<?php

namespace React\Socket;

use React\EventLoop\LoopInterface;
use React\Promise\Deferred;
use RuntimeException;
use UnexpectedValueException;

/**
 * This class is considered internal and its API should not be relied upon
 * outside of Socket.
 *
 * @internal
 */
class StreamEncryption
{
    private $loop;
    private $method;
    private $server;

    private $errstr;
    private $errno;

    public function __construct(LoopInterface $loop, $server = true)
    {
        $this->loop = $loop;
        $this->server = $server;

        // support TLSv1.0+ by default and exclude legacy SSLv2/SSLv3.
        // PHP 5.6+ supports bitmasks, legacy PHP only supports predefined
        // constants, so apply accordingly below.
        // Also, since PHP 5.6.7 up until before PHP 7.2.0 the main constant did
        // only support TLSv1.0, so we explicitly apply all versions.
        // @link http://php.net/manual/en/migration56.openssl.php#migration56.openssl.crypto-method
        // @link https://3v4l.org/plbFn
        if ($server) {
            $this->method = STREAM_CRYPTO_METHOD_TLS_SERVER;

            if (defined('STREAM_CRYPTO_METHOD_TLSv1_0_SERVER')) {
                $this->method |= STREAM_CRYPTO_METHOD_TLSv1_0_SERVER;
            }
            if (defined('STREAM_CRYPTO_METHOD_TLSv1_1_SERVER')) {
                $this->method |= STREAM_CRYPTO_METHOD_TLSv1_1_SERVER;
            }
            if (defined('STREAM_CRYPTO_METHOD_TLSv1_2_SERVER')) {
                $this->method |= STREAM_CRYPTO_METHOD_TLSv1_2_SERVER;
            }
        } else {
            $this->method = STREAM_CRYPTO_METHOD_TLS_CLIENT;

            if (defined('STREAM_CRYPTO_METHOD_TLSv1_0_CLIENT')) {
                $this->method |= STREAM_CRYPTO_METHOD_TLSv1_0_CLIENT;
            }
            if (defined('STREAM_CRYPTO_METHOD_TLSv1_1_CLIENT')) {
                $this->method |= STREAM_CRYPTO_METHOD_TLSv1_1_CLIENT;
            }
            if (defined('STREAM_CRYPTO_METHOD_TLSv1_2_CLIENT')) {
                $this->method |= STREAM_CRYPTO_METHOD_TLSv1_2_CLIENT;
            }
        }
    }

    public function enable(Connection $stream)
    {
        return $this->toggle($stream, true);
    }

    public function disable(Connection $stream)
    {
        return $this->toggle($stream, false);
    }

    public function toggle(Connection $stream, $toggle)
    {
        // pause actual stream instance to continue operation on raw stream socket
        $stream->pause();

        // TODO: add write() event to make sure we're not sending any excessive data

        $deferred = new Deferred(function ($_, $reject) use ($toggle) {
            // cancelling this leaves this stream in an inconsistent state…
            $reject(new RuntimeException('Cancelled toggling encryption ' . $toggle ? 'on' : 'off'));
        });

        // get actual stream socket from stream instance
        $socket = $stream->stream;

        // get crypto method from context options or use global setting from constructor
        $method = $this->method;
        $context = stream_context_get_options($socket);
        if (isset($context['ssl']['crypto_method'])) {
            $method = $context['ssl']['crypto_method'];
        }

        $that = $this;
        $toggleCrypto = function () use ($socket, $deferred, $toggle, $method, $that) {
            $that->toggleCrypto($socket, $deferred, $toggle, $method);
        };

        $this->loop->addReadStream($socket, $toggleCrypto);

        if (!$this->server) {
            $toggleCrypto();
        }

        $loop = $this->loop;

        return $deferred->promise()->then(function () use ($stream, $socket, $loop, $toggle) {
            $loop->removeReadStream($socket);

            $stream->encryptionEnabled = $toggle;
            $stream->resume();

            return $stream;
        }, function($error) use ($stream, $socket, $loop) {
            $loop->removeReadStream($socket);
            $stream->resume();
            throw $error;
        });
    }

    public function toggleCrypto($socket, Deferred $deferred, $toggle, $method)
    {
        set_error_handler(array($this, 'handleError'));
        $result = stream_socket_enable_crypto($socket, $toggle, $method);
        restore_error_handler();

        if (true === $result) {
            $deferred->resolve();
        } else if (false === $result) {
            $deferred->reject(new UnexpectedValueException(
                sprintf("Unable to complete SSL/TLS handshake: %s", $this->errstr),
                $this->errno
            ));
        } else {
            // need more data, will retry
        }
    }

    public function handleError($errno, $errstr)
    {
        $this->errstr = str_replace(array("\r", "\n"), ' ', $errstr);
        $this->errno  = $errno;
    }
}