<?php
/**
 * Cache based on SQLite 3 <https://www.sqlite.org>
 */
class SQLiteCache implements CacheInterface {
	protected $scope;
	protected $key;

	private $db = null;

	public function __construct() {
		if (!extension_loaded('sqlite3')) {
			die('"sqlite3" extension not loaded. Please check "php.ini"');
		}

		$file = Configuration::getConfig(get_called_class(), 'file');
		if (empty($file)) {
			die('Configuration for ' . get_called_class() . ' missing. Please check your ' . FILE_CONFIG);
		}
		if (dirname($file) == '.') {
			$file = PATH_CACHE . $file;
		} elseif (!is_dir(dirname($file))) {
			die('Invalid configuration for ' . get_called_class() . '. Please check your ' . FILE_CONFIG);
		}

		if (!is_file($file)) {
			$this->db = new SQLite3($file);
			$this->db->enableExceptions(true);
			$this->db->exec("CREATE TABLE storage ('key' BLOB PRIMARY KEY, 'value' BLOB, 'updated' INTEGER)");
		} else {
			$this->db = new SQLite3($file);
			$this->db->enableExceptions(true);
		}
		$this->db->busyTimeout(5000);
	}

	public function loadData(){
		$Qselect = $this->db->prepare('SELECT value FROM storage WHERE key = :key');
		$Qselect->bindValue(':key', $this->getCacheKey());
		$result = $Qselect->execute();
		if ($result instanceof SQLite3Result) {
			$data = $result->fetchArray(SQLITE3_ASSOC);
			if (isset($data['value'])) {
				return unserialize($data['value']);
			}
		}

		return null;
	}

	public function saveData($data){
		$Qupdate = $this->db->prepare('INSERT OR REPLACE INTO storage (key, value, updated) VALUES (:key, :value, :updated)');
		$Qupdate->bindValue(':key', $this->getCacheKey());
		$Qupdate->bindValue(':value', serialize($data));
		$Qupdate->bindValue(':updated', time());
		$Qupdate->execute();

		return $this;
	}

	public function getTime(){
		$Qselect = $this->db->prepare('SELECT updated FROM storage WHERE key = :key');
		$Qselect->bindValue(':key', $this->getCacheKey());
		$result = $Qselect->execute();
		if ($result instanceof SQLite3Result) {
			$data = $result->fetchArray(SQLITE3_ASSOC);
			if (isset($data['updated'])) {
				return $data['updated'];
			}
		}

		return null;
	}

	public function purgeCache($seconds){
		$Qdelete = $this->db->prepare('DELETE FROM storage WHERE updated < :expired');
		$Qdelete->bindValue(':expired', time() - $seconds);
		$Qdelete->execute();
	}

	/**
	* Set scope
	* @return self
	*/
	public function setScope($scope){
		if(is_null($scope) || !is_string($scope)) {
			throw new \Exception('The given scope is invalid!');
		}

		$this->scope = $scope;
		return $this;
	}

	/**
	* Set key
	* @return self
	*/
	public function setKey($key){
		if (!empty($key) && is_array($key)) {
			$key = array_map('strtolower', $key);
		}
		$key = json_encode($key);

		if (!is_string($key)) {
			throw new \Exception('The given key is invalid!');
		}

		$this->key = $key;
		return $this;
	}

	////////////////////////////////////////////////////////////////////////////

	private function getCacheKey(){
		if(is_null($this->key)) {
			throw new \Exception('Call "setKey" first!');
		}

		return hash('sha1', $this->scope . $this->key, true);
	}
}