"use client";

import {
  createContext,
  useCallback,
  useContext,
  useEffect,
  useMemo,
  useState,
} from "react";
import {
  addCartItem,
  getCart,
  removeCartItem,
  updateCartItem,
} from "@/lib/meshkee/api";
import {
  cartFromGuest,
  emptyCart,
  normalizeCartResponse,
} from "@/lib/meshkee/cart";
import {
  clearGuestCart,
  readGuestCart,
  writeGuestCart,
} from "@/lib/meshkee/guest-cart";
import type { CartState, GuestCartLine } from "@/lib/meshkee/types";
import { useAuth } from "@/app/providers/auth-provider";
import { useToast } from "@/app/providers/toast-provider";

type CartContextValue = {
  cart: CartState;
  itemCount: number;
  ready: boolean;
  loading: boolean;
  open: boolean;
  setOpen: (open: boolean) => void;
  refreshCart: () => Promise<void>;
  addItem: (item: {
    storeItemVariantId: string;
    name: string;
    price: number;
    quantity?: number;
    image?: string | null;
    slug?: string;
  }) => Promise<void>;
  updateQuantity: (itemId: string, quantity: number) => Promise<void>;
  removeItem: (itemId: string) => Promise<void>;
  guestItems: GuestCartLine[];
};

const CartContext = createContext<CartContextValue | null>(null);

export function CartProvider({ children }: { children: React.ReactNode }) {
  const { ready: authReady, isAuthenticated, businessId, getAccessToken } =
    useAuth();
  const { showToast } = useToast();
  const [cart, setCart] = useState<CartState>(emptyCart());
  const [ready, setReady] = useState(false);
  const [loading, setLoading] = useState(false);
  const [open, setOpen] = useState(false);
  const [guestItems, setGuestItems] = useState<GuestCartLine[]>([]);

  const refreshCart = useCallback(async () => {
    if (!authReady) return;
    const token = getAccessToken();
    if (isAuthenticated && token && businessId) {
      setLoading(true);
      try {
        const localGuest = readGuestCart();
        if (localGuest.length > 0) {
          for (const line of localGuest) {
            await addCartItem(businessId, token, {
              storeItemVariantId: line.id,
              quantity: line.quantity,
            });
          }
          clearGuestCart();
          setGuestItems([]);
        }
        const payload = await getCart(businessId, token);
        setCart(normalizeCartResponse(payload));
      } catch {
        setCart(emptyCart());
      } finally {
        setLoading(false);
        setReady(true);
      }
      return;
    }

    const guest = readGuestCart();
    setGuestItems(guest);
    setCart(cartFromGuest(guest));
    setReady(true);
  }, [authReady, businessId, getAccessToken, isAuthenticated]);

  useEffect(() => {
    void refreshCart().catch(() => {
      setCart(emptyCart());
      setReady(true);
    });
  }, [refreshCart]);

  const addItem = useCallback(
    async (item: {
      storeItemVariantId: string;
      name: string;
      price: number;
      quantity?: number;
      image?: string | null;
      slug?: string;
    }) => {
      const quantity = Math.max(1, Math.floor(item.quantity ?? 1));
      const token = getAccessToken();

      if (isAuthenticated && token && businessId) {
        setLoading(true);
        try {
          const payload = await addCartItem(businessId, token, {
            storeItemVariantId: item.storeItemVariantId,
            quantity,
          });
          setCart(normalizeCartResponse(payload));
          showToast("به سبد خرید اضافه شد");
          setOpen(true);
        } catch (error) {
          showToast(
            error instanceof Error ? error.message : "افزودن به سبد خرید ناموفق بود",
          );
        } finally {
          setLoading(false);
        }
        return;
      }

      const current = readGuestCart();
      const existing = current.find((line) => line.id === item.storeItemVariantId);
      const next = existing
        ? current.map((line) =>
            line.id === item.storeItemVariantId
              ? { ...line, quantity: line.quantity + quantity }
              : line,
          )
        : [
            ...current,
            {
              id: item.storeItemVariantId,
              name: item.name,
              price: item.price,
              image: item.image ?? null,
              slug: item.slug,
              quantity,
            },
          ];
      writeGuestCart(next);
      setGuestItems(next);
      setCart(cartFromGuest(next));
      showToast("به سبد خرید اضافه شد");
      setOpen(true);
    },
    [businessId, getAccessToken, isAuthenticated, showToast],
  );

  const updateQuantity = useCallback(
    async (itemId: string, quantity: number) => {
      const token = getAccessToken();
      if (isAuthenticated && token && businessId) {
        setLoading(true);
        try {
          const payload =
            quantity < 1
              ? await removeCartItem(businessId, token, itemId)
              : await updateCartItem(businessId, token, itemId, quantity);
          setCart(normalizeCartResponse(payload));
        } finally {
          setLoading(false);
        }
        return;
      }

      const current = readGuestCart();
      const next =
        quantity < 1
          ? current.filter((line) => line.id !== itemId)
          : current.map((line) =>
              line.id === itemId ? { ...line, quantity } : line,
            );
      writeGuestCart(next);
      setGuestItems(next);
      setCart(cartFromGuest(next));
    },
    [businessId, getAccessToken, isAuthenticated],
  );

  const removeItem = useCallback(
    async (itemId: string) => {
      await updateQuantity(itemId, 0);
    },
    [updateQuantity],
  );

  const itemCount = useMemo(
    () => cart.items.reduce((sum, line) => sum + line.quantity, 0),
    [cart.items],
  );

  const value = useMemo<CartContextValue>(
    () => ({
      cart,
      itemCount,
      ready,
      loading,
      open,
      setOpen,
      refreshCart,
      addItem,
      updateQuantity,
      removeItem,
      guestItems,
    }),
    [
      cart,
      itemCount,
      ready,
      loading,
      open,
      refreshCart,
      addItem,
      updateQuantity,
      removeItem,
      guestItems,
    ],
  );

  return <CartContext.Provider value={value}>{children}</CartContext.Provider>;
}

export function useCart() {
  const ctx = useContext(CartContext);
  if (!ctx) throw new Error("useCart must be used within CartProvider");
  return ctx;
}