from sqlalchemy import Select, Delete, cast, String
from src.acquisition_cost.model import AcquisitionData
from src.acquisition_cost.schema import AcquisitionCostDataCreate, AcquisitionCostDataUpdate
from src.database.service import search_filter_sort_paginate
from typing import Optional

from src.database.core import DbSession
from src.auth.service import CurrentUser
from src.equipment.model import Equipment


def _calculate_cost_unit_3(cost_unit_3_n_4: Optional[float]) -> Optional[float]:
    """Derive cost_unit_3 by splitting the combined unit 3&4 cost evenly."""
    if cost_unit_3_n_4 is None:
        return None
    return cost_unit_3_n_4 / 2


async def _sync_equipment_acquisition_costs(
    *, db_session: DbSession, category_no: Optional[str], cost_unit_3: Optional[float]
):
    """Keep equipment acquisition cost in sync for the affected category."""
    if not category_no or cost_unit_3 is None:
        return

    equipment_query = Select(Equipment).filter(Equipment.category_no == category_no)
    equipment_result = await db_session.execute(equipment_query)
    equipments = equipment_result.scalars().all()

    for equipment in equipments:
        if equipment.proportion is None:
            continue
        equipment.acquisition_cost = (equipment.proportion * 0.01) * cost_unit_3


async def get(*, db_session: DbSession, acquisition_cost_data_id: str) -> Optional[AcquisitionData]:
    """Returns a document based on the given document id."""
    query = Select(AcquisitionData).filter(AcquisitionData.id == acquisition_cost_data_id)
    result = await db_session.execute(query)
    return result.scalars().one_or_none()


async def get_all(
    *,
    db_session: DbSession,
    items_per_page: Optional[int],
    search: Optional[str] = None,
    common,
):
    """Returns all documents."""
    query = Select(AcquisitionData).order_by(AcquisitionData.name.asc())
    if search:
        query = query.filter(cast(AcquisitionData.name, String).ilike(f"%{search}%"))

    common["items_per_page"] = items_per_page
    results = await search_filter_sort_paginate(model=query, **common)

    # return results.scalars().all()
    return results


async def create(*, db_session: DbSession, acquisition_data_in: AcquisitionCostDataCreate):
    """Creates a new document."""
    data = acquisition_data_in.model_dump()
    cost_unit_changed = False

    if data.get("cost_unit_3_n_4") is not None:
        derived_cost_unit = _calculate_cost_unit_3(data["cost_unit_3_n_4"])
        data["cost_unit_3"] = derived_cost_unit
        cost_unit_changed = derived_cost_unit is not None

    acquisition_data = AcquisitionData(**data)
    db_session.add(acquisition_data)

    if cost_unit_changed:
        await _sync_equipment_acquisition_costs(
            db_session=db_session,
            category_no=acquisition_data.category_no,
            cost_unit_3=acquisition_data.cost_unit_3,
        )

    await db_session.commit()
    return acquisition_data


async def update(
    *, db_session: DbSession, acquisition_data: AcquisitionData, acquisition_data_in: AcquisitionCostDataUpdate
):
    """Updates a document."""
    data = acquisition_data_in.model_dump()
    update_data = acquisition_data_in.model_dump(exclude_defaults=True)

    cost_unit_changed = False
    if "cost_unit_3_n_4" in update_data:
        derived_cost_unit = _calculate_cost_unit_3(update_data.get("cost_unit_3_n_4"))
        update_data["cost_unit_3"] = derived_cost_unit
        cost_unit_changed = derived_cost_unit is not None

    for field in data:
        if field in update_data:
            setattr(acquisition_data, field, update_data[field])

    if cost_unit_changed:
        await _sync_equipment_acquisition_costs(
            db_session=db_session,
            category_no=acquisition_data.category_no,
            cost_unit_3=acquisition_data.cost_unit_3,
        )

    await db_session.commit()

    return acquisition_data


async def delete(*, db_session: DbSession, acquisition_cost_data_id: str):
    """Deletes a document."""
    query = Delete(AcquisitionData).where(AcquisitionData.id == acquisition_cost_data_id)
    await db_session.execute(query)
    await db_session.commit()