Magento Add Cancel link on order list page (frontend)

1. rewrite in config.xml:

<config>   
    <helpers>
      <mysales>
        <class>Bysoft_Mysales_Helper</class>
      </mysales>
    </helpers>
    <frontend>
        <routers>
            <mysales>
                <use>standard</use>
                <args>
                    <module>Bysoft_Mysales</module>
                    <frontName>mysales</frontName>
                </args>
            </mysales>
            <sales>
	            <args>
	                <modules>
	                    <Bysoft_Mysales before="Mage_Sales">Bysoft_Mysales</Bysoft_Mysales>
	                </modules>
	            </args>
        </sales>
        </routers>  
    </frontend>
</config> 

 

rewrite core sales order controller:

<?php
require_once Mage::getModuleDir('controllers', 'Mage_Sales').DS.'OrderController.php';
class Bysoft_Mysales_OrderController extends Mage_Sales_OrderController {
	public function cancelAction()
	{

		// Retrieve order_id passed by clicking on "Cancel Order" in customer account
		$orderId = $this->getRequest()->getParam('id');
		
		// Load Mage_Sales_Model_Order object
		$order = Mage::getModel('sales/order')->load($orderId);
		
		// Retrieve catalog session.
		// We must use catalog session as customer session messages are not initiated for sales order view
		// and this is where we want to redirect at the end of this action
		// @see Mage_Sales_Controller_Abstract::_viewAction()
		$session = Mage::getSingleton('catalog/session');
		
		try {
		
			// Make sure that the order can still be canceled since customer clicked on "Cancel Order"
			if(!Mage::helper('mysales')->canCancel($order)) {
				throw new Exception('Order cannot be canceled anymore.');
			}
		
			// Cancel and save the order
			$order->cancel();
			$order->save();
		
			// If sending transactionnal email is enabled in system configuration, we send the email
			if(Mage::getStoreConfigFlag('sales/cancel/send_email')) {
				$order->sendOrderUpdateEmail();
			}
		
			$session->addSuccess($this->__('The order has been canceled.'));
		}
		catch (Exception $e) {
			Mage::logException($e);
			$session->addError($this->__('The order cannot be canceled.'));
		}
		
		// Redirect to current sale order view
		$this->_redirect('sales/order/history');
	}
}

 Helper file for checking if the order can be canceled:

<?php
class Bysoft_Mysales_Helper_Data extends Mage_Core_Helper_Abstract
{
	public function canCancel(Mage_Sales_Model_Order $order)
	{

	
		// If Magento decides that this order cannot be canceled
		if(!$order->canCancel()) {
			return false;
		}
	
	
	
		// Else... return true
		return true;
	}
}
	 

 Add link to template file:

 <?php if (Mage::helper('mysales')->canCancel($_order)):?>
       <span class="separator">|</span> 
        <a href="<?php echo $this->getUrl('sales/order/cancel', array('id'=>$_order->getId()));?>" class="link-cancel"><?php echo $this->__('Cancel') ?>
        </a>                        
  <?php endif;?>