import json
from datetime import datetime
from fastapi import APIRouter, Depends, HTTPException, status, BackgroundTasks
from sqlalchemy.orm import Session
from typing import List, Optional

from database import get_db
from models.order import Order, OrderItem, OrderWaiter
from models.user import User, AssistantAssignment
from models.product import Product
from schemas.order import OrderCreate, OrderOut, OrderItemOut, AddItemsRequest, PayItemsRequest, AssignWaiterRequest
from routers.deps import get_current_user, require_manager
from services.printer_service import route_and_print

router = APIRouter()


def _can_access_order(order: Order, user: User, db: Session) -> bool:
    if user.role in ("manager", "sysadmin"):
        return True
    if order.opened_by == user.id:
        return True
    if any(ow.waiter_id == user.id for ow in order.waiters):
        return True
    # Assistant check: user is assistant to any waiter assigned to this order
    assigned_ids = {ow.waiter_id for ow in order.waiters}
    assistant_of = db.query(AssistantAssignment).filter(
        AssistantAssignment.assistant_waiter_id == user.id,
        AssistantAssignment.primary_waiter_id.in_(assigned_ids),
    ).first()
    return assistant_of is not None


@router.get("/", response_model=List[OrderOut])
def list_orders(
    order_status: Optional[str] = None,
    waiter_id: Optional[int] = None,
    db: Session = Depends(get_db),
    user: User = Depends(require_manager),
):
    q = db.query(Order)
    if order_status:
        q = q.filter(Order.status == order_status)
    if waiter_id:
        q = q.join(OrderWaiter).filter(OrderWaiter.waiter_id == waiter_id)
    return q.all()


@router.get("/my", response_model=List[OrderOut])
def my_orders(db: Session = Depends(get_db), user: User = Depends(get_current_user)):
    direct = db.query(Order).join(OrderWaiter).filter(
        OrderWaiter.waiter_id == user.id,
        Order.status.in_(["open", "partially_paid"]),
    ).all()
    # Also orders where user is opener but not explicitly assigned
    also_opened = db.query(Order).filter(
        Order.opened_by == user.id,
        Order.status.in_(["open", "partially_paid"]),
    ).all()
    seen = {o.id for o in direct}
    return direct + [o for o in also_opened if o.id not in seen]


@router.get("/{order_id}", response_model=OrderOut)
def get_order(order_id: int, db: Session = Depends(get_db), user: User = Depends(get_current_user)):
    order = db.query(Order).filter(Order.id == order_id).first()
    if not order:
        raise HTTPException(status_code=404, detail="Order not found")
    if not _can_access_order(order, user, db):
        raise HTTPException(status_code=403, detail="Access denied")
    return order


@router.post("/", response_model=OrderOut, status_code=status.HTTP_201_CREATED)
def open_order(body: OrderCreate, db: Session = Depends(get_db), user: User = Depends(get_current_user)):
    existing = db.query(Order).filter(
        Order.table_id == body.table_id,
        Order.status.in_(["open", "partially_paid"]),
    ).first()
    if existing:
        raise HTTPException(status_code=400, detail="Table already has an open order")
    order = Order(table_id=body.table_id, opened_by=user.id)
    db.add(order)
    db.flush()
    db.add(OrderWaiter(order_id=order.id, waiter_id=user.id))
    db.commit()
    db.refresh(order)
    return order


@router.post("/{order_id}/items", response_model=OrderOut)
def add_items(
    order_id: int,
    body: AddItemsRequest,
    background_tasks: BackgroundTasks,
    db: Session = Depends(get_db),
    user: User = Depends(get_current_user),
):
    order = db.query(Order).filter(Order.id == order_id).first()
    if not order:
        raise HTTPException(status_code=404, detail="Order not found")
    if not _can_access_order(order, user, db):
        raise HTTPException(status_code=403, detail="Access denied")
    if order.status not in ("open", "partially_paid"):
        raise HTTPException(status_code=400, detail="Order is not open")

    new_item_ids = []
    for item_in in body.items:
        product = db.query(Product).filter(Product.id == item_in.product_id).first()
        if not product or not product.is_available:
            raise HTTPException(status_code=400, detail=f"Product {item_in.product_id} not available")
        item = OrderItem(
            order_id=order_id,
            product_id=item_in.product_id,
            added_by=user.id,
            quantity=item_in.quantity,
            unit_price=product.base_price,  # price snapshot
            selected_options=json.dumps(item_in.selected_options) if item_in.selected_options else None,
            removed_ingredients=json.dumps(item_in.removed_ingredients) if item_in.removed_ingredients else None,
            notes=item_in.notes,
        )
        db.add(item)
        db.flush()
        new_item_ids.append(item.id)

    db.commit()
    db.refresh(order)

    # Printer routing runs in background — must never block the order save
    background_tasks.add_task(route_and_print, order_id, new_item_ids)

    return order


@router.put("/{order_id}/items/{item_id}", response_model=OrderItemOut)
def edit_item(order_id: int, item_id: int, notes: Optional[str] = None, db: Session = Depends(get_db), user: User = Depends(require_manager)):
    item = db.query(OrderItem).filter(OrderItem.id == item_id, OrderItem.order_id == order_id).first()
    if not item:
        raise HTTPException(status_code=404, detail="Item not found")
    if notes is not None:
        item.notes = notes
    db.commit()
    db.refresh(item)
    return item


@router.delete("/{order_id}/items/{item_id}", status_code=status.HTTP_204_NO_CONTENT)
def cancel_item(order_id: int, item_id: int, db: Session = Depends(get_db), user: User = Depends(require_manager)):
    item = db.query(OrderItem).filter(OrderItem.id == item_id, OrderItem.order_id == order_id).first()
    if not item:
        raise HTTPException(status_code=404, detail="Item not found")
    item.status = "cancelled"
    db.commit()


@router.post("/{order_id}/pay")
def pay_items(order_id: int, body: PayItemsRequest, db: Session = Depends(get_db), user: User = Depends(get_current_user)):
    order = db.query(Order).filter(Order.id == order_id).first()
    if not order:
        raise HTTPException(status_code=404, detail="Order not found")
    if not _can_access_order(order, user, db):
        raise HTTPException(status_code=403, detail="Access denied")

    items = db.query(OrderItem).filter(
        OrderItem.id.in_(body.item_ids),
        OrderItem.order_id == order_id,
        OrderItem.status == "active",
    ).all()
    for item in items:
        item.status = "paid"

    active_remaining = db.query(OrderItem).filter(
        OrderItem.order_id == order_id, OrderItem.status == "active"
    ).count()
    order.status = "paid" if active_remaining == 0 else "partially_paid"

    db.commit()
    return {"status": order.status, "paid_item_ids": [i.id for i in items]}


@router.post("/{order_id}/close")
def close_order(order_id: int, db: Session = Depends(get_db), user: User = Depends(get_current_user)):
    order = db.query(Order).filter(Order.id == order_id).first()
    if not order:
        raise HTTPException(status_code=404, detail="Order not found")
    if not _can_access_order(order, user, db):
        raise HTTPException(status_code=403, detail="Access denied")
    if order.status not in ("paid", "open", "partially_paid"):
        raise HTTPException(status_code=400, detail="Cannot close order in current status")
    order.status = "closed"
    order.closed_at = datetime.utcnow()
    order.closed_by = user.id
    db.commit()
    return {"status": "closed"}


@router.delete("/{order_id}", status_code=status.HTTP_204_NO_CONTENT)
def cancel_order(order_id: int, db: Session = Depends(get_db), user: User = Depends(require_manager)):
    order = db.query(Order).filter(Order.id == order_id).first()
    if not order:
        raise HTTPException(status_code=404, detail="Order not found")
    order.status = "cancelled"
    order.closed_at = datetime.utcnow()
    order.closed_by = user.id
    db.commit()


@router.put("/{order_id}/assign-waiter")
def assign_waiter(order_id: int, body: AssignWaiterRequest, db: Session = Depends(get_db), user: User = Depends(require_manager)):
    order = db.query(Order).filter(Order.id == order_id).first()
    if not order:
        raise HTTPException(status_code=404, detail="Order not found")
    existing = db.query(OrderWaiter).filter(
        OrderWaiter.order_id == order_id, OrderWaiter.waiter_id == body.waiter_id
    ).first()
    if existing:
        raise HTTPException(status_code=400, detail="Waiter already assigned")
    db.add(OrderWaiter(order_id=order_id, waiter_id=body.waiter_id))
    db.commit()
    return {"status": "assigned"}


@router.delete("/{order_id}/waiters/{waiter_id}", status_code=status.HTTP_204_NO_CONTENT)
def remove_waiter(order_id: int, waiter_id: int, db: Session = Depends(get_db), user: User = Depends(require_manager)):
    assignment = db.query(OrderWaiter).filter(
        OrderWaiter.order_id == order_id, OrderWaiter.waiter_id == waiter_id
    ).first()
    if not assignment:
        raise HTTPException(status_code=404, detail="Assignment not found")
    db.delete(assignment)
    db.commit()