"""Helper functions for interacting with spool database objects."""

from datetime import datetime
from typing import Optional

from sqlalchemy.ext.asyncio import AsyncSession

from spoolman.database import filament, models
from spoolman.exceptions import ItemCreateError, ItemNotFoundError
from spoolman.math import weight_from_length


async def create(
    *,
    db: AsyncSession,
    filament_id: int,
    weight: Optional[float] = None,
    first_used: Optional[datetime] = None,
    last_used: Optional[datetime] = None,
    location: Optional[str] = None,
    lot_nr: Optional[str] = None,
    comment: Optional[str] = None,
) -> models.Spool:
    """Add a new spool to the database. Leave weight empty to assume full spool."""
    filament_item = await filament.get_by_id(db, filament_id)
    if weight is None:
        if filament_item.weight is None:
            raise ItemCreateError("The weight for neither the spool nor its filament type is set.")
        weight = filament_item.weight

    db_item = models.Spool(
        filament=filament_item,
        weight=weight,
        first_used=first_used,
        last_used=last_used,
        location=location,
        lot_nr=lot_nr,
        comment=comment,
    )
    db.add(db_item)
    await db.flush()
    return db_item


async def get_by_id(db: AsyncSession, spool_id: int, with_for_update: Optional[bool] = None) -> models.Spool:
    """Get a spool object from the database by the unique ID."""
    spool = await db.get(models.Spool, spool_id, with_for_update=with_for_update)  # type: ignore  # noqa: PGH003
    if spool is None:
        raise ItemNotFoundError(f"No spool with ID {spool_id} found.")
    return spool


async def update(
    *,
    db: AsyncSession,
    spool_id: int,
    data: dict,
) -> models.Spool:
    """Update the fields of a spool object."""
    spool = await get_by_id(db, spool_id)
    for k, v in data.items():
        if k == "filament_id":
            spool.filament = await filament.get_by_id(db, v)
        else:
            setattr(spool, k, v)
    await db.flush()
    return spool


async def delete(db: AsyncSession, spool_id: int) -> None:
    """Delete a spool object."""
    spool = await get_by_id(db, spool_id)
    await db.delete(spool)


# TODO: Make unit tests for race conditions on these
async def use_weight(db: AsyncSession, spool_id: int, weight: float) -> models.Spool:
    """Reduce the weight of a spool.

    Does nothing if the spool is empty.

    Args:
        db (AsyncSession): Database session
        spool_id (int): Spool ID
        weight (float): Weight loss in grams

    Returns:
        models.Spool: Updated spool object
    """
    spool = await get_by_id(db, spool_id, with_for_update=True)
    spool.weight -= min(spool.weight, weight)
    await db.flush()
    return spool


async def use_length(db: AsyncSession, spool_id: int, length: float) -> models.Spool:
    """Reduce the weight of a spool by using a length of filament.

    Does nothing if the spool is empty.

    Args:
        db (AsyncSession): Database session
        spool_id (int): Spool ID
        length (float): Length of filament to reduce by

    Returns:
        models.Spool: Updated spool object
    """
    spool = await get_by_id(db, spool_id, with_for_update=True)

    filament = spool.filament

    weight = weight_from_length(
        length=length,
        radius=filament.diameter / 2,
        density=filament.density,
    )
    spool.weight -= min(spool.weight, weight)
    await db.flush()
    return spool