<?php

/*
 +--------------------------------------------------------------------+
 | CiviCRM version 3.0                                                |
 +--------------------------------------------------------------------+
 | Copyright CiviCRM LLC (c) 2004-2009                                |
 +--------------------------------------------------------------------+
 | This file is a part of CiviCRM.                                    |
 |                                                                    |
 | CiviCRM is free software; you can copy, modify, and distribute it  |
 | under the terms of the GNU Affero General Public License           |
 | Version 3, 19 November 2007.                                       |
 |                                                                    |
 | CiviCRM 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 Affero General Public License for more details.        |
 |                                                                    |
 | You should have received a copy of the GNU Affero General Public   |
 | License along with this program; if not, contact CiviCRM LLC       |
 | at info[AT]civicrm[DOT]org. If you have questions about the        |
 | GNU Affero General Public License or the licensing of CiviCRM,     |
 | see the CiviCRM license FAQ at http://civicrm.org/licensing        |
 +--------------------------------------------------------------------+
*/

/**
 *
 * @package CRM
 * @copyright CiviCRM LLC (c) 2004-2009
 * $Id$
 *
 */

class CRM_Contact_BAO_GroupNestingCache {
    static public function update( ) {
        // lets build the tree in memory first
        
        $sql = "
SELECT n.child_group_id  as child ,
       n.parent_group_id as parent
FROM   civicrm_group_nesting n,
       civicrm_group gc,
       civicrm_group gp
WHERE  n.child_group_id  = gc.id
  AND  n.parent_group_id = gp.id
";

        $dao =& CRM_Core_DAO::executeQuery( $sql );

        $tree = array( );
        while ( $dao->fetch( ) ) {
            if ( ! array_key_exists( $dao->child, $tree ) ) {
                $tree[$dao->child] = array( 'children' => array( ),
                                            'parents'  => array( ) );
            }

            if ( ! array_key_exists( $dao->parent, $tree ) ) {
                $tree[$dao->parent] = array( 'children' => array( ),
                                             'parents'  => array( ) );
            }

            $tree[$dao->child ]['parents' ][] = $dao->parent;
            $tree[$dao->parent]['children'][] = $dao->child;
        }
        
        if ( self::checkCyclicGraph( $tree ) ) {
            CRM_Core_Error::fatal( ts( 'We detected a cycle which we cant handle. aborting' ) );
        }

        // first reset the current cache entries
        $sql = "
UPDATE civicrm_group
SET    parents  = null,
       children = null
";
        CRM_Core_DAO::executeQuery( $sql );
        
        $values = array( );
        foreach ( array_keys( $tree ) as $id ) {
            $parents  = implode( ',', $tree[$id]['parents' ] );
            $children = implode( ',', $tree[$id]['children'] );
            $parents  = $parents  == null ? 'null' : "'$parents'" ;
            $children = $children == null ? 'null' : "'$children'";
            $sql = "
UPDATE civicrm_group
SET    parents  = $parents ,
       children = $children
WHERE  id = $id
";
            CRM_Core_DAO::executeQuery( $sql );
        }

        // this tree stuff is quite useful, so lets store it in the cache
        require_once 'CRM/Core/BAO/Cache.php';
        CRM_Core_BAO_Cache::setItem( $tree, 'contact groups', 'nestable tree hierarchy' );
    }

    static function checkCyclicGraph( &$tree ) {
        // lets keep this simple, we should probably use a graph algoritm here at some stage
        
        // foreach group that has a parent or a child, ensure that 
        // the ancestors and descendants dont intersect
        foreach ( $tree as $id => $dontCare ) {
            if ( self::isCyclic( $tree, $id ) ) {
                return true;
            }
        }

        return false;
    }

    static function isCyclic( &$tree, $id ) {
        $parents = $children = array( );
        self::getAll( $parent, $tree, $id, 'parents'  );
        self::getAll( $child , $tree, $id, 'children' );

        $one = array_intersect( $parents , $children );
        $two = array_intersect( $children, $parents  );
        if ( ! empty( $one ) ||
             ! empty( $two ) ) {
            CRM_Core_Error::debug( $id, $tree );
            CRM_Core_Error::debug( $id, $one  );
            CRM_Core_Error::debug( $id, $two  );
            return true;
        }
        return false;
    }

    static function getPotentialCandidates( $id, &$groups ) {
        require_once 'CRM/Core/BAO/Cache.php';
        $tree =& CRM_Core_BAO_Cache::getItem( 'contact groups', 'nestable tree hierarchy' );

        if ( $tree === null ) {
            self::update( );
            $tree =& CRM_Core_BAO_Cache::getItem( 'contact groups', 'nestable tree hierarchy' );
        }

        $potential = $groups;

        // remove all descendants
        self::invalidate( $potential, $tree, $id, 'children' );
        
        // remove all ancestors
        self::invalidate( $potential, $tree, $id, 'parents' );

        return array_keys( $potential );
    }

    static function invalidate( &$potential, &$tree, $id, $token ) {
        unset( $potential[$id] );

        if ( ! isset( $tree[$id] ) ||
             empty( $tree[$id][$token] ) ) {
            return;
        }

        foreach ( $tree[$id][$token] as $tokenID ) {
            self::invalidate( $potential, $tree, $tokenID, $token );
        }
    }

    static function getAll( &$all, &$tree, $id, $token ) {
        // if seen before, dont do anything
        if ( isset( $all[$id] ) ) {
            return;
        }

        $all[$id] = 1;
        if ( ! isset( $tree[$id] ) ||
             empty( $tree[$id][$token] ) ) {
            return;
        }

        foreach ( $tree[$id][$token] as $tokenID ) {
            self::getAll( $all, $tree, $tokenID, $token );
        }
    }

    static function json( ) {
        require_once 'CRM/Core/BAO/Cache.php';
        $tree =& CRM_Core_BAO_Cache::getItem( 'contact groups', 'nestable tree hierarchy' );

        if ( $tree === null ) {
            self::update( );
            $tree =& CRM_Core_BAO_Cache::getItem( 'contact groups', 'nestable tree hierarchy' );
        }

        // get all the groups
        $groups =& CRM_Core_PseudoConstant::group( );

        foreach ( $groups as $id => $name ) {
            $string = "id:'$id', name:'$name'";
            if ( isset( $tree[$id] ) ) {
                $children = array( );
                if ( ! empty( $tree[$id]['children'] ) ) {
                    foreach ( $tree[$id]['children'] as $child ) {
                        $children[] = "{_reference:'$child'}";
                    }
                    $children  = implode( ',', $children );
                    $string   .= ", children:[$children]";
                    if ( empty( $tree[$id]['parents'] ) ) {
                        $string .= ", type:'rootGroup'";
                    } else {
                        $string .= ", type:'middleGroup'";
                    }
                } else {
                    $string   .= ", type:'leafGroup'";
                }
            } else {
                $string .= ", children:[], type:'rootGroup'";
            }
            $values[] = "{ $string }";
        }

        $items = implode( ",\n", $values );
        $json = "{
  identifier:'id',
  label:'name',
  items:[ $items ]
}";
        return $json;
    }

}


