"""Product service — lookup/create products, link CAD files."""
import uuid
from sqlalchemy import select, func, update as sql_update
from sqlalchemy.ext.asyncio import AsyncSession

from app.models.product import Product

# Default render positions added to every newly created product.
DEFAULT_RENDER_POSITIONS = [
    {"name": "3/4 Front", "rotation_x": -15.0, "rotation_y":  45.0, "rotation_z": 0.0, "is_default": True,  "sort_order": 0},
    {"name": "3/4 Rear",  "rotation_x": -15.0, "rotation_y": -135.0, "rotation_z": 0.0, "is_default": False, "sort_order": 1},
    {"name": "Default",   "rotation_x":   0.0, "rotation_y":   0.0, "rotation_z": 0.0, "is_default": False, "sort_order": 2},
]


async def create_default_positions(db: AsyncSession, product_id: uuid.UUID) -> None:
    """Insert the default render positions for a newly created product."""
    from app.models.render_position import ProductRenderPosition
    for pos_data in DEFAULT_RENDER_POSITIONS:
        db.add(ProductRenderPosition(product_id=product_id, **pos_data))
    await db.flush()


def _fill_missing_fields(product: Product, pim_id: str | None, fields: dict) -> None:
    """Fill in null/empty fields on an existing product without overwriting manual edits."""
    if pim_id and not product.pim_id:
        product.pim_id = pim_id
    for attr in (
        "name", "category_key", "ebene1", "ebene2", "baureihe",
        "lagertyp", "name_cad_modell", "arbeitspaket",
    ):
        if fields.get(attr) and not getattr(product, attr, None):
            setattr(product, attr, fields[attr])
    # Update medias_rendering if not set
    if fields.get("medias_rendering") is not None and product.medias_rendering is None:
        product.medias_rendering = fields["medias_rendering"]
    # Always update components from the latest Excel import (needed for auto-reassign)
    if fields.get("components"):
        product.components = fields["components"]


async def lookup_product(
    db: AsyncSession, pim_id: str | None, produkt_baureihe: str | None
) -> Product | None:
    """Read-only lookup: produkt_baureihe (primary), then pim_id (fallback).

    Same cascade as lookup_or_create_product but never creates or mutates.
    """
    if produkt_baureihe:
        result = await db.execute(
            select(Product).where(
                func.lower(Product.produkt_baureihe) == produkt_baureihe.lower(),
                Product.is_active.is_(True),
            )
        )
        product = result.scalar_one_or_none()
        if product is not None:
            return product
        # baureihe provided but not found — skip pim_id fallback (same logic)
        return None

    if pim_id:
        result = await db.execute(
            select(Product).where(Product.pim_id == pim_id, Product.is_active.is_(True))
        )
        return result.scalar_one_or_none()

    return None



async def lookup_or_create_product(
    db: AsyncSession, pim_id: str | None, fields: dict
) -> tuple[Product, bool]:
    """Look up by produkt_baureihe (primary), then pim_id (fallback). Create if not found.

    Returns (product, was_created).
    Does NOT overwrite existing fields — preserves manual edits.
    """
    produkt_baureihe = fields.get("produkt_baureihe")

    # Primary lookup: by produkt_baureihe (case-insensitive)
    if produkt_baureihe:
        result = await db.execute(
            select(Product).where(
                func.lower(Product.produkt_baureihe) == produkt_baureihe.lower(),
                Product.is_active.is_(True),
            )
        )
        product = result.scalar_one_or_none()
        if product is not None:
            _fill_missing_fields(product, pim_id, fields)
            await db.flush()
            return product, False
        # produkt_baureihe was provided but not found — each baureihe is a
        # distinct product, so skip the pim_id fallback and create a new one.

    # Fallback lookup: by pim_id (only when produkt_baureihe is absent,
    # e.g. old per-category Excel files that don't have a Baureihe column).
    if not produkt_baureihe and pim_id:
        result = await db.execute(
            select(Product).where(Product.pim_id == pim_id, Product.is_active.is_(True))
        )
        product = result.scalar_one_or_none()
        if product is not None:
            _fill_missing_fields(product, pim_id, fields)
            await db.flush()
            return product, False

    product = Product(
        pim_id=pim_id or f"auto-{uuid.uuid4().hex[:8]}",
        name=fields.get("name"),
        category_key=fields.get("category_key"),
        ebene1=fields.get("ebene1"),
        ebene2=fields.get("ebene2"),
        baureihe=fields.get("baureihe"),
        produkt_baureihe=produkt_baureihe,
        lagertyp=fields.get("lagertyp"),
        name_cad_modell=fields.get("name_cad_modell"),
        arbeitspaket=fields.get("arbeitspaket"),
        components=fields.get("components", []),
        cad_part_materials=fields.get("cad_part_materials", []),
        source_excel=fields.get("source_excel"),
    )
    db.add(product)
    await db.flush()
    await create_default_positions(db, product.id)
    return product, True



async def link_cad_to_product(
    db: AsyncSession, product_id: uuid.UUID, cad_file_id: uuid.UUID
) -> Product:
    """Set product.cad_file_id via direct SQL UPDATE."""
    await db.execute(
        sql_update(Product)
        .where(Product.id == product_id)
        .values(cad_file_id=cad_file_id)
    )
    await db.commit()
    result = await db.execute(select(Product).where(Product.id == product_id))
    return result.scalar_one()