<?php

namespace Laminas\Mail\Protocol;

use Laminas\Validator;
use Laminas\Validator\ValidatorChain;

use function array_shift;
use function count;
use function fclose;
use function fgets;
use function fwrite;
use function implode;
use function in_array;
use function is_array;
use function is_resource;
use function preg_split;
use function restore_error_handler;
use function set_error_handler;
use function sprintf;
use function str_starts_with;
use function stream_get_meta_data;
use function stream_set_timeout;
use function stream_socket_client;

use const E_WARNING;
use const PREG_SPLIT_DELIM_CAPTURE;

/**
 * Provides low-level methods for concrete adapters to communicate with a
 * remote mail server and track requests and responses.
 *
 * @todo Implement proxy settings
 */
abstract class AbstractProtocol
{
    /**
     * Mail default EOL string
     */
    public const EOL = "\r\n";

    /**
     * Default timeout in seconds for initiating session
     */
    public const TIMEOUT_CONNECTION = 30;

    /**
     * Maximum of the transaction log
     *
     * @var int
     */
    protected $maximumLog = 64;

    /**
     * Hostname or IP address of remote server
     *
     * @var string
     */
    protected $host;

    /**
     * Instance of Laminas\Validator\ValidatorChain to check hostnames
     *
     * @var ValidatorChain
     */
    protected $validHost;

    /**
     * Socket connection resource
     *
     * @var null|resource
     */
    protected $socket;

    /**
     * Last request sent to server
     *
     * @var string
     */
    protected $request;

    /**
     * Array of server responses to last request
     *
     * @var array
     */
    protected $response;

    /**
     * Log of mail requests and server responses for a session
     */
    private array $log = [];

    /**
     * @param  string  $host OPTIONAL Hostname of remote connection (default: 127.0.0.1)
     * @param  int $port OPTIONAL Port number (default: null)
     * @throws Exception\RuntimeException
     */
    public function __construct($host = '127.0.0.1', protected $port = null)
    {
        $this->validHost = new Validator\ValidatorChain();
        $this->validHost->attach(new Validator\Hostname(Validator\Hostname::ALLOW_ALL));

        if (! $this->validHost->isValid($host)) {
            throw new Exception\RuntimeException(implode(', ', $this->validHost->getMessages()));
        }

        $this->host = $host;
    }

    /**
     * Class destructor to cleanup open resources
     */
    public function __destruct()
    {
        $this->_disconnect();
    }

    /**
     * Set the maximum log size
     *
     * @param int $maximumLog Maximum log size
     */
    public function setMaximumLog($maximumLog)
    {
        $this->maximumLog = (int) $maximumLog;
    }

    /**
     * Get the maximum log size
     *
     * @return int the maximum log size
     */
    public function getMaximumLog()
    {
        return $this->maximumLog;
    }

    /**
     * Create a connection to the remote host
     *
     * Concrete adapters for this class will implement their own unique connect
     * scripts, using the _connect() method to create the socket resource.
     */
    abstract public function connect();

    /**
     * Retrieve the last client request
     *
     * @return string
     */
    public function getRequest()
    {
        return $this->request;
    }

    /**
     * Retrieve the last server response
     *
     * @return array
     */
    public function getResponse()
    {
        return $this->response;
    }

    /**
     * Retrieve the transaction log
     *
     * @return string
     */
    public function getLog()
    {
        return implode('', $this->log);
    }

    /**
     * Reset the transaction log
     */
    public function resetLog()
    {
        $this->log = [];
    }

    /**
     * Add the transaction log
     *
     * @param  string $value new transaction
     */
    // @codingStandardsIgnoreLine PSR2.Methods.MethodDeclaration.Underscore
    protected function _addLog($value)
    {
        if ($this->maximumLog >= 0 && count($this->log) >= $this->maximumLog) {
            array_shift($this->log);
        }

        $this->log[] = $value;
    }

    /**
     * Connect to the server using the supplied transport and target
     *
     * An example $remote string may be 'tcp://mail.example.com:25' or 'ssh://hostname.com:2222'
     *
     * @deprecated Since 1.12.0. Implementations should use the ProtocolTrait::setupSocket() method instead.
     *
     * @todo Remove for 3.0.0.
     * @param  string $remote Remote
     * @throws Exception\RuntimeException
     * @return bool
     */
    // @codingStandardsIgnoreLine PSR2.Methods.MethodDeclaration.Underscore
    protected function _connect($remote)
    {
        $errorNum = 0;
        $errorStr = '';

        // open connection
        set_error_handler(
            static function ($error, $message = '') {
                throw new Exception\RuntimeException(sprintf('Could not open socket: %s', $message), $error);
            },
            E_WARNING
        );
        $this->socket = stream_socket_client($remote, $errorNum, $errorStr, self::TIMEOUT_CONNECTION);
        restore_error_handler();

        if ($this->socket === false) {
            if ($errorNum == 0) {
                $errorStr = 'Could not open socket';
            }
            throw new Exception\RuntimeException($errorStr);
        }

        if (($result = stream_set_timeout($this->socket, self::TIMEOUT_CONNECTION)) === false) {
            throw new Exception\RuntimeException('Could not set stream timeout');
        }

        return $result;
    }

    /**
     * Disconnect from remote host and free resource
     */
    // @codingStandardsIgnoreLine PSR2.Methods.MethodDeclaration.Underscore
    protected function _disconnect()
    {
        if (is_resource($this->socket)) {
            fclose($this->socket);
        }
    }

    /**
     * Send the given request followed by a LINEEND to the server.
     *
     * @param  string $request
     * @throws Exception\RuntimeException
     * @return int|bool Number of bytes written to remote host
     */
    // @codingStandardsIgnoreLine PSR2.Methods.MethodDeclaration.Underscore
    protected function _send($request)
    {
        if (! is_resource($this->socket)) {
            throw new Exception\RuntimeException('No connection has been established to ' . $this->host);
        }

        $this->request = $request;

        $result = fwrite($this->socket, $request . self::EOL);

        // Save request to internal log
        $this->_addLog($request . self::EOL);

        if ($result === false) {
            throw new Exception\RuntimeException('Could not send request to ' . $this->host);
        }

        return $result;
    }

    /**
     * Get a line from the stream.
     *
     * @param  int $timeout Per-request timeout value if applicable
     * @throws Exception\RuntimeException
     * @return string
     */
    // @codingStandardsIgnoreLine PSR2.Methods.MethodDeclaration.Underscore
    protected function _receive($timeout = null)
    {
        if (! is_resource($this->socket)) {
            throw new Exception\RuntimeException('No connection has been established to ' . $this->host);
        }

        // Adapters may wish to supply per-commend timeouts according to appropriate RFC
        if ($timeout !== null) {
            stream_set_timeout($this->socket, $timeout);
        }

        // Retrieve response
        $response = fgets($this->socket, 1024);

        // Save request to internal log
        $this->_addLog($response);

        // Check meta data to ensure connection is still valid
        $info = stream_get_meta_data($this->socket);

        if ($info['timed_out']) {
            throw new Exception\RuntimeException($this->host . ' has timed out');
        }

        if ($response === false) {
            throw new Exception\RuntimeException('Could not read from ' . $this->host);
        }

        return $response;
    }

    /**
     * Parse server response for successful codes
     *
     * Read the response from the stream and check for expected return code.
     * Throws a Laminas\Mail\Protocol\Exception\ExceptionInterface if an unexpected code is returned.
     *
     * @param  string|array $code One or more codes that indicate a successful response
     * @param  int $timeout Per-request timeout value if applicable
     * @throws Exception\RuntimeException
     * @return string Last line of response string
     */
    // @codingStandardsIgnoreLine PSR2.Methods.MethodDeclaration.Underscore
    protected function _expect($code, $timeout = null)
    {
        $this->response = [];
        $errMsg         = '';

        if (! is_array($code)) {
            $code = [$code];
        }

        do {
            $this->response[]   = $result = $this->_receive($timeout);
            [$cmd, $more, $msg] = preg_split('/([\s-]+)/', $result, 2, PREG_SPLIT_DELIM_CAPTURE);

            if ($errMsg !== '') {
                $errMsg .= ' ' . $msg;
            } elseif ($cmd === null || ! in_array($cmd, $code)) {
                $errMsg = $msg;
            }

        // The '-' message prefix indicates an information string instead of a response string.
        } while (str_starts_with($more, '-'));

        if ($errMsg !== '') {
            throw new Exception\RuntimeException($errMsg, (int) $cmd);
        }

        return $msg;
    }
}