// composables/useCart.ts

import type { CartSummary } from '~/types/cart'

/**
 * Shopping Cart composable
 *
 * Manages cart state and provides methods for cart operations
 *
 * Features:
 * - Reactive cart state (cart, items, total, itemCount)
 * - Auto-fetch cart on mount
 * - Add, update, and remove items
 * - Loading states for async operations
 * - Error handling with notifications for removed items
 *
 * Usage:
 * const { cart, items, total, itemCount, loading, addItem, updateItem, removeItem, fetchCart } = useCart()
 */

// Global cart state (shared across all components)
const cartState = ref<CartSummary | null>(null)
const loading = ref(false)
const initialized = ref(false)

export function useCart() {
  // Computed reactive properties
  const cart = computed(() => cartState.value?.cart ?? null)
  const items = computed(() => cartState.value?.items ?? [])
  const total = computed(() => cartState.value?.total ?? 0)
  const itemCount = computed(() => cartState.value?.itemCount ?? 0)

  /**
   * Fetch cart from server
   * Auto-cleans unavailable products and returns removed items
   */
  async function fetchCart() {
    loading.value = true
    try {
      const data = await $fetch<CartSummary>('/api/cart', {
        method: 'GET',
      })

      cartState.value = data

      // Show notification if products were removed
      if (data.removedItems && data.removedItems.length > 0) {
        // TODO: Show toast notification when toast composable is implemented
        // For now, log to console
        console.warn('Products removed from cart:', data.removedItems)
      }

      return data
    } catch (error) {
      console.error('Failed to fetch cart:', error)
      // Set to null on error
      cartState.value = null
      throw error
    } finally {
      loading.value = false
    }
  }

  /**
   * Add item to cart
   *
   * @param productId - Product UUID
   * @param quantity - Quantity to add (default: 1)
   */
  async function addItem(productId: string, quantity: number = 1) {
    loading.value = true
    try {
      await $fetch('/api/cart/items', {
        method: 'POST',
        body: {
          productId,
          quantity,
        },
      })

      // Refresh cart to get updated state
      await fetchCart()
    } catch (error) {
      console.error('Failed to add item to cart:', error)
      throw error
    } finally {
      loading.value = false
    }
  }

  /**
   * Update cart item quantity
   *
   * @param itemId - Cart item UUID
   * @param quantity - New quantity (must be >= 1)
   */
  async function updateItem(itemId: string, quantity: number) {
    if (quantity < 1) {
      throw new Error('Quantity must be at least 1')
    }

    loading.value = true
    try {
      await $fetch(`/api/cart/items/${itemId}`, {
        method: 'PATCH',
        body: {
          quantity,
        },
      })

      // Refresh cart to get updated state
      await fetchCart()
    } catch (error) {
      console.error('Failed to update cart item:', error)
      throw error
    } finally {
      loading.value = false
    }
  }

  /**
   * Remove item from cart
   *
   * @param itemId - Cart item UUID
   */
  async function removeItem(itemId: string) {
    loading.value = true
    try {
      await $fetch(`/api/cart/items/${itemId}`, {
        method: 'DELETE',
      })

      // Refresh cart to get updated state
      await fetchCart()
    } catch (error) {
      console.error('Failed to remove cart item:', error)
      throw error
    } finally {
      loading.value = false
    }
  }

  /**
   * Clear all items from cart
   * For future use (not implemented in API yet)
   */
  async function clearCart() {
    // TODO: Implement when API endpoint is ready
    console.warn('clearCart() not yet implemented')
  }

  /**
   * Initialize cart on mount
   * Only fetches once per session
   */
  onMounted(async () => {
    if (!initialized.value) {
      await fetchCart()
      initialized.value = true
    }
  })

  return {
    // State
    cart,
    items,
    total,
    itemCount,
    loading,

    // Methods
    fetchCart,
    addItem,
    updateItem,
    removeItem,
    clearCart,
  }
}