<?
class XMLDB{

	const SELECT = 'select';
	const INSERT = 'insert';
	const DELETE = 'delete';
	const UPDATE = 'update';

	/**
	 * Request
	 */
	protected $current_request;
	protected $operation;
	protected $from;
    protected $setID;
    protected $setChild;
	protected $whereID;
	protected $whereChildren;
    protected $position;

	// Path and name to the file
	protected $_file;

	// Primary key
	protected $_primaryKey;

	// Selected table
	protected $_table;

	// XPATH of the doc
	protected $_xpath;

	// Content of the XML DB File
	protected $_doc;

	// Name of the main root
	protected $_databaseName;

	// Name of each table root
	protected $_tableName;

	// Name of each item inside tables
	protected $_itemName;

	// Encoding used for the XML
	protected $_encoding;

	// Node buffered
	protected $_buffer;


	/**
	 * Constructor
	 * @param $file string path to the file to read/create
	 * @param $pk string name of the primary key
	 * @param $createIfNotExist bool create the file if it doesn't exist
	 */
	public function __construct($file, $pk = "id", $createIfNotExist = false, $databaseName = "Database", $tableName = "table", $itemName = "item", $encoding = "utf-8"){
		$this->_buffer			= null;
		$this->_databaseName 	= $databaseName;
		$this->_itemName 		= $itemName;
		$this->_tableName 		= $tableName;
		$this->_encoding 		= $encoding;
		$this->_primaryKey 		= $pk;
		$this->_file 			= $file;
		$this->_doc 			= new DOMDocument;
		$this->_doc->preserveWhiteSpace = false;
		$this->_doc->formatOutput = true;
		if($this->_doc->load($this->_file)){
			$this->_xpath = new DOMXpath($this->_doc);
		}
		else{
			if($createIfNotExist){
				$this->createDatabase($file);
			}else{
				$this->_file 	= null;
				$this->_doc 	= null;
				$this->xpath 	= null;
			}
		}
	}

    public function __destruct(){
        $this->commit();
    }

	public function createDatabase($file){
		$this->_file 	= $file;
		$this->_doc 	= DOMDocument::loadXML('<?xml version="1.0" encoding="' . $this->_encoding . '"?>
			<' . $this->_databaseName . '>
			</' . $this->_databaseName . '>');
		$this->_xpath 	= new DOMXpath($this->_doc);
		return $this->commit();
	}

	public function dropDatabase($definitely = false){
		if($definitely){
			unlink($this->_file);
		}else{
			$this->createDatabase($this->_file);
		}
	}

    /**
	 * @return bool
	 */
	public function tableAlreadyExists($tableName){
		$request = $this->_xpath->query('//' .  $this->_tableName . '[@name = "'.$tableName.'"]');
		if($this->getResult($request, 'count') >= 1)
			return true;
		return false;
	}

	public function isTableAI($tableName){
		if($this->tableAlreadyExists($tableName)){
			$table = $this->_xpath->query('//' .  $this->_tableName . '[@name = "'.$tableName.'"]');
			$ai = $this->getAttribute('autoincrement', $table);
			if($ai == 'true')
				return true;
		}
		return false;
	}

    public function isLoaded(){
		if($this->_doc != null)
			return true;
		else
			return false;
	}

   	public function setPrimaryKey($pk){
		$this->_primaryKey = $pk;
	}

	public function getPrimaryKey(){
		return $this->_primaryKey;
	}

	public function getXPath(){
		return $this->_xpath;
	}

	public function setBuffer($node){
		$this->_buffer = $node;
	}

	public function getBuffer($buffer){
		return $this->_buffer;
	}

    /**
	 * Saving the DB file
	 */
	 public function commit(){
		if($this->_doc != null && $this->_file != null){
			$this->_doc->preserveWhiteSpace = false;
			$this->_doc->formatOutput = true;
			$this->_doc->save($this->_file);
			return true;
		}else{
			return false;
		}
	 }
     
	public function createTable($name, $autoincrement = false, $aiDefaultValue = 0){
		if($name == '*' || $this->tableAlreadyExists($name))
			return false;
		else{
			if($autoincrement)
				return $this->_insert(array('name'=>$this->_tableName, 'attributes'=>array('name'=>$name, 'autoincrement'=>'true', 'aivalue'=>$aiDefaultValue)));
			else
				return $this->_insert(array('name'=>$this->_tableName, 'attributes'=>array('name'=>$name)));
		}
	}

	public function dropTable($table){
		return $this->_delete($table);
	}

	private function updateTableAIValue($table){
		if($this->tableAlreadyExists($table)){
			$table = $this->selectTable($table);
			$newValue = $table->item(0)->getAttribute('aivalue')+1;
			$table->item(0)->setAttribute('aivalue', $newValue);
			return $newValue;
		}
		return false;
	}

    private function _getNewIncrement($table){
		return $this->updateTableAIValue($table);
	}

	public function pkAlreadyExists($pk, $table = '*'){
		if($this->selectFromPK($table, $pk , 'count') > 0){
			return true;
		}
		return false;
	}


	private function getResult($request, $format){
		switch($format){
			case "node":
				return $request;
				break;
			case "count":
				return $request->length;
				break;
			case "array":
			default:
				return $this->requestToArray($request);
		}
	}

	public function select(array $what = array('*')){
		$this->current_request = self::SELECT;
		$this->operation = $what;
	}

    public function insert(array $what = null){
		$this->current_request = self::INSERT;
		if($what != null)
			$this->operation = $what;
		else
			throw new Exception('You must indicate something to insert');
	}

    public function delete(){
		$this->current_request = self::DELETE;
	}

    // TODO 
    public function update(string $from){
		$this->current_request = self::UPDATE;
        $this->from = $from;
	}

	public function from(string $from = '*'){
		if($this->tableAlreadyExists($from))
			$this->from = $from;
		else
			$this->from = '*';
	}

    public function set(array $setID = null, array $setChild = null){
        $this->setID    = $setID;
        $this->setChild = $setChild;
    }
    
	public function where(string $whereID = null, array $whereChildren = null){
		$this->whereID 			= $whereID;
		$this->whereChildren 	= $whereChildren;
	}

    public function toPosition(int $to){
        $this->position = $to;
    }

	public function query(){
		return $this->_prepareStmt();
	}

	private function _prepareStmt(){
		switch($this->current_request()){
			case self::SELECT:
				return $this->_select($this->what, $this->from, $this->whereID, $this->whereChildren);
				break;
			case self::INSERT:
                return $this->_insert($this->operation, $this->from, $this->position);
				break;
			case self::DELETE:
                return $this->_delete($this->from, $this->whereID);
				break;
			case self::UPDATE:
                return $this->_update($this->from, $this->setID, $this->setChild, $this->whereID, $this->whereChildren);
				break;
			default:
                throw new Exception('no request detected.');
				break;
		}
	}

	private function _getAttribute($attribute, $node){
		if($node->length == 1){
			return $node->item(0)->getAttribute($attribute);
		}else{
			return false;
		}
	}

	private function _getChildValue($child, $node){
        $nodeArray = array();
		if($node->length == 1){
			$nodeArray = $this->_requestToArray($node);
			if(isset($nodeArray[0]['childs'][$child]))
				return $nodeArray[0]['childs'][$child];
		}
		return false;
	}

	private function _requestToArray($request){
		$return = array();
		$number = 0;

		foreach($request as $element){
			/*if($childName != null && $childValue != null)
			$element = $element->parentNode;*/
			$elementValue = $element->attributes->item(0)->value;
			$return[$number]['name'] = $this->_itemName;
			$return[$number]['attributes'] = array($this->_primaryKey => $elementValue);
			$return[$number]['childs'] = array();

			//Retrieving Attributes
			$attributes = $element->attributes;
			$length = $attributes->length;
			for ($i = 0; $i <= $length; $i++) {
				if($attributes->item($i)->name != '')
				$return[$number]['attributes'][$attributes->item($i)->name] = $attributes->item($i)->value;
			}

			// Retrivieving childs
			$nodes = $element->childNodes;
			$length = $nodes->length;
			for ($i = 0; $i <= $length; $i++) {
				if($nodes->item($i)->nodeName != '')
				$return[$number]['childs'][$nodes->item($i)->nodeName] = $nodes->item($i)->nodeValue;
			}
			$number++;
		}
		return $return;
	}

    private function _update($from, $setID = null, $setChild = null, $whereID = null, $whereChildren = null){
        $node = $this->_select(array('*'), $from, $whereID, $whereChildren);
        if($node != null){
            $this->updateChildValue($from, $node, $setChild, $forceInsert);
            $this->updateItemAttribute($from, $node, $newAttribute, $forceInsert);
        }else{
            return false;
        }
    }
    
	private function _select(array $what, string $from, string $id = null, $childs = null, $item = ''){
        $attribute  = '';
        $child      = '';
		if($id != null && !is_array($id)){
			$attribute = '[@' . $this->_primaryKey . ' = "' . $id . '"]';
		}
		if($childs != null && is_array($childs)){
			foreach($childs as $childName=>$childValue)
				$child .= '[' . $childName . '="' . $childValue . '"]';
		}
		if($from == '*')
			$request = $this->_xpath->query('//item'.$attribute.$child);
		else
			$request = $this->_xpath->query('//' .  $this->_tableName . '[@name = "'.$from.'"]'.$item.$attribute.$child);
		if($what == '*')
			return $request;
		else{
			return $this->_getChildValue($what, $request);
		}
	}

	private function _arrayToNode($node){
		if(!is_array($node) || !in_array($node['name'], array($this->_tableName, $this->_itemName)))
			return;
		$element = $this->_doc->createElement($node['name']);
		if(isset($node['attributes'])){
			foreach($node['attributes'] as $attributeName=>$attributeValue){
				if($attributeName != '')
				$element->setAttribute($attributeName, $attributeValue);
			}
		}
		if(isset($node['childs'])){
			foreach($node['childs'] as $childName=>$childValue){
				if($childName != ''){
					$newElement = $this->_doc->createElement($childName, $childValue);
					$element->appendChild($newElement);
				}
			}
		}
		return $element;
	}


	/**
	 * Allows you to insert a node into your DB thanks to an array
	 * @param $node array with 'name' 'attributes' and 'childs'
	 * @param $table string in which node you want to put it. By default, the root of the xml file
	 * @param $position string 'before' or 'after'
	 * @return bool
	 */
	public function insertItem($id = null, $attributes = null, $childs = null, $table){
		if($id == null && $this->isTableAI($table)){
			$id = $this->_getNewIncrement($table);
		}
		else if(($id == null && !$this->isTableAI($table)) || ($id != null && $this->isTableAI($table)))
			return false;

		if($attributes == null)
			$attributes = array($this->_primaryKey=>$id);
		else
			$attributes += array($this->_primaryKey=>$id);
		if($this->tableAlreadyExists($table) && !$this->pkAlreadyExists($id, $table))
			return $this->_insert(array('name'=>$this->_itemName, 'attributes'=>$attributes, 'childs'=>$childs), $table);
		return false;
	}

	// TODO $position
	private function _insert(array $node, string $table = null, int $position = null){
		if(isset($node[0]))
			$node = $node[0];
		if(!is_array($node) || !isset($node['name']) || !isset($node['attributes'])){
			throw new Exception('The node is not well formated.');
		}
		// Creating the node from an array
		$element = $this->_arrayToNode($node);

		// Inserting the node into the DB
		// case : creation of a new table
		if($table == null &&  !$this->tableAlreadyExists($node['name'])){
			$this->_doc->firstChild->appendChild($element);
		}else if($table != null){
		// case : insertion into the end of table
			if(!$this->tableAlreadyExists($table) || $this->pkAlreadyExists($node['attributes'][$this->_primaryKey], $table)){
				return false;
			}
			$totalItemInTable = $this->selectAllFromTable($table, 'count');
			if($position == null || $position < $totalItemInTable){
				$request = $this->_xpath->query('//' .  $this->_tableName . '[@name = "'.$table.'"]');
				$request->item(0)->appendChild($element);
			}else{
				$itemsAfter = $this->selectAllFromTable($table, 'node');
				$itemAfter = $itemsAfter->item($position-1);
				$itemAfter->parentNode->insertBefore($element, $itemAfter);
			}
		}else{
			return false;
		}
		return $this->commit();
	}

	/**
	 *
	 * @param $table string
	 * @param $oldAttribute string name of the attribute you want to change
	 * @param $newAttribute array name/value of the attribute you want to add
	 * @param $forceInsert bool
	 * @return bool
	 */
	public function updateItemAttribute($table, $oldAttribute, $newAttribute, $forceInsert = false){
		$request = $this->select($table, null, array($oldAttribute[0]=>$oldAttribute[1]), null, 'node', '/'.$this->_itemName);
		if($request->length == 1){
			if(!$forceInsert){
				$request->item(0)->setAttribute($oldAttribute[0],$newAttribute[1]);
			}else{
				$request->item(0)->setAttribute($newAttribute[0],$newAttribute[1]);
			}
			return $this->commit();
		}
		else
			return false;
	}

	/**
	 *
	 * @param $table string
	 * @param $value string new value of the node
	 * @return bool
	 */
	public function updateItemValue($table, $attribute = null, $child = null, $value){
		$request = $this->select($table, null, array($attribute[0]=>$attribute[1]), $child, 'node', '/'.$this->_itemName);
		//$request = $this->_xpath->query('//'.$node.'[@' . $attribute[0] . ' = "' . $attribute[1] . '"]');
		if($request->length == 1){
			$request = $request->item(0);
			$newText = new DOMText($value);
			$request->removeChild($request->firstChild);
			$request->appendChild($newText);
			return $this->commit();
		}
		else
			return false;
	}

	public function updateChildValue($table, $node, $child, $value){
		if($node->length == 1){
			$node = $node->item(0);
			$newChild = $this->_doc->createElement($child, $value);
			$old_element_childNodes = $node->childNodes;
			$length = $old_element_childNodes->length;
			$index = 0;
			for($i = 0; $i < $length; $i++)
			{
				if($old_element_childNodes->item($i)->nodeName == $child){
					$index = $i;
					break;
				}
			}
			//$request = $node->getElementsByTagName($child)->item(0);
			if($node->replaceChild($newChild, $old_element_childNodes->item($index)))
			return $this->commit();
		}
		return false;
	}
    
	/**
	 * Delete an entry
	 * @param $table name of the table in which the entry is
	 * @param $id $attributes array where condition(s)
	 * @return bool
	 */
	private function _delete($table, $id = null){
		if($id != null)
            $request = $this->_select (array('*'), $table, $id, null);
			//$request = $this->selectFromPK($table, $id, 'node')->item(0);
		else
			$request = $this->_select (array('*'), $table);
		if($request == null)
			return false;
		try{
			$request->parentNode->removeChild($request);
		}catch(Exception $e){
			echo $e->getMessage();
			return false;
		}
		return $this->commit();
	}

	public function move($node, $to, $position = null){
		$this->_buffer = $node;
		if($this->deleteNode($node)){
			$nodeArray = $this->requestToArray($this->_buffer);
			return $this->_insert($nodeArray, $to, $position);
		}else
			return false;
	}
}