<?
/**
 *        @author         Varun Shoor <varun.shoor@kayako.com>
 */


namespace SWIFT\Library;


use SWIFT\Library\Exception;

/**
 * The lock class is used to prevent race conditions in tasks (recurring etc.).
 *
 * @author           Varun Shoor <varun.shoor@kayako.com>
 */
class Lock
{
    const DEFAULT_EXPIRY = 30; // in minutes

    // string
    protected $name;

    /**
     * @author Varun Shoor
     *
     * @param string $name
     */
    public function __construct($name)
    {
        $this->setName($name);
    }

    /**
     * @return Lock
     * @throws Exception\InvalidArgument
     */
    protected function setName($name)
    {
        if (empty($name)) {
            throw new Exception\InvalidArgument;
        }

        $this->name = $name;
    }

    /**
     * @author Varun Shoor <varun.shoor@kayako.com>
     *
     * @return string
     * @todo name should be returned instead of 'this'
     */
    public function getName()
    {
        return $this;
    }

    /**
     * Attempts to create a new lock, if one already exists, returns false
     *
     * @author Varun Shoor <varun.shoor@kayako.com>
     * @todo realease the lock, implement file time modification based on expiry
     *
     * @param string $name
     * @param int $expiry (OPTIONAL) In minutes
     *
     * @return Lock
     * @throws Exception\InvalidArgument
     */
    static public function create($name, $expiry = 0)
    {
        $name = clean($name);

        if (empty($name)) {
            throw new Exception\InvalidArgument;
        } // If the lock already exists, we need to check whether it has expired
        elseif (self::exists($name)) {
            $Lock = new self($name);

            // If the lock has expired, we need to release it before proceeding
            if (!$Lock->HasExpired()) {
                /*
                 * @todo Release the lock here
                 */
            } // Apparently the lock is still active, we cant proceed!
            else {
                return null;
            }
        }

        if (empty($expiry)) {
            $expiry = time() + (60 * self::DEFAULT_EXPIRY);
        }

        file_put_contents(self::getCacheName($name), self::getContents($expiry));

        /*
         * @todo Implement file time modification based on expiry
         */

        return new self($name);
    }

    /**
     * @author Varun Shoor <varun.shoor@kayako.com>
     *
     * @param string $name
     *
     * @return boolean
     */
    static public function exists($name)
    {
        $name = clean($name);

        if (empty($name)) {
            throw new Exception\InvalidArgument;
        }

        $cache = new self($name);

        if (!$cache->getJSON()) {
            return false;
        }

        $cache->increment();

        return true;
    }

    /**
     * @author Varun Shoor <varun.shoor@kayako.com>
     *
     * @param \stdClass $json
     *
     * @return Lock
     */
    public function update(\stdClass $json)
    {
        file_put_contents(self::getCacheName($this->getName()), json_encode($json));

        return $this;
    }

    /**
     * @author Varun Shoor <varun.shoor@kayako.com>
     *
     * @return Lock
     */
    function increment()
    {
        $json = $this->getJSON();
        if (!$json) {
            return $this;
        }

        // Extend the expiry
        $json->expiry = $json->expiry + (60 * self::DEFAULT_EXPIRY);

        $json->hits++;

        return $this->update($json);
    }

    /**
     * @author Varun Shoor <varun.shoor@kayako.com>
     *
     * @return object
     */
    public function ReleaseTheLock()
    {
        if (!self::exists($this->getName())) {
            return $this;
        }

        unlink(self::getCacheName($this->getName()));

        return $this;
    }

    /**
     * @author Varun Shoor <varun.shoor@kayako.com>
     *
     * @return int|false
     */
    public function getExpiry()
    {
        return $this->getValue('expiry');
    }

    /**
     * @author Varun Shoor <varun.shoor@kayako.com>
     *
     * @return int|false
     */
    public function getHits()
    {
        return $this->getValue('hits');
    }

    /**
     * @author Varun Shoor <varun.shoor@kayako.com>
     *
     * @return object
     */
    public function getJSON()
    {
        $json = file_get_contents(self::getCacheName($this->getName()));

        // JSON decoding failed? We will need to clean things up
        if ($json == false) {
            return null;
        }

        return (object) $json;
    }

    /**
     * @author Varun Shoor <varun.shoor@kayako.com>
     *
     * @param string $name
     *
     * @return string|false
     * @throws Exception\InvalidArgument
     */
    function getValue($name)
    {
        if (empty($name)) {
            throw new Exception\InvalidArgument;
        }

        $json = $this->getJSON();
        if (!$json || !isset($json->{$name})) {
            return false;
        }
        return $json->{$name};
    }

    /**
     * @author Varun Shoor <varun.shoor@kayako.com>
     *
     * @return boolean
     */
    function HasExpired()
    {
        $expiry = $this->getExpiry();
        if ($expiry === false || $expiry < NOW) {
            $this->ReleaseTheLock();
            return true;
        }
        return false;
    }

    /**
     * @author Varun Shoor <varun.shoor@kayako.com>
     *
     * @return json
     */
    public function __toString()
    {
        return json_encode ($this->getJSON(), JSON_PRETTY_PRINT);
    }

    /**
     * @author Varun Shoor <varun.shoor@kayako.com>
     *
     * @param string $name
     *
     * @return string
     */
    static protected function getCacheName($name)
    {
        return 'lock.' . $name;
    }

    /**
     * @author Varun Shoor <varun.shoor@kayako.com>
     *
     * @param  integer $expiry
     * @param  integer $hits
     *
     * @return object
     */
    static protected function getContents($expiry, $hits = 1)
    {
        return (object) array(
            'expiry' => $expiry,
            'hits'   => $hits
        );
    }
}

?>