[-] BO: FIX #PSCFV-5088 - cant add a tax rule to a group if one have already defined as unique

classes/tax/TaxRule.php

@@ -89,7 +89,9 @@ class TaxRuleCore extends ObjectModel
 				 t.`rate`,
 				 g.`zipcode_from`, g.`zipcode_to`,
 				 g.`description`,
-				 g.`behavior`
+				 g.`behavior`,
+				 g.`id_country`,
+				 g.`id_state`
 		FROM `'._DB_PREFIX_.'tax_rule` g
 		LEFT JOIN `'._DB_PREFIX_.'country_lang` c ON (g.`id_country` = c.`id_country` AND `id_lang` = '.(int)$id_lang.')
 		LEFT JOIN `'._DB_PREFIX_.'state` s ON (g.`id_state` = s.`id_state`)

classes/tax/TaxRulesGroup.php

@@ -113,6 +113,16 @@ class TaxRulesGroupCore extends ObjectModel
 	    WHERE `name` = \''.pSQL($name).'\''
 	    );
 	}
+	
+	public function hasUniqueTaxRuleForCountry($id_country, $id_state)
+	{
+		$rules = TaxRule::getTaxRulesByGroupId((int)Context::getContext()->language->id, (int)$this->id);
+		foreach ($rules as $rule)
+			if ($rule['id_country'] == $id_country && $id_state == $rule['id_state'] && !$rule['behavior'])
+				return true;
+
+		return false;
+	}
 
 	/**
 	* @deprecated since 1.5