:%%'
				""")).scalar() or 0

				# Защита от аномалии.
				if total_active > 100 and would_mark > total_active * 0.8:
					logger.error(
						"mark_sold safety abort: would mark %d/%d (%.0f%%) as sold — likely URL format mismatch",
						would_mark, total_active, would_mark / total_active * 100,
					)
					return 0

				# Массовая пометка sold.
				result = session.execute(text("""
					UPDATE cars
					SET is_sold = TRUE
					FROM (
						SELECT c.id
						FROM cars c
						LEFT JOIN _active_urls a ON replace(c.origin_url, '~', '-') = a.url
						WHERE a.url IS NULL
						AND c.is_sold = FALSE
						AND c.origin_id LIKE 'dubizzle:%%'
					) sub
					WHERE cars.id = sub.id
				"""))
				count = result.rowcount or 0
			else:
				# Упрощённый путь для SQLite.
				stmt = (
					update(Car)
					.where(Car.is_sold == False)  # noqa: E712
					.where(Car.origin_id.like("dubizzle:%"))
					.values(is_sold=True)
				)
				# Загружаем active URL.
				all_active = session.execute(
					select(Car.id, Car.origin_url).where(
						Car.is_sold == False, Car.origin_id.like("dubizzle:%")  # noqa: E712
					)
				).all()
				mark_ids = [row[0] for row in all_active if _norm(row[1]) not in normalized_urls]

				if not mark_ids:
					return 0
				total_active = len(all_active)
				if total_active > 100 and len(mark_ids) > total_active * 0.8:
					logger.error(
						"mark_sold safety abort: would mark %d/%d (%.0f%%) as sold — likely URL format mismatch",
						len(mark_ids), total_active, len(mark_ids) / total_active * 100,
					)
					return 0

				for i in range(0, len(mark_ids), _IN_CHUNK_SIZE):
					chunk = mark_ids[i:i + _IN_CHUNK_SIZE]
					session.execute(update(Car).where(Car.id.in_(chunk)).values(is_sold=True))
				count = len(mark_ids)

			if count:
				logger.info("Marked %d cars as sold by URL (no longer in listing)", count)
			return count

	def get_all_origin_ids_for_lane(self, prefix: str = "dubizzle:") -> set[str]:
		"""Возвращает все известные origin_id для заданного префикса.

		Использует yield_per для потоковой загрузки при большом количестве записей.
		"""
		with self.session_scope() as session:
			result = session.execute(
				select(Car.origin_id).where(Car.origin_id.like(f"{prefix}%")).execution_options(yield_per=10000)
			)
			return {str(row[0]) for row in result if row and row[0]}

	def get_all_active_origin_urls_for_lane(self, prefix: str = "dubizzle:") -> set[str]:
		"""Возвращает origin_url всех активных (не проданных) авто для заданного lane-префикса."""
		with self.session_scope() as session:
			result = session.execute(
				select(Car.origin_url).where(
					Car.origin_id.like(f"{prefix}%"),
					Car.is_sold == False,  # noqa: E712
				).execution_options(yield_per=10000)
			)
			return {str(row[0]) for row in result if row and row[0]}

	def count_active_cars_for_lane(self, prefix: str = "dubizzle:") -> int:
		"""Возвращает количество активных (не проданных) авто для заданного lane-префикса."""
		from sqlalchemy import func as sa_func
		with self.session_scope() as session:
			result = session.execute(
				select(sa_func.count()).select_from(Car).where(
					Car.origin_id.like(f"{prefix}%"),
					Car.is_sold == False,  # noqa: E712
				)
			)
			return int(result.scalar() or 0)

	def get_active_origin_urls_batch_for_refresh(
		self,
		prefix: str = "dubizzle:",
		offset: int = 0,
		limit: int = 500,
	) -> list[str]:
		"""Возвращает батч origin_url активных авто для rolling refresh.

		Сортировка по last_seen_at ASC — давно не обновлённые идут первыми.
		"""
		with self.session_scope() as session:
			result = session.execute(
				select(Car.origin_url).where(
					Car.origin_id.like(f"{prefix}%"),
					Car.is_sold == False,  # noqa: E712
				).order_by(Car.last_seen_at.asc()).offset(offset).limit(limit)
			)
			return [str(row[0]) for row in result if row and row[0]]