<?php
/**
 * Base class for filtering implementations,
 * which work together with {@link SearchContext}
 * to create or amend a query for {@link DataObject} instances.
 * See {@link SearchContext} for more information.
 *
 * @package framework
 * @subpackage search
 */
abstract class SearchFilter extends Object {
	
	/**
	 * @var string Classname of the inspected {@link DataObject}
	 */
	protected $model;
	
	/**
	 * @var string
	 */
	protected $name;
	
	/**
	 * @var string 
	 */
	protected $fullName;
	
	/**
	 * @var mixed
	 */
	protected $value;
	
	/**
	 * @var array
	 */
	protected $modifiers;

	/**
	 * @var string Name of a has-one, has-many or many-many relation (not the classname).
	 * Set in the constructor as part of the name in dot-notation, and used in 
	 * {@link applyRelation()}.
	 */
	protected $relation;
	
	/**
	 * @param string $fullName Determines the name of the field, as well as the searched database 
	 *  column. Can contain a relation name in dot notation, which will automatically join
	 *  the necessary tables (e.g. "Comments.Name" to join the "Comments" has-many relationship and
	 *  search the "Name" column when applying this filter to a SiteTree class).
	 * @param mixed $value
	 * @param array $modifiers
	 */
	public function __construct($fullName, $value = false, array $modifiers = array()) {
		$this->fullName = $fullName;
		// sets $this->name and $this->relation
		$this->addRelation($fullName);
		$this->value = $value;
		$this->setModifiers($modifiers);
	}
	
	/**
	 * Called by constructor to convert a string pathname into
	 * a well defined relationship sequence.
	 *
	 * @param string $name
	 */
	protected function addRelation($name) {
		if (strstr($name, '.')) {
			$parts = explode('.', $name);
			$this->name = array_pop($parts);
			$this->relation = $parts;
		} else {
			$this->name = $name;
		}
	}
	
	/**
	 * Set the root model class to be selected by this
	 * search query.
	 *
	 * @param string $className
	 */	
	public function setModel($className) {
		$this->model = $className;
	}
	
	/**
	 * Set the current value to be filtered on.
	 *
	 * @param string $value
	 */
	public function setValue($value) {
		$this->value = $value;
	}
	
	/**
	 * Accessor for the current value to be filtered on.
	 * Caution: Data is not escaped.
	 *
	 * @return string
	 */
	public function getValue() {
		return $this->value;
	}

	/**
	 * Set the current modifiers to apply to the filter
	 *
	 * @param array $modifiers
	 */
	public function setModifiers(array $modifiers) {
		$this->modifiers = array_map('strtolower', $modifiers);
	}

	/**
	 * Accessor for the current modifiers to apply to the filter.
	 *
	 * @return array
	 */
	public function getModifiers() {
		return $this->modifiers;
	}
	
	/**
	 * The original name of the field.
	 *
	 * @return string
	 */
	public function getName() {
		return $this->name;
	}

	/**
	 * @param String
	 */
	public function setName($name) {
		$this->name = $name;
	}
	
	/**
	 * The full name passed to the constructor,
	 * including any (optional) relations in dot notation.
	 * 
	 * @return string
	 */
	public function getFullName() {
		return $this->fullName;
	}

	/**
	 * @param String
	 */
	public function setFullName($name) {
		$this->fullName = $name;
	}
	
	/**
	 * Normalizes the field name to table mapping.
	 * 
	 * @return string
	 */
	public function getDbName() {
		// Special handler for "NULL" relations
		if($this->name == "NULL") return $this->name;
		
		// SRM: This code finds the table where the field named $this->name lives
		// Todo: move to somewhere more appropriate, such as DataMapper, the magical class-to-be?
		$candidateClass = $this->model;
		while($candidateClass != 'DataObject') {
			if(DataObject::has_own_table($candidateClass) 
					&& singleton($candidateClass)->hasOwnTableDatabaseField($this->name)) {
				break;
			}
			$candidateClass = get_parent_class($candidateClass);
		}
		if($candidateClass == 'DataObject') {
			user_error("Couldn't find field $this->name in any of $this->model's tables.", E_USER_ERROR);
		}
		
		return "\"$candidateClass\".\"$this->name\"";
	}
	
	/**
	 * Return the value of the field as processed by the DBField class
	 *
	 * @return string
	 */
	public function getDbFormattedValue() {
		// SRM: This code finds the table where the field named $this->name lives
		// Todo: move to somewhere more appropriate, such as DataMapper, the magical class-to-be?
		$candidateClass = $this->model;
		$dbField = singleton($this->model)->dbObject($this->name);
		$dbField->setValue($this->value);
		return $dbField->RAW();
	}

	
	/**
	 * Apply filter criteria to a SQL query.
	 *
	 * @param DataQuery $query
	 * @return DataQuery
	 */
	public function apply(DataQuery $query) {
		if(($key = array_search('not', $this->modifiers)) !== false) {
			unset($this->modifiers[$key]);
			return $this->exclude($query);
		}
		if(is_array($this->value)) {
			return $this->applyMany($query);
		} else {
			return $this->applyOne($query);
		}
	}

	/**
	 * Apply filter criteria to a SQL query with a single value.
	 *
	 * @param DataQuery $query
	 * @return DataQuery
	 */
	abstract protected function applyOne(DataQuery $query);

	/**
	 * Apply filter criteria to a SQL query with an array of values.
	 *
	 * @param DataQuery $query
	 * @return DataQuery
	 */
	protected function applyMany(DataQuery $query) {
		throw new InvalidArgumentException(get_class($this) . "can't be used to filter by a list of items.");
	}

	/**
	 * Exclude filter criteria from a SQL query.
	 *
	 * @param DataQuery $query
	 * @return DataQuery
	 */
	public function exclude(DataQuery $query) {
		if(($key = array_search('not', $this->modifiers)) !== false) {
			unset($this->modifiers[$key]);
			return $this->apply($query);
		}
		if(is_array($this->value)) {
			return $this->excludeMany($query);
		} else {
			return $this->excludeOne($query);
		}
	}

	/**
	 * Exclude filter criteria from a SQL query with a single value.
	 *
	 * @param DataQuery $query
	 * @return DataQuery
	 */
	abstract protected function excludeOne(DataQuery $query);

	/**
	 * Exclude filter criteria from a SQL query with an array of values.
	 *
	 * @param DataQuery $query
	 * @return DataQuery
	 */
	protected function excludeMany(DataQuery $query) {
		throw new InvalidArgumentException(get_class($this) . "can't be used to filter by a list of items.");
	}
	
	/**
	 * Determines if a field has a value,
	 * and that the filter should be applied.
	 * Relies on the field being populated with
	 * {@link setValue()}
	 * 
	 * @return boolean
	 */
	public function isEmpty() {
		return false;
	}

	/**
	 * Determines case sensitivity based on {@link getModifiers()}.
	 * 
	 * @return Mixed TRUE or FALSE to enforce sensitivity, NULL to use field collation.
	 */
	protected function getCaseSensitive() {
		$modifiers = $this->getModifiers();
		if(in_array('case', $modifiers)) return true;
		else if(in_array('nocase', $modifiers)) return false;
		else return null;
	}

}