<?php

namespace Vn\Web;

class DbSessionHandler implements \SessionHandlerInterface {
	const UPDATE_INTERVAL = 30;
	private $db;
	
	function __construct($db) {
		$this->db = $db;
	}

	function open($savePath, $name) {
		return TRUE;
	}

	function close() {
		return TRUE;
	}

	function read($sessionId) {
		$sessionData = $this->db->getValue(
			'SELECT data FROM userSession WHERE ssid = #', [$sessionId]);
		return isset($sessionData) ? $sessionData : '';
	}

	function write($sessionId, $sessionData) {
		$session = $this->db->getObject(
			'SELECT data, lastUpdate < (NOW() - INTERVAL # SECOND) hasToRefresh
				FROM userSession WHERE ssid = #',
			[self::UPDATE_INTERVAL, $sessionId]
		);

		if (!isset($session)
		|| $sessionData !== $session->data
		|| $session->hasToRefresh) {
			$this->db->query(
				'INSERT INTO userSession SET
						ssid = #, data = #, lastUpdate = NOW()
					ON DUPLICATE KEY UPDATE
						data = VALUES(data), lastUpdate = VALUES(lastUpdate)',
				[$sessionId, $sessionData]);
		}

		return TRUE;
	}

	function destroy($sessionId) {
		$this->db->query('DELETE FROM userSession WHERE ssid = #', [$sessionId]);
		return TRUE;	
	}

	function gc($maxLifeTime) {
		$this->db->query('DELETE FROM userSession
			WHERE lastUpdate < (NOW() - INTERVAL # SECOND)',
			[$maxLifeTime + self::UPDATE_INTERVAL + 1]
		);
		return TRUE;
	}
}