<?php

namespace App\Helpers;

use DateTimeImmutable;

class TokenHelper
{
    private static $secret = 'ufutx_love_util';

    /**
     * 生成 token
     * @param int $userId 用户ID
     * @param int $expiresIn 过期时间（分钟）
     * @return string
     */
    public static function generate($userId, $expiresIn = 60)
    {
        $now = time();
        $expires = $now + ($expiresIn * 60);

        $payload = [
            'user_id' => $userId,
            'iat' => $now,
            'exp' => $expires
        ];

        // 使用更简单的方式：base64 编码（避免版本兼容问题）
        $encoded = base64_encode(json_encode($payload));

        // 添加签名
        $signature = hash_hmac('sha256', $encoded, self::$secret);

        return $encoded . '.' . $signature;
    }

    /**
     * 验证 token
     * @return array|false
     */
    public static function verify($tokenString)
    {
        try {
            $parts = explode('.', $tokenString);
            if (count($parts) != 2) {
                return false;
            }

            list($payloadEncoded, $signature) = $parts;

            // 验证签名
            $expectedSignature = hash_hmac('sha256', $payloadEncoded, self::$secret);
            if (!hash_equals($expectedSignature, $signature)) {
                return false;
            }

            // 解码 payload
            $payload = json_decode(base64_decode($payloadEncoded), true);
            if (!$payload) {
                return false;
            }

            // 检查是否过期
            $now = time();
            if (isset($payload['exp']) && $payload['exp'] < $now) {
                return false;
            }

            return [
                'user_id' => $payload['user_id'],
                'expires_at' => $payload['exp']
            ];

        } catch (\Exception $e) {
            return false;
        }
    }

    /**
     * 刷新 token
     */
    public static function refresh($oldToken, $expiresIn = 60)
    {
        $payload = self::verify($oldToken);
        if (!$payload) {
            return false;
        }

        return self::generate($payload['user_id'], $expiresIn);
    }
}