<?php

require_once 'uc_vat.ca.inc';

/**
 * Implementation of hook_perm().
 */
function uc_vat_perm() {
  return array('show prices excluding VAT');
}

/**
 * Implementation of hook_menu().
 */
function uc_vat_menu() {
  $items = array();

  $items['admin/store/settings/taxes/vat'] = array(
    'title' => t('VAT settings'),
    'title callback' => 'uc_vat_menu_title',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('uc_vat_settings_form'),
    'access arguments' => array('configure taxes'),
    'type' => MENU_LOCAL_TASK,
    'file' => 'uc_vat.admin.inc',
  );

  $items['cart/checkout/cart_pane'] = array(
    'page callback' => 'uc_vat_update_cart_pane',
    'access arguments' => array('access content'),
    'type' => MENU_CALLBACK,
  );

  return $items;
}

/**
 * Menu title callback.
 */
function uc_vat_menu_title() {
  return t('!tax settings', array('!tax' => variable_get('uc_vat_name', 'VAT')));
}

/**
 * Implementation of hook_init().
 */
function uc_vat_init() {
  // Add the "tax name" setting as a translatable variable.
  global $conf;
  $conf['i18n_variables'][] = 'uc_vat_name';
}

/**
 * Implementation of hook_menu_alter().
 */
function uc_vat_menu_alter(&$items) {
  // Override uc_taxes JavaScript callback with our own version.
  $items['taxes/calculate']['page callback'] = 'uc_vat_uc_taxes_javascript';

  // Override admin order product edit callback with our own version.
  $items['admin/store/orders/%uc_order/products']['page callback'] = 'uc_vat_uc_order_edit_products';

  // Override checkout order preview pane callback with our own version.
  $items['cart/checkout/line_items']['page callback'] = 'uc_vat_uc_payment_get_totals';
}

/**
 * Implementation of hook_uc_price_handler().
 */
function uc_vat_uc_price_handler() {
  return array(
    'alter' => array(
      'title' => t('!tax price alterer', array('!tax' => variable_get('uc_vat_name', 'VAT'))),
      'description' => t('Modifies prices to include tax before checkout.'),
      'callback' => 'uc_vat_price_handler_alter',
    ),
  );
}

/**
 * Implementation of hook_theme().
 */
function uc_vat_theme($existing, $type, $theme, $path) {
  return array(
    'uc_vat_cart_review_table' => array(
      'arguments' => array('show_subtotal' => TRUE, 'order' => NULL),
      'file' => 'uc_vat.theme.inc',
    ),
    'uc_vat_excluding_shipping_costs' => array(
      'arguments' => array('element' => 'span'),
      'file' => 'uc_vat.theme.inc',
    ),
  );
}

/**
 * Implementation of hook_form_alter().
 */
function uc_vat_form_alter(&$form, $form_state) {
  if (uc_product_is_product_form($form)) {
    // Add VAT to product prices before editing.
    $taxes = uc_vat_load_taxes();
    if ($fields = _uc_vat_product_fields()) {
      foreach ($fields as $field) {
        $value = $form['base']['prices'][$field]['#default_value'];
        foreach ($taxes as $tax) {
          if (in_array($form['#node']->type, $tax->taxed_product_types) && ($tax->shippable == 0 || $form['#node']->shippable == 1)) {
            $value *= 1 + $tax->rate;
          }
        }
        $form['base']['prices'][$field]['#default_value'] = uc_store_format_price_field_value(round($value, 4));
      }

      if (module_exists('uc_multiprice')) {
        foreach (element_children($form['multiprice']['countries']) as $country) {
          foreach ($fields as $field) {
            $value = $form['multiprice']['countries'][$country][$field]['#default_value'];
            foreach ($taxes as $tax) {
              if (in_array($form['#node']->type, $tax->taxed_product_types) && ($tax->shippable == 0 || $form['#node']->shippable == 1)) {
                $value *= 1 + $tax->rate;
              }
            }
            $form['multiprice']['countries'][$country][$field]['#default_value'] = uc_store_format_price_field_value(round($value, 3));
          }
        }
      }

      $form['#submit'][] = 'uc_vat_uc_product_form_submit';
    }

    // Add help message to product price descriptions.
    foreach (array('list_price', 'cost', 'sell_price') as $field) {
      $desc = substr($form['base']['prices'][$field]['#description'], 0, -1) .', ';
      $desc .= variable_get('uc_vat_'. $field .'_inclusive', FALSE) ? t('including !tax.', array('!tax' => variable_get('uc_vat_name', 'VAT'))) : t('excluding !tax.', array('!tax' => variable_get('uc_vat_name', 'VAT')));
      $form['base']['prices'][$field]['#description'] = $desc;
    }
  }
}

/**
 * Remove VAT from product prices after editing but before saving.
 */
function uc_vat_uc_product_form_submit($form, &$form_state) {
  $taxes = uc_vat_load_taxes();
  $fields = _uc_vat_product_fields();

  foreach ($fields as $field) {
    $value = $form_state['values'][$field];
    foreach (array_reverse($taxes) as $tax) {
      if (in_array($form['#node']->type, $tax->taxed_product_types) && ($tax->shippable == 0 || $form['#node']->shippable == 1)) {
        $value /= (1 + $tax->rate);
      }
    }
    $form_state['values'][$field] = $value;
  }

  if (module_exists('uc_multiprice')) {
    foreach (array_keys($form_state['values']['multiprice']['countries']) as $country) {
      foreach ($fields as $field) {
        $value = $form_state['values']['multiprice']['countries'][$country][$field];
        foreach (array_reverse($taxes) as $tax) {
          if (in_array($form['#node']->type, $tax->taxed_product_types) && ($tax->shippable == 0 || $form['#node']->shippable == 1)) {
            $value /= (1 + $tax->rate);
          }
        }
        $form_state['values']['multiprice']['countries'][$country][$field] = $value;
      }
    }
  }
}

/**
 * Add VAT to product prices when editing orders.
 */
function uc_vat_form_uc_order_edit_form_alter(&$form, $form_state) {
  if (_uc_vat_attribute_fields()) {
    array_unshift($form['#submit'], 'uc_vat_uc_order_edit_form_submit');
  }
}

function uc_vat_form_uc_order_edit_products_form_alter(&$form, $form_state) {
  $order = uc_order_load($form['#parameters'][2][0]->order_id);
  $taxes = isset($order->data['taxes']) ? $order->data['taxes'] : uc_vat_load_taxes();

  // Use attribute field names as the true price field is named just "price" not "sell price".
  if ($fields = _uc_vat_attribute_fields()) {
    foreach (element_children($form['products']) as $i) {
      if (isset($form['products'][$i]['nid']['#value'])) {
        $node = node_load($form['products'][$i]['nid']['#value']);
        foreach ($fields as $field) {
          $value = $form['products'][$i][$field]['#value'];
          foreach ($taxes as $tax) {
            if (in_array($node->type, $tax->taxed_product_types) && ($tax->shippable == 0 || $node->shippable == 1)) {
              $value *= 1 + $tax->rate;
            }
          }
          $form['products'][$i][$field]['#value'] = uc_store_format_price_field_value(round($value, 4));
        }
      }
    }
  }
}

/**
 * Remove VAT from product prices when adding/editing products using the JavaScript functionality on the edit order page.
 */
function uc_vat_uc_order_edit_products($order) {
  _uc_vat_uc_order_edit_products_submit($order);
  uc_order_edit_products($order);
}

/**
 * Remove VAT from product prices when editing orders.
 */
function uc_vat_uc_order_edit_form_submit($form, &$form_state) {
  $order = uc_order_load($form_state['values']['order_id']);
  _uc_vat_uc_order_edit_products_submit($order);
}

function _uc_vat_uc_order_edit_products_submit($order) {
  $taxes = isset($order->data['taxes']) ? $order->data['taxes'] : uc_vat_load_taxes();
  $fields = _uc_vat_attribute_fields();

  // Modify $_POST directly, as products are subform elements injected into the form, not real Form API elements.
  foreach (element_children($_POST['products']) as $i) {
    if (isset($_POST['products'][$i]['nid'])) {
      $node = node_load($_POST['products'][$i]['nid']);
      foreach ($fields as $field) {
        $value = $_POST['products'][$i][$field];
        foreach (array_reverse($taxes) as $tax) {
          if (in_array($node->type, $tax->taxed_product_types) && ($tax->shippable == 0 || $node->shippable == 1)) {
            $value /= (1 + $tax->rate);
          }
        }
        $_POST['products'][$i][$field] = $value;
      }
    }
  }
}

/**
 * Alter default attribute options overview form to add VAT if necessary.
 */
function uc_vat_form_uc_attribute_options_form_alter(&$form, $form_state) {
  if ($fields = _uc_vat_attribute_fields()) {
    if (variable_get('uc_vat_default_attributes_inclusive', FALSE)) {
      $attribute = uc_attribute_load($form['aid']['#value']);
      $context = array(
        'revision' => 'themed',
        'type' => 'attribute_option',
        'subject' => array(
          'attribute' => $attribute,
        ),
      );
      $taxes = uc_vat_load_taxes();

      foreach ($attribute->options as $oid => $option) {
        foreach ($fields as $field) {
          $value = $option->$field;
          // Apply all taxes as this is a default attribute and product type is
          // not yet known.
          foreach ($taxes as $tax) {
            $value *= (1 + $tax->rate);
          }
          $context['subject']['option'] = $option;
          $context['field'] = $field;
          $form['options'][$oid][$field]['#value'] = uc_price($value, $context);
        }
      }

      $message = _uc_vat_attribute_description(t('Default cost'), t('Default price'));
    }
    else {
      $message = t('Prices shown here are exclusive of !tax. !tax will be added where applicable when these attributes are added to products.', array('!tax' => variable_get('uc_vat_name', 'VAT')));
    }

    $form['vat_note'] = array(
      '#type' => 'markup',
      '#value' => '<p>'. $message .'</p>',
    );
  }
}

/**
 * Alter default attribute options edit form to add VAT if necessary.
 */
function uc_vat_form_uc_attribute_option_form_alter(&$form, $form_state) {
  if ($fields = _uc_vat_attribute_fields()) {
    if (variable_get('uc_vat_default_attributes_inclusive', FALSE)) {
      $attribute = uc_attribute_load($form['aid']['#value']);
      $option = $attribute->options[$form['oid']['#value']];
      $taxes = uc_vat_load_taxes();

      foreach ($fields as $field) {
        $value = $option->$field;
        // Apply all taxes as this is a default attribute and product type is
        // not yet known.
        foreach ($taxes as $tax) {
          $value *= (1 + $tax->rate);
        }
        $form['adjustments'][$field]['#default_value'] = uc_store_format_price_field_value(round($value, 4));
      }

      // Ensure our submit handler gets called first to remove VAT from the
      // price entered.
      array_unshift($form['#submit'], 'uc_vat_uc_attribute_option_form_submit');

      $message = _uc_vat_attribute_description(t('Cost'), t('Price'));
    }
    else {
      $message = t('Prices entered must exclude !tax. !tax will be added where applicable when this attribute is added to a product.', array('!tax' => variable_get('uc_vat_name', 'VAT')));
    }

    $form['adjustments']['#description'] .= '<br />'. $message;
  }
}

/**
 * Remove VAT from default option prices.
 */
function uc_vat_uc_attribute_option_form_submit($form, &$form_state) {
  $taxes = uc_vat_load_taxes();

  foreach (_uc_vat_attribute_fields() as $field) {
    $value = $form_state['values'][$field];
    // Apply all taxes as this is a default attribute and product type is not
    // yet known.
    foreach (array_reverse($taxes) as $tax) {
      $value /= (1 + $tax->rate);
    }
    $form_state['values'][$field] = $value;
  }
}

/**
 * Alter product options form to add VAT if necessary.
 */
function uc_vat_form_uc_object_options_form_alter(&$form, $form_state) {
  $form['vat_note'] = array(
    '#type' => 'markup',
    '#value' => '<p>'. t('Note:') .' '. _uc_vat_attribute_description(t('Cost'), t('Price')) .'</p>',
  );

  if ($fields = _uc_vat_attribute_fields()) {
    // This form is used for products and product classes, and we need to know the node type.
    $object = $form['#parameters'][2];
    $type = $form['#parameters'][3] == 'product' ? $object->type : $object->pcid;
    $taxes = uc_vat_load_taxes();

    foreach (element_children($form['attributes']) as $aid) {
      foreach (element_children($form['attributes'][$aid]['options']) as $oid) {
        foreach ($fields as $field) {
          $value = $form['attributes'][$aid]['options'][$oid][$field]['#default_value'];
          foreach ($taxes as $tax) {
            if (in_array($type, $tax->taxed_product_types)) {
              $value *= (1 + $tax->rate);
            }
          }
          $form['attributes'][$aid]['options'][$oid][$field]['#default_value'] = uc_store_format_price_field_value(round($value, 4));
        }
      }
    }

    // Ensure our submit handler gets called first to remove VAT from the price entered.
    array_unshift($form['#submit'], 'uc_vat_uc_object_options_form_submit');
  }
}

/**
 * Remove VAT from product option prices.
 */
function uc_vat_uc_object_options_form_submit($form, &$form_state) {
  $object = $form['#parameters'][2];
  $type = $form['#parameters'][3] == 'product' ? $object->type : $object->pcid;
  $taxes = uc_vat_load_taxes();

  foreach (element_children($form['attributes']) as $aid) {
    foreach (element_children($form['attributes'][$aid]['options']) as $oid) {
      foreach (_uc_vat_attribute_fields() as $field) {
        $value = $form_state['values']['attributes'][$aid]['options'][$oid][$field];
        foreach (array_reverse($taxes) as $tax) {
          if (in_array($type, $tax->taxed_product_types)) {
            $value /= (1 + $tax->rate);
          }
        }
        $form_state['values']['attributes'][$aid]['options'][$oid][$field] = $value;
      }
    }
  }
}

/**
 * Description helper for attribute form alter functions.
 */
function _uc_vat_attribute_description($cost_field, $price_field) {
  $name = variable_get('uc_vat_name', 'VAT');
  if (variable_get('uc_vat_cost_inclusive', FALSE)) {
    $message = t('"!field" includes !tax.', array('!field' => $cost_field, '!tax' => $name));
  }
  else {
    $message = t('"!field" excludes !tax.', array('!field' => $cost_field, '!tax' => $name));
  }
  $message .= ' ';
  if (variable_get('uc_vat_sell_price_inclusive', FALSE)) {
    $message .= t('"!field" includes !tax.', array('!field' => $price_field, '!tax' => $name));
  }
  else {
    $message .= t('"!field" excludes !tax.', array('!field' => $price_field, '!tax' => $name));
  }
  return $message;
}

/**
 * Add price recalculation submit handler to tax edit forms.
 */
function uc_vat_form_uc_taxes_form_alter(&$form, $form_state) {
  if ($form['id']['#value'] && _uc_vat_product_fields()) {
    if (variable_get('uc_vat_recalculate_prices', FALSE)) {
      $form['recalculation_note'] = array(
        '#value' => '<p>'. t('If the rate is changed, product and attribute prices will be recalculated, so !tax exclusive prices will change but !tax inclusive prices will stay the same. Visit the <a href="!url">!tax settings</a> page to change this behaviour.', array('!tax' => variable_get('uc_vat_name', 'VAT'), '!url' => url('admin/store/settings/taxes/vat'))) .'</p>',
        '#weight' => -10,
      );
      module_load_include('inc', 'uc_vat', 'uc_vat.recalculate');
      $form['#submit'][] = 'uc_vat_recalculate_prices';
    }
    else {
      $form['recalculation_note'] = array(
        '#value' => '<p>'. t('If the rate is changed, product and attribute prices will not be recalculated, so !tax inclusive prices will change. Visit the <a href="!url">!tax settings</a> page to change this behaviour.', array('!tax' => variable_get('uc_vat_name', 'VAT'), '!url' => url('admin/store/settings/taxes/vat'))) .'</p>',
        '#weight' => -10,
      );
    }
  }
}

/**
 * Implementation of hook_order().
 *
 * Ensure tax rules have been saved with the order.
 */
function uc_vat_order($op, $arg1, $arg2) {
  switch ($op) {
    case 'save':
      $data = unserialize(db_result(db_query("SELECT data FROM {uc_orders} WHERE order_id = %d", $arg1->order_id)));
      if (!isset($data['taxes'])) {
        $data['taxes'] = uc_vat_load_taxes($arg1, user_load($arg1->uid));
        db_query("UPDATE {uc_orders} SET data = '%s' WHERE order_id = %d", serialize($data), $arg1->order_id);
      }
  }
}

/**
 * VAT price alterer callback function.
 */
function uc_vat_price_handler_alter(&$price, &$context, &$options) {
  // Do nothing if user has "show prices without VAT" permission.
  if (uc_vat_exclude_vat()) {
    return;
  }
// Don't do alterations if specific is asked.
  if (isset($options['uc_vat']) && $options['uc_vat'] == FALSE) {
    return;
  }
  if (isset($context['subject']['order']->data['taxes'])) {
    // Use stored tax rates from an existing order if available.
    $tax_rates = $context['subject']['order']->data['taxes'];
  }
  else {
    // Load tax rates according to conditional actions rules, using context where available.
    $tax_rates = uc_vat_load_taxes($context['subject']['order'], $context['account']);
  }

  switch ($context['type']) {
    case 'product':
    case 'cart_item':
    case 'order_product':
      $node = $context['subject']['node'];

      // Ensure that all the parts are there when the data comes from Views.
      if (!isset($node->type) || !isset($node->sell_price) || !isset($node->shippable)) {
        $node = node_load($node->nid);
      }

      uc_vat_product_price_alter($price, $context, $options, $tax_rates, $node);
      break;

    case 'attribute_option':
      $node = node_load($context['subject']['option']->nid);
      uc_vat_product_price_alter($price, $context, $options, $tax_rates, $node);
      break;

    case 'line_item':
      uc_vat_line_item_price_alter($price, $context, $options, $tax_rates);
      break;
  }
}

/**
 * Apply conditional actions to an order and return only the active set of taxes.
 * If no order is supplied, make a reasonable guess as to which country the user is in.
 */
function uc_vat_load_taxes($order = NULL, $account = NULL) {
  global $user;

  // Use the current user if none was supplied.
  if (!$account) {
    $account = $user;
  }

  // Build a fake order object if none was supplied.
  if (!$order) {
    $order = new stdClass();
    $order->uid = $account->uid;
    $order->order_id = 0;
    $order->order_status = uc_order_state_default('in_checkout');
  }

  // Ensure we have a country code for the order.
  if (!isset($order->billing_country) || !isset($order->delivery_country)) {
    // Default to store country.
    $country_id = variable_get('uc_store_country', 840);

    // TODO: find alternative ways of guessing the country if we do not know it
    // - If user is logged in, look for previous completed orders and assume the same country will be used?
    // - If that fails or user is not logged in, use geolocation if available?

    if (!isset($order->billing_country)) {
      $order->billing_country = $country_id;
    }
    if (!isset($order->delivery_country)) {
      $order->delivery_country = $country_id;
    }
  }

  // Run CA rules against the order.
  $predicates = ca_load_trigger_predicates('calculate_taxes');
  $arguments = array(
    'order' => array(
      '#entity' => 'uc_order',
      '#title' => t('Order'),
      '#data' => $order,
    ),
    'tax' => array(
      '#entity' => 'tax',
      '#title' => t('Tax rule'),
    ),
    'account' => array(
      '#entity' => 'user',
      '#title' => t('User'),
      '#data' => $account,
    ),
  );

  // Only use taxes that match the CA rules.
  $taxes = uc_taxes_rate_load();
  foreach ($taxes as $id => $tax) {
    $arguments['tax']['#data'] = $tax;
    if (!ca_evaluate_conditions($predicates['uc_taxes_'. $tax->id], $arguments)) {
      unset($taxes[$id]);
    }
  }
  return $taxes;
}

/**
 * Handle VAT on product-type prices.
 */
function uc_vat_product_price_alter(&$price, &$context, &$options, $tax_rates, $node) {
  $suffixes = array();

  $original_price = $price['price'];

  if ($node->type == 'product_kit') {
    // Special case for product kits; calculate VAT per-product including any kit discount.
    foreach ($node->products as $product) {
      foreach ($tax_rates as $tax) {
        if (in_array($product->type, $tax->taxed_product_types) && ($tax->shippable == 0 || $product->shippable == 1)) {
          // This uses the original sell_price, which will not necessarily be correct if another price alterer is enabled.
          // Instead, should we try to proportionally back-calculate the individual product prices from the price we were passed?
          if ($context['field'] == 'sell_price') {
            $price['price'] += ($product->sell_price + $product->discount) * $product->qty * $tax->rate;
          }
          else {
            $price['price'] += $product->sell_price * $product->qty * $tax->rate;
          }
          $suffixes[$tax->id] = $tax->name;
        }
      }
    }
  }
  else {
    $taxed_price = $price['price'];
    foreach ($tax_rates as $tax) {
      if (in_array($node->type, $tax->taxed_product_types) && ($tax->shippable == 0 || $node->shippable == 1)) {
        $price['price'] += $taxed_price * $tax->rate;
        $suffixes[$tax->id] = $tax->name;
      }
    }
  }

  if ($context['type'] == 'product') {
    if (!empty($suffixes) && variable_get('uc_vat_suffix_tax', FALSE)) {
      $options['suffixes'][] = ' <span class="price-vat-suffix">'. t('including !taxes', array('!taxes' => implode(', ', $suffixes))) .'</span>';
    }

    if (variable_get('uc_vat_suffix_shipping', FALSE) && $node->shippable) {
      $options['suffixes'][] = ' ' . theme('uc_vat_excluding_shipping_costs');
    }

    if (!empty($suffixes) && variable_get('uc_vat_suffix_exclusive', FALSE)) {
      $options['suffixes'][] = ' <span class="price-vat-exclusive">('. uc_currency_format($original_price) . ' ' . t('excluding !tax', array('!tax' => variable_get('uc_vat_name', 'VAT'))) .')</span>';
    }

    if (empty($suffixes) && variable_get('uc_vat_suffix_zero_rated', FALSE)) {
      $options['suffixes'][] = ' <span class="price-no-vat">('. t('no !tax applicable', array('!tax' => variable_get('uc_vat_name', 'VAT'))) .')</span>';
    }
  }
}

/**
 * Handle VAT on line items.
 */
function uc_vat_line_item_price_alter(&$price, &$context, &$options, $tax_rates) {
  $order = $context['subject']['order'];
  $line_item = (array)$context['subject']['line_item'];

  // If we are in the order preview pane at checkout, the tax conditions may have changed,
  // so force recalculation of the subtotal line item here.
  if ($_GET['q'] == 'cart/checkout/line_items' && $line_item['type'] == 'subtotal') {
    $price['price'] = uc_order_get_total($order, TRUE);
  }

  // Add the taxes that satisfy the conditions and apply to this line item
  // to its amount.
  foreach ($tax_rates as $tax_rate) {
    // Special handling for modules that provide their own tax adjustments.
    $callback = _line_item_data($line_item['type'], 'tax_adjustment');
    if (variable_get('uc_vat_line_item_adjustment', FALSE) && $callback && function_exists($callback)) {
      $price['price'] += $callback($line_item['amount'], $order, $tax_rate);
    }
    else {
      $taxed_line_items = $tax_rate->taxed_line_items;
      if (is_array($taxed_line_items) && in_array($line_item['type'], $taxed_line_items)) {
        if ($line_item['type'] == 'tax' && $line_item['weight'] >= $tax_rate->weight) {
          continue;
        }

        // The total tax amount comes from many sources, so only add the tax
        // that was applied to this line item.
        $price['price'] += $line_item['amount'] * $tax_rate->rate;
      }
    }
  }
}

/**
 * Implementation of hook_line_item_data_alter().
 */
function uc_vat_line_item_data_alter(&$items) {
  foreach ($items as &$item) {
    switch ($item['id']) {
      case 'shipping':
        // This only takes effect if line item tax adjustments are enabled.
        switch (variable_get('uc_vat_apply_shipping', 'normal')) {
          case 'highest':
            $item['tax_adjustment'] = 'uc_vat_shipping_tax_adjustment_highest';
            break;

          case 'proportional':
            $item['tax_adjustment'] = 'uc_vat_shipping_tax_adjustment_proportional';
            break;
        }
        break;

      case 'subtotal':
        // Hide the standard subtotal line.
        if (variable_get('uc_vat_hide_subtotal', FALSE)) {
          $item['callback'] = NULL;
        }
        break;

      case 'tax':
        // Allow per-line item tax adjustments.
      //  if (variable_get('uc_vat_line_item_adjustment', FALSE)) {
          $item['callback'] = 'uc_vat_line_item_tax';
      //  }

        // Tax amounts are added in to other line items, so the actual tax line
        // items should not be added to the order total - unless VAT is excluded
        // from display, when it will not have been included already.
        if (!uc_vat_exclude_vat()) {
          $item['calculated'] = FALSE;
        }
        break;

      case 'tax_subtotal':
        if (uc_vat_exclude_vat() || variable_get('uc_vat_hide_checkout_exclusive', FALSE)) {
          // Hide the subtotal excluding VAT line entirely.
          $item['callback'] = NULL;
        }
        else {
          // Show the subtotal excluding VAT line if any VAT was applied.
          $item['callback'] = 'uc_vat_line_item_tax_subtotal';
        }
        break;
    }
  }
}

/**
 * Handle tax on shipping using EU VAT rules.
 * Shipping tax is applied at the highest rate used in items in the order.
 */
function uc_vat_shipping_tax_adjustment_highest($price, $order, $current_tax) {
  $tax_rates = isset($order->data['taxes']) ? $order->data['taxes'] : uc_taxes_rate_load();
  $apply = FALSE;

  // Figure out whether the current rate is the highest rate on shippable items.
  foreach ($order->products as $item) {
    $node = node_load($item->nid);
    if ($node->shippable) {
      foreach ($tax_rates as $tax) {
        if (in_array($node->type, $tax->taxed_product_types) && ($tax->shippable == 0 || $node->shippable == 1)) {
          // Tax applies to this item.
          if ($tax->rate > $current_tax->rate) {
            // Bail out immediately, as we found a product with a higher tax rate.
            return 0;
          }
          if ($tax->id == $current_tax->id) {
            // Mark this tax to be applied (unless we find a higher one).
            $apply = TRUE;
          }
        }
      }
    }
  }

  return $apply ? ($price * $current_tax->rate) : 0;
}

/**
 * Handle tax on shipping using EU VAT rules.
 * Shipping tax is applied proportionally based on items in the order.
 */
function uc_vat_shipping_tax_adjustment_proportional($price, $order, $tax) {
  // Calculate subtotal of items with this tax rate, and total of all items.
  $subtotal = 0;
  $total = 0;
  foreach ($order->products as $item) {
    $node = node_load($item->nid);
    if ($node->shippable) {
      $total += $item->price * $item->qty;
      if (in_array($node->type, $tax->taxed_product_types) && ($tax->shippable == 0 || $node->shippable == 1)) {
        // Tax applies to this item.
        $subtotal += $item->price * $item->qty;
      }
    }
  }

  if ($total == 0) {
    return 0;
  }

  // Return proportional amount that applies to this tax rate.
  return $price * ($subtotal / $total) * $tax->rate;
}

/**
 * Callback for tax line item.
 *
 * @see uc_line_item_tax()
 */
function uc_vat_line_item_tax($op, $order) {
  switch ($op) {
    case 'load':
      $lines = array();
      $taxes = uc_vat_calculate_vat($order);
      foreach ($taxes as $tax) {
        $lines[] = array(
          'id' => ($tax->summed ? 'tax' : 'tax_included'),
          'title' => $tax->name,
          'amount' => $tax->amount,
          'weight' => variable_get('uc_li_tax_weight', 9) + $tax->weight / 10,
          'data' => $tax->data,
        );
      }
      return $lines;
  }

}

/**
* Implements hook_calculate_tax()
*/
function uc_vat_calculate_tax($order) {
  $taxes = uc_taxes_calculate_tax(drupal_clone($order));
  $vats = uc_vat_calculate_vat($order);
  foreach (array_keys($vats) as $id) {
    $vats[$id]->amount -= $taxes[$id]->amount;
  }
  return $vats;
}

/**
 * Calculate all taxes on an order using VAT rules.
 *
 * @see uc_taxes_calculate_tax()
 */
function uc_vat_calculate_vat($order) {
  global $user;
  if (is_numeric($order)) {
    $order = uc_order_load($order);
    $account = user_load(array('uid' => $order->uid));
  }
  elseif ((int)$order->uid) {
    $account = user_load(array('uid' => intval($order->uid)));
  }
  else {
    $account = $user;
  }
  if (!is_object($order)) {
    return array();
  }
  if (empty($order->delivery_postal_code)) {
    $order->delivery_postal_code = $order->billing_postal_code;
  }
  if (empty($order->delivery_zone)) {
    $order->delivery_zone = $order->billing_zone;
  }
  if (empty($order->delivery_country)) {
    $order->delivery_country = $order->billing_country;
  }

  $order->taxes = array();

  if (isset($order->order_status)) {
    $state = uc_order_status_data($order->order_status, 'state');
    $use_same_rates = in_array($state, array('payment_received', 'completed'));
  }
  else {
    $use_same_rates = FALSE;
  }

  $arguments = array(
    'order' => array(
      '#entity' => 'uc_order',
      '#title' => t('Order'),
      '#data' => $order,
    ),
    'tax' => array(
      '#entity' => 'tax',
      '#title' => t('Tax rule'),
      // #data => each $tax in the following foreach() loop;
    ),
    'account' => array(
      '#entity' => 'user',
      '#title' => t('User'),
      '#data' => $account,
    ),
  );

  $predicates = ca_load_trigger_predicates('calculate_taxes');
  foreach (uc_taxes_rate_load() as $tax) {
    if ($use_same_rates) {
      foreach ((array)$order->line_items as $old_line) {
        if ($old_line['type'] == 'tax' && $old_line['data']['tax_id'] == $tax->id) {
          $tax->rate = $old_line['data']['tax_rate'];
          break;
        }
      }
    }

    $arguments['tax']['#data'] = $tax;
    if (ca_evaluate_conditions($predicates['uc_taxes_'. $tax->id], $arguments)) {
      $line_item = uc_vat_apply_tax($order, $tax);
      if ($line_item) {
        $order->taxes[$line_item->id] = $line_item;
      }
    }
  }

  return $order->taxes;
}

/**
 * Apply a VAT tax to an order.
 *
 * @see uc_taxes_apply_tax()
 */
function uc_vat_apply_tax($order, $tax) {
  $taxable_amount = 0;
  if (is_array($order->products)) {
    foreach ($order->products as $item) {
      // We call our own function for applying taxes here, because we don't want to calculate a tax
      // based on a price altered by this module. If we don't do this, the calculated tax will be
      // based on a price inclusive tax.
      $taxable_amount += uc_vat_uc_taxes_apply_item_tax($item, $tax);
    }
  }
  $taxed_line_items = $tax->taxed_line_items;
  if (is_array($order->line_items) && is_array($taxed_line_items)) {
    foreach ($order->line_items as $key => $line_item) {
      // Special handling for modules that provide their own tax adjustments.
      $callback = _line_item_data($line_item['type'], 'tax_adjustment');
      if ($callback && function_exists($callback)) {
        $taxable_amount += $callback($line_item['amount'], $order, $tax) / $tax->rate;
        continue;
      }

      if ($line_item['type'] == 'tax') {
        // Don't tax old taxes.
        continue;
      }
      if (in_array($line_item['type'], $taxed_line_items)) {
        $taxable_amount += $line_item['amount'];
      }
    }
  }
  if (isset($taxed_line_items['tax'])) {
    // Tax taxes that were just calculated.
    foreach ($order->taxes as $other_tax) {
      $taxable_amount += $other_tax->amount;
    }
  }
  $amount = $taxable_amount * $tax->rate;
  if ($amount) {
    $line_item = (object)array(
      'id' => $tax->id,
      'name' => $tax->name,
      'amount' => $amount,
      'weight' => $tax->weight,
      'summed' => 1,
    );
    $line_item->data = array(
      'tax_id' => $tax->id,
      'tax_rate' => $tax->rate,
      'taxable_amount' => $taxable_amount,
      'tax_jurisdiction' => $tax->name,
    );
    return $line_item;
  }
}

/**
 * Calculates tax for a single product.
 *
 * This function is similar to uc_taxes_apply_item_tax(), but with one difference:
 * It set's an option called uc_vat to FALSE which means to this module that any
 * price altering by this module should be canceled.
 * If this module *does* do a price alter when applying taxes, then the tax amount
 * will be based on the tax inclusive price. And taxes should be based on the tax 
 * *exclusive* price of course!
 *
 * @param object $item
 * @param object $tax
 * @return float
 */
function uc_vat_uc_taxes_apply_item_tax($item, $tax) {
  $node = node_load($item->nid);

  // Special handling for manually added "Blank line" products.
  if (!$node) {
    $node = new stdClass();
    $node->type = 'blank-line';
    $node->shippable = $item->weight > 0;
  }

  // Tax products if they are of a taxed type and if it is shippable if
  // the tax only applies to shippable products.
  if (in_array($node->type, $tax->taxed_product_types) && ($tax->shippable == 0 || $node->shippable == 1)) {
    $context = array(
      'revision' => 'altered',
      'type' => 'cart_item',
      'subject' => array(
        'cart_item' => $item,
        'node' => $item->nid ? $node : FALSE,
      ),
    );
    $price_info = array(
      'price' => $item->price,
      'qty' => $item->qty,
    );

    // Calculate price, but bypass any alterations normally done in uc_vat.
    return uc_price($price_info, $context, $options = array('uc_vat' => FALSE));
  }
}

/**
 * Callback for "subtotal excluding VAT" line item.
 */
function uc_vat_line_item_tax_subtotal($op, $order) {
  $amount = 0;
  if (is_array($order->products)) {
    foreach ($order->products as $item) {
      $amount += $item->price * $item->qty;
    }
  }
  if (is_array($order->line_items)) {
    foreach ($order->line_items as $key => $line_item) {
      if ($line_item['type'] == 'tax') {
        $has_taxes = TRUE;
      }
      if (_line_item_data($line_item['type'], 'calculated') == TRUE) {
        $amount += $line_item['amount'];
      }
    }
  }
  if (is_array($order->taxes)) {
    $has_taxes = TRUE;
  }
  if ($has_taxes) {
    switch ($op) {
      case 'cart-preview':
        drupal_add_js("if (Drupal.jsEnabled) { \$(document).ready(function() {
          if (window.set_line_item) {
            set_line_item('tax_subtotal', '". t('Subtotal excluding !tax', array('!tax' => variable_get('uc_vat_name', 'VAT'))) ."', ". $amount .", ". variable_get('uc_li_tax_subtotal_weight', 8) .");
          }
        })};", 'inline');
      break;
      case 'load':
        return array(array(
          'id' => 'tax_subtotal',
          'title' => t('Subtotal excluding !tax', array('!tax' => variable_get('uc_vat_name', 'VAT'))),
          'amount' => $amount,
          'weight' => variable_get('uc_li_tax_subtotal_weight', 7),
        ));
    }
  }
}

/**
 * Implementation of hook_line_item_alter().
 */
function uc_vat_line_item_alter(&$item, $order) {
  // If we are hiding the exclusive subtotal, add prefix and move to the bottom of the list.
  if (is_array($item) && $item['type'] == 'tax' && variable_get('uc_vat_hide_checkout_exclusive', FALSE)) {
    $item['title'] = t('incl. !tax', array('!tax' => $item['title']));
    $item['weight'] = 16;
  }
}

/**
 * AJAX callback for order preview, overridden from uc_taxes.
 *
 * Calculate tax amounts for an order in the payment checkout pane.
 */
function uc_vat_uc_taxes_javascript() {
  $order = $_POST['order'];
  if ($order = unserialize(rawurldecode($order))) {
    $taxes = uc_vat_calculate_vat($order);

    // Add incl. to tax line items if we are hiding the exclusive subtotal.
    if (variable_get('uc_vat_hide_checkout_exclusive', FALSE)) {
      foreach ($taxes as $id => $tax) {
        $taxes[$id]->name = t('incl. !tax', array('!tax' => $tax->name));
      }
    }

    $callback = _line_item_data('tax_subtotal', 'callback');
    if (function_exists($callback)) {
      $subtotal = $callback('load', $order);
      if (is_array($subtotal) && !empty($taxes)) {
        $taxes['subtotal'] = (object)array(
          'id' => 'subtotal',
          'name' => $subtotal[0]['title'],
          'amount' => $subtotal[0]['amount'],
          'weight' => -10,
          'summed' => 0,
        );
      }
    }
  }
  drupal_json((array) $taxes);
}

/**
 * Implementation of hook_cart_pane_alter().
 */
function uc_vat_cart_pane_alter(&$panes) {
  if (uc_cart_is_shippable() && variable_get('uc_vat_suffix_shipping', FALSE)) {
    foreach ($panes as &$pane) {
      if ($pane['id'] == 'cart_form') {
        $pane['body'] = str_replace('<div id="cart-form-buttons">', theme('uc_vat_excluding_shipping_costs', 'div') . '<div id="cart-form-buttons">', $pane['body']);
      }
    }
  }
}

/**
 * Implementation of hook_tapir_table_alter().
 */
function uc_vat_tapir_table_alter(&$table, $table_id) {
  if ($table_id == 'uc_cart_view_table' && variable_get('uc_vat_show_cart_vat', FALSE) && !uc_vat_exclude_vat()) {
    uc_vat_uc_cart_view_table_alter($table);
  }
}

/**
 * Add VAT subtotals to cart table.
 */
function uc_vat_uc_cart_view_table_alter(&$table) {
  $taxes = uc_vat_load_taxes();
  $cart = uc_cart_get_contents();

  $subtotal = 0;
  $tax_subtotals = array();
  $extra_rows = array();

  foreach (element_children($table) as $i) {
    if (isset($table[$i]['#total'])) {
      $node = node_load($table[$i]['nid']['#value']);
      if ($node) {
        $subtotal += $table[$i]['#total'];
        foreach ($taxes as $id => $tax) {
          if (in_array($node->type, $tax->taxed_product_types) && ($tax->shippable == 0 || $node->shippable == 1)) {
            if (!isset($tax_subtotals[$id])) {
              $tax_subtotals[$id] = 0;
            }
            $tax_subtotals[$id] += $table[$i]['#total'] - $table[$i]['#total'] / (1 + $tax->rate);
          }
        }

        // Product_kits special handling: check through product_kits
        if ($node->type == 'product_kit' && is_array($node->products)) {
          foreach ($node->products as $pk_nid => $pk_node) {
            if (in_array($pk_node->type, $tax->taxed_product_types) && ($tax->shippable == 0 || $pk_node->shippable == 1)) {
              $tax_subtotal += ($pk_node->sell_price+$pk_node->discount) * $pk_node->qty * $table[$i]['qty']['#default_value'] * ($tax->rate);
            }
          }
        }

      }
      else {
        // No node data means no tax information available, so move this line to after the tax summary.
        $extra_rows[] = $table[$i];
        unset($table[$i]);
      }
    }
    else {
      unset($table[$i]);
    }
  }

  $context = array(
    'revision' => 'themed-original',
    'type' => 'amount',
  );

  if ($tax_subtotals && !variable_get('uc_vat_hide_checkout_exclusive', FALSE)) {
    $table[] = array(
      'total' => array(
        '#value' => '<strong>'. t('Subtotal excluding !tax', array('!tax' => variable_get('uc_vat_name', 'VAT'))) .':</strong> '. uc_price($subtotal - array_sum($tax_subtotals), $context),
        '#cell_attributes' => array(
          'colspan' => 'full',
          'align' => 'right',
          'class' => 'subtotal excl-vat',
        ),
      ),
    );
  }

  foreach ($taxes as $id => $tax) {
    if ($tax_subtotals[$id]) {
      $tax_name = variable_get('uc_vat_hide_checkout_exclusive', FALSE) ? t('incl. !tax', array('!tax' => $tax->name)) : $tax->name;
      $table[] = array(
        'total' => array(
          '#value' => '<strong>'. $tax_name .':</strong> '. uc_price($tax_subtotals[$id], $context),
          '#cell_attributes' => array(
            'colspan' => 'full',
            'align' => 'right',
            'class' => 'subtotal vat',
          ),
        ),
      );
    }
  }

  // Rebuild the original "subtotal" line.
  $table[] = array(
    'total' => array(
      '#value' => '<strong>'. t('Subtotal') .':</strong> '. uc_price($subtotal, $context),
      '#cell_attributes' => array(
        'colspan' => 'full',
        'align' => 'right',
        'class' => 'subtotal',
      ),
    ),
  );

  // Add in extra rows that have no tax information available.
  if ($extra_rows) {
    $table = array_merge($table, $extra_rows);
    foreach ($extra_rows as $row) {
      $subtotal += $row['#total'];
    }

    $table[] = array(
      'total' => array(
        '#value' => '<strong>'. t('Total') .':</strong> '. uc_price($subtotal, $context),
        '#cell_attributes' => array(
          'colspan' => 'full',
          'align' => 'right',
          'class' => 'subtotal',
        ),
      ),
    );
  }
}

/**
 * Implementation of hook_checkout_pane_alter().
 */
function uc_vat_checkout_pane_alter(&$panes) {
  if (variable_get('uc_vat_show_cart_vat', FALSE) || variable_get('uc_vat_show_cart_columns', FALSE)) {
    foreach ($panes as &$pane) {
      if ($pane['id'] == 'cart') {
        $pane['callback'] = 'uc_checkout_pane_cart_vat';
      }
    }
  }
}

/**
 * Checkout cart pane callback.
 */
function uc_checkout_pane_cart_vat($op, &$arg1, $arg2) {
  switch ($op) {
    case 'view':
      drupal_add_js('misc/progress.js');
      drupal_add_js(drupal_get_path('module', 'uc_vat') .'/uc_vat.js');
      drupal_add_js(array(
        'ucURL' => array(
          'updateCartPane' => url('cart/checkout/cart_pane'),
        ),
      ), 'setting');

      $contents['cart'] = array(
        '#value' => '<div></div>',
      );
      if (uc_cart_is_shippable() && variable_get('uc_vat_suffix_shipping', FALSE)) {
        $contents['cart']['#suffix'] = theme('uc_vat_excluding_shipping_costs', 'div');
      }

      return array('contents' => $contents, 'next-button' => FALSE);

    case 'review':
      $output = '<table>';
      $context = array(
        'revision' => 'themed',
        'type' => 'order_product',
        'subject' => array(),
      );
      foreach ($arg1->products as $item) {
        $desc = check_plain($item->title) . uc_product_get_description($item);

        $price_info = array(
          'price' => $item->price,
          'qty' => $item->qty,
        );
        $context['subject'] = array(
          'order' => $arg1,
          'product' => $item,
          'node' => node_load($item->nid),
        );
        $output .= '<tr valign="top"><td>'. $item->qty .'&times;</td><td width="100%">'. $desc
                  .'</td><td nowrap="nowrap">'. uc_price($price_info, $context) .'</td></tr>';
      }
      $output .= '</table>';
      $review[] = $output;
      return $review;
  }
}

/**
 * AJAX callback to update checkout cart pane.
 */
function uc_vat_update_cart_pane() {
  $data = array();
  if ($order = unserialize(rawurldecode($_POST['order']))) {
    $data['cart'] = theme('uc_vat_cart_review_table', TRUE, $order);
  }
  drupal_json($data);
}

/**
 * Return a formatted list of line items for an order total preview.
 *
 * @see uc_payment_get_totals()
 */
function uc_vat_uc_payment_get_totals() {
  if (!variable_get('uc_vat_show_cart_columns', FALSE) || uc_vat_exclude_vat()) {
    uc_payment_get_totals();
    exit;
  }
 
  $order = unserialize($_POST['order']);
  if (!$order) {
    return '';
  }

  usort($order->line_items, 'uc_weight_sort');

  $context = array(
    'revision' => 'altered',
    'subject' => array(
      'order' => $order,
    ),
  );

  $header = array(
    array(
      'data' => t('Price excl. !tax', array('!tax' => variable_get('uc_vat_name', 'VAT'))),
      'style' => 'text-align:right;',
      'colspan' => 2.
    ),
    array(
      'data' => t('!tax', array('!tax' => variable_get('uc_vat_name', 'VAT'))),
      'style' => 'text-align:right;',
    ),
    array(
      'data' => t('Total'),
      'style' => 'text-align:right;',
    ),
  );

  $rows = array();
  $total = 0;
  $altered_total = 0;
  $include_summary = FALSE;
  foreach ($order->line_items as $line) {
    if (!$line['summed'] || $line['type'] == 'tax') {
      continue;
    }

    // Show a summary if this line item is non-negative and there was a previous discount line item.
    if ($include_summary && $line['amount'] >= 0) {
      $rows[] = array(array('data' => '<hr />', 'colspan' => 4));
      $rows[] = $summary_row;
    }

    if ($line['type'] == 'subtotal') {
      // Recalculate order subtotal, as the supplied value already includes VAT.
      // (this is a bug in uc_order, but we can only work around it)
      $context['type'] = 'order_product';
      $line['amount'] = 0;
      $altered = 0;
      foreach ($order->products as $item) {
        $context['subject']['product'] = $item;
        $context['subject']['node'] = node_load($item->nid);
        $price = uc_price($item->price * $item->qty, $context);

        $line['amount'] += $item->price * $item->qty;
        $altered += $price;
      }
    }
    else {
      $context['type'] = 'line_item';
      $context['subject']['line_item'] = $line;
      $altered = uc_price($line['amount'], $context);
    }

    $rows[] = array(
      array('data' => '<b>' . check_plain($line['title']) . ':</b>', 'align' => 'right'),
      array('data' => uc_currency_format($line['amount']), 'align' => 'right'),
      array('data' => uc_currency_format($altered - $line['amount']), 'align' => 'right'),
      array('data' => uc_currency_format($altered), 'align' => 'right'),
    );

    $total += $line['amount'];
    $altered_total += $altered;

    // If this line item is a discount, remember it to use as a summary, if there is another
    // non-negative item below.
    if ($line['amount'] < 0) {
      $summary_row = array(
        array('data' => uc_currency_format($total), 'align' => 'right', 'colspan' => 2),
        array('data' => uc_currency_format($altered_total - $total), 'align' => 'right'),
        array('data' => uc_currency_format($altered_total), 'align' => 'right'),
      );
      $include_summary = TRUE;
    }
    else {
      $include_summary = FALSE;
    }
  }

  $rows[] = array(
    array('data' => '<b>' . t('Order total:') . '</b>', 'align' => 'right'),
    array('data' => uc_currency_format($total), 'align' => 'right'),
    array('data' => uc_currency_format($altered_total - $total), 'align' => 'right'),
    array('data' => uc_currency_format($altered_total), 'align' => 'right'),
  );

  $output = theme('table', $header, $rows);

  // Ugly hack to remove zebra stripes from the table.
  $output = str_replace(array('class="odd"', 'class="even"'), '', $output);

  print t('Order total preview:') .' <span id="order-total-throbber"></span>';
  print $output;
  exit;
}

/**
 * "Show prices excluding VAT" permission helper function.
 */
function uc_vat_exclude_vat() {
  global $user;
  return $user->uid == 1 ? variable_get('uc_vat_exclude_superuser', FALSE) : user_access('show prices excluding VAT');
}

/**
 * Helper function to determine which product fields should be edited VAT inclusive.
 */
function _uc_vat_product_fields() {
  $fields = array(
    'list_price' => variable_get('uc_vat_list_price_inclusive', FALSE),
    'cost' => variable_get('uc_vat_cost_inclusive', FALSE),
    'sell_price' => variable_get('uc_vat_sell_price_inclusive', FALSE),
  );
  return array_keys(array_filter($fields));
}

/**
 * Helper function to determine which attribute fields should be edited VAT inclusive.
 */
function _uc_vat_attribute_fields() {
  $fields = array(
    'cost' => variable_get('uc_vat_cost_inclusive', FALSE),
    'price' => variable_get('uc_vat_sell_price_inclusive', FALSE),
  );
  return array_keys(array_filter($fields));
}

/**
 * Implementation of hook_views_api().
 */
function uc_vat_views_api() {
  return array(
    'api' => '2.0',
  );
}

/**
 * Implementation of hook_views_data_alter().
 */
function uc_vat_views_data_alter(&$data) {
  foreach (array('list_price', 'cost', 'sell_price') as $field) {
    $data['uc_products'][$field]['field']['handler'] = 'uc_vat_handler_field_price';
  }
}

/**
 * Implementation of hook_views_handlers().
 */
function uc_vat_views_handlers() {
  return array(
    'handlers' => array(
      'uc_vat_handler_field_price' => array(
        'parent' => 'uc_product_handler_field_price',
      ),
    ),
  );
}