/**
  * Validate the checkout
  */
 public function validate_checkout()
 {
     if (fflcommerce_cart::is_empty()) {
         fflcommerce::add_error(sprintf(__('Sorry, your session has expired. <a href="%s">Return to homepage &rarr;</a>', 'fflcommerce'), home_url()));
     }
     // Process Discount Codes
     if (!empty($_POST['coupon_code'])) {
         $coupon = sanitize_title($_POST['coupon_code']);
         fflcommerce_cart::add_discount($coupon);
     }
     foreach (fflcommerce_cart::get_coupons() as $coupon) {
         fflcommerce_cart::is_valid_coupon($coupon);
     }
     // Checkout fields
     $this->posted['shipping_method'] = '';
     $this->posted['shipping_service'] = '';
     if (isset($_POST['shipping_method'])) {
         $shipping_method = fflcommerce_clean($_POST['shipping_method']);
         $shipping_data = explode(':', $shipping_method);
         $this->posted['shipping_method'] = $shipping_data[0];
         $this->posted['shipping_service'] = $shipping_data[1];
     }
     $this->posted['shiptobilling'] = isset($_POST['shiptobilling']) ? fflcommerce_clean($_POST['shiptobilling']) : '';
     $this->posted['payment_method'] = isset($_POST['payment_method']) ? fflcommerce_clean($_POST['payment_method']) : '';
     $this->posted['order_comments'] = isset($_POST['order_comments']) ? fflcommerce_clean($_POST['order_comments']) : '';
     $this->posted['terms'] = isset($_POST['terms']) ? fflcommerce_clean($_POST['terms']) : '';
     $this->posted['create_account'] = isset($_POST['create_account']) ? fflcommerce_clean($_POST['create_account']) : '';
     $this->posted['account_username'] = isset($_POST['account_username']) ? fflcommerce_clean($_POST['account_username']) : '';
     $this->posted['account_password'] = isset($_POST['account_password']) ? fflcommerce_clean($_POST['account_password']) : '';
     $this->posted['account_password_2'] = isset($_POST['account_password_2']) ? fflcommerce_clean($_POST['account_password_2']) : '';
     if (fflcommerce_cart::get_total(false) == 0) {
         $this->posted['payment_method'] = 'no_payment';
     }
     // establish customer billing and shipping locations
     if (fflcommerce_cart::ship_to_billing_address_only()) {
         $this->posted['shiptobilling'] = 'true';
     }
     $country = isset($_POST['billing_country']) ? fflcommerce_clean($_POST['billing_country']) : '';
     $state = isset($_POST['billing_state']) ? fflcommerce_clean($_POST['billing_state']) : '';
     $allowed_countries = FFLCommerce_Base::get_options()->get('fflcommerce_allowed_countries');
     if ($allowed_countries === 'specific') {
         $specific_countries = FFLCommerce_Base::get_options()->get('fflcommerce_specific_allowed_countries');
         if (!in_array($country, $specific_countries)) {
             fflcommerce::add_error(__('Invalid billing country.', 'fflcommerce'));
             return;
         }
     }
     if (fflcommerce_countries::country_has_states($country)) {
         $states = fflcommerce_countries::get_states($country);
         if (!in_array($state, array_keys($states))) {
             fflcommerce::add_error(__('Invalid billing state.', 'fflcommerce'));
             return;
         }
     }
     $postcode = isset($_POST['billing_postcode']) ? fflcommerce_clean($_POST['billing_postcode']) : '';
     $ship_to_billing = FFLCommerce_Base::get_options()->get('fflcommerce_ship_to_billing_address_only') == 'yes';
     fflcommerce_customer::set_location($country, $state, $postcode);
     if (FFLCommerce_Base::get_options()->get('fflcommerce_calc_shipping') == 'yes') {
         if ($ship_to_billing || !empty($_POST['shiptobilling'])) {
             fflcommerce_customer::set_shipping_location($country, $state, $postcode);
         } else {
             $country = isset($_POST['shipping_country']) ? fflcommerce_clean($_POST['shipping_country']) : '';
             $state = isset($_POST['shipping_state']) ? fflcommerce_clean($_POST['shipping_state']) : '';
             $postcode = isset($_POST['shipping_postcode']) ? fflcommerce_clean($_POST['shipping_postcode']) : '';
             if ($allowed_countries === 'specific') {
                 $specific_countries = FFLCommerce_Base::get_options()->get('fflcommerce_specific_allowed_countries');
                 if (!in_array($country, $specific_countries)) {
                     fflcommerce::add_error(__('Invalid shipping country.', 'fflcommerce'));
                     return;
                 }
             }
             if (fflcommerce_countries::country_has_states($country)) {
                 $states = fflcommerce_countries::get_states($country);
                 if (!in_array($state, array_keys($states))) {
                     fflcommerce::add_error(__('Invalid shipping state.', 'fflcommerce'));
                     return;
                 }
             }
             fflcommerce_customer::set_shipping_location($country, $state, $postcode);
         }
     }
     // Billing Information
     foreach ($this->billing_fields as $field) {
         $field = apply_filters('fflcommerce_billing_field', $field);
         $this->posted[$field['name']] = isset($_POST[$field['name']]) ? fflcommerce_clean($_POST[$field['name']]) : '';
         // Format
         if (isset($field['format'])) {
             switch ($field['format']) {
                 case 'postcode':
                     $this->posted[$field['name']] = strtolower(str_replace(' ', '', $this->posted[$field['name']]));
                     break;
             }
         }
         // Required
         if ($field['name'] == 'billing_state' && fflcommerce_customer::has_valid_shipping_state()) {
             $field['required'] = false;
         }
         if (isset($field['required']) && $field['required'] && empty($this->posted[$field['name']])) {
             fflcommerce::add_error($field['label'] . __(' (billing) is a required field.', 'fflcommerce'));
         }
         if ($field['name'] == 'billing_euvatno') {
             $vatno = isset($this->posted['billing_euvatno']) ? $this->posted['billing_euvatno'] : '';
             $vatno = str_replace(' ', '', $vatno);
             $country = fflcommerce_tax::get_customer_country();
             // strip any country code from the beginning of the number
             if (strpos($vatno, $country) === 0) {
                 $vatno = substr($vatno, strlen($country));
             }
             if ($vatno != '') {
                 $url = 'http://isvat.appspot.com/' . $country . '/' . $vatno . '/';
                 $httpRequest = curl_init();
                 curl_setopt($httpRequest, CURLOPT_FAILONERROR, true);
                 curl_setopt($httpRequest, CURLOPT_RETURNTRANSFER, true);
                 curl_setopt($httpRequest, CURLOPT_HEADER, false);
                 curl_setopt($httpRequest, CURLOPT_URL, $url);
                 $result = curl_exec($httpRequest);
                 curl_close($httpRequest);
                 if ($result === 'false') {
                     fflcommerce_log('EU VAT validation error with URL: ' . $url);
                     fflcommerce::add_error($field['label'] . __(' (billing) is not a valid VAT Number.  Leave it blank to disable VAT validation. (VAT may be charged depending on your location)', 'fflcommerce'));
                 } else {
                     $this->valid_euvatno = fflcommerce_countries::get_base_country() != fflcommerce_tax::get_customer_country() && fflcommerce_countries::is_eu_country(fflcommerce_tax::get_customer_country());
                 }
             }
         }
         // Validation
         if (isset($field['validate']) && !empty($this->posted[$field['name']])) {
             switch ($field['validate']) {
                 case 'phone':
                     if (!fflcommerce_validation::is_phone($this->posted[$field['name']])) {
                         fflcommerce::add_error($field['label'] . __(' (billing) is not a valid number.', 'fflcommerce'));
                     }
                     break;
                 case 'email':
                     if (!fflcommerce_validation::is_email($this->posted[$field['name']])) {
                         fflcommerce::add_error($field['label'] . __(' (billing) is not a valid email address.', 'fflcommerce'));
                     }
                     break;
                 case 'postcode':
                     if (!fflcommerce_validation::is_postcode($this->posted[$field['name']], $_POST['billing_country'])) {
                         fflcommerce::add_error($field['label'] . __(' (billing) is not a valid postcode/ZIP.', 'fflcommerce'));
                     } else {
                         $this->posted[$field['name']] = fflcommerce_validation::format_postcode($this->posted[$field['name']], $_POST['billing_country']);
                     }
                     break;
             }
         }
     }
     // Shipping Information
     if (fflcommerce_shipping::is_enabled() && !fflcommerce_cart::ship_to_billing_address_only() && empty($this->posted['shiptobilling'])) {
         foreach ($this->shipping_fields as $field) {
             $field = apply_filters('fflcommerce_shipping_field', $field);
             if (isset($_POST[$field['name']])) {
                 $this->posted[$field['name']] = fflcommerce_clean($_POST[$field['name']]);
             } else {
                 $this->posted[$field['name']] = '';
             }
             // Format
             if (isset($field['format'])) {
                 switch ($field['format']) {
                     case 'postcode':
                         $this->posted[$field['name']] = strtolower(str_replace(' ', '', $this->posted[$field['name']]));
                         break;
                 }
             }
             // Required
             if ($field['name'] == 'shipping_state' && fflcommerce_customer::has_valid_shipping_state()) {
                 $field['required'] = false;
             }
             if (isset($field['required']) && $field['required'] && empty($this->posted[$field['name']])) {
                 fflcommerce::add_error($field['label'] . __(' (shipping) is a required field.', 'fflcommerce'));
             }
             // Validation
             if (isset($field['validate']) && !empty($this->posted[$field['name']])) {
                 switch ($field['validate']) {
                     case 'postcode':
                         if (!fflcommerce_validation::is_postcode($this->posted[$field['name']], $country)) {
                             fflcommerce::add_error($field['label'] . __(' (shipping) is not a valid postcode/ZIP.', 'fflcommerce'));
                         } else {
                             $this->posted[$field['name']] = fflcommerce_validation::format_postcode($this->posted[$field['name']], $country);
                         }
                         break;
                 }
             }
         }
     }
     if ($this->must_register && empty($this->posted['create_account'])) {
         fflcommerce::add_error(__('Sorry, you must agree to creating an account', 'fflcommerce'));
     }
     if ($this->must_register || empty($user_id) && $this->posted['create_account']) {
         if (!$this->show_signup) {
             fflcommerce::add_error(__('Sorry, the shop owner has disabled guest purchases.', 'fflcommerce'));
         }
         if (empty($this->posted['account_username'])) {
             fflcommerce::add_error(__('Please enter an account username.', 'fflcommerce'));
         }
         if (empty($this->posted['account_password'])) {
             fflcommerce::add_error(__('Please enter an account password.', 'fflcommerce'));
         }
         if ($this->posted['account_password_2'] !== $this->posted['account_password']) {
             fflcommerce::add_error(__('Passwords do not match.', 'fflcommerce'));
         }
         // Check the username
         if (!validate_username($this->posted['account_username'])) {
             fflcommerce::add_error(__('Invalid email/username.', 'fflcommerce'));
         } elseif (username_exists($this->posted['account_username'])) {
             fflcommerce::add_error(__('An account is already registered with that username. Please choose another.', 'fflcommerce'));
         }
         // Check the e-mail address
         if (email_exists($this->posted['billing_email'])) {
             fflcommerce::add_error(__('An account is already registered with your email address. Please login.', 'fflcommerce'));
         }
     }
     // Terms
     if (!isset($_POST['update_totals']) && empty($this->posted['terms']) && fflcommerce_get_page_id('terms') > 0) {
         fflcommerce::add_error(__('You must accept our Terms &amp; Conditions.', 'fflcommerce'));
     }
     if (fflcommerce_cart::needs_shipping()) {
         // Shipping Method
         $available_methods = fflcommerce_shipping::get_available_shipping_methods();
         if (!isset($available_methods[$this->posted['shipping_method']])) {
             fflcommerce::add_error(__('Invalid shipping method.', 'fflcommerce'));
         }
     }
 }