<?php

declare(strict_types=1);

namespace App\Support;

use App\Models\Customer;
use Illuminate\Support\Facades\DB;

final class PasswordResetToken
{
    public const LENGTH = 80;

    private const ALPHABET = '0123456789abcdefghijklmnopqrstuvwxyz';

    private const TABLE = 'password_resets';

    /**
     * @return string|null null khi email vừa được cấp token trong khoảng throttle
     */
    public static function issue(Customer $customer): ?string
    {
        $email = strtolower($customer->email);
        $lastIssuedAt = DB::table(self::TABLE)->where('email', $email)->max('created_at');

        if ($lastIssuedAt && now()->subSeconds(self::throttleSeconds())->lt($lastIssuedAt)) {
            return null;
        }

        $body = '';
        for ($i = 0; $i < self::LENGTH - 1; $i++) {
            $body .= self::ALPHABET[random_int(0, strlen(self::ALPHABET) - 1)];
        }
        $token = $body . self::checkCharacter($body);

        DB::transaction(function () use ($email, $token) {
            DB::table(self::TABLE)->where('email', $email)->delete();
            DB::table(self::TABLE)->insert([
                'email'      => $email,
                'token'      => self::hash($token),
                'created_at' => now(),
            ]);
        });

        return $token;
    }

    public static function isWellFormed(string $token): bool
    {
        if (strlen($token) !== self::LENGTH || strspn($token, self::ALPHABET) !== self::LENGTH) {
            return false;
        }

        return self::checkCharacter(substr($token, 0, -1)) === $token[self::LENGTH - 1];
    }

    public static function findCustomer(string $token): ?Customer
    {
        if (!self::isWellFormed($token)) {
            return null;
        }

        $row = DB::table(self::TABLE)
            ->where('token', self::hash($token))
            ->where('created_at', '>=', now()->subMinutes(self::expireMinutes()))
            ->first();

        if (!$row) {
            return null;
        }

        return Customer::whereRaw('LOWER(email) = ?', [$row->email])->first();
    }

    public static function revokeFor(Customer $customer): void
    {
        DB::table(self::TABLE)->where('email', strtolower($customer->email))->delete();
    }

    private static function checkCharacter(string $body): string
    {
        $base = strlen(self::ALPHABET);
        $sum = 0;
        $double = true;

        for ($i = strlen($body) - 1; $i >= 0; $i--) {
            $value = strpos(self::ALPHABET, $body[$i]);
            if ($double) {
                $value *= 2;
                $value = intdiv($value, $base) + $value % $base;
            }
            $sum += $value;
            $double = !$double;
        }

        return self::ALPHABET[($base - $sum % $base) % $base];
    }

    private static function hash(string $token): string
    {
        return hash('sha256', $token);
    }

    private static function expireMinutes(): int
    {
        return (int) config('auth.passwords.users.expire', 60);
    }

    private static function throttleSeconds(): int
    {
        return (int) config('auth.passwords.users.throttle', 60);
    }
}