<?php
session_start();

require_once 'db/config.php';

// Initialize cart if it doesn't exist
if (!isset($_SESSION['cart'])) {
    $_SESSION['cart'] = [];
    $_SESSION['cart_restaurant'] = null;
}

$action = $_POST['action'] ?? $_GET['action'] ?? null;
$menu_item_id = $_POST['menu_item_id'] ?? $_GET['menu_item_id'] ?? null;
$restaurant_id = $_POST['restaurant_id'] ?? null;
$quantity = $_POST['quantity'] ?? 1;

switch ($action) {
    case 'add':
        if ($menu_item_id && $restaurant_id && $quantity > 0) {
            // If cart is not empty and new item is from a different restaurant, clear the cart
            if (!empty($_SESSION['cart']) && $_SESSION['cart_restaurant'] != $restaurant_id) {
                $_SESSION['cart'] = [];
            }

            $_SESSION['cart_restaurant'] = $restaurant_id;

            // Add or update item in cart
            if (isset($_SESSION['cart'][$menu_item_id])) {
                $_SESSION['cart'][$menu_item_id] += $quantity;
            } else {
                $_SESSION['cart'][$menu_item_id] = $quantity;
            }
        }
        header('Location: menu.php?id=' . $restaurant_id);
        exit;

    case 'update':
        if ($menu_item_id && $quantity > 0) {
            $_SESSION['cart'][$menu_item_id] = $quantity;
        }
        header('Location: cart.php');
        exit;

    case 'remove':
        if ($menu_item_id) {
            unset($_SESSION['cart'][$menu_item_id]);
        }
        header('Location: cart.php');
        exit;

    case 'clear':
        $_SESSION['cart'] = [];
        $_SESSION['cart_restaurant'] = null;
        header('Location: cart.php');
        exit;
}