<?php
/**
 * The Strangecode Codebase - a general application development framework for PHP
 * For details visit the project site: <http://trac.strangecode.com/codebase/>
 * Copyright 2001-2012 Strangecode, LLC
 *
 * This file is part of The Strangecode Codebase.
 *
 * The Strangecode Codebase is free software: you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as published by the
 * Free Software Foundation, either version 3 of the License, or (at your option)
 * any later version.
 *
 * The Strangecode Codebase is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License along with
 * The Strangecode Codebase. If not, see <http://www.gnu.org/licenses/>.
 */

/**
 * Lock.inc.php
 *
 * The Lock class provides a system for locking abstract DB rows.
 *
 * @author  Quinn Comendant <quinn@strangecode.com>
 * @version 2.1
 */
class Lock
{
    // A place to keep an object instance for the singleton pattern.
    protected static $instance = null;

    // Configuration of this object.
    protected $_params = array(
        // The time required to pass before a user can forcibly unlock a locked record.
        'timeout' => 600,

        // The time after which a record will automatically become unlocked.
        'auto_timeout' => 1800,

        // The URL to the lock script.
        'error_url' => '/lock.php',

        // The name of the database table to store locks.
        'db_table' => 'lock_tbl',

        // Automatically create table and verify columns. Better set to false after site launch.
        // This value is overwritten by the $app->getParam('db_create_tables') setting if it is available.
        'create_table' => true,
    );

    // Store lock data from DB.
    protected $data = array();

    // Auth_SQL object from which to access a current user_id.
    protected $_auth = null;

    /**
     * This method enforces the singleton pattern for this class.
     *
     * @return  object  Reference to the global Lock object.
     * @access  public
     * @static
     */
    public static function &getInstance($auth_object=null)
    {
        if (self::$instance === null) {
            self::$instance = new self($auth_object);
        }

        return self::$instance;
    }

    /**
     * Constructor. Pass an Auth object on which to perform user lookups.
     *
     * @param mixed  $auth_object  An Auth_SQL or Auth_FILE object.
     */
    public function __construct($auth_object=null)
    {
        $app =& App::getInstance();

        if (!is_null($auth_object) || is_null($this->_auth)) {
            if (!method_exists($auth_object, 'get') || !method_exists($auth_object, 'getUsername')) {
                trigger_error('Constructor not provided a valid Auth_* object.', E_USER_ERROR);
            }

            $this->_auth = $auth_object;
        }

        // Get create tables config from global context.
        if (!is_null($app->getParam('db_create_tables'))) {
            $this->setParam(array('create_table' => $app->getParam('db_create_tables')));
        }
    }

    /**
     * Setup the database table for this class.
     *
     * @access  public
     * @author  Quinn Comendant <quinn@strangecode.com>
     * @since   26 Aug 2005 17:09:36
     */
    public function initDB($recreate_db=false)
    {
        $app =& App::getInstance();
        $db =& DB::getInstance();

        static $_db_tested = false;

        if ($recreate_db || !$_db_tested && $this->getParam('create_table')) {
            if ($recreate_db) {
                $db->query("DROP TABLE IF EXISTS " . $this->getParam('db_table'));
                $app->logMsg(sprintf('Dropping and recreating table %s.', $this->getParam('db_table')), LOG_INFO, __FILE__, __LINE__);
            }
            $db->query(sprintf("CREATE TABLE IF NOT EXISTS %s (
                lock_id INT UNSIGNED NOT NULL PRIMARY KEY AUTO_INCREMENT,
                record_table varchar(255) NOT NULL default '',
                record_key varchar(255) NOT NULL default '',
                record_val varchar(255) NOT NULL default '',
                title varchar(255) NOT NULL default '',
                set_by_admin_id smallint(11) NOT NULL default '0',
                lock_datetime datetime NOT NULL default '%s 00:00:00',
                KEY record_table (record_table),
                KEY record_key (record_key),
                KEY record_val (record_val)
            )", $db->escapeString($this->getParam('db_table')), $db->getParam('zero_date')));

            if (!$db->columnExists($this->getParam('db_table'), array(
                'lock_id',
                'record_table',
                'record_key',
                'record_val',
                'title',
                'set_by_admin_id',
                'lock_datetime',
            ), false, false)) {
                $app->logMsg(sprintf('Database table %s has invalid columns. Please update this table manually.', $this->getParam('db_table')), LOG_ALERT, __FILE__, __LINE__);
                trigger_error(sprintf('Database table %s has invalid columns. Please update this table manually.', $this->getParam('db_table')), E_USER_ERROR);
            }
        }
        $_db_tested = true;
    }

    /**
     * Set the params of this object.
     *
     * @param  array $params   Array of param keys and values to set.
     */
    public function setParam($params=null)
    {
        if (isset($params) && is_array($params)) {
            // Merge new parameters with old overriding only those passed.
            $this->_params = array_merge($this->_params, $params);
        }
    }

    /**
     * Return the value of a parameter, if it exists.
     *
     * @access public
     * @param string $param        Which parameter to return.
     * @return mixed               Configured parameter value.
     */
    public function getParam($param)
    {
        $app =& App::getInstance();

        if (array_key_exists($param, $this->_params)) {
            return $this->_params[$param];
        } else {
            $app->logMsg(sprintf('Parameter is not set: %s', $param), LOG_DEBUG, __FILE__, __LINE__);
            return null;
        }
    }

    /**
     * Select the lock to manipulate.
     *
     * @param mixed  $record_table_or_lock_id  The table containing the record to lock,
     *                                         or a numeric lock_id.
     * @param string $record_key  The key column for the record to lock.
     * @param string $record_val  The value of the key column for the record to lock.
     */
    public function select($record_table_or_lock_id, $record_key=null, $record_val=null)
    {
        $app =& App::getInstance();
        $db =& DB::getInstance();

        $this->initDB();

        // Expire old locks.
        $this->_auto_timeout();

        if (is_numeric($record_table_or_lock_id) && !isset($record_key) && !isset($record_val)) {
            // Get lock data by lock_id.
            $qid = $db->query("
                SELECT * FROM " . $db->escapeString($this->getParam('db_table')) . "
                WHERE lock_id = '" . $db->escapeString($record_table_or_lock_id) . "'
            ");
        } else {
            // Get lock data by record specs
            $qid = $db->query("
                SELECT * FROM " . $db->escapeString($this->getParam('db_table')) . "
                WHERE record_table = '" . $db->escapeString($record_table_or_lock_id) . "'
                AND record_key = '" . $db->escapeString($record_key) . "'
                AND record_val = '" . $db->escapeString($record_val) . "'
            ");
        }
        if ($this->data = mysql_fetch_assoc($qid)) {
            $app->logMsg(sprintf('Selecting %slocked record: %s %s %s', ($this->data['set_by_admin_id'] == $this->_auth->get('user_id') ? 'self-' : ''), $record_table_or_lock_id, $record_key, $record_val), LOG_DEBUG, __FILE__, __LINE__);
            // FIXME: What if admin set lock, but public user is current lock user?
            $this->data['editor'] = $this->_auth->getUsername($this->data['set_by_admin_id']);
            return true;
        } else {
            return false;
        }
    }

    /**
     * Returns true if the record we instantiated with is locked.
     *
     * @return bool            True if locked.
     */
    public function isLocked()
    {
        return isset($this->data['lock_id']);
    }

    /**
     * Returns the status of who set the lock. Use this to ignore locks set by
     * the current user.
     *
     * @return bool            True if current user set the lock.
     */
    public function isMine()
    {
        $db =& DB::getInstance();

        $this->initDB();

        if ($this->isLocked()) {
            $qid = $db->query("SELECT * FROM " . $db->escapeString($this->getParam('db_table')) . " WHERE lock_id = '" . $db->escapeString($this->data['lock_id']) . "'");
            if ($lock = mysql_fetch_assoc($qid)) {
                return ($lock['set_by_admin_id'] == $this->_auth->get('user_id'));
            } else {
                return false;
            }
        } else {
            return false;
        }
    }

    /**
     * Create a new lock for the specified table/key/value.
     *
     * @param string $record_table  The table containing the record to lock.
     * @param string $record_key  The key column for the record to lock.
     * @param string $record_val  The value of the key column for the record to lock.
     * @param string $title       A title to apply to the lock, for display purposes.
     *
     * @return int            The id for the lock (mysql last insert id).
     */
    public function set($record_table, $record_key, $record_val, $title='')
    {
        $app =& App::getInstance();
        $db =& DB::getInstance();

        $this->initDB();

        if ($this->_auth->get('user_id') == '' || filter_var($this->_auth->get('user_id'), FILTER_VALIDATE_INT) === false) {
            $app->logMsg(sprintf("auth->get('user_id') returns a non-integer: %s", $this->_auth->get('user_id')), LOG_ERR, __FILE__, __LINE__);
            return false;
        }

        // Expire old locks.
        $this->_auto_timeout();

        // Remove previous locks if exist. Is this better than using a REPLACE INTO?
        $db->query("
            DELETE FROM " . $db->escapeString($this->getParam('db_table')) . "
            WHERE record_table = '" . $db->escapeString($record_table) . "'
            AND record_key = '" . $db->escapeString($record_key) . "'
            AND record_val = '" . $db->escapeString($record_val) . "'
        ");

        // Set new lock.
        $db->query("
            INSERT INTO " . $db->escapeString($this->getParam('db_table')) . " (
                record_table,
                record_key,
                record_val,
                title,
                set_by_admin_id,
                lock_datetime
            ) VALUES (
                '" . $db->escapeString($record_table) . "',
                '" . $db->escapeString($record_key) . "',
                '" . $db->escapeString($record_val) . "',
                '" . $db->escapeString($title) . "',
                '" . $db->escapeString($this->_auth->get('user_id')) . "',
                NOW()
            )
        ");
        $lock_id = mysql_insert_id($db->getDBH());

        // Must register this locked record as the current.
        $this->select($lock_id);

        return $lock_id;
    }

    /**
     * Unlock the currently selected record.
     */
    public function remove()
    {
        $app =& App::getInstance();
        $db =& DB::getInstance();

        $this->initDB();

        // Expire old locks.
        $this->_auto_timeout();

        if (!$this->isLocked()) {
            // No lock selected.
            return false;
        }

        // Delete a specific lock.
        $db->query("
            DELETE FROM " . $db->escapeString($this->getParam('db_table')) . "
            WHERE lock_id = '" . $db->escapeString($this->data['lock_id']) . "'
        ");

        $app->logMsg(sprintf('Removing lock: %s', $this->data['lock_id']), LOG_DEBUG, __FILE__, __LINE__);
        return true;
    }

    /**
     * Unlock all records, or all records for a specified user.
     */
    public function removeAll($user_id=null)
    {
        $app =& App::getInstance();
        $db =& DB::getInstance();

        $this->initDB();

        // Expire old locks.
        $this->_auto_timeout();

        if (isset($user_id)) {
            // Delete specific user's locks.
            $db->query("DELETE FROM " . $db->escapeString($this->getParam('db_table')) . " WHERE set_by_admin_id = '" . $db->escapeString($user_id) . "'");
            $app->logMsg(sprintf('Record locks owned by user %s have been deleted', $this->_auth->getUsername($user_id)), LOG_DEBUG, __FILE__, __LINE__);
        } else {
            // Delete ALL locks.
            $db->query("DELETE FROM " . $db->escapeString($this->getParam('db_table')) . "");
            $app->logMsg(sprintf('All record locks deleted by user %s', $this->_auth->get('username')), LOG_DEBUG, __FILE__, __LINE__);
        }
    }

    /**
     * Deletes all locks that are older than auto_timeout.
     */
    public function _auto_timeout()
    {
        $db =& DB::getInstance();

        static $_timeout_run = false;

        $this->initDB();

        if (!$_timeout_run) {
            // Delete all old locks.
            $db->query("
                DELETE FROM " . $db->escapeString($this->getParam('db_table')) . "
                WHERE DATE_ADD(lock_datetime, INTERVAL '" . $db->escapeString($this->getParam('auto_timeout')) . "' SECOND) < NOW()
            ");
            $_timeout_run = true;
        }
    }

    /**
     * Redirect to record lock error page.
     */
    public function dieErrorPage()
    {
        $app =& App::getInstance();

        $app->dieURL($this->getParam('error_url'), array('lock_id' => $this->data['lock_id'], 'boomerang' => urlencode(getenv('REQUEST_URI'))));
    }

    /**
     * Print error page. This method is probably not used anywhere; instead, we're including this via the template codebase/services/templates/lock.ihtml
     */
    public function printErrorHTML()
    {
        $app =& App::getInstance();
        ?>
        <form method="post" action="<?php echo oTxt($_SERVER['PHP_SELF']); ?>">
            <?php $app->printHiddenSession() ?>
            <input type="hidden" name="lock_id" value="<?php echo $this->getID(); ?>" />
            <div id="sc-msg" class="sc-msg">
                <div class="sc-msg-notice">
                <?php printf(_("<em>%s</em> is currently being edited by %s (%d minutes elapsed). You cannot modify this database record while it is locked. Please try again later."),
                    ucfirst($this->getTitle()),
                    $this->getEditor(),
                    date('i', $this->getSecondsElapsed() + 60)
                ); ?>
                </div>
                <?php if ($this->getSecondsElapsed() >= $this->getParam('timeout')) { ?>
                    <div class="sc-msg-notice"><?php printf(_("You can forcibly unlock the record if you believe the editing session has expired. You might want to confirm with %s before doing this."), $this->getEditor()) ?></div>
                    <div class="sc-msg-notice">
                        <input type="submit" name="unlock" value="<?php echo _("Unlock"); ?>" />
                        <input type="submit" name="cancel" value="<?php echo _("Cancel"); ?>" />
                    </div>
                <?php } else { ?>
                    <div class="sc-msg-notice">
                        <input type="submit" name="cancel" value="<?php echo _("Cancel"); ?>" />
                    </div>
                <?php } ?>
            </div>
        </form>
        <?php
    }

    /**
     * Return lock_id of locked record.
     */
    public function getID()
    {
        return $this->data['lock_id'];
    }

    /**
     * Return title of locked record.
     */
    public function getTitle()
    {
        return $this->data['title'];
    }

    /**
     * Return administrator username for locked record.
     */
    public function getEditor()
    {
        return $this->data['editor'];
    }

    /**
     * Return total seconds since the record was locked.
     */
    public function getSecondsElapsed()
    {
        if (isset($this->data['lock_datetime']) && false !== ($lock_timestamp = strtotime($this->data['lock_datetime'])) && $lock_timestamp < time()) {
            return time() - $lock_timestamp;
        } else {
            return 0;
        }
    }


} // End of class.