<?php

namespace Libs;

use Exception;

/**
 * Validator - DuckBrain
 *
 * Complementary library to the Request library.
 * Simplifies value verification.
 *
 * It has the ability to verify both individual rules and in batches.
 *
 * |----------+--------------------------------------------------------|
 * | Rule     | Description                                            |
 * |----------+--------------------------------------------------------|
 * | not      | Negates the next rule. Ex: not:float                   |
 * | exists   | Is required; must be defined and can be empty          |
 * | required | Is required; must be defined and not empty             |
 * | number   | Is numeric                                             |
 * | int      | Is an integer                                          |
 * | float    | Is a float                                             |
 * | bool     | Is a boolean                                           |
 * | email    | Is an email                                            |
 * | enum     | Is in a list of values. Ex: enum:admin,user,guest      |
 * | url      | Is a valid URL                                         |
 * |----------+--------------------------------------------------------|
 *
 * Rule lists are separated by |, e.g., required|email
 *
 * @author KJ
 * @website https://kj2.me
 * @license MIT
 */
class Validator
{
    /**
     * Stores the last failed rule.
     *
     * @var string
     */
    public static string $lastFailed = '';

    /**
     * Validates a list of rules against the properties of an object.
     *
     * @param array  $rulesList The list of rules.
     * @param Neuron $haystack  The object whose properties will be validated.
     *
     * @return bool Returns true only if all rules are met, and false as soon as one fails.
     */
    public static function validateList(array $rulesList, Neuron $haystack): bool
    {
        foreach ($rulesList as $target => $rules) {
            $rules = preg_split('/\|/', $rules);
            foreach ($rules as $rule) {
                if (static::checkRule($haystack->{$target}, $rule)) {
                    continue;
                }
                static::$lastFailed = $target . '.' . $rule;
                return false;
            }
        }

        return true;
    }

    /**
     * Checks if a rule is met.
     *
     * @param mixed  $subject The value to verify.
     * @param string $rule    The rule to test.
     *
     * @return bool
     * @throws Exception If the rule is not callable.
     */
    public static function checkRule(mixed $subject, string $rule): bool
    {
        $arguments    = preg_split('/[:,]/', $rule);
        $rule         = [static::class, $arguments[0]];
        $arguments[0] = $subject;

        if (is_callable($rule)) {
            return call_user_func_array($rule, $arguments);
        }

        throw new Exception('Bad rule: "' . preg_split('/::/', $rule)[1] . '"');
    }

    /**
     * Verifies the rule in a negative way.
     *
     * @param mixed $subject The value to verify.
     * @param mixed $rule    The rule to test.
     *
     * @return bool
     */
    public static function not(mixed $subject, ...$rule): bool
    {
        return !static::checkRule($subject, join(':', $rule));
    }

    /**
     * Checks if the value is defined/exists.
     *
     * @param mixed $subject The value to check.
     *
     * @return bool
     */
    public static function exists(mixed $subject): bool
    {
        return isset($subject);
    }

    /**
     * Checks if the value is defined and not empty.
     *
     * @param mixed $subject The value to check.
     *
     * @return bool
     */
    public static function required(mixed $subject): bool
    {
        return isset($subject) && !empty($subject);
    }

    /**
     * Checks if the value is numeric.
     *
     * @param mixed $subject The value to check.
     *
     * @return bool
     */
    public static function number(mixed $subject): bool
    {
        return is_numeric($subject);
    }

    /**
     * Checks if the value is an integer.
     *
     * @param mixed $subject The value to check.
     *
     * @return bool
     */
    public static function int(mixed $subject): bool
    {
        return filter_var($subject, FILTER_VALIDATE_INT) !== false;
    }

    /**
     * Checks if the value is a float.
     *
     * @param mixed $subject The value to check.
     *
     * @return bool
     */
    public static function float(mixed $subject): bool
    {
        return filter_var($subject, FILTER_VALIDATE_FLOAT) !== false;
    }

    /**
     * Checks if the value is a boolean.
     *
     * @param mixed $subject The value to check.
     *
     * @return bool
     */
    public static function bool(mixed $subject): bool
    {
        return filter_var($subject, FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE) !== null;
    }

    /**
     * Checks if the value is a valid email address.
     *
     * @param mixed $subject The value to check.
     *
     * @return bool
     */
    public static function email(mixed $subject): bool
    {
        return filter_var($subject, FILTER_VALIDATE_EMAIL) !== false;
    }

    /**
     * Checks if the value is a valid URL.
     *
     * @param mixed $subject The value to check.
     *
     * @return bool
     */
    public static function url(mixed $subject): bool
    {
        return filter_var($subject, FILTER_VALIDATE_URL) !== false;
    }

    /**
     * Checks if the value is present in a list of allowed values.
     *
     * @param mixed $subject The value to check.
     * @param mixed ...$values A variable number of allowed values.
     *
     * @return bool
     */
    public static function enum(mixed $subject, ...$values): bool
    {
        return in_array($subject, $values);
    }
}