"""Vehicle service: CRUD, filtering, sorting, and soft-delete operations."""

from __future__ import annotations

import uuid
from datetime import datetime, timezone
from typing import Any

from sqlalchemy import and_, func, or_, select
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy.orm import selectinload

from app.models.vehicle import Vehicle


# Fields that are safe to sort by
_SORTABLE_FIELDS: set[str] = {
    "make",
    "model",
    "fin",
    "year",
    "price",
    "vehicle_type",
    "availability",
    "condition",
    "created_at",
    "updated_at",
    "power_kw",
    "mileage_km",
}


def _apply_filters(
    stmt: select,
    vehicle_type: str | None = None,
    availability: str | None = None,
    min_price: float | None = None,
    max_price: float | None = None,
    search: str | None = None,
) -> select:
    """Apply WHERE filters to a select statement (always excludes soft-deleted)."""
    conditions = [Vehicle.deleted_at.is_(None)]

    if vehicle_type:
        conditions.append(Vehicle.vehicle_type == vehicle_type)
    if availability:
        conditions.append(Vehicle.availability == availability)
    if min_price is not None:
        conditions.append(Vehicle.price >= min_price)
    if max_price is not None:
        conditions.append(Vehicle.price <= max_price)
    if search:
        search_pattern = f"%{search}%"
        conditions.append(
            or_(
                Vehicle.make.ilike(search_pattern),
                Vehicle.model.ilike(search_pattern),
                Vehicle.fin.ilike(search_pattern),
                Vehicle.location.ilike(search_pattern),
            )
        )

    return stmt.where(and_(*conditions))


def _apply_sort(stmt: select, sort: str | None = None) -> select:
    """Apply ORDER BY to a select statement based on sort param.

    Format: 'field' for ascending, '-field' for descending.
    """
    if not sort:
        return stmt.order_by(Vehicle.created_at.desc())

    descending = sort.startswith("-")
    field_name = sort.lstrip("-")

    if field_name not in _SORTABLE_FIELDS:
        return stmt.order_by(Vehicle.created_at.desc())

    column = getattr(Vehicle, field_name)
    if descending:
        return stmt.order_by(column.desc())
    return stmt.order_by(column.asc())


async def list_vehicles(
    db: AsyncSession,
    page: int = 1,
    page_size: int = 20,
    vehicle_type: str | None = None,
    availability: str | None = None,
    min_price: float | None = None,
    max_price: float | None = None,
    search: str | None = None,
    sort: str | None = None,
) -> tuple[list[Vehicle], int]:
    """List vehicles with pagination, filtering, and sorting.

    Returns (vehicles, total_count).
    """
    # Build count query
    count_stmt = select(func.count(Vehicle.id))
    count_stmt = _apply_filters(
        count_stmt,
        vehicle_type=vehicle_type,
        availability=availability,
        min_price=min_price,
        max_price=max_price,
        search=search,
    )
    total_result = await db.execute(count_stmt)
    total = total_result.scalar_one()

    # Build data query
    data_stmt = select(Vehicle)
    data_stmt = _apply_filters(
        data_stmt,
        vehicle_type=vehicle_type,
        availability=availability,
        min_price=min_price,
        max_price=max_price,
        search=search,
    )
    data_stmt = _apply_sort(data_stmt, sort)

    offset = (page - 1) * page_size
    data_stmt = data_stmt.offset(offset).limit(page_size)

    result = await db.execute(data_stmt)
    vehicles = list(result.scalars().all())

    return vehicles, total


async def get_vehicle_by_id(
    db: AsyncSession, vehicle_id: uuid.UUID
) -> Vehicle | None:
    """Get a single vehicle by ID, excluding soft-deleted."""
    stmt = select(Vehicle).where(
        and_(Vehicle.id == vehicle_id, Vehicle.deleted_at.is_(None))
    )
    result = await db.execute(stmt)
    return result.scalar_one_or_none()


async def get_vehicle_by_fin(
    db: AsyncSession, fin: str
) -> Vehicle | None:
    """Get a single vehicle by FIN, excluding soft-deleted."""
    stmt = select(Vehicle).where(
        and_(Vehicle.fin == fin, Vehicle.deleted_at.is_(None))
    )
    result = await db.execute(stmt)
    return result.scalar_one_or_none()


async def create_vehicle(
    db: AsyncSession, data: dict[str, Any]
) -> Vehicle:
    """Create a new vehicle.

    Raises ValueError if FIN already exists.
    """
    existing = await get_vehicle_by_fin(db, data["fin"])
    if existing is not None:
        raise ValueError(f"Vehicle with FIN '{data['fin']}' already exists")

    vehicle = Vehicle(**data)
    db.add(vehicle)
    await db.flush()
    await db.refresh(vehicle)
    return vehicle


async def update_vehicle(
    db: AsyncSession, vehicle_id: uuid.UUID, updates: dict[str, Any]
) -> Vehicle | None:
    """Update a vehicle's fields. Returns None if not found or deleted."""
    vehicle = await get_vehicle_by_id(db, vehicle_id)
    if vehicle is None:
        return None

    # If FIN is being updated, check for duplicates
    if "fin" in updates and updates["fin"] != vehicle.fin:
        existing = await get_vehicle_by_fin(db, updates["fin"])
        if existing is not None:
            raise ValueError(f"Vehicle with FIN '{updates['fin']}' already exists")

    for key, value in updates.items():
        if hasattr(vehicle, key):
            setattr(vehicle, key, value)

    await db.flush()
    await db.refresh(vehicle)
    return vehicle


async def soft_delete_vehicle(
    db: AsyncSession, vehicle_id: uuid.UUID
) -> Vehicle | None:
    """Soft-delete a vehicle by setting deleted_at. Returns None if not found."""
    vehicle = await get_vehicle_by_id(db, vehicle_id)
    if vehicle is None:
        return None

    vehicle.deleted_at = datetime.now(timezone.utc)
    await db.flush()
    await db.refresh(vehicle)
    return vehicle