<?php
/**
 * Insipid
 * Personal web-bookmark-system
 *
 * Copyright 2016-2023 Johannes Keßler
 *
 * Development starting from 2011: Johannes Keßler
 * https://www.bananas-playground.net/projekt/insipid/
 *
 * creator:
 * Luke Reeves <luke@neuro-tech.net>
 *
 * simple IMAP SSL/TLS email connection based on the imap PHP functions
 * the code supports SSL/TLS and IMAP only
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see http://www.gnu.org/licenses/gpl-3.0.
 *
 */

/**
 * Class SimpleImap
 * read and manage email messages over imap. Sending not included. Use PHPMailer instead.
 */
class SimpleImap {

    private IMAP\Connection $_connection;

    private string $_server = EMAIL_SERVER;
    private string $_user = EMAIL_SERVER_USER;
    private string $_pass = EMAIL_SERVER_PASS;
    private int $_port = EMAIL_SERVER_PORT_IMAP;
    private string $_mailbox = EMAIL_SERVER_MAILBOX;

    private string $_connectionstring = '';

    /**
     * SimpleImap constructor.
     */
    function __construct() {
        # create the mailboxstring
        $this->_connectionstring = '{'.$this->_server.':'.$this->_port.'/imap/ssl/novalidate-cert}';
    }

    /**
     *
     */
    function __destruct() {
        //imap_close($this->_connection);
    }

    /**
     * connect to the e-mail server
     * with this code SSL/TLS only
     *
     * @see http://ca.php.net/manual/en/function.imap-open.php
     * @throws Exception
     */
    public function connect(): void {

        if(empty($this->_server)) {
            throw new Exception('Missing EMAIL_SERVER');
        }
        if(empty($this->_port)) {
            throw new Exception('Missing EMAIL_SERVER_PORT');
        }
        if(empty($this->_user)) {
            throw new Exception('Missing EMAIL_SERVER_USER');
        }

        # create the connection
        $this->_connection = imap_open($this->_connectionstring.$this->_mailbox, $this->_user, $this->_pass);

        if(!$this->_connection) {
            throw new Exception('Failed IMAP connection: '.var_export(imap_last_error(),true));
        }
    }

    /**
     * process the given mailbox and check for the special messages
     * return the body and headers from the found message
     *
     * @param string $subjectmarker
     * @return array emailId => array(body, header);
     * @throws Exception
     */
    function messageWithValidSubject(string $subjectmarker): array {
        $ret = array();

        $messagecount = imap_num_msg($this->_connection);

        if($messagecount === false) {
            throw new Exception('Can not read the messages in given mailbox');
        }

        $processedmessagescount = 0;
        for($i = 1; $i <= $messagecount; $i++) {
            $subject = $this->_extractSubject($i);

            if(!empty($subject)) {
                # check the special stuff
                $markerextract = substr($subject, 0, strlen($subjectmarker));
                if($markerextract == $subjectmarker) {
                    $processedmessagescount++;
                    # valid message
                    # get the body
                    $ret[$i]['body'] = $this->_extractBody($i);
                    $ret[$i]['header'] = $this->emailHeaders($i);
                    $ret[$i]['header_rfc822'] = $this->emailHeaders_rfc822($i);
                    $ret[$i]['header_array'] = $this->emailHeadersAsArray($i);
                    # @see https://www.php.net/manual/en/function.imap-uid.php
                    $ret[$i]['uid'] = imap_uid($this->_connection,$i);
                }
            }
        }

        # log messages processed to all messages
        Summoner::sysLog("INFO Read ".$messagecount." messages");
        Summoner::sysLog("INFO Processed ".$processedmessagescount." messages");

        return $ret;

    }

    /**
     * the current status about the mail connection and INBOX
     * kinda debug only
     *
     * @see http://ca.php.net/manual/en/function.imap-status.php
     */
    public function mailboxStatus(): void {
        if($this->_connection !== false) {
            $status = imap_status($this->_connection, $this->_connectionstring.$this->_mailbox, SA_ALL);

            if(DEBUG === true) {
                Summoner::sysLog("messages " . $status->messages);
                Summoner::sysLog("recent " . $status->recent);
                Summoner::sysLog("unseen " . $status->unseen);
                Summoner::sysLog("uidnext " . $status->uidnext);
                Summoner::sysLog("uidvalidity " . $status->uidvalidity);
            }

            $list = imap_getmailboxes($this->_connection, $this->_connectionstring, "*");
            if (is_array($list)) {
                foreach ($list as $key => $val) {
                    echo "($key) ";
                    echo imap_utf7_decode($val->name) . ",";
                    echo "'" . $val->delimiter . "',";
                    echo $val->attributes . "<br />\n";
                }
            } else {
                Summoner::sysLog("ERROR imap_getmailboxes failed: ".var_export(imap_last_error()));
            }
        }
    }

    /**
     * This function causes a fetch of the complete, unfiltered RFC2822 format header of the specified message.
     *
     * @param integer $messagenum
     * @return string
     */
    public function emailHeaders(int $messagenum): string {
        return imap_fetchheader($this->_connection, $messagenum);
    }

    /**
     * return the email headers by given emailid
     *
     * @param integer $messagenum
     * @return object
     */
    public function emailHeaders_rfc822(int $messagenum): object {
        return imap_rfc822_parse_headers($this->emailHeaders($messagenum));
    }

    /**
     * Email headers parsed as an array
     *
     * @param integer $messagenum
     * @return array
     */
    public function emailHeadersAsArray(int $messagenum): array {
        preg_match_all('/([^: ]+): (.+?(?:\r\n\s(?:.+?))*)\r\n/m', $this->emailHeaders($messagenum), $matches );
        return array_combine( $matches[1], $matches[2]);
    }

    /**
     * Move given message to given folder
     *
     * @param integer $messageUid This is the message Uid as an int
     * @param string $folder This is the target folder. Default is EMAIL_ARCHIVE_FOLDER
     */
    public function moveMessage(int $messageUid, string $folder=EMAIL_ARCHIVE_FOLDER): void {
        if(!empty($messageUid) && !empty($folder)) {
            $messageUid = (string)$messageUid;
            imap_setflag_full($this->_connection,$messageUid,"\SEEN", ST_UID);
            imap_mail_move($this->_connection, $messageUid, $folder,CP_UID);
            imap_expunge($this->_connection);
        }
    }

    /**
     * extract the subject from the email headers and decode
     * A subject can be split into multiple parts...
     *
     * @param int $messagenum
     * @return string
     */
    private function _extractSubject(int $messagenum): string {
        $ret = '';

        $headerinfo = $this->emailHeaders_rfc822($messagenum);
        $subjectArr = imap_mime_header_decode($headerinfo->subject);
        foreach ($subjectArr as $el) {
            $ret .= $el->text;
        }

        return $ret;
    }

    /**
     * extract the body of the given message
     *
     * @see http://php.net/manual/en/function.imap-fetchstructure.php
     *
     * @param int $messagenum
     * @return string
     */
    private function _extractBody(int $messagenum): string {
        $ret = '';

        $emailstructure = imap_fetchstructure($this->_connection, $messagenum);

        # simple or multipart?
        if(isset($emailstructure->parts)) {
            exit("multipart todo");
        }
        else {
            $body = imap_body($this->_connection, $messagenum);
        }

        # encoding
        switch ($emailstructure->encoding) {
            case ENC8BIT: # 1 8BIT
                $ret = quoted_printable_decode(imap_8bit($body));
            break;

            case ENCBINARY: # 2 BINARY
                $ret = imap_binary($body);
            break;

            case ENCBASE64: # 3 BASE64
                $ret = imap_base64($body);
            break;

            case ENCQUOTEDPRINTABLE: # 4 QUOTED-PRINTABLE
                $ret = quoted_printable_decode($body);
            break;

            case ENC7BIT: # 0 7BIT
                // imap_qprint($body); does throws notices
                $ret = quoted_printable_decode($body);
            break;

            case ENCOTHER: # 5 OTHER

            default: # UNKNOWN
                $ret = $body;
        }

        return $ret;
    }

    /**
     * close the imap connection
     */
    function close(): void {
        imap_close($this->_connection);
    }
}