import authService from './authService';

// === مفاتيح التخزين ===
const CART_KEY = 'activeCartId';

// === LocalStorage Helpers ===
export const setActiveCartId = (id) => {
  try { localStorage.setItem(CART_KEY, String(id)); } catch {}
};
export const getActiveCartId = () => {
  try { return localStorage.getItem(CART_KEY); } catch { return null; }
};
export const clearActiveCartId = () => {
  try { localStorage.removeItem(CART_KEY); } catch {}
};

// === تحويل عناصر الكارت لصيغة JSON:API ===
export const buildCartPayload = (items, totalPrice) => ({
  data: {
    type: "cart",
    attributes: {
      totalPrice: typeof totalPrice === 'number' ? Number(totalPrice) : undefined,
    },
    relationships: {
      cartItems: items.map(it => ({
        attributes: { quantity: Number(it.quantity) },
        relationships: {
          product: { data: { id: it.productId } }
        }
      }))
    }
  }
});

// === استخراج الـ productId من أي شكل محتمل ===
export const extractProductId = (product) => (
  product?.relationships?.supplier_product?.id ||
  product?.relationships?.product?.data?.id ||
  product?.supplier_product_id ||
  product?.product_id ||
  product?.id
);

// === استخراج عناصر الكارت من استجابة الباك ===
export const getItemsFromCart = (cartData) => {
  const rel = cartData?.relationships || {};
  const list = rel.cartItems || rel.cart_items || [];
  return list.map(item => ({
    id: item.id,
    productId: item.relationships?.supplier_product?.id ||
               item.relationships?.product?.data?.id,
    quantity: Number(item?.attributes?.quantity || 0),
  })).filter(x => x.productId);
};

// === إضافة/تحديث عنصر في قائمة الكارت ===
export const upsertItem = (items, productId, quantity) => {
  const idx = items.findIndex(x => String(x.productId) === String(productId));
  if (idx >= 0) {
    const merged = [...items];
    merged[idx] = { ...merged[idx], quantity: Number(merged[idx].quantity) + Number(quantity) };
    return merged;
  }
  return [...items, { productId, quantity: Number(quantity) }];
};

// === حساب إجمالي مؤقت إن توفر priceMap ===
export const estimateTotal = (items, priceMap) => {
  if (!priceMap) return undefined;
  return items.reduce((sum, it) => sum + (Number(priceMap[it.productId]) || 0) * Number(it.quantity), 0);
};

// === التأكد من وجود كارت فعّالة وإنشاؤها إذا لم توجد ===
export const ensureActiveCart = async () => {
  const existing = getActiveCartId();
  if (existing) return existing;

  const token = localStorage.getItem('token');
  if (!token) return null;

  const payload = {
    data: {
      type: "cart",
      attributes: { totalPrice: 0 },
      relationships: { cartItems: [] }
    }
  };

  const res = await authService.createCart(payload);
  if (res?.success && res?.data?.id) {
    setActiveCartId(res.data.id);
    return res.data.id;
  }
  return null;
};

// === إضافة منتج للكارت الفعّالة ===
export const addItemToActiveCart = async ({ product, quantity = 1, priceMap = null }) => {
  const token = localStorage.getItem('token');
  if (!token) return { success: false, message: 'No token found' };

  const cartId = await ensureActiveCart();
  if (!cartId) return { success: false, message: 'Failed to create or get cart' };

  const current = await authService.getCartById(cartId);
  if (!current?.success || !current?.data) return { success: false, message: 'Failed to fetch active cart' };

  const existingItems = getItemsFromCart(current.data);
  const productId = extractProductId(product);
  if (!productId) return { success: false, message: 'Invalid product id' };

  const mergedItems = upsertItem(existingItems, productId, quantity);
  const totalPrice = estimateTotal(mergedItems, priceMap);
  const updatePayload = buildCartPayload(mergedItems, totalPrice);

  const updated = await authService.updateCart(cartId, updatePayload);
  if (updated?.success && updated?.data?.id) {
    setActiveCartId(updated.data.id);
    return { success: true, data: updated.data, cartId: updated.data.id };
  }

  return { success: false, message: updated?.message || 'Failed to update cart', errors: updated?.errors || null };
};

// === تصدير الأدوات كموديل واحد ===
const cartHelpers = {
  setActiveCartId,
  getActiveCartId,
  clearActiveCartId,
  ensureActiveCart,
  addItemToActiveCart,
  buildCartPayload,
  extractProductId,
  getItemsFromCart,
  upsertItem,
  estimateTotal,
};

export default cartHelpers;