Drupal Commerce Discount - amount

<?php

function commerce_discounts_commerce_tax_type_calculate_rates($tax_type, $line_item) {
  // An implementation might contact a web service and apply the tax to the unit
  // price of the line item based on the returned data.

  dsm($tax_type, 'taxtype');
  if ($tax_type['name'] == 'discount' ) {

     global $user;
     $order = commerce_cart_order_load($user->uid);
     dsm($order->commerce_order_total['und'][0]['amount'], 'order commerce order total - amount');
     dsm($order, 'order');
     $discount_rate = commerce_discounts_get_rate($order->commerce_order_total['und'][0]['data']['components'][0]['price']['amount']);
     dsm($line_item, '$line_item');
     if ($discount_rate) {
       $item_base_price = $line_item->commerce_unit_price['und'][0]['amount'];
       $amount_discount = $item_base_price * $discount_rate;
       dsm('$item_base_price = ' . $item_base_price . ' $discount_rate=' . $discount_rate . ' $amount_discount=' . $amount_discount);
       $line_item->commerce_unit_price['und'][0]['data']['components'][] = array(
           'name' => 'tax|discount_7_',
           'price' => array(
               'amount' => $amount_discount,
               'currency_code' => 'USD',
               'data' => array(
                   'tax_name' => array(
                       'name' => 'discount_7_',
                       'display_title' => 'Discount 7%',
                       'rate' => -0.07,
                       'price_component' => 'tax|discount_7_',
                       'calculation_callback ' => 'commerce_tax_rate_calculate',
                       'module' => 'commerce_tax_ui',
                       'title' => 'Discount 7%',
                   ),
               ),
           ),
           'included' => FALSE,
       );
     }
     dsm($line_item, '$line_item2');
     //dsm($line_item['commerce_total']['und'][0]->amount, '$line_item');
     dsm($line_item->commerce_total['und']['0']['amount'], '$line_item3');
  }
  dsm($tax_type, 'taxtype2');
}


/**
 * Get discount rate based on amount.
 * @param type $amount
 * @return type
 */
function commerce_discounts_get_rate($amount) {
  // @TODO
  $discount = 0;
  if ($amount >= 6000 && $amount < 12000) {
    $discount = -0.07;
  }
  else if ($amount >= 12000 && $amount < 35000) {
    $discount = -0.15;
  }
  else if ($amount >= 35000) {
    $discount = -0.20;
  }
  return $discount;
}