from typing import Union

from sqlalchemy import select, insert, delete

from models import Position, user_position
from schemas.position import *
from services.base import BaseService


class PositionService(BaseService):
    async def get_all(self) -> GetAllPositionsResponse:
        stmt = select(Position).order_by(Position.key)
        positions = (await self.session.scalars(stmt)).all()
        positions_schemas = [PositionSchema.model_validate(position) for position in positions]
        response = GetAllPositionsResponse(positions=positions_schemas)
        return response

    async def get_by_key(self, key: str) -> Union[Position, None]:
        stmt = select(Position).where(Position.key == key)
        return await self.session.scalar(stmt)

    async def create(self, request: CreatePositionRequest) -> CreatePositionResponse:
        try:
            if await self.get_by_key(request.data.key):
                return CreatePositionResponse(ok=False, message='Должность с таким ключом уже существует')
            stmt = insert(Position).values(request.data.model_dump())
            await self.session.execute(stmt)
            await self.session.commit()
            return CreatePositionResponse(ok=True, message='Должность успешно создана')
        except Exception as e:
            return CreatePositionResponse(ok=False, message=str(e))

    async def delete(self, request: DeletePositionRequest) -> DeletePositionResponse:
        try:
            # Prevent deleting if existing on users
            stmt = (
                select(
                    user_position
                )
                .where(
                    user_position.c.position_key == request.position_key
                )
            )
            if await self.session.scalar(stmt):
                return DeletePositionResponse(ok=False, message='Должность привязана к существующим сотрудникам')
            delete_stmt = (
                delete(
                    Position
                )
                .where(
                    Position.key == request.position_key
                )
            )
            await self.session.execute(delete_stmt)
            await self.session.commit()
            return DeletePositionResponse(ok=True, message="Должность успешно удалена!")
        except Exception as e:
            return DeletePositionResponse(ok=False, message=str(e))