<?php

namespace Firebase\JWT;

use ArrayAccess;
use InvalidArgumentException;
use LogicException;
use OutOfBoundsException;
use Psr\Cache\CacheItemInterface;
use Psr\Cache\CacheItemPoolInterface;
use Psr\Http\Client\ClientInterface;
use Psr\Http\Message\RequestFactoryInterface;
use RuntimeException;
use UnexpectedValueException;

/**
 * @implements ArrayAccess<string, Key>
 */
class CachedKeySet implements ArrayAccess
{
    /**
     * @var string
     */
    private $jwksUri;
    /**
     * @var ClientInterface
     */
    private $httpClient;
    /**
     * @var RequestFactoryInterface
     */
    private $httpFactory;
    /**
     * @var CacheItemPoolInterface
     */
    private $cache;
    /**
     * @var ?int
     */
    private $expiresAfter;
    /**
     * @var ?CacheItemInterface
     */
    private $cacheItem;
    /**
     * @var array<string, array<mixed>>
     */
    private $keySet;
    /**
     * @var string
     */
    private $cacheKey;
    /**
     * @var string
     */
    private $cacheKeyPrefix = 'jwks';
    /**
     * @var int
     */
    private $maxKeyLength = 64;
    /**
     * @var bool
     */
    private $rateLimit;
    /**
     * @var string
     */
    private $rateLimitCacheKey;
    /**
     * @var int
     */
    private $maxCallsPerMinute = 10;
    /**
     * @var string|null
     */
    private $defaultAlg;

    public function __construct(
        string $jwksUri,
        ClientInterface $httpClient,
        RequestFactoryInterface $httpFactory,
        CacheItemPoolInterface $cache,
        int $expiresAfter = null,
        bool $rateLimit = false,
        string $defaultAlg = null
    ) {
        $this->jwksUri = $jwksUri;
        $this->httpClient = $httpClient;
        $this->httpFactory = $httpFactory;
        $this->cache = $cache;
        $this->expiresAfter = $expiresAfter;
        $this->rateLimit = $rateLimit;
        $this->defaultAlg = $defaultAlg;
        $this->setCacheKeys();
    }

    /**
     * @param string $keyId
     * @return Key
     */
    public function offsetGet($keyId): Key
    {
        if (!$this->keyIdExists($keyId)) {
            throw new OutOfBoundsException('Key ID not found');
        }
        return JWK::parseKey($this->keySet[$keyId], $this->defaultAlg);
    }

    /**
     * @param string $keyId
     * @return bool
     */
    public function offsetExists($keyId): bool
    {
        return $this->keyIdExists($keyId);
    }

    /**
     * @param string $offset
     * @param Key $value
     */
    public function offsetSet($offset, $value): void
    {
        throw new LogicException('Method not implemented');
    }

    /**
     * @param string $offset
     */
    public function offsetUnset($offset): void
    {
        throw new LogicException('Method not implemented');
    }

    /**
     * @return array<mixed>
     */
    private function formatJwksForCache(string $jwks): array
    {
        $jwks = json_decode($jwks, true);

        if (!isset($jwks['keys'])) {
            throw new UnexpectedValueException('"keys" member must exist in the JWK Set');
        }

        if (empty($jwks['keys'])) {
            throw new InvalidArgumentException('JWK Set did not contain any keys');
        }

        $keys = [];
        foreach ($jwks['keys'] as $k => $v) {
            $kid = isset($v['kid']) ? $v['kid'] : $k;
            $keys[(string) $kid] = $v;
        }

        return $keys;
    }

    private function keyIdExists(string $keyId): bool
    {
        if (null === $this->keySet) {
            $item = $this->getCacheItem();
            // Try to load keys from cache
            if ($item->isHit()) {
                // item found! retrieve it
                $this->keySet = $item->get();
                // If the cached item is a string, the JWKS response was cached (previous behavior).
                // Parse this into expected format array<kid, jwk> instead.
                if (\is_string($this->keySet)) {
                    $this->keySet = $this->formatJwksForCache($this->keySet);
                }
            }
        }

        if (!isset($this->keySet[$keyId])) {
            if ($this->rateLimitExceeded()) {
                return false;
            }
            $request = $this->httpFactory->createRequest('GET', $this->jwksUri);
            $jwksResponse = $this->httpClient->sendRequest($request);
            if ($jwksResponse->getStatusCode() !== 200) {
                throw new UnexpectedValueException(
                    sprintf('HTTP Error: %d %s for URI "%s"',
                        $jwksResponse->getStatusCode(),
                        $jwksResponse->getReasonPhrase(),
                        $this->jwksUri,
                    ),
                    $jwksResponse->getStatusCode()
                );
            }
            $this->keySet = $this->formatJwksForCache((string) $jwksResponse->getBody());

            if (!isset($this->keySet[$keyId])) {
                return false;
            }

            $item = $this->getCacheItem();
            $item->set($this->keySet);
            if ($this->expiresAfter) {
                $item->expiresAfter($this->expiresAfter);
            }
            $this->cache->save($item);
        }

        return true;
    }

    private function rateLimitExceeded(): bool
    {
        if (!$this->rateLimit) {
            return false;
        }

        $cacheItem = $this->cache->getItem($this->rateLimitCacheKey);
        if (!$cacheItem->isHit()) {
            $cacheItem->expiresAfter(1); // # of calls are cached each minute
        }

        $callsPerMinute = (int) $cacheItem->get();
        if (++$callsPerMinute > $this->maxCallsPerMinute) {
            return true;
        }
        $cacheItem->set($callsPerMinute);
        $this->cache->save($cacheItem);
        return false;
    }

    private function getCacheItem(): CacheItemInterface
    {
        if (\is_null($this->cacheItem)) {
            $this->cacheItem = $this->cache->getItem($this->cacheKey);
        }

        return $this->cacheItem;
    }

    private function setCacheKeys(): void
    {
        if (empty($this->jwksUri)) {
            throw new RuntimeException('JWKS URI is empty');
        }

        // ensure we do not have illegal characters
        $key = preg_replace('|[^a-zA-Z0-9_\.!]|', '', $this->jwksUri);

        // add prefix
        $key = $this->cacheKeyPrefix . $key;

        // Hash keys if they exceed $maxKeyLength of 64
        if (\strlen($key) > $this->maxKeyLength) {
            $key = substr(hash('sha256', $key), 0, $this->maxKeyLength);
        }

        $this->cacheKey = $key;

        if ($this->rateLimit) {
            // add prefix
            $rateLimitKey = $this->cacheKeyPrefix . 'ratelimit' . $key;

            // Hash keys if they exceed $maxKeyLength of 64
            if (\strlen($rateLimitKey) > $this->maxKeyLength) {
                $rateLimitKey = substr(hash('sha256', $rateLimitKey), 0, $this->maxKeyLength);
            }

            $this->rateLimitCacheKey = $rateLimitKey;
        }
    }
}

• [F] BeforeValidException.php
  Delete
• [F] CachedKeySet.php
  Delete
• [F] ExpiredException.php
  Delete
• [F] JWK.php
  Delete
• [F] JWT.php
  Delete
• [F] JWTExceptionWithPayloadInterface.php
  Delete
• [F] Key.php
  Delete
• [F] SignatureInvalidException.php
  Delete

About Section

About NFC Pay: Our Story and Mission

NFC Pay was founded with a vision to transform the way people handle transactions. Our journey is defined by a commitment to innovation, security, and convenience. We strive to deliver seamless, user-friendly payment solutions that make everyday transactions effortless and secure. Our mission is to empower you to pay with ease and confidence, anytime, anywhere.

• Simplifying Payments, One Tap at a Time.
• Reinventing Your Wallet for Modern Convenience.
• Smart Payments for a Effortless Lifestyle.
• Experience the Ease of Tap and Pay.
• Innovative Solutions for Your Daily Transactions.

FAQ Section

Frequently Asked Questions About NFC Pay

Here are answers to some common questions about NFC Pay. We aim to provide clear and concise information to help you understand how our platform works and how it can benefit you. If you have any further inquiries, please don’t hesitate to contact our support team.

How do I register for NFC Pay?

Download the app and sign up using your email or phone number, then complete the verification process.

Is my payment information secure?

Yes, we use advanced encryption and security protocols to protect your payment details.

Can I add multiple cards to my NFC Pay wallet?

Absolutely, you can link multiple debit or credit cards to your wallet.

How do I transfer money to another user?

Go to the transfer section, select the recipient, enter the amount, and authorize the transfer.

What should I do if I forget my PIN?

Use the “Forgot PIN” feature in the app to reset it following the provided instructions.

How can I activate my merchant account?

Sign up for a merchant account through the app and follow the setup instructions to start accepting payments.

Can I track my payment status?

Yes, you can view and track your payment status in the account dashboard