"""
infrastructure/database/repositories/sqlalchemy_base.py
─────────────────────────────────────────────────────────
SQLAlchemyBaseRepository[T, M] — generic CRUD implementation (DRY).

All concrete repositories inherit from this class, which provides the
four standard operations. Subclasses only need to implement:
  • _to_entity(model) → domain entity
  • _to_model(entity) → ORM model

Error translation:
  All SQLAlchemy / asyncpg errors are caught here and re-raised as domain
  exceptions, ensuring the Application and Domain layers never receive or
  import SQLAlchemy types:
    • IntegrityError (unique / FK violation) → ConflictError
    • OperationalError / DBAPIError         → DatabaseError
    • Any other SQLAlchemyError             → DatabaseError

Generic type parameters:
    T — domain entity type (e.g. PPGSignal)
    M — SQLAlchemy ORM model type (e.g. PPGModel)
"""
from __future__ import annotations

from abc import abstractmethod
from typing import Generic, Optional, Type, TypeVar

from sqlalchemy import select
from sqlalchemy.exc import IntegrityError, OperationalError, SQLAlchemyError
from sqlalchemy.ext.asyncio import AsyncSession

from src.domain.exceptions.domain_exceptions import ConflictError, DatabaseError
from src.domain.interfaces.repositories.base_repository import BaseRepository
from src.infrastructure.database.models.base import Base
from src.shared.logger import get_logger

T = TypeVar("T")              # Domain entity
M = TypeVar("M", bound=Base)  # ORM model

logger = get_logger(__name__)


class SQLAlchemyBaseRepository(BaseRepository[T], Generic[T, M]):
    """
    Generic async CRUD repository backed by SQLAlchemy.

    Subclasses must:
        1. Set ``_model_class`` to the ORM model class.
        2. Implement ``_to_entity(model: M) → T``.
        3. Implement ``_to_model(entity: T) → M``.
    """

    _model_class: Type[M]

    def __init__(self, session: AsyncSession) -> None:
        self._session = session

    # ── Abstract Mapping Methods ──────────────────────────────────────────────

    @abstractmethod
    def _to_entity(self, model: M) -> T:
        """Convert an ORM model instance to a domain entity."""
        ...

    @abstractmethod
    def _to_model(self, entity: T) -> M:
        """Convert a domain entity to an ORM model instance."""
        ...

    # ── BaseRepository Implementation ─────────────────────────────────────────

    async def add(self, entity: T) -> T:
        """Persist a new entity and return it (with server-generated fields)."""
        model = self._to_model(entity)
        try:
            self._session.add(model)
            await self._session.flush()   # write to DB within current transaction
            await self._session.refresh(model)
        except IntegrityError as exc:
            await self._session.rollback()
            entity_name = self._model_class.__name__
            detail = str(exc.orig) if exc.orig else str(exc)
            logger.warning("IntegrityError in add() [%s]: %s", entity_name, detail)
            raise ConflictError(
                entity_type=entity_name,
                detail=f"A record with the same unique key already exists. ({detail})",
            ) from exc
        except OperationalError as exc:
            await self._session.rollback()
            detail = str(exc.orig) if exc.orig else str(exc)
            logger.error("OperationalError in add() [%s]: %s", self._model_class.__name__, detail)
            raise DatabaseError(operation="add", reason=detail) from exc
        except SQLAlchemyError as exc:
            await self._session.rollback()
            logger.error("SQLAlchemyError in add() [%s]: %s", self._model_class.__name__, exc)
            raise DatabaseError(operation="add", reason=str(exc)) from exc

        logger.debug("add() — %s id=%s", self._model_class.__name__, model.id)
        return self._to_entity(model)

    async def get_by_id(self, entity_id: str) -> Optional[T]:
        """Return the entity with the given UUID, or None."""
        try:
            result = await self._session.get(self._model_class, entity_id)
        except OperationalError as exc:
            detail = str(exc.orig) if exc.orig else str(exc)
            logger.error("OperationalError in get_by_id() [%s]: %s", self._model_class.__name__, detail)
            raise DatabaseError(operation="get_by_id", reason=detail) from exc
        except SQLAlchemyError as exc:
            logger.error("SQLAlchemyError in get_by_id() [%s]: %s", self._model_class.__name__, exc)
            raise DatabaseError(operation="get_by_id", reason=str(exc)) from exc

        if result is None:
            return None
        return self._to_entity(result)

    async def get_all(self, limit: int = 50, offset: int = 0) -> list[T]:
        """Return a paginated list of all entities."""
        stmt = (
            select(self._model_class)
            .order_by(self._model_class.created_at.desc())
            .limit(limit)
            .offset(offset)
        )
        try:
            result = await self._session.execute(stmt)
        except OperationalError as exc:
            detail = str(exc.orig) if exc.orig else str(exc)
            logger.error("OperationalError in get_all() [%s]: %s", self._model_class.__name__, detail)
            raise DatabaseError(operation="get_all", reason=detail) from exc
        except SQLAlchemyError as exc:
            logger.error("SQLAlchemyError in get_all() [%s]: %s", self._model_class.__name__, exc)
            raise DatabaseError(operation="get_all", reason=str(exc)) from exc

        models = result.scalars().all()
        return [self._to_entity(m) for m in models]

    async def delete(self, entity_id: str) -> bool:
        """Delete an entity by ID. Returns True if found and deleted."""
        try:
            model = await self._session.get(self._model_class, entity_id)
            if model is None:
                return False
            await self._session.delete(model)
            await self._session.flush()
        except OperationalError as exc:
            await self._session.rollback()
            detail = str(exc.orig) if exc.orig else str(exc)
            logger.error("OperationalError in delete() [%s]: %s", self._model_class.__name__, detail)
            raise DatabaseError(operation="delete", reason=detail) from exc
        except SQLAlchemyError as exc:
            await self._session.rollback()
            logger.error("SQLAlchemyError in delete() [%s]: %s", self._model_class.__name__, exc)
            raise DatabaseError(operation="delete", reason=str(exc)) from exc

        logger.debug("delete() — %s id=%s", self._model_class.__name__, entity_id)
        return True