from typing import Optional, Tuple, List, Dict, Any

from sqlalchemy.orm import Session
from sqlalchemy import text

from . import dto, models

TRAILER_ID_SEQ = "a76.trailer_trailer_id_seq"


def allocate_trailer_id(db: Session) -> int:
    """Next surrogate trailer_id (sequence from migration ca7d3c4e8b2a)."""
    return db.execute(text(f"SELECT nextval('{TRAILER_ID_SEQ}')")).scalar()


class TrailerService:
    """Service for Trailer CRUD operations with tenant support"""

    @staticmethod
    def get_all(
        db: Session,
        tenant_id: int,
        company_id: int,
        skip: int = 0,
        limit: int = 50,
        filters: Optional[Dict[str, Any]] = None,
    ) -> Tuple[List[models.Trailer], int]:
        """Get all trailers for a tenant/company with pagination"""
        query = db.query(models.Trailer).filter(
            models.Trailer.tenant_id == tenant_id,
            models.Trailer.company_id == company_id,
        )

        # Apply filters if provided
        if filters:
            if filters.get("trailer_number"):
                query = query.filter(
                    models.Trailer.trailer_number.ilike(f"%{filters['trailer_number']}%")
                )
            if filters.get("plate_number"):
                query = query.filter(
                    models.Trailer.plate_number.ilike(f"%{filters['plate_number']}%")
                )
            if filters.get("trailer_type_key"):
                query = query.filter(
                    models.Trailer.trailer_type_key == filters["trailer_type_key"]
                )

        total = query.count()
        trailers = query.offset(skip).limit(limit).all()

        return trailers, total

    @staticmethod
    def get_by_id(
        db: Session, trailer_number: str, tenant_id: int, company_id: int
    ) -> Optional[models.Trailer]:
        """Get trailer by trailer_number"""
        return (
            db.query(models.Trailer)
            .filter(
                models.Trailer.trailer_number == trailer_number,
                models.Trailer.tenant_id == tenant_id,
                models.Trailer.company_id == company_id,
            )
            .first()
        )

    @staticmethod
    def create(
        db: Session,
        trailer_data: dto.TrailerCreateDTO,
        tenant_id: int,
        company_id: int,
    ) -> models.Trailer:
        """Create a new trailer"""
        data = trailer_data.model_dump()
        if data.get("trailer_id") is None:
            data["trailer_id"] = allocate_trailer_id(db)
        new_trailer = models.Trailer(
            **data, tenant_id=tenant_id, company_id=company_id
        )
        db.add(new_trailer)
        db.commit()
        db.refresh(new_trailer)
        return new_trailer

    @staticmethod
    def update(
        db: Session,
        trailer_number: str,
        tenant_id: int,
        trailer_data: dto.TrailerUpdateDTO,
        company_id: int,
    ) -> Optional[models.Trailer]:
        """Update a trailer"""
        trailer = TrailerService.get_by_id(db, trailer_number, tenant_id, company_id)
        if not trailer:
            return None

        # Update fields (excluding trailer_number as it's the primary key)
        update_data = trailer_data.model_dump(
            exclude_unset=True, exclude={"trailer_number"}
        )
        for field, value in update_data.items():
            setattr(trailer, field, value)

        db.commit()
        db.refresh(trailer)
        return trailer

    @staticmethod
    def delete(
        db: Session, trailer_number: str, tenant_id: int, company_id: int
    ) -> bool:
        """Delete a trailer"""
        trailer = TrailerService.get_by_id(db, trailer_number, tenant_id, company_id)
        if not trailer:
            return False

        db.delete(trailer)
        db.commit()
        return True