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<?php

/**
 * MvcCore
 *
 * This source file is subject to the BSD 3 License
 * For the full copyright and license information, please view 
 * the LICENSE.md file that are distributed with this source code.
 *
 * @copyright   Copyright (c) 2016 Tom Flídr (https://github.com/mvccore/mvccore)
 * @license     https://mvccore.github.io/docs/mvccore/4.0.0/LICENCE.md
 */

namespace MvcCore;

/**
 * Core session:
 * - session safe starting
 * - session writing and closing
 *   - by registered shutdown function
 *   - \MvcCore\Session::Close() - how to register the handler
 *   - close handler called registered by \MvcCore::Terminate();
 * - session namespaces management
 *   - variables expiration by seconds
 *   - variables expiration by request hoops
 */
class Session extends \ArrayObject {
    /**
     * Metadata key in $_SESSION
     * @var string
     */
    const SESSION_METADATA_KEY = '__MC';

    /**
     * Default namespace name
     * @var string
     */
    protected $__name = 'default';

    /**
     * Boolean telling about if session is started
     * @var bool
     */
    protected static $started = FALSE;

    /**
     * Metadata array or stdClass with elements: names, hoops and expirations - all items are arrays
     * @var array|\stdClass
     */
    protected static $meta = array();

    /**
     * Array of created \MvcCore\Session instances, keys in array are session namespaces names
     * @var array
     */
    protected static $instances = array();

    /**
     * Start session, called in Controller::Init();
     * It's also possible to call this anywhere sooner, for example in bootstrap by: \MvcCore::SessionStart();
     * @return void
     */
    public static function Start () {
        if (static::$started) return;
        if (!\MvcCore::GetInstance()->GetRequest()->IsAppRequest()) return;
        $sessionNotStarted = function_exists('session_status') ? session_status() == PHP_SESSION_NONE : session_id() == '' ;
        if ($sessionNotStarted) {
            session_start();
            static::setUpMeta();
            static::setUpData();
        }
        static::$started = TRUE;
    }

    /**
     * Set up session metadata about namespaces names, hoops and expirations
     * @return void
     */
    protected static function setUpMeta () {
        $metaKey = static::SESSION_METADATA_KEY;
        $meta = array();
        if (isset($_SESSION[$metaKey])) {
            $meta = @unserialize($_SESSION[$metaKey]);
        }
        if (!$meta) {
            $meta = array(
                'names'         => array(),
                'hoops'         => array(),
                'expirations'   => array(),
            );
        }
        static::$meta = (object) $meta;
    }

    /**
     * Set up namespaces data - only if they has not expired
     * @return void
     */
    protected static function setUpData () {
        $hoops = & static::$meta->hoops;
        $names = & static::$meta->names;
        $expirations = & static::$meta->expirations;
        foreach ($hoops as $name => $hoop) {
            $hoops[$name] -= 1;
        }
        $now = time();
        foreach ($names as $name => $one) {
            $unset = array();
            if (isset($hoops[$name])) {
                if ($hoops[$name] < 0) $unset[] = 'hoops';
            }
            if (isset($expirations[$name])) {
                if ($expirations[$name] < $now) $unset[] = 'expirations';
            }
            if ($unset) {
                $currentErrRepLevels = error_reporting();
                error_reporting(0);
                foreach ($unset as $unsetKey) {
                    if (isset(static::$meta->$unsetKey) && isset(static::$meta->$unsetKey[$name])) 
                        unset(static::$meta->$unsetKey[$name]);
                }
                error_reporting($currentErrRepLevels);
                unset($names[$name]);
                unset($_SESSION[$name]);
            }
        }
    }

    /**
     * Write and close session in \MvcCore::Terminate();
     * Serialize all metadata and call php function to write session.
     * @return void
     */
    public static function Close () {
        register_shutdown_function(function () {
            foreach (static::$instances as & $instance) {
                if (count($instance) === 0) $instance->Destroy();
            }
            $metaKey = static::SESSION_METADATA_KEY;
            $_SESSION[$metaKey] = serialize(static::$meta);
            @session_write_close();
        });
    }

    /**
     * Get new or existed session namespace
     * @param string $name 
     * @return \MvcCore\Session
     */
    public static function & GetNamespace ($name = 'default') {
        if (!isset(static::$instances[$name])) {
            static::$instances[$name] = new static($name);
        }
        return static::$instances[$name];
    }

    /**
     * Get new or existed session namespace
     * @param string $name 
     * @return \MvcCore\Session
     */
    public function __construct ($name = 'default') {
        if (!static::$started) static::Start();
        $this->__name = $name;
        static::$meta->names[$name] = 1;
        if (!isset($_SESSION[$name])) $_SESSION[$name] = array();
        static::$instances[$name] = $this;
    }

    /**
     * Set expiration page requests count
     * @param int $hoops
     * @return \MvcCore\Session
     */
    public function SetExpirationHoops ($hoops) {
        static::$meta->hoops[$this->__name] = $hoops;
        return $this;
    }

    /**
     * Set expiration seconds
     * @param int $hoops
     * @return \MvcCore\Session
     */
    public function SetExpirationSeconds ($seconds) {
        static::$meta->expirations[$this->__name] = time() + $seconds;
        return $this;
    }

    /**
     * Destroy whole session namespace
     * @return void
     */
    public function Destroy () {
        $name = $this->__name;
        $names = & static::$meta->names;
        $hoops = & static::$meta->hoops;
        $expirations = & static::$meta->expirations;
        $instances = & static::$instances;
        if (isset($names[$name])) unset($names[$name]);
        if (isset($hoops[$name])) unset($hoops[$name]);
        if (isset($expirations[$name])) unset($expirations[$name]);
        if (isset($_SESSION[$name])) unset($_SESSION[$name]);
        if (isset($instances[$name])) unset($instances[$name]);
    }

    /**
     * Magic function triggered by: isset($session->key);
     * @param string $key 
     * @return bool
     */
    public function __isset ($key) {
        return isset($_SESSION[$this->__name][$key]);
    }

    /**
     * Magic function triggered by: unset($session->key);
     * @param string $key 
     * @return void
     */
    public function __unset ($key) {
        $name = $this->__name;
        if (isset($_SESSION[$name][$key])) unset($_SESSION[$name][$key]);
    }

    /**
     * Magic function triggered by: $value = $session->key;
     * @param string $key 
     * @return mixed
     */
    public function __get ($key) {
        $name = $this->__name;
        if (isset($_SESSION[$name][$key])) return $_SESSION[$name][$key];
        return NULL;
    }

    /**
     * Magic function triggered by: $session->key = "value";
     * @param string $key 
     * @param mixed $value
     * @return void
     */
    public function __set ($key, $value) {
        $_SESSION[$this->__name][$key] = $value;
    }

    /**
     * ArrayObject function triggered by: count($session;
     * @return int
     */
    public function count () {
        return count($_SESSION[$this->__name]);
    }
}