from sqlalchemy.orm import Session
from sqlalchemy.exc import IntegrityError
from fastapi import HTTPException, status
from . import repository
from .schema import DepartmentCreate, DepartmentUpdate


def create_department(db: Session, data: DepartmentCreate):
    try:
        department = repository.create(db, data.model_dump())
        db.commit()
        db.refresh(department)
        return department
    except IntegrityError as exc:
        db.rollback()
        msg = str(exc.orig).lower() if exc.orig else ""
        if "unique" in msg or "duplicate" in msg:
            raise HTTPException(
                status_code=status.HTTP_409_CONFLICT,
                detail="Department name already exists."
            )
        if "foreign key" in msg:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="Referenced resource does not exist."
            )
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="Data integrity error."
        )
    except HTTPException:
        db.rollback()
        raise
    except Exception:
        db.rollback()
        raise


def list_departments(db: Session, limit: int, offset: int, search: Optional[str] = None) -> dict:
    filters = {}
    if search:
        filters["search"] = search
    items = repository.list_all(db, limit=limit, offset=offset, **filters)
    total = repository.count_all(db, **filters)
    return {"items": items, "total": total, "limit": limit, "offset": offset}


def get_department(db: Session, department_id: str):
    department = repository.get_by_id(db, department_id)
    if not department:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Department not found"
        )
    return department


def update_department(db: Session, department_id: str, data: DepartmentUpdate):
    update_data = data.model_dump(exclude_unset=True)
    if not update_data:
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="No fields to update"
        )
    try:
        department = repository.update(db, department_id, update_data)
        if not department:
            raise HTTPException(
                status_code=status.HTTP_404_NOT_FOUND,
                detail="Department not found"
            )
        db.commit()
        db.refresh(department)
        return department
    except IntegrityError as exc:
        db.rollback()
        msg = str(exc.orig).lower() if exc.orig else ""
        if "unique" in msg or "duplicate" in msg:
            raise HTTPException(
                status_code=status.HTTP_409_CONFLICT,
                detail="Department name already exists."
            )
        if "foreign key" in msg:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="Referenced resource does not exist."
            )
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="Data integrity error."
        )
    except HTTPException:
        db.rollback()
        raise
    except Exception:
        db.rollback()
        raise


def delete_department(db: Session, department_id: str):
    try:
        success = repository.delete(db, department_id)
        if not success:
            raise HTTPException(
                status_code=status.HTTP_404_NOT_FOUND,
                detail="Department not found"
            )
        db.commit()
        return {"detail": "Department deleted successfully"}
    except IntegrityError as exc:
        db.rollback()
        msg = str(exc.orig).lower() if exc.orig else ""
        if "foreign key" in msg:
            raise HTTPException(
                status_code=status.HTTP_409_CONFLICT,
                detail="Cannot delete department while it is referenced by other records."
            )
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="Data integrity error."
        )
    except HTTPException:
        db.rollback()
        raise
    except Exception:
        db.rollback()
        raise