trueskill/src/Guard.php

<?php namespace DNW\Skills;

use Exception;

/**
 * Verifies argument contracts.
 *
 * @see http://www.moserware.com/2008/01/borrowing-ideas-from-3-interesting.html
 */
class Guard
{
    public static function argumentNotNull($value, $parameterName)
    {
        if ($value == null) {
            throw new Exception($parameterName . " can not be null");
        }
    }

    public static function argumentIsValidIndex($index, $count, $parameterName)
    {
        if (($index < 0) || ($index >= $count)) {
            throw new Exception($parameterName . " is an invalid index");
        }
    }

    public static function argumentInRangeInclusive($value, $min, $max, $parameterName)
    {
        if (($value < $min) || ($value > $max)) {
            throw new Exception($parameterName . " is not in the valid range [" . $min . ", " . $max . "]");
        }
    }
}