<?php
//
// cmSlu CMS POC
//
//   Database singleton and request factory
//

class DB {
  // The instance of the real driver object
  private static $instance;

  // Disable construction and cloning
  private function __construct() {}
  private function __clone() {}
  private function __sleep() {}
  private function __wakeUp() {}

  // return the only instance
  public static function singleton() {
    $class = 'DB_' . DB_DRIVER;
    if (!class_exists($class)) 
      throw new Exception('Missing database driver '. DB_DRIVER);
    if (!is_object(self::$instance)) {
      self::$instance = new $class(DB_HOST, DB_USERNAME, DB_PASSWORD, DB_DATABASE);
    }
    return self::$instance;
  }

  // construct query - need to be overridden by a driver
  public function ConstructQuery($sql, $limit, $start) {
    self::singleton(); // assure to have an instance
    return self::$instance->ConstructQuery($sql, $limit, $start);
  }

  // request factory
  // parameters are passed to as '?(name)'
  public static function Query($sql, $limit = NULL, $start = 0) {
    self::singleton(); // assure to have an instance
    return self::$instance->ConstructQuery($sql, $limit, $start);
  }

  // automatic parameter substitution, get result
  public static function QueryResult($sql) {
    $q = self::Query($sql);
    $a = func_get_args();
    array_shift($a);
    foreach($a as $n=>&$v) {
      $q->SetParameter($n, $v);
    }
    $r = $q->Execute();
    return $r;
  }

  // automatic parameter substitution, get result, return value of first row, first column
  public static function QueryResultValue($sql) {
    $a = func_get_args();
    $r = call_user_func_array(array(__CLASS__, 'QueryResult'), $a);
    if($r->NumRows() == 0) return NULL;
    return $r->FetchValue();
  }

  // automatic parameter substitution, get result, return hash of first row
  public static function QueryResultAssoc($sql) {
    $a = func_get_args();
    $r = call_user_func_array(array(__CLASS__, 'QueryResult'), $a);
    if($r->NumRows() == 0) return NULL;
    return $r->FetchAssoc();
  }

  // automatic parameter substitution, get all result rows as a hash
  public static function QueryAllResultsAssoc($sql) {
    $a = func_get_args();
    $r = call_user_func_array(array(__CLASS__, 'QueryResult'), $a);
    if($r->NumRows() == 0) return NULL;
    return $r->FetchAllAssoc();
  }

  // automatic parameter substitution, get all result values as an array
  public static function QueryAllResultValues($sql) {
    $a = func_get_args();
    $r = call_user_func_array(array(__CLASS__, 'QueryResult'), $a);
    if($r->NumRows() == 0) return NULL;
    return $r->FetchAllValues();
  }

  // automatic parameter substitution, get affected rows
  public static function UpdateQuery($sql) {
    $a = func_get_args();
    $r = call_user_func_array(array(__CLASS__, 'QueryResult'), $a);
    return $r->AffectedRows();
  }

  // automatic parameter substitution, get insert id
  public static function InsertQuery($sql) {
    $a = func_get_args();
    $r = call_user_func_array(array(__CLASS__, 'QueryResult'), $a);
    if (is_null($r->AffectedRows())) return NULL;
    return $r->InsertId();
  }

}

?>