/** @typedef {{ productId: string; slug: string; name: string; price: number; image?: string | null; category?: string | null; quantity: number }} CartItem */

const STORAGE_KEY = "kikomiko-cart-v1";

/** @type {CartItem[]} */
let items = [];
let hydrated = false;
const listeners = new Set();

function notify() {
  for (const fn of listeners) fn(getSnapshot());
}

function persist() {
  if (!hydrated) return;
  try {
    localStorage.setItem(STORAGE_KEY, JSON.stringify(items));
  } catch {
    /* ignore */
  }
}

export function hydrateCart() {
  if (hydrated) return;
  try {
    const raw = localStorage.getItem(STORAGE_KEY);
    items = raw ? JSON.parse(raw) : [];
    if (!Array.isArray(items)) items = [];
  } catch {
    items = [];
  }
  hydrated = true;
  notify();
}

export function subscribe(fn) {
  listeners.add(fn);
  return () => listeners.delete(fn);
}

export function getSnapshot() {
  const itemCount = items.reduce((n, i) => n + i.quantity, 0);
  const subtotal = items.reduce((n, i) => n + i.price * i.quantity, 0);
  return { items: [...items], itemCount, subtotal, hydrated };
}

export function addItem(item) {
  hydrateCart();
  const qty = Math.max(1, item.quantity ?? 1);
  const existing = items.find((i) => i.productId === item.productId);
  if (existing) {
    existing.quantity += qty;
    if (item.category && !existing.category) existing.category = item.category;
    if (item.image && !existing.image) existing.image = item.image;
  } else {
    items.push({
      productId: item.productId,
      slug: item.slug,
      name: item.name,
      price: item.price,
      image: item.image ?? null,
      category: item.category ?? null,
      quantity: qty,
    });
  }
  persist();
  notify();
}

export function updateQuantity(productId, quantity) {
  hydrateCart();
  if (quantity <= 0) {
    items = items.filter((i) => i.productId !== productId);
  } else {
    const row = items.find((i) => i.productId === productId);
    if (row) row.quantity = quantity;
  }
  persist();
  notify();
}

export function removeItem(productId) {
  hydrateCart();
  items = items.filter((i) => i.productId !== productId);
  persist();
  notify();
}

export function clearCart() {
  hydrateCart();
  items = [];
  persist();
  notify();
}

export function formatPrice(price) {
  const amount = Number.isFinite(price) ? Math.round(price) : 0;
  return `${new Intl.NumberFormat("fa-IR", {
    maximumFractionDigits: 0,
  }).format(amount)} تومان`;
}