create-validator.php

<?php

class Utility
{
  public function createValidator($spec)
  {
    list($type, $name) = explode(":", $spec, 2) + ['', ''];
    $options = ["default" => null];
    switch($type)
    {
      case 'dummy': // Dummy "non-empty" validator
        return function($var)
        {
          $var = trim((string)$var);
          return strlen($var) ? $var : null;
        };
        break;

      case 'bool': // "Boolean" validator. Accepts toggle words like yes/no and on/off.
        $filter = \filter_id("boolean");

        return function($var)
        use($filter)
        {
          return \filter_var($var, $filter, FILTER_NULL_ON_FAILURE);
        };
        break;

      case 'float': // C-type floating point number validator
        $filter = \filter_id("float");

        return function($var)
        use($filter, $options)
        {
          return \filter_var($var, $filter, ["options" => $options]);
        };

        break;
      case 'int': // "int" [ ":" [<min>] [ ":" <max> ] ]
        $filter = \filter_id("int");
        if(strlen($name))
        {
          $pattern = explode(":", $name, 2) + ['', ''];
          if(strlen($pattern[0])) $options['min_range'] = (int)$pattern[0];
          if(strlen($pattern[1])) $options['max_range'] = (int)$pattern[1];
        }

        return function($var)
        use($filter, $options)
        {
          return \filter_var($var, $filter, ["options" => $options]);
        };
        break;

      case 'string': // "string" [ ":" <regexp> ]
        $filter = \filter_id("validate_regexp");
        $options["regexp"] = $name;

        return function($var)
        use($filter, $options)
        {
          if(!strlen($options["regexp"]))
            return $var;

          return \filter_var($var, $filter, ["options" => $options]);
        };
        break;

      case 'dict': // "dict:" <dictionary>
        $dict = $this->getDictionary($name);
        if(empty($dict))
          throw new Exceptions\InvalidConfigurationException("Unknown dictionary '{$name}'.");

        return function($var)
        use($dict)
        {
          $result = $dict->get($var);
          return is_null($result) ? null : $var;
        };
        break;
/*
      case "custom": // Warning: extremely unsafe!
        // Use a strong whitelisting approach to validate origins for this spec.
        // For a more sane approach, see dict: specification above.
        list($class, $method) = explode("::", $name, 2) + [null, null];
        if(empty($method))
          throw new Exceptions\InvalidConfigurationException("Validators may only be public class methods.");
        if($class === "@")
          $class = null;

        return function($var)
        use($class, $method)
        {
          $var = (string)$var;
          return empty($class) ? $this->$method($var) : $class::$method($var);
        };
        break;
*/
      default:
        throw new Exceptions\InvalidConfigurationException("Unknown validator type '{$type}'.");
    }
  }
}