<?xml version="1.0"?>
<config>
 <modules>
   <Eyemagine_Taxbycity>
     <version>0.1.0</version>
   </Eyemagine_Taxbycity>
 </modules>
 <global>
   <resources>
     <taxbycity_setup>
       <setup>
         <module>Eyemagine_Taxbycity</module>
       </setup>
       <connection>
         <use>core_setup</use>
       </connection>
     </taxbycity_setup>
   </resources>
   <models>
     <tax>
       <rewrite>
         <calculation>Eyemagine_Taxbycity_Model_Calculation</calculation>
       </rewrite>
     </tax>
     <tax_mysql4>
       <rewrite>
         <calculation>Eyemagine_Taxbycity_Model_Mysql4_Calculation</calculation>
       </rewrite>
     </tax_mysql4>
   </models>
 </global>
</config>

/**
 * mysql-install-0.1.0.php
 * @author EyeMagine
 */
/* @var $this Mage_Core_Model_Resource_Setup */
$installer  = $this;
$db         = $installer->getConnection();
$installer->startSetup();
$installer->run("
ALTER TABLE {$installer->getTable('tax_calculation_rate')} CHANGE `tax_postcode` `tax_postcode` VARCHAR( 32 ) NOT NULL
");

/**
 * Calculation.php
 * @author EyeMagine
 *
 */
/**
 * Overload the tax calculation class
 * @author EyeMagine
 *
 */
class Eyemagine_Taxbycity_Model_Calculation extends Mage_Tax_Model_Calculation
{
    /**
     * override the getRateRequest to add the city information to the request
     * @see Mage_Tax_Model_Calculation::getRateRequest
     */
    public function getRateRequest($shippingAddress = null, $billingAddress = null, $customerTaxClass = null, $store = null)
    {
        $address = new Varien_Object();
        $session = Mage::getSingleton('customer/session');
        $basedOn = Mage::getStoreConfig(Mage_Tax_Model_Config::CONFIG_XML_PATH_BASED_ON, $store);
        if (($shippingAddress === false && $basedOn == 'shipping') || ($billingAddress === false && $basedOn == 'billing')) {
            $basedOn = 'default';
        } else {
            if ((($billingAddress === false || is_null($billingAddress) || !$billingAddress->getCountryId()) && $basedOn == 'billing') || (($shippingAddress === false || is_null($shippingAddress) || !$shippingAddress->getCountryId()) && $basedOn == 'shipping')){
                if (!$session->isLoggedIn()) {
                    $basedOn = 'default';
                } else {
                    $defBilling = $session->getCustomer()->getDefaultBillingAddress();
                    $defShipping = $session->getCustomer()->getDefaultShippingAddress();
 
                    if ($basedOn == 'billing' && $defBilling && $defBilling->getCountryId()) {
                        $billingAddress = $defBilling;
                    } else if ($basedOn == 'shipping' && $defShipping && $defShipping->getCountryId()) {
                        $shippingAddress = $defShipping;
                    } else {
                        $basedOn = 'default';
                    }
                }
            }
        }
 
        switch ($basedOn) {
            case 'billing':
                $address = $billingAddress;
                break;
 
            case 'shipping':
                $address = $shippingAddress;
                break;
 
            case 'origin':
                $address
                    ->setCountryId(Mage::getStoreConfig('shipping/origin/country_id', $store))
                    ->setRegionId(Mage::getStoreConfig('shipping/origin/region_id', $store))
                    ->setPostcode(Mage::getStoreConfig('shipping/origin/postcode', $store));
                break;
 
            case 'default':
                $address
                    ->setCountryId(Mage::getStoreConfig(Mage_Tax_Model_Config::CONFIG_XML_PATH_DEFAULT_COUNTRY, $store))
                    ->setRegionId(Mage::getStoreConfig(Mage_Tax_Model_Config::CONFIG_XML_PATH_DEFAULT_REGION, $store))
                    ->setPostcode(Mage::getStoreConfig(Mage_Tax_Model_Config::CONFIG_XML_PATH_DEFAULT_POSTCODE, $store));
                break;
        }
 
        if (is_null($customerTaxClass) && $session->isLoggedIn()) {
            $customerTaxClass = $session->getCustomer()->getTaxClassId();
        } elseif (($customerTaxClass === false) || !$session->isLoggedIn()) {
            $defaultCustomerGroup = Mage::getStoreConfig('customer/create_account/default_group', $store);
            $customerTaxClass = Mage::getModel('customer/group')->getTaxClassId($defaultCustomerGroup);
        }
        $request = new Varien_Object();
        $request
            ->setCountryId($address->getCountryId())
            ->setRegionId($address->getRegionId())
            ->setPostcode($address->getPostcode())
            ->setStore($store)
            ->setCustomerClassId($customerTaxClass)
            ->setCity($address->getCity());
        return $request;
    }
}

/**
 * Calculation.php
 * @author EyeMagine
 *
 */
/**
 * Overload the mysql4 calculation class
 * @author EyeMagine
 *
 */
class Eyemagine_Taxbycity_Model_Mysql4_Calculation extends Mage_Tax_Model_Mysql4_Calculation
{
    /**
     * override getRates method to add city to where clause
     * @see Mage_Tax_Model_Mysql4_Calculation::_getRates
     */
    protected function _getRates($request)
    {
        $storeId = Mage::app()->getStore($request->getStore())->getId();
 
        $select = $this->_getReadAdapter()->select();
        $select
            ->from(array('main_table'=>$this->getMainTable()))
            ->where('customer_tax_class_id = ?', $request->getCustomerClassId())
            ->where('product_tax_class_id = ?', $request->getProductClassId());
 
        $select->join(array('rule'=>$this->getTable('tax/tax_calculation_rule')), 'rule.tax_calculation_rule_id = main_table.tax_calculation_rule_id', array('rule.priority', 'rule.position'));
        $select->join(array('rate'=>$this->getTable('tax/tax_calculation_rate')), 'rate.tax_calculation_rate_id = main_table.tax_calculation_rate_id', array('value'=>'rate.rate', 'rate.tax_country_id', 'rate.tax_region_id', 'rate.tax_postcode', 'rate.tax_calculation_rate_id', 'rate.code'));
 
        $select
            ->where("rate.tax_country_id = ?", $request->getCountryId())
            ->where("rate.tax_region_id in ('*', '', ?)", $request->getRegionId());
        $city = $request->getCity();
        if (!empty($city)) {//add city only if we know we have it, default to old behavior otherwise
            $select->where("LOWER(rate.tax_postcode) in ('*', '', ?)", array($request->getPostcode(),strtolower($request->getCity())));
        } else {
            $select->where("rate.tax_postcode in ('*', '', ?)", $request->getPostcode());
        }
 
        $select->joinLeft(array('title_table'=>$this->getTable('tax/tax_calculation_rate_title')), "rate.tax_calculation_rate_id = title_table.tax_calculation_rate_id AND title_table.store_id = '{$storeId}'", array('title'=>'IFNULL(title_table.value, rate.code)'));
 
        $order = array('rule.priority ASC', 'rule.tax_calculation_rule_id ASC', 'rate.tax_country_id DESC', 'rate.tax_region_id DESC', 'rate.tax_postcode DESC', 'rate.rate DESC');
        $select->order($order);
 
        return $this->_getReadAdapter()->fetchAll($select);
    }
}