<?php

define('DEBUG_RELATIONS',TRUE);
function node_relation_signature() {
  $sig['fields']['n'][]= 'nid';
  $sig['fields']['n'][]= 'vid';
  $sig['fields']['n'][]= 'type';
  $sig['fields']['n'][]= 'title';
  $sig['fields']['n'][]= 'uid';
  $sig['fields']['n'][]= 'status';
  $sig['fields']['n'][]= 'created';
  $sig['fields']['n'][]= 'changed';
  $sig['fields']['n'][]= 'comment';
  $sig['fields']['n'][]= 'promote';
  $sig['fields']['n'][]= 'moderate';
  $sig['fields']['n'][]= 'sticky';
  $sig['aliases']['n']='node';
  return $sig;
}

function user_relation_signature() {
  $sig['aliases']['u']='user';
  $sig['fields']['u'][]= 'uid'; 
  $sig['fields']['u'][]= 'name';
  $sig['fields']['u'][]= 'pass';
  $sig['fields']['u'][]= 'mail';
  $sig['fields']['u'][]= 'mode';
  $sig['fields']['u'][]= 'sort';
  $sig['fields']['u'][]= 'threshold';
  $sig['fields']['u'][]= 'theme';
  $sig['fields']['u'][]= 'signature';
  $sig['fields']['u'][]= 'created';
  $sig['fields']['u'][]= 'access';
  $sig['fields']['u'][]= 'login';
  $sig['fields']['u'][]= 'status';
  $sig['fields']['u'][]= 'timezone';
  $sig['fields']['u'][]= 'language';
  $sig['fields']['u'][]= 'picture';
  $sig['fields']['u'][]= 'init';
  $sig['fields']['u'][]= 'data';
  return $sig;
}

function node_revisions_relation_signature() {
  $sig['fields']['r'][]= 'nid';
  $sig['fields']['r'][]= 'vid';
  $sig['fields']['r'][]= 'uid';
  $sig['fields']['r'][]= 'title';
  $sig['fields']['r'][]= 'body';
  $sig['fields']['r'][]= 'teaser';
  $sig['fields']['r'][]= 'log';
  $sig['fields']['r'][]= 'timestamp';
  $sig['fields']['r'][]= 'format';
  $sig['aliases']['r']= 'node_revisions';
  return $sig;
}

function node_user_relation_signature(){
  /** this is just an example node-user relation
   * first create the node_user table CREATE TABLE node_user (nid INTEGER, uid INTEGER, rid INTEGER);
   */
  $sig['fields']['nu'][]= 'nid';
  $sig['fields']['nu'][]= 'uid';
  $sig['fields']['nu'][]= 'rid';
  $sig['aliases']['nu']= 'node_user';
  return $sig;
}


function relation_fields_filter($sig,$fsig) {
  $sig['fields']=$fsig;
  return $sig;
}
function relation_param_filter($sig,$param) {
  return $sig;
}
/** Relation function signature
 * Computes the signature of a relation, the signature is used to
 * generate the SQL statements at the later stages
 *a typical call of this could be:
 * $relation_signature=RFS('node_node',array('name'=>'left','mapping',$nid))
 * or a more complex:
 * $relation_signature=RFS('node_node',
 *          array('arg'=>array('name'=>'nn.left','mapping','nu.nid'),
 *	         RFS('node_user',array('name'=>'nu.uid','mapping'=>$uid));
 *
 */
function RFS($relation_name ) {
  $f=$relation_name.'_relation_signature';
  $sig=$f();
  
  $nargs=func_num_args();
  $args=func_get_args();
  
  //skip the first argument - it is the relation name
  for($i=1;$i<$nargs;$i++){
    $arg=$args[$i];
    
    $arguments=explode(',',$arg['arg']['name']);
    $mapping=explode(',',$arg['arg']['mapping']);
    foreach($arguments as $key=>$param) {
      //assign the mappings for the parameters from the arguments, the alias collisons are handled later
      $temp_param[$param]=$mapping[$key];
    }
    if(is_array($arg)&&!empty($arg['aliases'])) { //this is actually a relation signature
      //check for alias clashes
      foreach($arg['aliases'] as $alias=>$table){
        $new_alias=$alias;
        
	if(array_key_exists($alias,$sig['aliases'])) { //alias collision, change the bastard
          //change fields
	  
	  while(array_key_exists($new_alias.='_',$sig['aliases'])) {}; // create a unique alias
	  
	  if(!empty( $arg['fields'] )) {
	    $arg['fields'][$new_alias]=$arg['fields'][$alias];//change the fields
	    unset($arg['fields'][$alias]);  //remove the redundant fields
	  }

	  if(!empty( $arg['field_functions'] )) {
	    $arg['field_functions'][$new_alias]=$arg['field_functions'][$alias];//change the fields
	    unset($arg['field_functions'][$alias]);  //remove the redundant fields
	  }

	  if(!empty( $arg['conditions'] )) {
            foreach($arg['conditions'] as $key=>$condition ) {  //modify the conditions
              $arg['conditions'][$key]=preg_replace($alias.'\.',$new_alias.'\.',$condition);
            }
          }

          //not sure if this is required, needs more thought
	  if(!empty($arg['groups'])){
	    foreach($arg['groups'] as $key=>$group ) {  //modify the conditions
	      $arg['groups'][$key]=preg_replace($alias.'\.',$new_alias.'\.',$group);
	    }
          }
	  
	  //THERE ARE PROBLEMS WITH JOINS,  CAN BE DONE IN A SIMILAR FASHION TO THE REST, ie aliases + conditions
	  
	  foreach($temp_param as $key=>$param ) {  
	    $temp_param[$key]=preg_replace($alias.'\.',$new_alias.'\.',$param);
	  }
        }
        $aliases[$new_alias]=$table; //prep the new aliases table
      }
      $arg['aliases']=$aliases;//update the aliases to reflect the possible alias updates
      //aliases
    }
    if(!empty($sig['param'])) {
      $sig['param']=array_merge($sig['param'],$temp_param);
    }
    $sig=array_merge_recursive($sig,$arg);
  }
  return $sig;
}

/**generates an SQL SELECT statement from a relation signature
 *
 * no JOIN  or GROUP statements yet
 */
function RSQL($sig) {
  $query='SELECT ';

  if(!empty($sig['field_functions'])) {
    foreach($sig['field_functions'] as $alias=>$fs) {
      foreach($fs as $func) {
        unset($sig['fields'][$alias][$func['field']]);
        $functions[]=$func['func'].'('.$alias.'.'.$func['field'].')' . (empty($func['alias'])?' ':' AS '.$func['alias'].' ');
      }
    }
  }
  foreach($sig['fields'] as $alias=>$fs) {
    foreach($fs as $field) {
     $fields[]=$alias.'.'.$field;
    }
  }
  $query .= implode(' , ', $fields);
  if(!empty($functions)) {
    $query .= ', '.implode(' , ', $functions);
  }
  $query .= ' FROM ';
  foreach($sig['aliases'] as $alias=>$table) {
    $tables[]=$table .' AS '.$alias;
  }
  
  $query .= implode(' , ', $tables);
  if(!empty($sig['conditions'])){
    $query .= ' WHERE '. implode(' ',$sig['conditions']);
  }
  
  if(!empty($sig['param'])){
    $query .= (empty($sig['conditions'])?' WHERE ':' AND '). implode(' ',$sig['param']);
  }
  
  if(!empty($sig['order'])){
    $query .= ' ORDER BY '.implode(', ',$sig['order']);
  }
  
  if(!empty($sig['groups'])){
    $query .= ' GROUP BY '.implode(', ',$sig['groups']);
  }

  return $query;
};

if(DEBUG_RELATIONS){
  var_dump($test=RFS('node'));
  var_dump($test=RSQL(RFS('node', RFS('node_revisions'))));
  var_dump($test=RSQL(RFS('node', array_merge_recursive(RFS('node_revisions'), array('conditions'=>array('n.nid=r.nid','AND','n.nid=1'),'order'=>array('n.nid DESC','n.sticky ASC'))))));
  var_dump($test=RSQL($t=RFS('node', array_merge_recursive(RFS('node_revisions'), array('conditions'=>array('n.nid=r.nid','AND','n.nid=1'),'order'=>array('n.nid DESC','n.sticky ASC'),'field_functions'=>array('n'=>array(array('field'=>'nid','func'=>'count','alias'=>'metric'))))))));
  $sig['n'][]= 'nid';
  $sig['n'][]= 'vid';
  $sig['n'][]= 'type';
  $sig['n'][]= 'title';
  $sig['n'][]= 'uid';
  var_dump(RSQL(relation_fields_filter($t,$sig)));

  //if the 'node author' relation has rid=1000
  
  $node_authors=RFS('user',RFS('node',RFS('node_user',array('conditions'=>array('nu.nid=n.nid','AND','u.uid=nu.uid','AND','nu.rid=1000')))));
  $authors_sig['u'][]= 'uid';
  $authors_sig['u'][]= 'name';
  $authors_sig['u'][]= 'mail';
  var_dump(RSQL(relation_fields_filter($node_authors,$authors_sig)));
  var_dump($test=RSQL(RFS('node', RFS('node_revisions'),array('param'=>array('n.nid=%d','n.uid=%d')))));
  $node_authors=RFS('user',RFS('node', array('param'=>array('nu.nid=%d',' AND ','nu.uid=%d')),RFS('node_user',array('conditions'=>array('nu.nid=n.nid','AND','u.uid=nu.uid','AND','nu.rid=1000')))));
  var_dump(RSQL(relation_fields_filter($node_authors,$authors_sig)));
}

?>