<?php

use dokuwiki\Extension\Plugin;
use dokuwiki\File\PageResolver;

/**
 * DokuWiki Plugin lms (Helper Component)
 *
 * @license GPL 2 http://www.gnu.org/licenses/gpl-2.0.html
 * @author  Andreas Gohr <dokuwiki@cosmocode.de>
 */
class helper_plugin_lms extends Plugin
{
    /**
     * Return all lessons and info about the user's current completion status
     *
     * @param string|null $user Username, null for no user data
     * @return array A list of lesson infos
     */
    public function getLessons($user = null)
    {
        $cp = $this->getControlPage();
        if (!$cp) return [];

        $lessons = array_fill_keys($this->parseControlPage($cp), 0);
        if ($user !== null) {
            $lessons = array_merge($lessons, $this->getUserLessons($user));
        }

        return $lessons;
    }

    /**
     * Find the nearest controlpage
     *
     * @return false|string
     */
    public function getControlPage()
    {
        global $ID;
        global $INFO;

        $cp = $this->getConf('controlpage');
        $oldid = $ID;
        $ID = $INFO['id'];
        $cp = page_findnearest($cp, false);
        $ID = $oldid;
        return $cp;
    }

    /**
     * @param string $id Page ID of the lesson
     * @param bool $seen Mark as seen or unseen
     * @param string $user Username
     * @return bool
     */
    public function markLesson($id, $user, $seen = true)
    {
        if ($user === null) return false;

        $file = $this->getUserFile($user);
        $line = time() . "\t" . $id . "\t" . ($seen ? 1 : 0) . "\n";
        return io_saveFile($file, $line, true);
    }

    /**
     * Get the list of completed lessons for a user
     *
     * This skips all lessons that used to be seen but have been marked unseen later
     *
     * @param string $user
     * @return array
     */
    public function getUserLessons($user)
    {
        $file = $this->getUserFile($user);
        if (!file_exists($file)) return [];

        $lessons = [];
        $lines = file($file);
        foreach ($lines as $line) {
            [$time, $id, $seen] = explode("\t", trim($line));

            // we use simple log files
            if ($seen) {
                $lessons[$id] = $time;
            } elseif (isset($lessons[$id])) {
                // an already seen lesson might have been marked unseen later
                unset($lessons[$id]);
            }
        }

        return $lessons;
    }

    /**
     * Get Seen-Info of a single lesson
     *
     * @param string $id Page ID of the lesson
     * @return int|false Either the lesson info or fals if given ID is not a lesson
     */
    public function getLesson($id, $user)
    {
        $all = $this->getLessons($user);
        return $all[$id] ?? false;
    }

    /**
     * Get the next lesson relative to the given one
     *
     * @param string $id current lesson
     * @param null|string $user When user is given, next unseen lesson is returned
     * @return string
     */
    public function getNextLesson($id, $user = null)
    {
        $all = $this->getLessons($user);

        if (!isset($all[$id])) return false; // current page is not a lesson

        $keys = array_keys($all);
        $self = array_search($id, $keys);
        $len = count($keys);

        for ($i = $self + 1; $i < $len; $i++) {
            if ($user !== null && $all[$keys[$i]] !== 0) {
                continue; // next element has already been seen by user
            }
            return $keys[$i];
        }

        // no more lessons
        return false;
    }

    /**
     * Get the previous lesson relative to the given one
     *
     * @param string $id current lesson
     * @param null|string $user When user is given, previous unseen lesson is returned
     * @return string
     */
    public function getPrevLesson($id, $user = null)
    {
        $all = $this->getLessons($user);

        if (!isset($all[$id])) return false; // current page is not a lesson

        $keys = array_keys($all);
        $self = array_search($id, $keys);

        for ($i = $self - 1; $i >= 0; $i--) {
            if ($user !== null && $all[$keys[$i]] !== 0) {
                continue; // next element has already been seen by user
            }
            return $keys[$i];
        }

        // no more lessons
        return false;
    }


    /**
     * Get the filename used for storing lesson completions
     *
     * @param string $user username
     */
    protected function getUserFile($user)
    {
        global $conf;

        // we're not using cache files but our own meta directory
        $user = utf8_encodeFN($user); // make sure the user is clean for directories
        return $conf['metadir'] . '_lms/' . $user . '.lms';
    }

    public function getKnownUsers()
    {
        global $conf;

        $lmsData = $conf['metadir'] . '_lms/';

        $s = scandir($lmsData);

        $users = array_map(function ($file) {
            if (!in_array($file, ['.', '..'])) {
                return str_replace('.lms', '', $file);
            }
            return null;
        }, $s);

        return array_filter($users);
    }

    /**
     * Get a list of links from the given control page
     *
     * @param string $cp The control page
     * @return array
     */
    protected function parseControlPage($cp)
    {
        $cpns = getNS($cp);
        $pages = [];

        $instructions = p_cached_instructions(wikiFN($cp), false, $cp);
        if ($instructions === null) return [];


        $resolver = new PageResolver($cp);

        foreach ($instructions as $instruction) {
            if ($instruction[0] !== 'internallink') continue;
            $link = $instruction[1][0];
            $link = $resolver->resolveId($link);

            // Only pages below the control page's namespace are considered lessons
            $ns = getNS($link);
            $check = $cpns ? ":$cpns" : '';
            if (!preg_match("/^$check(:|$)/", ":$ns")) {
                continue;
            }

            $pages[] = $link;
        }

        $pages = array_values(array_unique($pages));
        return $pages;
    }
}