<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle 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.
//
// Moodle 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 Moodle.  If not, see <http://www.gnu.org/licenses/>.

/**
 * New messaging manager class.
 *
 * @package   core_message
 * @since     Moodle 2.8
 * @copyright 2014 Totara Learning Solutions Ltd {@link http://www.totaralms.com/}
 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 * @author    Petr Skoda <petr.skoda@totaralms.com>
 */

namespace core\message;

defined('MOODLE_INTERNAL') || die();

/**
 * Class used for various messaging related stuff.
 *
 * Note: Do NOT use directly in your code, it is intended to be used from core code only.
 *
 * @access private
 *
 * @package   core_message
 * @since     Moodle 2.8
 * @copyright 2014 Totara Learning Solutions Ltd {@link http://www.totaralms.com/}
 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 * @author    Petr Skoda <petr.skoda@totaralms.com>
 */
class manager {
    /** @var array buffer of pending messages */
    protected static $buffer = array();

    /**
     * Do the message sending.
     *
     * NOTE: to be used from message_send() only.
     *
     * @param \stdClass $eventdata fully prepared event data for processors
     * @param \stdClass $savemessage the message saved in 'message' table
     * @param array $processorlist list of processors for target user
     * @return int $messageid the id from 'message' or 'message_read' table (false is not returned)
     */
    public static function send_message(\stdClass $eventdata, \stdClass $savemessage, array $processorlist) {
        global $CFG;
        require_once($CFG->dirroot.'/message/lib.php'); // This is most probably already included from messagelib.php file.

        if (empty($processorlist)) {
            // Trigger event for sending a message - we need to do this before marking as read!
            \core\event\message_sent::create_from_ids($eventdata->userfrom->id, $eventdata->userto->id, $savemessage->id)->trigger();

            if ($savemessage->notification or empty($CFG->messaging)) {
                // If they have deselected all processors and its a notification mark it read. The user doesn't want to be bothered.
                // The same goes if the messaging is completely disabled.
                // We cannot insert directly to the message_read table because we want to get all events in proper order!
                $messageid = message_mark_message_read($savemessage, time(), true);

            } else {
                // Just add it to the list of unread messages, there is no way it could be delivered to them,
                // but they can read it via the messaging UI later.
                $messageid = $savemessage->id;
            }

            return $messageid;
        }

        // Let the manager do the sending or buffering when db transaction in progress.
        return self::send_message_to_processors($eventdata, $savemessage, $processorlist);
    }

    /**
     * Send message to message processors.
     *
     * @param \stdClass $eventdata
     * @param \stdClass $savemessage
     * @param array $processorlist
     * @return int $messageid
     */
    protected static function send_message_to_processors(\stdClass $eventdata, \stdClass $savemessage, array $processorlist) {
        global $CFG, $DB;

        // We cannot communicate with external systems in DB transactions,
        // buffer the messages if necessary.

        if ($DB->is_transaction_started()) {
            // We need to clone all objects so that devs may not modify it from outside later.
            $eventdata = clone($eventdata);
            $eventdata->userto = clone($eventdata->userto);
            $eventdata->userfrom = clone($eventdata->userfrom);

            // Conserve some memory the same was as $USER setup does.
            unset($eventdata->userto->description);
            unset($eventdata->userfrom->description);

            self::$buffer[] = array($eventdata, $savemessage, $processorlist);
            return $savemessage->id;
        }

        $processors = get_message_processors(true);

        $failed = false;
        foreach ($processorlist as $procname) {
            if (!$processors[$procname]->object->send_message($eventdata)) {
                debugging('Error calling message processor ' . $procname);
                $failed = true;
                // Previously the $messageid = false here was overridden
                // by other processors and message_mark_message_read() below.
            }
        }

        // Trigger event for sending a message - must be done before marking as read.
        \core\event\message_sent::create_from_ids($eventdata->userfrom->id, $eventdata->userto->id, $savemessage->id)->trigger();

        if (empty($CFG->messaging)) {
            // If messaging is disabled and they previously had forum notifications handled by the popup processor
            // or any processor that puts a row in message_working then the notification will remain forever
            // unread. To prevent this mark the message read if messaging is disabled.
            $messageid = message_mark_message_read($savemessage, time());

        } else if ($failed) {
            // Something failed, better keep it as unread then.
            $messageid = $savemessage->id;

        } else if ($DB->count_records('message_working', array('unreadmessageid' => $savemessage->id)) == 0) {
            // If there is no more processors that want to process this we can move message to message_read.
            $messageid = message_mark_message_read($savemessage, time(), true);

        } else {
            // Some processor is still working on the data, let's keep it unread.
            $messageid = $savemessage->id;
        }

        return $messageid;
    }

    /**
     * Notification from DML layer.
     *
     * Note: to be used from DML layer only.
     */
    public static function database_transaction_commited() {
        if (!self::$buffer) {
            return;
        }
        self::process_buffer();
    }

    /**
     * Notification from DML layer.
     *
     * Note: to be used from DML layer only.
     */
    public static function database_transaction_rolledback() {
        self::$buffer = array();
    }

    /**
     * Sent out any buffered messages if necessary.
     */
    protected static function process_buffer() {
        // Reset the buffer first in case we get exception from processor.
        $messages = self::$buffer;
        self::$buffer = array();

        foreach ($messages as $message) {
            list($eventdata, $savemessage, $processorlist) = $message;
            self::send_message_to_processors($eventdata, $savemessage, $processorlist);
        }
    }
}
