/app/code/core/Mage/Payment/Block/Form/Container.php

<?php
/**
 * Magento
 *
 * NOTICE OF LICENSE
 *
 * This source file is subject to the Open Software License (OSL 3.0)
 * that is bundled with this package in the file LICENSE.txt.
 * It is also available through the world-wide-web at this URL:
 * http://opensource.org/licenses/osl-3.0.php
 * If you did not receive a copy of the license and are unable to
 * obtain it through the world-wide-web, please send an email
 * to license@magentocommerce.com so we can send you a copy immediately.
 *
 * DISCLAIMER
 *
 * Do not edit or add to this file if you wish to upgrade Magento to newer
 * versions in the future. If you wish to customize Magento for your
 * needs please refer to http://www.magentocommerce.com for more information.
 *
 * @category    Mage
 * @package     Mage_Payment
 * @copyright   Copyright (c) 2010 Magento Inc. (http://www.magentocommerce.com)
 * @license     http://opensource.org/licenses/osl-3.0.php  Open Software License (OSL 3.0)
 */

/**
 * Base container block for payment methods forms
 *
 * @category   Mage
 * @package    Mage_Payment
 * @author      Magento Core Team <core@magentocommerce.com>
 */
class Mage_Payment_Block_Form_Container extends Mage_Core_Block_Template
{
    /**
     * Prepare children blocks
     */
    protected function _prepareLayout()
    {
        /**
         * Create child blocks for payment methods forms
         */
        foreach ($this->getMethods() as $method) {
            $this->setChild(
               'payment.method.'.$method->getCode(),
               $this->helper('payment')->getMethodFormBlock($method)
            );
        }

        return parent::_prepareLayout();
    }

    protected function _canUseMethod($method)
    {
        if (!$method->canUseForCountry($this->getQuote()->getBillingAddress()->getCountry())) {
            return false;
        }

        if (!$method->canUseForCurrency(Mage::app()->getStore()->getBaseCurrencyCode())) {
            return false;
        }

        /**
         * Checking for min/max order total for assigned payment method
         */
        $total = $this->getQuote()->getBaseGrandTotal();
        $minTotal = $method->getConfigData('min_order_total');
        $maxTotal = $method->getConfigData('max_order_total');

        if((!empty($minTotal) && ($total < $minTotal)) || (!empty($maxTotal) && ($total > $maxTotal))) {
            return false;
        }
        return true;
    }

    /**
     * Check and prepare payment method model
     *
     * Redeclare this method in child classes for declaring method info instance
     *
     * @return bool
     */
    protected function _assignMethod($method)
    {
        $method->setInfoInstance($this->getQuote()->getPayment());
        return $this;
    }

    /**
     * Declare template for payment method form block
     *
     * @param   string $method
     * @param   string $template
     * @return  Mage_Payment_Block_Form_Container
     */
    public function setMethodFormTemplate($method='', $template='')
    {
        if (!empty($method) && !empty($template)) {
            if ($block = $this->getChild('payment.method.'.$method)) {
                $block->setTemplate($template);
            }
        }
        return $this;
    }

    /**
     * Retrieve availale payment methods
     *
     * @return array
     */
    public function getMethods()
    {
        $methods = $this->getData('methods');
        if (is_null($methods)) {
            $quote = $this->getQuote();
            $store = $quote ? $quote->getStoreId() : null;
            $methods = $this->helper('payment')->getStoreMethods($store, $quote);
            $total = $quote->getBaseSubtotal();
            foreach ($methods as $key => $method) {
                if ($this->_canUseMethod($method)
                    && ($total != 0
                        || $method->getCode() == 'free'
                        || ($quote->hasRecurringItems() && $method->canManageRecurringProfiles()))) {
                    $this->_assignMethod($method);
                } else {
                    unset($methods[$key]);
                }
            }
            $this->setData('methods', $methods);
        }
        return $methods;
    }

    /**
     * Retrieve code of current payment method
     *
     * @return mixed
     */
    public function getSelectedMethodCode()
    {
        $methods = $this->getMethods();
        if (!empty($methods)) {
            reset($methods);
            return current($methods)->getCode();
        }
        return false;
    }
}