<?php

/**
 * This file is part of the Nette Framework (https://nette.org)
 * Copyright (c) 2004 David Grudl (https://davidgrudl.com)
 */

declare(strict_types=1);

namespace Nette\Mail;

use Nette;


/**
 * Sends emails via the SMTP server.
 */
class SmtpMailer implements Mailer
{
	use Nette\SmartObject;

	/** @var Signer|null */
	private $signer;

	/** @var resource|null */
	private $connection;

	/** @var string */
	private $host;

	/** @var int */
	private $port;

	/** @var string */
	private $username;

	/** @var string */
	private $password;

	/** @var string ssl | tls | (empty) */
	private $secure;

	/** @var int */
	private $timeout;

	/** @var resource */
	private $context;

	/** @var bool */
	private $persistent;

	/** @var string */
	private $clientHost;


	public function __construct(array $options = [])
	{
		if (isset($options['host'])) {
			$this->host = $options['host'];
			$this->port = isset($options['port'])
				? (int) $options['port']
				: null;
		} else {
			$this->host = ini_get('SMTP');
			$this->port = (int) ini_get('smtp_port');
		}
		$this->username = $options['username'] ?? '';
		$this->password = $options['password'] ?? '';
		$this->secure = $options['secure'] ?? '';
		$this->timeout = isset($options['timeout'])
			? (int) $options['timeout']
			: 20;
		$this->context = isset($options['context'])
			? stream_context_create($options['context'])
			: stream_context_get_default();
		if (!$this->port) {
			$this->port = $this->secure === 'ssl' ? 465 : 25;
		}
		$this->persistent = !empty($options['persistent']);
		if (isset($options['clientHost'])) {
			$this->clientHost = $options['clientHost'];
		} else {
			$this->clientHost = isset($_SERVER['HTTP_HOST']) && preg_match('#^[\w.-]+$#D', $_SERVER['HTTP_HOST'])
				? $_SERVER['HTTP_HOST']
				: 'localhost';
		}
	}


	/** @return static */
	public function setSigner(Signer $signer): self
	{
		$this->signer = $signer;
		return $this;
	}


	/**
	 * Sends email.
	 * @throws SmtpException
	 */
	public function send(Message $mail): void
	{
		$tmp = clone $mail;
		$tmp->setHeader('Bcc', null);

		$data = $this->signer
			? $this->signer->generateSignedMessage($tmp)
			: $tmp->generateMessage();

		try {
			if (!$this->connection) {
				$this->connect();
			}

			if (
				($from = $mail->getHeader('Return-Path'))
				|| ($from = array_keys((array) $mail->getHeader('From'))[0])
			) {
				$this->write("MAIL FROM:<$from>", 250);
			}

			foreach (array_merge(
				(array) $mail->getHeader('To'),
				(array) $mail->getHeader('Cc'),
				(array) $mail->getHeader('Bcc')
			) as $email => $name) {
				$this->write("RCPT TO:<$email>", [250, 251]);
			}

			$this->write('DATA', 354);
			$data = preg_replace('#^\.#m', '..', $data);
			$this->write($data);
			$this->write('.', 250);

			if (!$this->persistent) {
				$this->write('QUIT', 221);
				$this->disconnect();
			}
		} catch (SmtpException $e) {
			if ($this->connection) {
				$this->disconnect();
			}
			throw $e;
		}
	}


	/**
	 * Connects and authenticates to SMTP server.
	 */
	protected function connect(): void
	{
		$this->connection = @stream_socket_client(// @ is escalated to exception
			($this->secure === 'ssl' ? 'ssl://' : '') . $this->host . ':' . $this->port,
			$errno,
			$error,
			$this->timeout,
			STREAM_CLIENT_CONNECT,
			$this->context
		);
		if (!$this->connection) {
			throw new SmtpException($error ?: error_get_last()['message'], $errno);
		}
		stream_set_timeout($this->connection, $this->timeout, 0);
		$this->read(); // greeting

		if ($this->secure === 'tls') {
			$this->write("EHLO $this->clientHost", 250);
			$this->write('STARTTLS', 220);
			if (!stream_socket_enable_crypto(
				$this->connection,
				true,
				STREAM_CRYPTO_METHOD_TLS_CLIENT | STREAM_CRYPTO_METHOD_TLSv1_1_CLIENT | STREAM_CRYPTO_METHOD_TLSv1_2_CLIENT
			)) {
				throw new SmtpException('Unable to connect via TLS.');
			}
			$this->write("EHLO $this->clientHost");
			$ehloResponse = $this->read();
			if ((int) $ehloResponse !== 250) {
				throw new SmtpException('SMTP server did not accept EHLO with error: ' . trim($response));
			}

		} else {
			$this->write("EHLO $this->clientHost");
			$ehloResponse = $this->read();
			if ((int) $ehloResponse !== 250) {
				$this->write("HELO $this->clientHost", 250);
			}
		}

		if ($this->username !== '') {
			$authMechanisms = [];
			if (preg_match('~^250[ -]AUTH (.*)$~im', $ehloResponse, $matches)) {
				$authMechanisms = explode(' ', trim($matches[1]));
			}

			if (in_array('PLAIN', $authMechanisms, true)) {
				$credentials = $this->username . "\0" . $this->username . "\0" . $this->password;
				$this->write('AUTH PLAIN ' . base64_encode($credentials), 235, 'PLAIN credentials');
			} else {
				$this->write('AUTH LOGIN', 334);
				$this->write(base64_encode($this->username), 334, 'username');
				if ($this->password !== '') {
					$this->write(base64_encode($this->password), 235, 'password');
				}
			}
		}
	}


	/**
	 * Disconnects from SMTP server.
	 */
	protected function disconnect(): void
	{
		fclose($this->connection);
		$this->connection = null;
	}


	/**
	 * Writes data to server and checks response against expected code if some provided.
	 * @param  int|int[]  $expectedCode
	 */
	protected function write(string $line, $expectedCode = null, string $message = null): void
	{
		fwrite($this->connection, $line . Message::EOL);
		if ($expectedCode) {
			$response = $this->read();
			if (!in_array((int) $response, (array) $expectedCode, true)) {
				throw new SmtpException('SMTP server did not accept ' . ($message ?: $line) . ' with error: ' . trim($response));
			}
		}
	}


	/**
	 * Reads response from server.
	 */
	protected function read(): string
	{
		$s = '';
		while (($line = fgets($this->connection, 1000)) != null) { // intentionally ==
			$s .= $line;
			if (substr($line, 3, 1) === ' ') {
				break;
			}
		}
		return $s;
	}
}
