"""
Device management service.
"""

from datetime import datetime, timezone

from sqlalchemy import func, select
from sqlalchemy.ext.asyncio import AsyncSession

from app.models.device import Device
from app.schemas.device import DeviceCreate, DeviceUpdate


async def create_device(
    db: AsyncSession,
    data: DeviceCreate,
) -> Device:
    """
    Create a new device.

    Args:
        db: Database session
        data: Device creation data

    Returns:
        Created device
    """
    # Check if MAC address already exists
    result = await db.execute(
        select(Device).where(Device.mac_address == data.mac_address)
    )
    existing_device = result.scalar_one_or_none()

    if existing_device:
        raise ValueError(f"Device with MAC {data.mac_address} already exists")

    device = Device(
        mac_address=data.mac_address,
        organization_id=data.organization_id,
        status="offline",
        config=data.config or {},
        # simple_id will be auto-generated by PostgreSQL sequence
    )

    db.add(device)
    await db.commit()
    await db.refresh(device)

    return device


async def get_device(db: AsyncSession, device_id: int) -> Device | None:
    """
    Get device by ID.

    Args:
        db: Database session
        device_id: Device ID

    Returns:
        Device or None
    """
    result = await db.execute(select(Device).where(Device.id == device_id))
    return result.scalar_one_or_none()


async def get_device_by_mac(db: AsyncSession, mac_address: str) -> Device | None:
    """
    Get device by MAC address.

    Args:
        db: Database session
        mac_address: Device MAC address

    Returns:
        Device or None
    """
    result = await db.execute(
        select(Device).where(Device.mac_address == mac_address)
    )
    return result.scalar_one_or_none()


async def list_devices(
    db: AsyncSession,
    skip: int = 0,
    limit: int = 100,
    organization_id: int | None = None,
    status: str | None = None,
) -> tuple[list[Device], int]:
    """
    List devices with pagination and filters.

    Args:
        db: Database session
        skip: Number of records to skip
        limit: Maximum number of records to return
        organization_id: Filter by organization (optional)
        status: Filter by status (optional)

    Returns:
        Tuple of (devices list, total count)
    """
    # Build query
    query = select(Device)

    if organization_id is not None:
        query = query.where(Device.organization_id == organization_id)

    if status:
        query = query.where(Device.status == status)

    # Get total count
    count_query = select(func.count()).select_from(Device)

    if organization_id is not None:
        count_query = count_query.where(Device.organization_id == organization_id)

    if status:
        count_query = count_query.where(Device.status == status)

    total_result = await db.execute(count_query)
    total = total_result.scalar_one()

    # Get paginated results
    query = query.offset(skip).limit(limit).order_by(Device.simple_id)
    result = await db.execute(query)
    devices = list(result.scalars().all())

    return devices, total


async def update_device(
    db: AsyncSession,
    device_id: int,
    data: DeviceUpdate,
) -> Device | None:
    """
    Update device.

    Args:
        db: Database session
        device_id: Device ID
        data: Update data

    Returns:
        Updated device or None if not found
    """
    result = await db.execute(select(Device).where(Device.id == device_id))
    device = result.scalar_one_or_none()

    if not device:
        return None

    # Update fields
    update_data = data.model_dump(exclude_unset=True)
    for field, value in update_data.items():
        setattr(device, field, value)

    await db.commit()
    await db.refresh(device)

    return device


async def delete_device(
    db: AsyncSession,
    device_id: int,
) -> bool:
    """
    Delete device.

    Args:
        db: Database session
        device_id: Device ID

    Returns:
        True if deleted, False if not found
    """
    result = await db.execute(select(Device).where(Device.id == device_id))
    device = result.scalar_one_or_none()

    if not device:
        return False

    await db.delete(device)
    await db.commit()

    return True


async def update_device_heartbeat(
    db: AsyncSession,
    mac_address: str,
) -> Device | None:
    """
    Update device last_seen_at timestamp (heartbeat).

    Args:
        db: Database session
        mac_address: Device MAC address

    Returns:
        Updated device or None if not found
    """
    result = await db.execute(
        select(Device).where(Device.mac_address == mac_address)
    )
    device = result.scalar_one_or_none()

    if not device:
        return None

    device.last_seen_at = datetime.now(timezone.utc)
    device.status = "online"

    await db.commit()
    await db.refresh(device)

    return device