First commit

README.md

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+# Tax framework for the SilverStripe Shop module
+
+Tax is a fee that a merchant collects from the customer by law for the government. Some governments have
+different tax rates for different kinds of products.
+
+Different countries, and governing sub-regions have different laws for tax collection. Some sub-regions
+charge taxes on top of their parent region tax, so the tax is 'compounding'.
+
+Tax can be a complex thing to calculate. Different combinations of factors need to be taken into account:
+
+ * Locality / sub-locality of:
+ 	* Merchant
+ 	* Delivery
+ 	* Customer
+ * Type of product being sold
+ * Value of product
+ * Value of shipping
+
+Because tax can be different per product, then we need to work out tax on a per-product basis. Total tax
+can be displayed at the checkout. Tax could also be displayed on product pages.
+
+### US Tax system
+
+The US taxation system is one where state has it's own tax rate. At the time of writing New York state tax rate 
+is 8.875%. New Jersey is 7%. Connecticut is 6.35%, and so on. 50 states, 50 different tax rates.
+If a merchant residing in New York is selling to a customer residing in New York, then the merchant collect 
+New York sales tax. If the merchant is selling to any other state, they do not need to collect any sales tax,
+as it becomes the buyer's responsibility to report the purchase at the end of the year when preparing their 
+year-end taxes.
+
+## Inclusive or exclusive
+
+Sometimes you want to include tax in pricing, but still display the amount of tax being charged. Otherwise
+tax should be displayed, and added on top of the amount being taxed.
+
+## Compounding tax
+
+Compounding tax is where a sub-locality (county) tax rate, is added to it's parent locality (state) rate.
+You can manually add parent locality rates to sub-locality and store as a combined rate.
+
+## Model
+
+ * TaxClass - type of tax, and whether it is the default. Each product, and shipping method has a tax class.
+  * TaxRate - region(s) to apply tax to, their corresponding rates, priority, name and whether it should be compounding
+ * TaxFrameworkModifier - applies tax to order
+
+# Configuration options
+
+ * Base tax on billing address instead of shipping
+
+## Provided data
+
+Potentially the tax system could be pre-populated with data from a data source.
+
+## Questions to be answered:
+
+How is tax applied to products being sold to customers overseas?
+
+## Client requirement:
+
+Our end goal is to have the tax added, based on the state/region selected from a drop-down.
+In the case of the U.S., there are 50 states, so somehow we'd need to manage the tax rate for each state.
+In our current usage, we're only really interested in collecting sales tax if the product ships within the state of New York.
+All other states would be 0 tax collected.

_config.php

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+<?php
+
+Object::add_extension("Product", "TaxedProductDecorator");
+Object::add_extension("PopulateShopTask", "PopulateShopTaxClassesTask");

code/TaxFrameworkModifier.php

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+<?php
+
+class TaxFrameworkModifier extends OrderModifier{
+
+	public static $singular_name = "Tax";
+	function i18n_singular_name() {
+		return _t("TaxModifier.SINGULAR", self::$singular_name);
+	}
+	public static $plural_name = "Taxes";
+	function i18n_plural_name() {
+		return _t("TaxModifier.PLURAL", self::$plural_name);
+	}
+
+	/**
+	 * TODO: reduce the number of database calls
+	 */
+	function value($incoming){
+		$order = $this->Order();
+		$value = 0;
+		if($order && $address = $order->ShippingAddress()){
+			$defaultclass = DataObject::get_one("TaxClass","\"Default\" = 1"); //get default rate
+			//sum taxe rates
+			foreach($order->Items() as $item){
+				$taxclass = ($item->Product()->TaxClass()->exists()) ? $item->Product()->TaxClass() : $defaultclass;
+				if($taxclass && $rate = $taxclass->getRate($address)){
+					$value += $item->Total() * $rate; //tax is total x rate
+				}
+			}
+		}
+		return $value;
+	}
+
+}

code/cms/TaxAdmin.php

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+<?php
+
+class TaxAdmin extends ModelAdmin{
+
+	static $url_segment = "tax";
+	static $menu_title = "Tax";
+
+	static $managed_models = array(
+		"TaxClass"
+	);
+
+}

code/model/TaxClass.php

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+<?php
+
+class TaxClass extends DataObject{
+
+	static $db = array(
+		'Name' => 'Varchar',
+		'Default' => 'Boolean'
+	);
+
+	static $has_many = array(
+		'TaxRates' => 'TaxRate'
+	);
+
+	static $summary_fields = array(
+		'Name',
+		'Default'
+	);
+
+	function getCMSFields(){
+		$fields = parent::getCMSFields();
+		$fieldList = array_merge(RegionRestriction::$field_labels,array(
+			'Rate' => 'Rate',
+			'Name' => 'Name',
+			//'Priority' => 'Priority',
+			//'Compounding' => 'Compounding'
+		));
+		$fieldTypes = array_merge(RegionRestriction::get_table_field_types(),array(
+			'Rate' => 'TextField',
+			'Name' => 'TextField',
+			//'Priority' => 'TextField',
+			//'Compounding' => 'CheckboxField'
+		));
+		$fields->fieldByName("Root")->removeByName('TaxRates'); //remove tax rates tab
+		if($this->isInDB()){
+			$tablefield = new TableField("TaxRates", "TaxRate", $fieldList, $fieldTypes);
+			$tablefield->setCustomSourceItems($this->TaxRates());
+			$fields->addFieldsToTab("Root.Main", array(
+				new LabelField("TaxRatesHelp", "Enter tax class rates for specific regions. Rates should be entered in decimal form, for example 0.05 = 5%."),
+				$tablefield
+			));
+		}
+		return $fields;
+	}
+
+	static function get_by_address(Address $address){
+		$where = RegionRestriction::address_filter($address);
+		$join = "INNER JOIN \"TaxRate\" ON \"TaxClass\".\"ID\" = \"TaxRate\".\"TaxClassID\" ";
+		return DataObject::get("TaxClass",$where, $sort = "", $join);		
+	}
+
+	function getRate($address = null){
+		if(!$address){
+			$address = singleton('Address');
+		}
+		$where = array(
+			"\"TaxRate\".\"TaxClassID\" = {$this->ID}",
+			RegionRestriction::address_filter($address)
+		);
+		$sort = implode(', ',array(
+			RegionRestriction::wildcard_sort("PostalCode"),
+			RegionRestriction::wildcard_sort("City"),
+			RegionRestriction::wildcard_sort("State"),
+			RegionRestriction::wildcard_sort("Country"),
+			"\"Rate\" ASC"
+		));
+		if($rate = DataObject::get_one("TaxRate","(".implode(") AND (",$where).")",true,$sort)){
+			return $rate->Rate;
+		}
+		return 0;
+	}
+
+	function getTax($value){
+		return $value * $this->getRate();
+	}
+
+	function onBeforeWrite(){
+		parent::onBeforeWrite();
+		if($this->Default){
+			DB::query("UPDATE \"TaxClass\" SET \"Default\" = 0"); //clear any other default
+		}
+	}
+
+}

code/model/TaxRate.php

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+<?php
+class TaxRate extends RegionRestriction{
+
+	static $db = array(
+		'Rate' => 'Percentage',
+		'Priority' => 'Int',
+		'Name' => 'Varchar', //eg: 'gst'
+		'Compounding' => 'Boolean'
+	);
+
+	static $has_one = array(
+		'TaxClass' => 'TaxClass'
+	);
+
+	static $defaults = array(
+		'Name' => 'TAX'	
+	);
+
+	/**
+	 * Prevent empty defaults
+	 */
+	function onBeforeWrite(){
+		foreach(self::$defaults as $field => $value){
+			if(empty($this->$field)){
+				$this->$field = $value;
+			}
+		}
+		parent::onBeforeWrite();
+	}
+
+}

code/model/TaxedProductDecorator.php

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+<?php
+
+class TaxedProductDecorator extends DataObjectDecorator{
+
+	function extraStatics(){
+		return array(
+			'has_one' => array(
+				'TaxClass' => 'TaxClass'
+			)
+		);
+	}
+
+	function updateCMSFields($fields){
+		if($taxclasses = DataObject::get("TaxClass","","\"Name\" ASC")){
+			$fields->addFieldsToTab("Root.Content.Pricing", array(
+				new DropdownField("TaxClass","Tax Class",$taxclasses->map('ID','Name'))	
+			));
+		}
+	}
+
+	function updateSellingPrice(&$price){
+		if($taxclass = $this->owner->TaxClass()){
+			$price += $taxclass->getTax($price); //TODO: specify address
+		}
+	}
+
+}

code/tasks/PopulateTaxClassesTask.php

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+<?php
+
+class PopulateTaxClassesTask extends BuildTask{
+
+	protected $title = "Populate Tax Classes";
+	protected $description = "Creates tax classes";
+
+	function run($request = null){
+		if(!DataObject::get_one('TaxClass')){
+			$fixture = new YamlFixture('shop_taxframework/tests/fixtures/TaxClasses.yml');
+			$fixture->saveIntoDatabase();
+			DB::alteration_message('Created tax classes', 'created');
+		}else{
+			DB::alteration_message('Some tax classes already exist. None were created.');
+		}
+	}
+
+}
+
+class PopulateShopTaxClassesTask extends Extension{
+
+	function beforePopulate(){
+		$task = new PopulateTaxClassesTask();
+		$task->run();
+	}
+
+}

tests/TaxClassTest.php

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+<?php
+class TaxClassTest extends SapphireTest{
+
+	static $fixture_file = array(
+		'shop/tests/fixtures/dummyproducts.yml',
+		'shop/tests/fixtures/Addresses.yml',
+		'shop_taxframework/tests/fixtures/TaxClasses.yml'
+	);
+
+	function testTaxRates(){
+		$producttaxclass = $this->objFromFixture("TaxClass", "products");
+		$groceriestaxclass = $this->objFromFixture("TaxClass", "groceries");
+
+		$us_arizona = $this->objFromFixture("Address", "aus85728");
+		$this->assertEquals($producttaxclass->getRate($us_arizona),0.066); //6.6%
+
+		//test other classes
+		$this->assertEquals($groceriestaxclass->getRate($us_arizona),0); //not charged tax
+
+		//test specificity
+		$anz1010 = $this->objFromFixture("Address", "anz1010");
+		$this->assertEquals($producttaxclass->getRate($anz1010),0.15); //15%
+
+		$wnz6012 = $this->objFromFixture("Address", "wnz6012");
+		$this->assertEquals($producttaxclass->getRate($wnz6012),0.50); //50%
+
+	}
+
+	/*function testTaxFrameworkModifier(){
+		
+	}*/
+
+}