/lib/context.php

<?php

/**

 * Liquid for PHP

 * 

 * @package Liquid

 * @copyright Copyright (c) 2006 Mateo Murphy, 

 * based on Liquid for Ruby (c) 2006 Tobias Luetke

 * @license http://www.opensource.org/licenses/mit-license.php

 *

 */



/**

 * Context keeps the variable stack and resolves variables, as well as keywords

 *

 * @package Liquid

 */

class LiquidContext {

	

	/**

	 * Local scopes

	 *

	 * @var array

	 */

	var $assigns;



	/**

	 * Registers for non-variable state data

	 *

	 * @var array

	 */

	var $registers;

	

	/**

	 * The filterbank holds all the filters

	 *

	 * @var LiquidFilterbank

	 */

	var $filterbank;

	

	/**

	 * Constructor

	 *

	 * @param array $assigns

	 * @param array $registers

	 * @return LiquidContext

	 */

	function LiquidContext($assigns = null, $registers = null) {

		if (isset($assigns)) {

			$this->assigns = array($assigns);

			

		} else {

			$this->assigns = array(array());

			

		}

		

		if (isset($registers)) {

			$this->registers = $registers;

			

		} else {

			$this->registers = array();

			

		}

		

		$this->filterbank = new LiquidFilterbank($this);

		

		

	}

	

	/**

	 * Add a filter to the context

	 *

	 * @param mixed $filter

	 */

	function add_filters($filter) {

		$this->filterbank->add_filter($filter);

		

		

	}

	

	/**

	 * Invoke the filter that matches given name

	 *

	 * @param string $name The name of the filter

	 * @param mixed $value The value to filter

	 * @param array $args Additional arguments for the filter

	 * @return string

	 */

	function invoke($name, $value, $args = null) {

		return $this->filterbank->invoke($name, $value, $args);

			

	}

	

	/**

	 * Merges the given assigns into the current assigns

	 *

	 * @param array $new_assigns

	 */

	function merge($new_assigns) {

		$this->assigns[0] = array_merge($this->assigns[0], $new_assigns);

		

	}	

	

	/**

	 * Push new local scope on the stack.

	 *

	 * @return bool

	 */

	function push() {

		array_unshift($this->assigns, array());

		return true;

		

	}

	

	/**

	 * Pops the current scope from the stack.

	 *

	 * @return bool

	 */

	function pop() {

		if (count($this->assigns) == 1) {

			trigger_error('No elements to pop', E_USER_ERROR);

			return false;	

		}

		

		array_shift($this->assigns);

	}

	

	/**

	 * Replaces []

	 * 

	 * @param string

	 * @return mixed

	 */

	function get($key) {

		return $this->resolve($key);

		

	}

	

	/**

	 * Replaces []=

	 *

	 * @param string $key

	 * @param mixed $value

	 */

	function set($key, $value) {

		$this->assigns[0][$key] = $value;

		

	}

	

	/**

	 * Returns true if the given key will properly resolve

	 *

	 * @param string $key

	 * @return bool

	 */

	function has_key($key) {

		return (!is_null($this->resolve($key)));

		

	}

	

	/**

	 * Resolve a key by either returning the appropriate literal or by looking up the appropriate variable

	 * 

	 * Test for empty has been moved to interpret condition, in LiquidDecisionBlock

	 *

	 * @param string $key

	 * @return mixed

	 */

	function resolve($key) {

		// this shouldn't happen

		if (is_array($key)) {

			trigger_error("Cannot resolve arrays as key", E_USER_ERROR);

			return null;

		}

		

		if (is_null($key) || $key == 'null') {

			return null;

		}

	

		if ($key == 'true') {

			return true;

		}

		

		if ($key == 'false') {

			return false;

		}

		

		if (preg_match('/^\'(.*)\'$/', $key, $matches)) {

			return $matches[1];

		}



		if (preg_match('/^"(.*)"$/', $key, $matches)) {

			return $matches[1];

		}



		if (preg_match('/^(\d+)$/', $key, $matches)) {

			return $matches[1];

		}



		if (preg_match('/^(\d[\d\.]+)$/', $key, $matches)) {

			return $matches[1];

		}			

		

		return $this->variable($key);

		

	}

	

	/**

	 * Fetches the current key in all the scopes

	 *

	 * @param string $key

	 * @return mixed

	 */

	function fetch($key) {

		foreach ($this->assigns as $scope) {

			if (array_key_exists($key, $scope)) {

				$obj = $scope[$key];

				

				if (is_a($obj, 'LiquidDrop')) {

					$obj->context = $this;

				}

				

				return $obj;

				

			}

			

		}

		

	}

	

	/**

	 * Resolved the namespaced queries gracefully.

	 *

	 * @param string $key

	 * @return mixed

	 */

	function variable($key) {

		$parts = explode(LIQUID_VARIABLE_ATTRIBUTE_SEPERATOR, $key);

		

		$object = $this->fetch(array_shift($parts));

		

		if (is_object($object)) {

			$object = $object->to_liquid();

		}

		

		

		if (!is_null($object)) {

			while (count($parts) > 0) {

				if (is_a($object, 'LiquidDrop')) {

					$object->context = $this;

				}	

				

				$next_part_name = array_shift($parts);

				

				if (is_array($object)) {

					

					// if the last part of the context variable is .size we just return the count

					if ($next_part_name == 'size' && count($parts) == 0 && !array_key_exists('size', $object)) {

						return count($object);	

						

					}					

					

					if (array_key_exists($next_part_name, $object)) {

						$object = $object[$next_part_name];

					} else {

						return null;

						

					}

					

				} else if (is_object($object)) {

					

					

					if (is_a($object, 'LiquidDrop')) {

						// if the object is a drop, make sure it supports the given method

						if (!$object->has_key($next_part_name)) {

							return null;

						}

						

						// php4 doesn't support array access, so we have

						// to use the invoke method instead

						$object = $object->invoke_drop($next_part_name);

						

					} elseif(method_exists($object, LIQUID_HAS_PROPERTY_METHOD)) {

						

						if (!call_user_method(LIQUID_HAS_PROPERTY_METHOD, $object, $next_part_name)) {

							return null;

							

						}

						

						$object = call_user_method(LIQUID_GET_PROPERTY_METHOD, $object, $next_part_name);

						

						

					} else {

						// if it's just a regular object, attempt to access a property

						if (!property_exists($object, $next_part_name)) {

							return null;	

							

						}

						

						$object = $object->$next_part_name;	



					}

					

					

				}



				if (is_object($object) && method_exists($object, 'to_liquid')) {

					$object = $object->to_liquid();

				}



			}



			return $object;		

			

		} else {

			return null;

			

		}

		

				

	}

	

}





?>