<?php
/**
 * @package     Joomla.Platform
 * @subpackage  Access
 *
 * @copyright   Copyright (C) 2005 - 2011 Open Source Matters, Inc. All rights reserved.
 * @license     GNU General Public License version 2 or later; see LICENSE
 */

defined('JPATH_PLATFORM') or die;

/**
 * @package     Joomla.Platform
 * @subpackage  Access
 * @since       11.1
 */
class JRule
{
    /**
     * @var array   A named array
     */
    protected $_data = array();

    /**
     * Constructor.
     *
     * The input array must be in the form: array(-42 => true, 3 => true, 4 => false)
     * or an equivalent JSON encoded string.
     *
     * @param   mixed   A JSON format string (probably from the database), or a named array.
     */
    public function __construct($identities)
    {
        // Convert string input to an array.
        if (is_string($identities)) {
            $identities = json_decode($identities, true);
        }

        $this->mergeIdentities($identities);
    }

    /**
     * Get the data for the action.
     *
     * @return  array   A named array identities.
     */
    public function getData()
    {
        return $this->_data;
    }

    /**
     * Merges the identities
     */
    public function mergeIdentities($identities)
    {
        if ($identities instanceof JRule) {
            $identities = $identities->getData();
        }

        if (is_array($identities))
        {
            foreach ($identities as $identity => $allow) {
                $this->mergeIdentity($identity, $allow);
            }
        }
    }

    /**
     * Merges the value for an identity.
     *
     * @param   int     The identity.
     * @param   boolean The value for the identity (true == allow, false == deny).
     */
    public function mergeIdentity($identity, $allow)
    {
        $identity   = (int) $identity;
        $allow      = (int) ((boolean) $allow);

        // Check that the identity exists.
        if (isset($this->_data[$identity]))
        {
            // Explicit deny always wins a merge.
            if ($this->_data[$identity] !== 0) {
                $this->_data[$identity] = $allow;
            }
        }
        else {
            $this->_data[$identity] = $allow;
        }
    }

    /**
     * Checks that this action can be performed by an identity.
     *
     * The identity is an integer where +ve represents a user group,
     * and -ve represents a user.
     *
     * @param   mixed       An integer or array of integers representing the identities to check.
     *
     * @return  mixed       True if allowed, false for an explicit deny, null for an implicit deny.
     */
    public function allow($identities)
    {
        // Implicit deny by default.
        $result = null;

        // Check that the inputs are valid.
        if (!empty($identities))
        {
            if (!is_array($identities)) {
                $identities = array($identities);
            }

            foreach ($identities as $identity)
            {
                // Technically the identity just needs to be unique.
                $identity = (int) $identity;

                // Check if the identity is known.
                if (isset($this->_data[$identity]))
                {
                    $result = (boolean) $this->_data[$identity];

                    // An explicit deny wins.
                    if ($result === false) {
                        break;
                    }
                }

            }
        }

        return $result;
    }

    /**
     * Convert this object into a JSON encoded string.
     *
     * @return  string
     */
    public function __toString()
    {
        return json_encode($this->_data);
    }
}