<?php

if ( !defined( 'ABSPATH' ) && !defined('_JEXEC') ) { 
	die( 'Direct Access to ' . basename( __FILE__ ) . ' is not allowed.' );
}

/**
 * Shipping By Rules Framework for general, rules-based shipments, like regular postal services with complex shipping cost structures
 *
 * @package ShippingByRules e-commerce system-agnostic framework for shipping plugins.
 * @subpackage Plugins - shipment
 * @copyright Copyright (C) 2013 Reinhold Kainhofer, reinhold@kainhofer.com
 * @license http://www.gnu.org/copyleft/gpl.html GNU/GPL, see LICENSE.txt
 *
 * @author Reinhold Kainhofer, Open Tools
 *
 */
// Only declare the class once...
if (class_exists ('RulesShippingFramework')) {
	return;
}


function print_array($obj) {
	$res = "";
	if (is_array($obj)) {
		$res .= "array(";
		$sep = "";
		foreach ($obj as $e) {
			$res .= $sep . print_array($e);
			$sep = ", ";
		}
		$res .= ")";
	} elseif (is_string($obj)) {
		$res .= "\"$obj\"";
	} else {
		$res .= (string)$obj;
	}
	return $res;
}

function is_equal($a, $b) {
	if (is_array($a) && is_array($b)) {
		return !array_diff($a, $b) && !array_diff($b, $a);
	} elseif (is_string($a) && is_string($b)) {
		return strcmp($a,$b) == 0;
	} else {
		return $a == $b;
	}
}

class RulesShippingFramework {
	static $_version = "0.1";
	protected $_callbacks = array();
	// Store the parsed and possibly evaluated rules for each method (method ID is used as key)
	protected $rules = array();
	protected $match = array();
	var $custom_functions = array ();
	
	function __construct() {
// 		$this->registerCallback('addCustomCartValues',	array($this, 'addCustomCartValues'));
	}
	
	
	/* Callback handling */
	
	/**
	 * Register a callback for one of the known callback hooks. 
	 * Valid callbacks are (together with their arguments):
	 *   - translate($string)
	 *  @param string $callback 
	 *     The name of the callback hook (string)
	 *  @param function $func 
	 *     The function (usually a member of the plugin object) for the callback
	 *  @return none
	 */
	public function registerCallback($callback, $func) {
		$this->callbacks[$callback] = $func;
	}
	
	public function readableString($string) {
		switch ($string) {
			case "OTSHIPMENT_RULES_CUSTOMFUNCTIONS_ALREADY_DEFINED":
					return "Custom function %s already defined. Ignoring this definition and using previous one.";
			case "OTSHIPMENT_RULES_CUSTOMFUNCTIONS_NOARRAY":
					return "Definition of custom functions (returned by a plugin) is not a proper array. Ignoring.";
			case "OTSHIPMENT_RULES_EVALUATE_ASSIGNMENT_TOPLEVEL":
					return "Assignments are not allowed inside expressions (rule given was '%s')";
			case "OTSHIPMENT_RULES_EVALUATE_LISTFUNCTION_ARGS":
					return "List function '%s' requires all arguments to be lists. (Full rule: '%s')";
			case "OTSHIPMENT_RULES_EVALUATE_LISTFUNCTION_CONTAIN_ARGS":
					return "List function '%s' requires the first argument to be lists. (Full rule: '%s')";
			case "OTSHIPMENT_RULES_EVALUATE_LISTFUNCTION_UNKNOWN":
					return "Unknown list function '%s' encountered. (Full rule: '%s')";
			case "OTSHIPMENT_RULES_EVALUATE_SYNTAXERROR":
					return "Syntax error during evaluation, RPN is not well formed! (Full rule: '%s')";
			case "OTSHIPMENT_RULES_EVALUATE_UNKNOWN_ERROR":
					return "Unknown error occurred during evaluation of rule '%s'.";
			case "OTSHIPMENT_RULES_EVALUATE_UNKNOWN_FUNCTION":
					return "Unknown function '%s' encountered during evaluation of rule '%s'.";
			case "OTSHIPMENT_RULES_EVALUATE_UNKNOWN_VALUE":
					return "Evaluation yields unknown value while evaluating rule part '%s'.";
			case "OTSHIPMENT_RULES_NOSHIPPING_MESSAGE":
					return "%s";
			case "OTSHIPMENT_RULES_PARSE_FUNCTION_NOT_CLOSED":
					return "Error during parsing expression '%s': A function call was not closed properly!";
			case "OTSHIPMENT_RULES_PARSE_MISSING_PAREN":
					return "Error during parsing expression '%s': Opening parenthesis cannot be found!";
			case "OTSHIPMENT_RULES_PARSE_PAREN_NOT_CLOSED":
					return "Error during parsing expression '%s': A parenthesis was not closed properly!";
			case "OTSHIPMENT_RULES_UNKNOWN_OPERATOR":
					return "Unknown operator '%s' in shipment rule '%s'";
			case "OTSHIPMENT_RULES_UNKNOWN_TYPE":
					return "Unknown rule type '%s' encountered for rule '%s'";
			case "OTSHIPMENT_RULES_UNKNOWN_VARIABLE":
					return "Unknown variable '%s' in rule '%s'";
			default:
					return $string;
		}
	}
	
	public function __($string) {
		$args = func_get_args();

		if (isset($this->callbacks["translate"])) {
			return call_user_func_array($this->callbacks["translate"], $args);
		} else {
			if (count($args)>1) {
				return call_user_func_array("sprintf", $args);
			} else {
				return $string;
			}
		}
	}

	/** @tag system-specific
	 *  @function getCustomFunctions() 
	 *    Let other plugins add custom functions! 
	 *    This function is expected to return an array of the form:
	 *        array ('functionname1' => 'function-to-be-called',
	 *               'functionname2' => array($classobject, 'memberfunc')),
	 *               ...);
	 */
	function getCustomFunctions() {
		return array ();
	}
	
	/** @tag system-specific
	 *  @function printWarning()
	 *    Print a warning in the system-specific way.
	 *  @param $message the warning message to be printed (already properly translated)
	 */
	protected function printWarning($message) {
		echo($message);
	}
	
	/** @tag public-api
	 *  @tag system-specific
	 *  @function warning()
	 *    Print a warning (to be translated) in the system-specific way.
	 *  @param $message the warning message to be printed 
	 *  @param $args optional arguments to be inserted into the translated message in sprintf-style
	 */
	public function warning($message) {
		$args = func_get_args();
		$msg = call_user_func_array(array($this, "__"), $args);
		$this->printWarning($msg);
	}
	
	/** @tag public-api
	 *  @function debug()
	 *    Print a debug message (untranslated) in the system-specific way.
	 *  @param $message the debug message to be printed 
	 */
	public function debug($message) {
	}
	
	/** @tag public-api
	 *  @function setup
	 *    Initialize the framework. Currently this only sets up plugin-defined custom functions
	 */
	public function setup() {
		$custfuncdefs = $this->getCustomFunctions();
		// Loop through the return values of all plugins:
		foreach ($custfuncdefs as $custfuncs) {
			if (empty($custfuncs))
				continue;
			if (!is_array($custfuncs)) {
				$this->warning('OTSHIPMENT_RULES_CUSTOMFUNCTIONS_NOARRAY');
			}
			// Now loop through all custom function definitions of this plugin
			// If a function was registered before, print a warning and use the first definition
			foreach ($custfuncs as $fname => $func) {
				if (isset($this->custom_functions[$fname])) {
					$this->warning('OTSHIPMENT_RULES_CUSTOMFUNCTIONS_ALREADY_DEFINED', $fname);
				} else {
					$this->debug("Defining custom function $fname");
					$this->custom_functions[strtolower($fname)] = $func;
				}
			}
		}
	}
	
	protected function getMethodId($method) {
		return 0;
	}
	protected function getMethodName($method) {
		return '';
	}

	/**
	 * Functions to calculate the cart variables:
	 *   - getOrderArticles($cart, $products)
	 *   - getOrderProducts
	 *   - getOrderDimensions
	 */
	/** Functions to calculate all the different variables for the given cart and given (sub)set of products in the cart */
	protected function getOrderCounts ($cart, $products, $method) {
		return array(
			'articles' => 0, 
			'products' => count($products),
			'minquantity' => 9999999999,
			'maxquantity' => 0,
		);
	}
	
	protected function getDateTimeVariables($cart, $products, $method) {
		$utime = microtime(true);
		$milliseconds = (int)(1000*($utime - (int)$utime));
		$millisecondsstring = sprintf('%03d', $milliseconds);
		return array(
			'year'        => date("Y", $utime),
			'year2'       => date("y", $utime),
			'month'       => date("m", $utime),
			'day'         => date("d", $utime),
			'weekday'     => date("N", $utime),
			'hour'        => date("H", $utime),
			'hour12'      => date("h", $utime),
			'ampm'        => date("a", $utime),
			'minute'      => date("i", $utime),
			'second'      => date("s", $utime),
			'decisecond'  => $millisecondsstring[0],
			'centisecond' => substr($millisecondsstring, 0, 2),
			'millisecond' => $millisecondsstring,
		);
	}

	protected function getOrderDimensions ($cart, $products, $method) {
		return array();
	}
	
	protected function getOrderWeights ($cart, $products, $method) {
		return array();
	}
	
	protected function getOrderListProperties ($cart, $products, $method) {
		return array();
	}
	
	protected function getOrderAddress ($cart, $method) {
		return array();
	}
	
	protected function getOrderPrices ($cart, $products, $method) {
		return array();
	}
	
	/** 
	 * Extract information about non-numerical zip codes (UK and Canada) from the postal code
	 */
	protected function getAddressZIP ($zip) {
		$values = array();

		// Postal code Check for UK postal codes: Use regexp to determine if ZIP structure matches and also to extract the parts.
		// Also handle UK overseas areas/islands that use four-letter outward codes rather than "A{1,2}0{1,2}A{0,1} 0AA"
		$zip=strtoupper($zip);
		if (isset($zip) and preg_match('/^\s*(([A-Z]{1,2})(\d{1,2})([A-Z]?)|[A-Z]{4}|GIR)\s*(\d[A-Z]{2})\s*$/', $zip, $match)) {
			$values['uk_outward'] = $match[1];
			$values['uk_area'] = $match[2];
			$values['uk_district'] = $match[3];
			$values['uk_subdistrict'] = $match[4];
			$values['uk_inward'] = $match[5];
		} else {
			$values['uk_outward'] = NULL;
			$values['uk_area'] = NULL;
			$values['uk_district'] = NULL;
			$values['uk_subdistrict'] = NULL;
			$values['uk_inward'] = NULL;
		}
		// Postal code Check for Canadian postal codes: Use regexp to determine if ZIP structure matches and also to extract the parts.
		if (isset($zip) and preg_match('/^\s*(([A-Za-z])(\d)([A-Za-z]))\s*(\d[A-Za-z]\d)\s*$/', $zip, $match)) {
			$values['canada_fsa'] = $match[1];
			$values['canada_area'] = $match[2];
			$values['canada_urban'] = $match[3];
			$values['canada_subarea'] = $match[4];
			$values['canada_ldu'] = $match[5];
		} else {
			$values['canada_fsa'] = NULL;
			$values['canada_area'] = NULL;
			$values['canada_urban'] = NULL;
			$values['canada_subarea'] = NULL;
			$values['canada_ldu'] = NULL;
		}
		// print("<pre>values: ".print_r($values,1)."</pre>");
		return $values;
	}

	/** Allow child classes to add additional variables for the rules or modify existing one
	 */
	protected function addCustomCartValues ($cart, $products, $method, &$values) {
		if (isset($this->callbacks['addCustomCartValues'])) {
			return $this->callbacks['addCustomCartValues']($cart, $products, $method, $values);
		}
	}
	protected function addPluginCartValues($cart, $products, $method, &$values) {
	}
	
	public function getCartValues ($cart, $products, $method) {
		$cartvals = array_merge (
			$this->getDateTimeVariables($cart, $products, $method),
			$this->getOrderCounts($cart, $products, $method),
			// Add the prices, optionally calculated from the products subset of the cart
			$this->getOrderPrices ($cart, $products, $method),
			// Add 'skus', 'categories', 'vendors' variables:
			$this->getOrderListProperties ($cart, $products, $method),
			// Add country / state variables:
			$this->getOrderAddress ($cart, $method),
			// Add Total/Min/Max weight and dimension variables:
			$this->getOrderWeights ($cart, $products, $method),
			$this->getOrderDimensions ($cart, $products, $method)
		);
		// Let child classes update the $cartvals array, or add new variables
		$this->addCustomCartValues($cart, $products, $method, $cartvals);
		// Let custom plugins update the $cartvals array or add new variables
		$this->addPluginCartValues($cart, $products, $method, $cartvals);

		return $cartvals;
	}
	
	protected function getCartProducts($cart, $method) {
		return array();
	}

	/** This function evaluates all rules, one after the other until it finds a matching rule that
	 *  defines shipping costs (or uses NoShipping). If a modifier or definition is encountered,
	 *  its effect is stored, but the loop continues */
	protected function evaluateMethodRules ($cart, $method) {
		$id = $this->getMethodId($method);
		// $this->match will cache the matched rule and the modifiers
		if (isset($this->match[$id])) {
			return $this->match[$id];
		} else {
			// Evaluate all rules and find the matching ones (including modifiers and definitions!)
			$cartvals = $this->getCartValues ($cart, $this->getCartProducts($cart, $method), $method);
			$result = array(
				"rule" => Null,
				"rule_name" => "",
				"modifiers_add"=> array(),
				"modifiers_multiply" => array(),
				"cartvals" => $cartvals,
			);
			// Pass a callback function to the rules to obtain the cartvals for a subset of the products
			$this_class = $this;
			$cartvals_callback = function ($products) use ($this_class, $cart, $method) {
				return $this_class->getCartValues ($cart, $products, $method, NULL);
			};
			if (isset($this->rules[$id])) {
				foreach ($this->rules[$id] as $r) {
					if ($r->matches($cartvals, $this->getCartProducts($cart, $method), $cartvals_callback)) {
						$rtype = $r->getType();
						switch ($rtype) {
							case 'shipping': 
							case 'shippingwithtax':
							case 'noshipping': 
									$result["rule"] = $r;
									$result["rule_name"] = $r->getRuleName();
									break;
							case 'modifiers_add':
							case 'modifiers_multiply':
									$result[$rtype][] = $r;
									break;
							case 'definition': // A definition updates the $cartvals, but has no other effects
									$cartvals[strtolower($r->getRuleName())] = $r->getValue();
									break;
							default:
									$this->warning('OTSHIPMENT_RULES_UNKNOWN_TYPE', $r->getType(), $r->rulestring);
									break;
						}
					}
					if (!is_null($result["rule"])) {
						$this->match[$id] = $result;
						return $result; // <- This also breaks out of the foreach loop!
					}
				}
			}
		}
		// None of the rules matched, so return NULL, but keep the evaluated results;
		$this->match[$id] = $result;
		return NULL;
	}

	protected function handleNoShipping($match, $method) {
		if ($match['rule']->isNoShipping()) {
			if (!empty($match["rule_name"]))
				$this->warning('OTSHIPMENT_RULES_NOSHIPPING_MESSAGE', $match["rule_name"]);
			$name = $this->getMethodName($method);
			$this->debug('checkConditions '.$name.' indicates NoShipping for this method, specified by rule "'.$match["rule_name"].'" ('.$match['rule']->rulestring.').');
			return true;
		} else {
			return false;
		}
	}
	
	/**
	 * @param $cart
	 * @param int             $method
	 * @return bool
	 */
	public function checkConditions ($cart, $method) {
		$id = $this->getMethodId($method);
		$name = $this->getMethodName($method);
		if (!isset($this->rules[$id])) 
			$this->parseMethodRules($method);
		// TODO: This needs to be redone sooner or later!
		$match = $this->evaluateMethodRules ($cart, $method);
		if ($match && !is_null ($match['rule'])) {
			$this->setMethodCosts($method, $match, null);
			// If NoShipping is set, this method should NOT offer any shipping at all, so return FALSE, otherwise TRUE
			// If the rule has a name, print it as warning (otherwise don't print anything)
			if ($this->handleNoShipping($match, $method)) {
				return FALSE;
			}
			return TRUE;
		}
		$this->debug('checkConditions '.$name.' does not fulfill all conditions, no rule matches');
		return FALSE;
	}
	
	/**
	 * @tag system-specific
	 */
	protected function setMethodCosts($method, $match, $costs) {
		// Allow some system-specific code, e.g. setting some members of $method, etc.
	}

	/**
	 * @param $cart
	 * @param                $method
	 * @return int
	 */
	function getCosts ($cart, $method) {
		$results = array();
		$id = $this->getMethodId($method);
		if (!isset($this->rules[$id])) 
			$this->parseMethodRules($method);
		$match = $this->evaluateMethodRules ($cart, $method);
		if ($match) {
			if ($this->handleNoShipping($match, $method)) {
				return $results;
			}
		
			$r = $match["rule"];
			$this->debug('Rule ' . $match["rule_name"] . ' ('.$r->rulestring.') matched.');

			// Final shipping costs are calculated as:
			//   Shipping*ExtraShippingMultiplier + ExtraShippingCharge
			// with possibly multiple modifiers
			$cost = $r->getShippingCosts();
			foreach ($match['modifiers_multiply'] as $modifier) {
				$cost *= $modifier->getValue();
			}
			foreach ($match['modifiers_add'] as $modifier) {
				$cost += $modifier->getValue();
			}
			$this->setMethodCosts($method, $match, $cost);

			$res = array(
				'method' =>   $id,
				'name' =>     $this->getMethodName($method),
// 				'rulesetname'=>$match['ruleset_name'],
				'rulename' => $match["rule_name"],
				'cost' =>     $cost,
			);
			$results[] = $res;
		}
		
		if (empty($results)) {
			$this->debug('getCosts '.$this->getMethodName($method).' does not return shipping costs');
		}
		return $results;
	}
	
	public function getRuleName($methodid) {
		if (isset($this->match[$methodid])) {
			return $this->match[$methodid]["rule_name"];
		} else {
			return '';
		}
	}

	public function getRuleVariables($methodid) {
		if (isset($this->match[$methodid])) {
			return $this->match[$methodid]["cartvals"];
		} else {
			return array();
		}
	}

	protected function createMethodRule ($r, $countries, $ruleinfo) {
		if (isset($this->callbacks['initRule'])) {
			return $this->callbacks['initRule']($this, $r, $countries, $ruleinfo);
		} else {
			return new ShippingRule($this, $r, $countries, $ruleinfo);
		}
	}

	// Parse the rule and append all rules to the rule set of the current shipment method (country/tax are already included in the rule itself!)
	protected function parseMethodRule ($rulestring, $countries, $ruleinfo, &$method) {
		$id = $this->getMethodId($method);
		foreach ($this->parseRuleSyntax($rulestring, $countries, $ruleinfo) as $r) {
			$this->rules[$id][] = $r;
		}
	}
	
	public function parseRuleSyntax($rulestring, $countries, $ruleinfo) {
		$result = array();
		$rules1 = preg_split("/(\r\n|\n|\r)/", $rulestring);
		foreach ($rules1 as $r) {
			// Ignore empty lines
			if (empty($r)) continue;
			$result[] = $this->createMethodRule ($r, $countries, $ruleinfo);
		}
		return $result;
	}
	
	protected function parseMethodRules (&$method) {
		$this->warning("parseMethodRules not reimplemented => No rules will be loaded!");
	}

	/** Filter the given array of products and return only those that belong to the categories, manufacturers, 
	 *  vendors or products given in the $filter_conditions. The $filter_conditions is an array of the form:
	 *     array( 'skus'=>array(....), 'categories'=>array(1,2,3,42), 'manufacturers'=>array(77,78,83), 'vendors'=>array(1,2))
	 *  Notice that giving an empty array for any of the keys means "no restriction" and is exactly the same 
	 *  as leaving out the enty altogether
	 */
	public function filterProducts($products, $filter_conditions) {
		return array();
	}
}

class ShippingRule {
	var $framework = Null;
	var $rulestring = '';
	var $name = '';
	var $ruletype = '';
	var $evaluated = False;
	var $match = False;
	var $value = Null;
	
	var $shipping = 0;
	var $conditions = array();
	var $countries = array();
	var $ruleinfo = 0;
	var $includes_tax = 0;
	
	function __construct ($framework, $rule, $countries, $ruleinfo) {
		$this->framework = $framework;
		if (is_array($countries)) {
			$this->countries = $countries;
		} elseif (!empty($countries)) {
			$this->countries[0] = $countries;
		}
		$this->ruleinfo = $ruleinfo;
		$this->rulestring = $rule;
		$this->parseRule($rule);
	}
	
	protected function parseRule($rule) {
		$ruleparts=explode(';', $rule);
		foreach ($ruleparts as $p) {
			$this->parseRulePart($p);
		}
	}
	
	protected function handleAssignment ($var, $value, $rulepart) {
		switch (strtolower($var)) {
			case 'name':            $this->name = $value; break;
			case 'shipping':        $this->shipping = $value; $this->includes_tax = False; $this->ruletype='shipping'; break;
			case 'shippingwithtax': $this->shipping = $value; $this->includes_tax = True; $this->ruletype='shipping'; break;
			case 'variable':        // Variable=... is the same as Definition=...
			case 'definition':      $this->name = strtolower($value); $this->ruletype = 'definition'; break;
			case 'value':           $this->shipping = $value; $this->ruletype = 'definition'; break; // definition values are also stored in the shipping member!
			case 'extrashippingcharge': $this->shipping = $value; $this->ruletype = 'modifiers_add'; break; // modifiers are also stored in the shipping member!
			case 'extrashippingmultiplier': $this->shipping = $value; $this->ruletype = 'modifiers_multiply'; break; // modifiers are also stored in the shipping member!
			case 'comment':         break; // Completely ignore all comments!
			case 'condition':       $this->conditions[] = $value; break;
			default:                $this->framework->warning('OTSHIPMENT_RULES_UNKNOWN_VARIABLE', $var, $rulepart);
		}
	}
	
	protected function tokenize_expression ($expression) {
		// First, extract all strings, delimited by quotes, then all text operators 
		// (OR, AND, in; but make sure we don't capture parts of words, so we need to 
		// use lookbehind/lookahead patterns to exclude OR following another letter 
		// or followed by another letter) and then all arithmetic operators
		$re = '/\s*("[^"]*"|\'[^\']*\'|<=|=>|>=|=<|<>|!=|==|<|=|>)\s*/i';
		$atoms = preg_split($re, $expression, -1, PREG_SPLIT_DELIM_CAPTURE|PREG_SPLIT_NO_EMPTY);
		return $atoms;
	}
	
	protected function parseRulePart($rulepart) {
		/* In the basic version, we only split at the comparison operators and assume each term on the LHS and RHS is one variable or constant */
		/* In the advanced version, all conditions and costs can be given as a full mathematical expression */
		/* Both versions create an expression tree, which can be easily evaluated in evaluateTerm */
		$rulepart = trim($rulepart);
		if (empty($rulepart)) return;

		
		// Special-case the name assignment, where we don't want to interpret the value as an arithmetic expression!
		if (preg_match('/^\s*(name|variable|definition)\s*=\s*(["\']?)(.*)\2\s*$/i', $rulepart, $matches)) {
			$this->handleAssignment ($matches[1], $matches[3], $rulepart);
			return;
		}

		// Split at all operators:
		$atoms = $this->tokenize_expression ($rulepart);
		
		/* Starting from here, the advanced plugin is different! */
		$operators = array('<', '<=', '=', '>', '>=', '=>', '=<', '<>', '!=', '==');
		if (count($atoms)==1) {
			$this->shipping = $this->parseShippingTerm($atoms[0]);
			$this->ruletype = 'shipping';
		} elseif ($atoms[1]=='=') {
			$this->handleAssignment ($atoms[0], $atoms[2], $rulepart);
		} else {
			// Conditions, need at least three atoms!
			while (count($atoms)>1) {
				if (in_array ($atoms[1], $operators)) {
					$this->conditions[] = array($atoms[1], $this->parseShippingTerm($atoms[0]), $this->parseShippingTerm($atoms[2]));
					array_shift($atoms);
					array_shift($atoms);
				} else {
					$this->framework->warning('OTSHIPMENT_RULES_UNKNOWN_OPERATOR', $atoms[1], $rulepart);
					$atoms = array();
				}
			}
		}
	}

	protected function parseShippingTerm($expr) {
		/* In the advanced version, shipping cost can be given as a full mathematical expression */
		// If the shipping term starts with a double quote, it is a string, so don't turn it into lowercase.
		// All other expressions need to be turned into lowercase, because variable names are case-insensitive!
		if (substr($expr, 0, 1) === '"') {
			return $expr;
		} else {
			return strtolower($expr);
		}
	}
	
	protected function evaluateComparison ($terms, $vals) {
		while (count($terms)>2) {
			$res = false;
			switch ($terms[1]) {
				case '<':  $res = ($terms[0] < $terms[2]);  break;
				case '<=':
				case '=<': $res = ($terms[0] <= $terms[2]); break;
				case '==': $res = is_equal($terms[0], $terms[2]); break;
				case '!=':
				case '<>': $res = ($terms[0] != $terms[2]); break;
				case '>=':
				case '=>': $res = ($terms[0] >= $terms[2]); break;
				case '>':  $res = ($terms[0] >  $terms[2]);  break;
				case '~':
					$l=min(strlen($terms[0]), strlen($terms[2]));
					$res = (strncmp ($terms[0], $terms[2], $l) == 0);
					break;
				default:
					$this->framework->warning('OTSHIPMENT_RULES_UNKNOWN_OPERATOR', $terms[1], $this->rulestring);
					$res = false;
			}

			if ($res==false) return false;
			// Remove the first operand and the operator from the comparison:
			array_shift($terms);
			array_shift($terms);
		}
		if (count($terms)>1) {
			// We do not have the correct number of terms for chained comparisons, i.e. two terms leftover instead of one!
			$this->framework->warning('OTSHIPMENT_RULES_EVALUATE_UNKNOWN_ERROR', $this->rulestring);
			return false;
		}
		// All conditions were fulfilled, so we can return true
		return true;
	}
	
	protected function evaluateListFunction ($function, $args) {
		# First make sure that all arguments are actually lists:
		$allarrays = True;
		foreach ($args as $a) {
			$allarrays = $allarrays && is_array($a);
		}
		if (!$allarrays) {
			$this->framework->warning('OTSHIPMENT_RULES_EVALUATE_LISTFUNCTION_ARGS', $function, $this->rulestring);
			return false;
			
		}
		switch ($function) {
			case "length":		return count($args[0]); break;
			case "union": 
			case "join":		return call_user_func_array( "array_merge" , $args); break;
			case "complement":	return call_user_func_array( "array_diff" , $args); break;
			case "intersection":	return call_user_func_array( "array_intersect" , $args); break;
			case "issubset":	# Remove all of superset's elements to see if anything else is left: 
						return !array_diff($args[0], $args[1]); break;
			case "contains":	# Remove all of superset's elements to see if anything else is left: 
						# Notice the different argument order compared to issubset!
						return !array_diff($args[1], $args[0]); break;
			case "list_equal":	return array_unique($args[0])==array_unique($args[1]); break;
			default: 
				$this->framework->warning('OTSHIPMENT_RULES_EVALUATE_LISTFUNCTION_UNKNOWN', $function, $this->rulestring);
				return false;
		}
	}
	
	protected function evaluateListContainmentFunction ($function, $args) {
		# First make sure that the first argument is a list:
		if (!is_array($args[0])) {
			$this->framework->warning('OTSHIPMENT_RULES_EVALUATE_LISTFUNCTION_CONTAIN_ARGS', $function, $this->rulestring);
			return false;
		}
		// Extract the array from the args, the $args varialbe will now only contain the elements to be checked:
		$array = array_shift($args);
		switch ($function) {
			case "contains_any": // return true if one of the $args is in the $array
					foreach ($args as $a) { 
						if (in_array($a, $array)) 
							return true; 
					}
					return false;
			
			case "contains_all": // return false if one of the $args is NOT in the $array
					foreach ($args as $a) { 
						if (!in_array($a, $array)) 
							return false; 
					}
					return true;
			case "contains_only": // return false if one of the $array elements is NOT in $args
					foreach ($array as $a) {
						if (!in_array($a, $args))
							return false;
					}
					return true;
			case "contains_none": // return false if one of the $args IS in the $array
					foreach ($args as $a) {
						if (in_array($a, $array))
							return false;
					}
					return true;
			default: 
				$this->framework->warning('OTSHIPMENT_RULES_EVALUATE_LISTFUNCTION_UNKNOWN', $function, $this->rulestring);
				return false;
		}
	}
	
	/** Evaluate the given expression $expr only for the products that match the filter given by the scoping 
	 * function and the corresponding conditions */
	protected function evaluateScoping($expr, $scoping, $conditionvals, $vals, $products, $cartvals_callback) {
		if (count($conditionvals)<1)
			return $this->evaluateTerm($expr, $vals, $products, $cartvals_callback);

		// TODO: Make this more general!
		$filterkeys = array( 
			"evaluate_for_categories" =>    'categories',
			"evaluate_for_products" =>      'products',
			"evaluate_for_skus" =>      'products',
			"evaluate_for_vendors" =>       'vendors',
			"evaluate_for_manufacturers" => 'manufacturers',
		);
		
		$conditions = array();
		if (isset($filterkeys[$scoping])) 
			$conditions[$filterkeys[$scoping]] = $conditionvals;

		// Pass the conditions to the parent plugin class to filter the current list of products:
		$filteredproducts = $this->framework->filterProducts($products, $conditions);
		// We have been handed a callback function to calculate the cartvals for the filtered list of products, so use it:
		$filteredvals = $cartvals_callback($filteredproducts);
		return $this->evaluateTerm ($expr, $filteredvals, $filteredproducts, $cartvals_callback);
	}

	protected function evaluateFunction ($function, $args) {
		$func = strtolower($function);
		// Check if we have a custom function definition and use that if so.
		// This is done first to allow plugins to override even built-in functions!
		if (isset($this->plugin->custom_functions[$func])) {
			$this->framework->debug("Evaluating custom function $function, defined by a plugin");
			return call_user_func_array($this->plugin->custom_functions[$func], $args, $this);
		}

		// Functions with no argument:
		if (count($args) == 0) {
			$dt = getdate();
			switch ($func) {
				case "second": return $dt['seconds']; break;
				case "minute": return $dt['minutes']; break;
				case "hour":   return $dt['hours']; break;
				case "day":    return $dt['mday']; break;
				case "weekday":return $dt['wday']; break;
				case "month":  return $dt['mon']; break;
				case "year":   return $dt['year']; break;
				case "yearday":return $dt['yday']; break;
			}
		}
		// Functions with exactly one argument:
		if (count($args) == 1) {
			switch ($func) {
				case "round": return round($args[0]); break;
				case "ceil":  return ceil ($args[0]); break;
				case "floor": return floor($args[0]); break;
				case "abs":   return abs($args[0]); break;
				case "not":   return !$args[0]; break;
				case "print_r": return print_r($args[0],1); break; 
			}
		}
		if (count($args) == 2) {
			switch ($func) {
				case "digit": return substr($args[0], $args[1]-1, 1); break;
				case "round": return round($args[0]/$args[1])*$args[1]; break;
				case "ceil":  return ceil($args[0]/$args[1])*$args[1]; break;
				case "floor": return floor($args[0]/$args[1])*$args[1]; break;
			}
		}
		if (count($args) == 3) {
			switch ($func) {
				case "substring": return substr($args[0], $args[1]-1, $args[2]); break;
			}
		}
		// Functions with variable number of args
		switch ($func) {
			case "max": 
					return max($args);
			case "min": 
					return min($args);
			case "list": 
			case "array": 
					return $args;
			// List functions:
		    case "length":
		    case "complement":
		    case "issubset":
		    case "contains":
		    case "union":
		    case "join":
		    case "intersection":
		    case "list_equal":
					return $this->evaluateListFunction ($func, $args);
			case "contains_any": 
			case "contains_all":
			case "contains_only":
			case "contains_none":
					return $this->evaluateListContainmentFunction($func, $args);
			
		}
		
		// None of the built-in function 
		// No known function matches => print an error, return 0
		$this->framework->warning('OTSHIPMENT_RULES_EVALUATE_UNKNOWN_FUNCTION', $function, $this->rulestring);
		return 0;
	}

	protected function evaluateVariable ($expr, $vals) {
		$varname = strtolower($expr);
		if (array_key_exists(strtolower($expr), $vals)) {
			return $vals[strtolower($expr)];
		} elseif ($varname=='noshipping') {
			return $varname;
		} elseif ($varname=='values') {
			return $vals;
		} elseif ($varname=='values_debug') {
			return print_r($vals,1);
		} else {
			$this->framework->warning('OTSHIPMENT_RULES_EVALUATE_UNKNOWN_VALUE', $expr, $this->rulestring);
			return null;
		}
	}

	protected function evaluateTerm ($expr, $vals, $products, $cartvals_callback) {
		// The scoping functions need to be handled differently, because they first need to adjust the cart variables to the filtered product list
		// before evaluating its first argument. So even though parsing the rules handles scoping functions like any other function, their 
		// evaluation is fundamentally different and is special-cased here:
		$scoping_functions = array("evaluate_for_categories", "evaluate_for_products", "evaluate_for_vendors", "evaluate_for_manufacturers");
		$is_scoping = is_array($expr) && ($expr[0]=="FUNCTION") && (count($expr)>1) && in_array($expr[1], $scoping_functions);

		if (is_null($expr)) {
			return $expr;
		} elseif (is_numeric ($expr)) {
			return $expr;
		} elseif (is_string ($expr)) {
			// Explicit strings are delimited by '...' or "..."
			if (($expr[0]=='\'' || $expr[0]=='"') && ($expr[0]==substr($expr,-1)) ) {
				return substr($expr,1,-1);
			} else {
				return $this->evaluateVariable($expr, $vals);
			}
		} elseif ($is_scoping) {
			$op = array_shift($expr); // ignore the "FUNCTION"
			$func = array_shift($expr); // The scoping function name
			$expression = array_shift($expr); // The expression to be evaluated
			$conditions = $expr; // the remaining $expr list now contains the conditions
			return $this->evaluateScoping ($expression, $func, $conditions, $vals, $products, $cartvals_callback);
			
		} elseif (is_array($expr)) {
			// Operator
			$op = array_shift($expr);
			$args = array();
			// First evaluate all operands and only after that apply the function / operator to the already evaluated arguments
			$evaluate = true;
			if ($op == "FUNCTION") {
				$evaluate = false;
			}
			foreach ($expr as $e) {
				$term = $evaluate ? ($this->evaluateTerm($e, $vals, $products, $cartvals_callback)) : $e;
				if ($op == 'COMPARISON') {
					// For comparisons, we only evaluate every other term (the operators are NOT evaluated!)
					// The data format for comparisons is: array('COMPARISON', $operand1, '<', $operand2, '<=', ....)
					$evaluate = !$evaluate;
				}
				if ($op == "FUNCTION") {
					$evaluate = true;
				}
				if (is_null($term)) return null;
				$args[] = $term;
			}
			$res = false;
			// Finally apply the operaton to the evaluated argument values:
			switch ($op) {
				// Logical operators:
				case 'OR':  foreach ($args as $a) { $res = ($res || $a); }; break;
				case '&&':
				case 'AND':  $res = true; foreach ($args as $a) { $res = ($res && $a); }; break;
				case 'IN': $res = in_array($args[0], $args[1]);  break;
				
				// Comparisons:
				case '<':
				case '<=':
				case '=<':
				case '==':
				case '!=':
				case '<>':
				case '>=':
				case '=>':
				case '>':
				case '~':
					$res = $this->evaluateComparison(array($args[0], $op, $args[1]), $vals); break;
				case 'COMPARISON':
					$res = $this->evaluateComparison($args, $vals); break;
				
				// Unary operators:
				case '.-': $res = -$args[0]; break;
				case '.+': $res = $args[0]; break;
				
				// Binary operators
				case "+":  $res = ($args[0] +  $args[1]); break;
				case "-":  $res = ($args[0] -  $args[1]); break;
				case "*":  $res = ($args[0] *  $args[1]); break;
				case "/":  $res = ($args[0] /  $args[1]); break;
				case "%":  $res = (fmod($args[0],  $args[1])); break;
				case "^":  $res = ($args[0] ^  $args[1]); break;
				
				// Functions:
				case "FUNCTION": $func = array_shift($args); $res = $this->evaluateFunction($func, $args); break;
				
				default:   $res = false;
			}
			
			return $res;
		} else {
			// Neither string nor numeric, nor operator...
			$this->framework->warning('OTSHIPMENT_RULES_EVALUATE_UNKNOWN_VALUE', $expr, $this->rulestring);
			return null;
		}
	}

	protected function calculateShipping ($vals, $products, $cartvals_callback) {
		return $this->evaluateTerm($this->shipping, $vals, $products, $cartvals_callback);
	}

	protected function evaluateRule (&$vals, $products, $cartvals_callback) {
		if ($this->evaluated) 
			return; // Already evaluated

		$this->evaluated = True;
		$this->match = False; // Default, set it to True below if all conditions match...
		// First, check the country, if any conditions are given:
		if (count ($this->countries) > 0 && !in_array ($vals['countryid'], $this->countries)) {
// 			$this->framework->debug('Rule::matches: Country check failed: countryid='.print_r($vals['countryid'],1).', countries are: '.print_r($this->countries,1).'...');
			return;
		}

		foreach ($this->conditions as $c) {
			// All conditions have to match!
			$ret = $this->evaluateTerm($c, $vals, $products, $cartvals_callback);

			if (is_null($ret) || (!$ret)) {
				return;
			}
		}
		// All conditions match
		$this->match = True;
		// Calculate the value (i.e. shipping cost or modifier)
		$this->value = $this->calculateShipping($vals, $products, $cartvals_callback);
		// Evaluate the rule name as a translatable string with variables inserted:
		// Replace all {variable} tags in the name by the variables from $vals
		$matches = array();
		$name = $this->framework->__($this->name);
		preg_match_all('/{([A-Za-z0-9_]+)}/', $name, $matches);
		
		foreach ($matches[1] as $m) {
			$val = $this->evaluateVariable($m, $vals);
			if ($val !== null) {
				$name = str_replace("{".$m."}", $val, $name);
			}
		}
		$this->rulename = $name;
	}

	function matches(&$vals, $products, $cartvals_callback) {
		$this->evaluateRule($vals, $products, $cartvals_callback);
		return $this->match;
	}

	function getType() {
		return $this->ruletype;
	}

	function getRuleName() {
		if (!$this->evaluated)
			$this->framework->debug('WARNING: getRuleName called without prior evaluation of the rule, e.g. by calling rule->matches(...)');
		return $this->rulename;
	}
	
	function getValue() {
		if (!$this->evaluated)
			$this->framework->debug('WARNING: getValue called without prior evaluation of the rule, e.g. by calling rule->matches(...)');
		return $this->value;
	}
	function getShippingCosts() {
		return $this->getValue();
	}
	
	function isNoShipping() {
		// NoShipping is set, so if the rule matches, this method should not offer any shipping at all
		return (is_string($this->shipping) && (strtolower($this->shipping)=="noshipping"));
	}

}

/** Extend the shipping rules by allowing arbitrary mathematical expressions
 */
class ShippingRule_Advanced extends ShippingRule {
	function __construct ($framework, $rule, $countries, $ruleinfo) {
		parent::__construct ($framework, $rule, $countries, $ruleinfo);
	}
	
	function tokenize_expression ($expression) {
		// First, extract all strings, delimited by quotes, then all text operators 
		// (OR, AND, in; but make sure we don't capture parts of words, so we need to 
		// use lookbehind/lookahead patterns to exclude OR following another letter 
		// or followed by another letter) and then all arithmetic operators
		$re = '/\s*("[^"]*"|\'[^\']*\'|(?<![A-Za-z0-9])(?:OR|AND|IN)(?![A-Za-z0-9])|&&|<=|=>|>=|=<|<>|!=|==|<|=|>|~|\+|-|\*|\/|%|\(|\)|\^|,)\s*/i';
		$atoms = preg_split($re, $expression, -1, PREG_SPLIT_DELIM_CAPTURE|PREG_SPLIT_NO_EMPTY);
		// $this->framework->warning("TOKENIZING '$expression' returns: <pre>".print_r($atoms,1)."</pre>");
		return $atoms;
	}
	

	/** parse the mathematical expressions using the Shunting Yard Algorithm by Dijkstra (with some extensions to allow arbitrary functions):
	 *  First parse the string into an array of tokens (operators and operands) by a simple regexp with known operators as separators)
	 * TODO: Update this description to include unary operators and general function calls
	 *  Then convert the infix notation into postfix (RPN), taking care of operator precedence
	 *    1) Initialize empty stack and empty result variable
	 *    2) Read infix expression from left to right, one atom at a time
	 *    3) If operand => Append to result
	 *    4) If operator:
	 *        4a) Pop operators from stack until opening parenthesis, operator of 
	 *            lower precedence or right-associative symbol of equal precedence.
	 *        4b) Push operator onto stack
	 *    5) If opening parenthesis => push onto stack
	 *    6) If closing parenthesis:
	 *        6a) Pop operators from stack until opening parenthesis is found
	 *        6b) push them to the result (not the opening parenthesis, of course)
	 *    7) At the end of the input, pop all operators from the stack and onto the result
	 *
	 *  Afterwards, convert this RPN list into an expression tree to be evaluated
	 * 
	 *  For the full algorithm, including function parsing, see Wikipedia:
	 *    http://en.wikipedia.org/wiki/Shunting_yard_algorithm
	 *
	 */
	function parseRulePart($rulepart) {
		/* In the basic version, we only split at the comparison operators and assume each term on the LHS and RHS is one variable or constant */
		/* In the advanced version, all conditions and costs can be given as a full mathematical expression */
		/* Both versions create an expression tree, which can be easily evaluated in evaluateTerm */
		$rulepart = trim($rulepart);
		if (!isset($rulepart) || $rulepart==='') return;

		
		// Special-case the name assignment, where we don't want to interpret the value as an arithmetic expression!
		if (preg_match('/^\s*(name|variable|definition)\s*=\s*(["\']?)(.*)\2\s*$/i', $rulepart, $matches)) {
			$this->handleAssignment ($matches[1], $matches[3], $rulepart);
			return;
		}

		// Split at all operators:
		$atoms = $this->tokenize_expression ($rulepart);
		
		$operators = array(
			".-" => 100, ".+" => 100,
			"IN" => 80, 
			"^"  => 70, 
			"*"  => 60, "/"  => 60, "%"  => 60, 
			"+"  => 50, "-"  => 50, 
			"<"  => 40, "<=" => 40, ">"  => 40, ">=" => 40, "=>" => 40, "=<" => 40,
			"==" => 40, "!=" => 40, "<>" => 40, "~" => 40,
			"&&"  => 21, "AND" => 21,
			"OR"  => 20,
			"="  => 10,
			"("  =>  0, ")"  =>0 
		);
		$unary_ops = array("-" => ".-", "+" => ".+");

		// Any of these indicate a comparison and thus a condition:
		$condition_ops = array('<', '<=', '=<', '<>', '!=', '==', '>', '>=', '=>', '~', 'OR', 'AND', '&&', 'IN');
		$comparison_ops = array('<', '<=', '=<', '<>', '!=', '==', '>', '>=', '=>', '~');
		$is_condition = false;
		$is_assignment = false;
		
		$stack = array ();  // 1)/
		$prev_token_operator = true;
		$function_args = array();
		$out_stack = array();
		foreach ($atoms as $a) { // 2)
			$aupper = strtoupper($a); # All operators are converted to uppercase!
		
			if ($a == ",") { // A function argument separator
				// pop-and-apply all operators back to the left function paren
				while (count($stack)>0) { // 4a)
					$op = array_pop ($stack);
					if ($op != "FUNCTION(") {
						array_push ($out_stack, $op);
					} else {
						// No unary operator -> add it back to stack, exit loop
						array_push ($stack, $op);
						break;
					}
				} while (0);
				$this_func = array_pop($function_args);
				// Add current output stack as argument, reset temporary output stack
				if (!empty($out_stack)) $this_func[] = $out_stack;
				$function_args[] = $this_func;
				$out_stack = array();
				$prev_token_operator = true;
				
			} elseif ($a == "(" and !$prev_token_operator) { // 5) parenthesis after operand -> FUNCTION CALL
				array_push ($stack, "FUNCTION(");
				// retrieve function name from RPN list (remove last entry from operand stack!)
				$function = strtolower(array_pop ($out_stack));
				$new_stack = array();
				// Set up function call data structure on function_args stack:
				$function_args[] = array(/* old operand stack: */$out_stack, $function);
				// Use a the temporary operand stack until the closing paren restores the previous operand stack again
				$out_stack = array();
				$prev_token_operator = true;

			} elseif ($a == "(" and $prev_token_operator) { // 5) real parenthesis 
				$stack[] = $a;
				$prev_token_operator = true;
				
			} elseif ($a == ")") { // 6) parenthesis
				do {
					$op=array_pop($stack); // 6a)
					if ($op == "(") {
						break; // We have found the opening parenthesis
					} elseif ($op =="FUNCTION(") { // Function call
						// Remove function info from the functions stack; Format is array(PREVIOUS_OPERAND_STACK, FUNCTION, ARGS...)
						$this_func = array_pop ($function_args);
						// Append last argument (if not empty)
						if (!empty($out_stack)) $this_func[] = $out_stack;
						// restore old output/operand stack
						$out_stack = array_shift($this_func);
						// Function name is the next entry
						$function = array_shift($this_func);
						// All other entries are function arguments, so append them to the current operand stack
						foreach ($this_func as $a) {
							foreach ($a as $aa) {
								$out_stack[] = $aa;
							}
						}
						$out_stack[] = array("FUNCTION", $function, count($this_func));
						break; // We have found the opening parenthesis
					} elseif (!is_null($op)) {
						$out_stack[]=$op; // 6b) "normal" operators
					} else {
						// no ( and no operator, so the expression is wrong!
						$this->framework->warning('OTSHIPMENT_RULES_PARSE_MISSING_PAREN', $rulepart);
						break;
					}
				} while (true);
				$prev_token_operator = false;
				
			} elseif (isset($unary_ops[$aupper]) && $prev_token_operator) { // 4) UNARY operators
				// Unary and binary operators need to be handled differently: 
				// Unary operators must only pop other unary operators, never any binary operator
				$unary_op = $unary_ops[$aupper];
				// For unary operators, pop other unary operators from the stack until you reach an opening parenthesis, 
				// an operator of lower precedence, or a right associative symbol of equal precedence. 
				while (count($stack)>0) { // 4a)
					$op = array_pop ($stack);
					// Remove all other unary operators:
					if (in_array ($op, $unary_ops)) {
						array_push ($out_stack, $op);
					} else {
						// No unary operator -> add it back to stack, exit loop
						array_push ($stack, $op);
						break;
					}
				} while (0);
				array_push ($stack, $unary_op); // 4b)
				$prev_token_operator = true;
				
			} elseif (isset($operators[$aupper])) { // 4) BINARY operators
				$prec = $operators[$aupper];
				$is_condition |= in_array($aupper, $condition_ops);
				$is_assignment |= ($aupper == "=");
				
				// For operators, pop operators from the stack until you reach an opening parenthesis, 
				// an operator of lower precedence, or a right associative symbol of equal precedence. 
				while (count($stack)>0) { // 4a)
					$op = array_pop ($stack);
					// The only right-associative operator is =, which we allow at most once!
					if ($op == "(" || $op == "FUNCTION(") {
						// add it back to the stack!
						array_push ($stack, $op);
						break;
					} elseif ($operators[$op]<$prec) {
						// We found an operator with lower precedence, add it back to the stack!
						array_push ($stack, $op); // 4b)
						break;
					} else {
						array_push ($out_stack, $op);
					}
				} while (0);
				array_push ($stack, $aupper); // 4b)
				$prev_token_operator = true;
				
			} else { // 3) Everything else is an Operand
				$out_stack[] = $a;
				$prev_token_operator = false;
			}
		}
		// Finally, pop all operators from the stack and append them to the result
		while ($op=array_pop($stack)) {
			// Opening parentheses should not be found on the stack any more. That would mean a closing paren is missing!
			if ($op == "(") {
				$this->framework->warning('OTSHIPMENT_RULES_PARSE_PAREN_NOT_CLOSED', $rulepart);
			} else {
				array_push ($out_stack, $op);
			}
		}
		if (!empty($function_args)) {
				$this->framework->warning('OTSHIPMENT_RULES_PARSE_FUNCTION_NOT_CLOSED', $rulepart);
		}


		/** Now, turn the RPN into an expression tree (i.e. "evaluate" it into a tree structure), according to Knuth:
		 *   1) Initialize an empty stack
		 *   2) Read the RPN from left to right
		 *   3) If operand, push it onto the stack
		 *   4) If operator:
		 *       4a) pop two operands
		 *       4b) perform operation
		 *       4c) push result onto stack
		 *       4d) (If less than two operands => ERROR, invalid syntax)
		 *   5) At the end of the RPN, pop the result from the stack. 
		 *       5a) The stack should now be empty (otherwise, ERROR, invalid syntax)
		 */

		$stack=array(); // 1)
		foreach ($out_stack as $e) { // 2)
			if (is_array($e) && $e[0]=="FUNCTION") { // A function call (#args is saved as $e[2], so remove that number of operands from the stack)
				$function = $e[1];
				$argc = $e[2];
				$args = array();
				for ($i = $argc; $i > 0; $i--) {
					$a = array_pop($stack);
					array_unshift($args, $a);
				}
				array_unshift($args, $function);
				array_unshift($args, "FUNCTION"); 
				$stack[] = $args;
			} elseif (in_array($e, $unary_ops)) { // 4) unary operators
				// Operator => apply to the last value on the stack
				if (count($stack)<1) { // 4d)
					$this->framework->warning('OTSHIPMENT_RULES_EVALUATE_SYNTAXERROR', $rulepart);
					array_push($stack, 0);
					continue;
				}
				$o1 = array_pop($stack);
				// Special-case chained comparisons: if e is a comparison, and operator(o1) is also a comparison, 
				// insert the arguments to the existing comparison instead of creating a new one
				$op = array ($e, $o1); // 4b)
				array_push ($stack, $op); // 4c)
			} elseif (isset($operators[$e])) { // 4) binary operators
				// Operator => apply to the last two values on the stack
				if (count($stack)<2) { // 4d)
					$this->framework->warning('OTSHIPMENT_RULES_EVALUATE_SYNTAXERROR', $rulepart);
					array_push($stack, 0);
					continue;
				}
				$o2 = array_pop($stack); // 4a)
				$o1 = array_pop($stack);
				// Special-case chained comparisons, e.g. 1<=Amount<100:
				// if e is a comparison, and operator(o1) is also a comparison, 
				// insert the arguments to the existing comparison instead of creating a new one
				if (in_array ($e, $comparison_ops)) {
					if ($o1[0]=='COMPARISON') {
						$op = $o1;
						// Append the new comparison to the existing one
						array_push($op, $e, $o2);
					} else {
						$op = array ('COMPARISON', $o1, $e, $o2);
					}
				} else {
					$op = array ($e, $o1, $o2); // 4b)
				}
				array_push ($stack, $op); // 4c)
			} else { // 3)
				// Operand => push onto stack
				array_push ($stack, $e);
			}
			
		}
		// 5a)
		if (count($stack) != 1) {
			$this->framework->warning('OTSHIPMENT_RULES_EVALUATE_UNKNOWN_ERROR', $rulepart);
			$this->framework->warning('Outstack: <pre>%s</pre>', print_r($out_stack,1));
			
			$stack = array (0);
		}
		$res = array_pop($stack); // 5)
		
		if ($is_assignment) { // Assignments are handled first, so conditions can be assigned to variables
			if ($res[0]=='=') {
				$this->handleAssignment ($res[1], $res[2], $rulepart);
			} else {
				// Assignment has to be top-level!
				$this->framework->warning('OTSHIPMENT_RULES_EVALUATE_ASSIGNMENT_TOPLEVEL', $rulepart);
			}
		} elseif ($is_condition) { // Comparisons are conditions
			$this->conditions[] = $res;
		} else {
			// Terms without comparisons or assignments are shipping cost expressions
			$this->shipping = $res;
			$this->ruletype = 'shipping';
			$this->includes_tax = False;
		}
// 		$this->framework->warning("<pre>Rule part '$rulepart' (type $this->ruletype) parsed into (condition=".print_r($is_condition,1).", assignment=".print_r($is_assignment,1)."): ".print_r($res,1)."</pre>");
	}


}

// No closing tag