<?php

class Validator {
    private static function getValue($array, $keys) {
        $key = $keys[0];
        return $array[$key];
    }

    private static function getValues($array, $keys) {
        $list = [];
        foreach ($keys as $key) {
            $list[] = $array[$key];
        }
        return $list;
    }

    public function required($name, $array, $keys) {
        $value = Validator::getValue($array, $keys);
        if ($value == "" || $value == null || trim($value) == "") {
            return "{$name} field is required";
        }
        return null;
    }
    
    public function mail($name, $array, $keys) {
        $value = Validator::getValue($array, $keys);
        if (!is_email($value)) {
            return "{$name} field must be valid";
        }
        return null;
    }

    public function equals($name, $array, $keys) {
        $values = Validator::getValues($array, $keys);
        $match = true;
        $firstValue = $values[0];

        foreach ($values as $value) {
            if ($value !== $firstValue) {
                $match = false;
            }
        }

        if (!$match) {
            return "{$name} fields must match";
        }

        return null;
    }

    public function alphanumeric($name, $array, $keys) {
        $value = Validator::getValue($array, $keys);
        if (preg_match("/[^A-z0-9_\-]/", $value)==1) { // Thanks to "Carlos Pires" from php.net!
            return "{$name} fields must be alphanumeric";
        }
        return null;
    }

    public function unique($name, $array, $keys, $database) {
        global $db;

        $value = Validator::getValue($array, $keys);
        $table = $database["table"];
        $dbField = $database["field"];

        if ($db->checkUnique($table, $dbField, $value)) {
            return "{$value} already taken, it must be unique";
        }

        return null;
    }
}