"""Inventory sync engine.

Refreshes supplier_products inventory from each adapter, writes inventory_history,
and flags zero/unavailable stock (pauses published products + audit log alert).
"""
from datetime import datetime, timezone

from app.engines.suppliers.base import build_adapter
from app.models import AuditLog, InventoryHistory, Supplier, SupplierProduct


def sync_inventory(db, supplier=None):
    if supplier is not None:
        suppliers = [supplier]
    else:
        suppliers = db.query(Supplier).filter(Supplier.status == "active").all()

    stats = {"suppliers": len(suppliers), "checked": 0, "changed": 0, "zeroed": 0}

    for s in suppliers:
        try:
            adapter = build_adapter(s)
            current = {r["supplier_sku"]: int(r["inventory"]) for r in adapter.get_inventory()}
        except Exception as exc:  # noqa: BLE001 — log and continue to next supplier
            db.add(
                AuditLog(
                    actor="inventory",
                    action="sync_failed",
                    entity="supplier",
                    entity_id=str(s.id),
                    detail={"supplier": s.name, "error": str(exc)},
                )
            )
            continue

        for sp in db.query(SupplierProduct).filter(SupplierProduct.supplier_id == s.id).all():
            stats["checked"] += 1
            new_value = current.get(sp.supplier_sku)
            if new_value is None:
                continue

            if sp.supplier_inventory != new_value:
                stats["changed"] += 1
                sp.supplier_inventory = new_value
                sp.last_updated = datetime.now(timezone.utc)
                db.add(InventoryHistory(supplier_product_id=sp.id, inventory=new_value))

            if new_value <= 0:
                stats["zeroed"] += 1
                db.add(
                    AuditLog(
                        actor="inventory",
                        action="inventory_zero",
                        entity="supplier_product",
                        entity_id=str(sp.id),
                        detail={"supplier_sku": sp.supplier_sku, "inventory": 0},
                    )
                )
                if sp.product is not None and sp.product.status == "published":
                    sp.product.status = "paused"
                    db.add(
                        AuditLog(
                            actor="inventory",
                            action="product_paused_zero_inventory",
                            entity="product",
                            entity_id=str(sp.product.id),
                            detail={"sku": sp.product.sku},
                        )
                    )

    db.commit()
    return stats