<?php
/**
 * Dropdown-like field that allows you to select an item from a hierachical AJAX-expandable tree
 *
 * @package forms
 * @subpackage fields-relational
 */
class TreeDropdownField extends FormField {
	
	public static $url_handlers = array (
		'$Action!/$ID' => '$Action'
	);
	
	public static $allowed_actions = array (
		'tree'
	);
	
	/**
	 * @ignore
	 */
	protected $sourceObject, $keyField, $labelField, $filterCallback, $baseID = 0;
	
	/**
	 * @param string $name the field name
	 * @param string $title the field label
	 * @param string $souceClass the class to display in the tree, must have the "Hierachy" extension.
	 * @param string $keyField to field on the source class to save as the field value (default ID).
	 * @param string $labelField the field name to show as the human-readable value on the tree (default Title).
	 */
	public function __construct($name, $title = null, $sourceObject = 'Group', $keyField = 'ID', $labelField = 'Title') {
		$this->sourceObject = $sourceObject;
		$this->keyField     = $keyField;
		$this->labelField   = $labelField;
		
		if(!Object::has_extension($this->sourceObject, 'Hierarchy')) {
			throw new Exception (
				"TreeDropdownField: the source class '$this->sourceObject' must have the Hierarchy extension applied"
			);
		}
		
		Requirements::add_i18n_javascript(SAPPHIRE_DIR . '/javascript/lang');
		
		Requirements::javascript(THIRDPARTY_DIR . '/behaviour.js');
		Requirements::javascript(THIRDPARTY_DIR . '/tree/tree.js');
		Requirements::javascript(SAPPHIRE_DIR   . '/javascript/TreeSelectorField.js');
		
		Requirements::css(THIRDPARTY_DIR . '/tree/tree.css');
		Requirements::css(SAPPHIRE_DIR   . '/css/TreeDropdownField.css');
		
		parent::__construct($name, $title);
	}
	
	/**
	 * Set the ID of the root node of the tree. This defaults to 0 - i.e. displays the whole tree.
	 *
	 * @param int $ID
	 */
	public function setTreeBaseID($ID) {
		$this->baseID = (int) $ID;
	}
	
	/**
	 * Set a callback used to filter the values of the tree before displaying to the user.
	 *
	 * @param callback $callback
	 */
	public function setFilterFunction($callback) {
		if(!is_callable($callback, true)) {
			throw new InvalidArgumentException('TreeDropdownField->setFilterCallback(): not passed a valid callback');
		}
		
		$this->filterCallback = $callback;
	}
	
	/**
	 * @return string
	 */
	public function Field() {
		if($this->Value() && $record = $this->objectForKey($this->Value())) {
			$title = $record->{$this->labelField};
		} else {
			$title = _t('DropdownField.CHOOSE', '(Choose)', PR_MEDIUM, 'start value of a dropdown');
		}
		
		return $this->createTag (
			'div',
			array (
				'id'    => "TreeDropdownField_{$this->id()}",
				'class' => 'TreeDropdownField single' . ($this->extraClass() ? " {$this->extraClass()}" : '')
			),
			$this->createTag (
				'input',
				array (
					'id'    => $this->id(),
					'type'  => 'hidden',
					'name'  => $this->name,
					'value' => $this->value
				)
			) . $this->createTag (
				'span',
				array (
					'class' => 'items'
				),
				$title
			) . $this->createTag (
				'a',
				array (
					'href'  => '#',
					'title' => 'open',
					'class' => 'editLink'
				),
				'&nbsp;'
			)
		);
	}
	
	/**
	 * Get the whole tree of a part of the tree via an AJAX request.
	 *
	 * @param HTTPRequest $request
	 * @return string
	 */
	public function tree(HTTPRequest $request) {
		$isSubTree = false;
		
		if($ID = (int) $request->param('ID')) {
			$obj       = DataObject::get_by_id($this->sourceObject, $ID);
			$isSubTree = true;
			
			if(!$obj) {
				throw new Exception (
					"TreeDropdownField->tree(): the object #$ID of type $this->sourceObject could not be found"
				);
			}
		} else {
			if($this->baseID) {
				$obj = DataObject::get_by_id($this->sourceObject, $this->baseID);
			}
			
			if(!$this->baseID || !$obj) $obj = singleton($this->sourceObject);
		}
		
		if($this->filterCallback) {
			$obj->setMarkingFilterFunction($this->filterCallback);
		} elseif($this->sourceObject == 'Folder') {
			$obj->setMarkingFilter('ClassName', 'Folder');
		}
		
		$obj->markPartialTree();
		
		if($forceValues = $this->value) {
			if(($values = preg_split('/,\s*/', $forceValues)) && count($values)) foreach($values as $value) {
				$obj->markToExpose($this->objectForKey($value));
			}
		}
		
		$eval = '"<li id=\"selector-' . $this->Name() . '-{$child->' . $this->keyField . '}\" class=\"$child->class"' .
				' . $child->markingClasses() . "\"><a rel=\"$child->ID\">" . $child->' . $this->labelField . ' . "</a>"';
		
		if($isSubTree) {
			return substr(trim($obj->getChildrenAsUL('', $eval, null, true)), 4, -5);
		}
		
		return $obj->getChildrenAsUL('class="tree"', $eval, null, true);
	}
	
	/**
	 * Get the object where the $keyField is equal to a certain value
	 *
	 * @param string|int $key
	 * @return DataObject
	 */
	protected function objectForKey($key) {
		if($this->keyField == 'ID') {
			return DataObject::get_by_id($this->sourceObject, $key);
		} else {
			return DataObject::get_one($this->sourceObject, "\"{$this->keyField}\" = '" . Convert::raw2sql($key) . "'");
		}
	}
	
}