<?php

use Carbon\CarbonImmutable;
use Illuminate\Support\Facades\Hash;

if (!function_exists('utc_now')) {
    function utc_now(): string
    {
        return CarbonImmutable::now('UTC')->toDateTimeString();
    }
}

if (!function_exists('local_date')) {
    function local_date(string $utcDateTime, string $format = 'Y-m-d H:i:s'): string
    {
        try {
            $carbon = CarbonImmutable::parse($utcDateTime)->setTimezone(config('app.timezone'));
            return $carbon->format($format);
        } catch (\Throwable $e) {
            return CarbonImmutable::parse($utcDateTime)->format($format);
        }
    }
}

if (!function_exists('user_timezone')) {
    function user_timezone(): string
    {
        return (string) (config('School')->attendance['timezone'] ?? config('app.timezone', 'America/New_York'));
    }
}

if (!function_exists('pbkdf2_hash')) {
    function pbkdf2_hash(string $password, string $algo = 'sha256', int $iterations = 100000, int $length = 64): string
    {
        $salt = random_bytes(16);
        $saltHex = bin2hex($salt);
        $derived = hash_pbkdf2($algo, $password, $salt, $iterations, $length, true);
        $derivedHex = bin2hex($derived);

        return implode('$', [$algo, $iterations, $saltHex, $derivedHex]);
    }
}

if (!function_exists('pbkdf2_verify')) {
    function pbkdf2_verify(string $password, string $storedHash): bool
    {
        $delim = strpos($storedHash, '$') !== false ? '$' : ':';
        $parts = explode($delim, $storedHash);
        if (count($parts) !== 4) {
            return false;
        }

        [$algo, $iterations, $saltHex, $derivedHex] = $parts;
        if ($saltHex === '' || $derivedHex === '') {
            return false;
        }

        $salt = ctype_xdigit($saltHex) ? hex2bin($saltHex) : false;
        $derived = ctype_xdigit($derivedHex) ? hex2bin($derivedHex) : false;
        if ($salt === false || $derived === false) {
            return false;
        }

        $calc = hash_pbkdf2($algo, $password, $salt, (int) $iterations, strlen($derived), true);
        return hash_equals($derived, $calc);
    }
}

if (!function_exists('verify_stored_password')) {
    function verify_stored_password(string $password, ?string $storedHash): bool
    {
        if (!$storedHash) {
            return false;
        }

        $hashInfo = password_get_info($storedHash);
        if (($hashInfo['algo'] ?? null) !== null) {
            return Hash::check($password, $storedHash);
        }

        $parts = preg_split('/[:$]/', $storedHash);
        if (is_array($parts) && count($parts) === 4) {
            return pbkdf2_verify($password, $storedHash);
        }

        return Hash::check($password, $storedHash);
    }
}