"""
Background work that shouldn't run on the GUI thread.

FetchOrdersWorker runs a service's fetch_orders() call off the main
thread and reports back via signals. As we add more long-running
operations (creating ShipStation labels, pushing to Odoo, etc.) they
should follow this same pattern rather than blocking the UI.
"""
from __future__ import annotations

from typing import List

from PyQt6.QtCore import QThread, pyqtSignal
from sqlalchemy import select

from app.database import get_session
from app.models import Order
from app.services.base import OrderService, NormalizedOrder


class FetchOrdersWorker(QThread):
    """Fetches orders from a given service and saves new/updated ones to the DB."""

    finished_ok = pyqtSignal(int, int)   # (new_count, updated_count)
    failed = pyqtSignal(str)

    def __init__(self, service: OrderService, parent=None):
        super().__init__(parent)
        self.service = service

    def run(self) -> None:
        try:
            orders = self.service.fetch_orders()
        except Exception as exc:  # noqa: BLE001 - surface any failure to the UI
            self.failed.emit(str(exc))
            return

        try:
            new_count, updated_count = save_orders(orders)
        except Exception as exc:  # noqa: BLE001
            self.failed.emit(f"Fetched {len(orders)} orders but failed to save them: {exc}")
            return

        self.finished_ok.emit(new_count, updated_count)


def save_orders(orders: List[NormalizedOrder]) -> tuple[int, int]:
    """Insert new orders / update existing ones (matched by source + external_id)."""
    session = get_session()
    new_count = 0
    updated_count = 0
    try:
        for order in orders:
            existing = session.execute(
                select(Order).where(
                    Order.source == order["source"],
                    Order.external_id == order["external_id"],
                )
            ).scalar_one_or_none()

            if existing is None:
                session.add(
                    Order(
                        source=order["source"],
                        external_id=order["external_id"],
                        ticket_number=order.get("ticket_number"),
                        company=order.get("company", "Unknown"),
                        skus=order.get("skus", []),
                        summary=order["summary"],
                        status=order["status"],
                        source_created_at=order["source_created_at"],
                        raw_data=order["raw_data"],
                    )
                )
                new_count += 1
            else:
                existing.ticket_number = order.get("ticket_number")
                existing.company = order.get("company", "Unknown")
                existing.skus = order.get("skus", [])
                existing.summary = order["summary"]
                existing.status = order["status"]
                existing.source_created_at = order["source_created_at"]
                existing.raw_data = order["raw_data"]
                updated_count += 1

        session.commit()
    finally:
        session.close()

    return new_count, updated_count


def load_all_orders() -> List[Order]:
    session = get_session()
    try:
        return list(
            session.execute(select(Order).order_by(Order.source_created_at.desc())).scalars()
        )
    finally:
        session.close()


def get_dashboard_stats() -> dict:
    """
    Counts for the dashboard tab: totals by company and by source, plus
    how many orders are only in one source so far (imported from JIRA
    but not yet seen in ShipStation, or vice versa) - useful as an
    at-a-glance "what's still missing" signal since the two sources are
    pulled independently.
    """
    orders = load_all_orders()

    by_company: dict[str, int] = {}
    by_source: dict[str, int] = {}
    tickets_by_source: dict[str, set] = {}

    for order in orders:
        by_company[order.company] = by_company.get(order.company, 0) + 1
        by_source[order.source] = by_source.get(order.source, 0) + 1
        if order.ticket_number:
            tickets_by_source.setdefault(order.source, set()).add(order.ticket_number)

    jira_tickets = tickets_by_source.get("jira", set())
    shipstation_tickets = tickets_by_source.get("shipstation", set())

    return {
        "total": len(orders),
        "by_company": by_company,
        "by_source": by_source,
        "jira_only_count": len(jira_tickets - shipstation_tickets),
        "shipstation_only_count": len(shipstation_tickets - jira_tickets),
        "matched_count": len(jira_tickets & shipstation_tickets),
    }