<?php

namespace Sudzy;

/**
 * Singleton valdation engine
 **/
class Engine
{
    /**
    * Validation methods are stored here so they can easily be overwritten
    */
    protected $_checks;

    public function __construct()
    {
        $this->_checks = array(
            'required'  => array($this, '_required'),
            'minLength' => array($this, '_minLength'),
            'maxLength' => array($this, '_maxLength'),
            'isEmail'   => array($this, '_isEmail'),
            'isInteger'   => array($this, '_isInteger'),
            'isNumeric'   => array($this, '_isNumeric')
        );
    }

    public function __call($name, $args)
    {
        if (!isset($this->_checks[$name]))
            throw new \InvalidArgumentException("{$name} is not a valid validation function.");

        $val = array_shift($args);
        $args = array_shift($args);

        return call_user_func($this->_checks[$name], $val, $args);
    }

    public function executeOne($check, $val, $params=array())
    {
      $callback = __NAMESPACE__ .'\Engine::'.$check;
      if (is_callable($callback)) {
        return call_user_func($callback, $val, $params);
      }
    }

    /**
     * @param string $label label used to call function
     * @param Callable $function function with params (value, additional params as array)
     * @throws \Exception
     */
    public function addValidator($label, $function)
    {
        if (isset($this->_checks[$label])) throw new \Exception();
        $this->setValidator($label, $function);
    }

    public function setValidator($label, $function)
    {
        $this->_checks[$label] = $function;
    }

    public function removeValidator($label)
    {
        unset($this->_checks[$label]);
    }

    /**
    * @return array<int, int|string> The list of usable validator methods
    */
    public function getValidators()
    {
        return array_keys($this->_checks);
    }

    ///// Validator methods
    protected function _isEmail($val, $params)
    {
        return FALSE !== filter_var($val, FILTER_VALIDATE_EMAIL);
    }

    protected function _isInteger($val, $params)
    {
        if (!is_numeric($val)) return false;
        return intval($val) == $val;
    }

    protected function _isNumeric($val, $params)
    {
        return is_numeric($val);
    }

    protected function _minLength($val, $params)
    {
        $len = array_shift($params);
        return strlen($val) >= $len;
    }

    protected function _maxLength($val, $params)
    {
        $len = array_shift($params);
        return strlen($val) <= $len;
    }

    protected function _required($val, $params=array())
    {
        return !(($val === null) || ('' === trim($val)));
    }
}