<?php

namespace Syde\Vendor\Cawl\OnlinePayments\Sdk\Webhooks;

/**
 * Class SignatureValidator
 *
 * @package OnlinePayments\Sdk\Webhooks
 */
class SignatureValidator
{
    /** @var SecretKeyStore */
    private $secretKeyStore;
    /**
     * @param SecretKeyStore $secretKeyStore
     */
    public function __construct(SecretKeyStore $secretKeyStore)
    {
        $this->secretKeyStore = $secretKeyStore;
    }
    /**
     * Validates the given body using the given request headers.
     * @param string $body
     * @param array $requestHeaders
     * @throws SignatureValidationException
     */
    public function validate($body, $requestHeaders)
    {
        $this->validateBody($body, $requestHeaders);
    }
    // utility methods
    private function validateBody($body, $requestHeaders)
    {
        $signature = $this->getHeaderValue($requestHeaders, 'X-GCS-Signature');
        $keyId = $this->getHeaderValue($requestHeaders, 'X-GCS-KeyId');
        $secretKey = $this->secretKeyStore->getSecretKey($keyId);
        $expectedSignature = \base64_encode(\hash_hmac("sha256", $body, $secretKey, \true));
        $isValid = \hash_equals($signature, $expectedSignature);
        if (!$isValid) {
            throw new SignatureValidationException("failed to validate signature '{$signature}'");
        }
    }
    // general utility methods
    private function getHeaderValue($requestHeaders, $headerName)
    {
        $lowerCaseHeaderName = \strtolower($headerName);
        foreach ($requestHeaders as $name => $value) {
            if ($lowerCaseHeaderName === \strtolower($name)) {
                return $value;
            }
        }
        throw new SignatureValidationException("could not find header '{$headerName}'");
    }
}
