<?php

/**
 * Timekeeper timer endpoint: timekeeperClientServices/timer.php?user=<name>&game=<process>
 *
 * Called once a minute by timekeeperLocal.php on the student's machine. The
 * reply is either the number of play minutes remaining (a number) or a
 * message explaining why play isn't allowed (any non-number: the client
 * shows it and closes the game).
 *
 * Changes from the current repo version:
 *  - ?user= and ?game= were concatenated straight into SQL with no login
 *    required (SQL injection), and ?user= was also used to build a file name
 *    for debug output (arbitrary file write). Both are now validated against
 *    a strict pattern and escaped, and the debug file is gone (that's what
 *    the *debug.dat files in the repo were)
 *  - unknown users are only auto-created if they have an e107 account (any
 *    visitor could create rows by requesting ?user=anything)
 *  - removed the leftover "reply 31 until 2026-05-13" override
 *  - counters are updated with atomic UPDATE ... SET x = x + 1 instead of
 *    writing back a value read earlier in the request
 *  - when the free minutes run out the game was killed even if the student
 *    had earned minutes: remaining free time of exactly 0 replied "0".
 *    Earned minutes now take over, and the reply is 0 (never negative)
 *    once there are none, so the client keeps closing the game
 *  - new ?peek=1: reply with the minutes remaining WITHOUT using one up.
 *    The client calls it when it first sees a game so the first minute is no
 *    longer charged twice
 *  - plain-text response header
 *  - a student with Timekeeper switched off gets 1440 (was 30, which the
 *    Java client would read as a real 30 minutes and warn about every minute)
 */
if (!defined('e107_INIT')) {
    require_once('../../../class2.php');
}
if (!e107::isInstalled('timekeeper')) {
    e107::redirect();
    exit;
}

/**
 * The Timekeeper's timer connection class.
 *
 * This class checks if a user has the right to play games and if not states why.
 * This is an adapter to the local Timekeeper application monitor.
 *
 * @author gregory
 */
class timer {

    private $user = null;
    private $game = '';
    private $invalid = false;
    private $peek = false;
    private $debug = false;
    private $sql;
    private $settings;

    function __construct() {
        $user = filter_input(INPUT_GET, 'user');
        if (is_string($user) && preg_match('/^[A-Za-z0-9_.-]{1,50}$/', $user)) {
            $this->user = $user;
        } else {
            $this->invalid = true;
        }

        $game = filter_input(INPUT_GET, 'game');
        if (is_string($game) && $game !== '') {
            if (preg_match('/^[\w.+: ()\-]{1,100}$/', $game)) {
                $this->game = $game;
            } else {
                $this->invalid = true;
            }
        }

        $this->peek = filter_input(INPUT_GET, 'peek') ? true : false;
        $this->debug = filter_input(INPUT_GET, 'dbg') ? true : false;
        $this->sql = e107::getDb();
        date_default_timezone_set('Australia/Perth');
    }

    private function q($value) {
        return $this->sql->escape($value);
    }

    private function debug($text) {
        if ($this->debug) {
            echo "Entered " . $text . "<br/>";
        }
    }

    /**
     * Main entry point.
     */
    public function main() {
        if (!headers_sent()) {
            header('Content-Type: text/plain; charset=utf-8');
        }

        if ($this->invalid || $this->user === null) {
            echo 'Invalid request.';
            return;
        }

        $this->debug(__FUNCTION__);

        // load the settings and init values from the database
        $this->getSettings();

        // Check if user is allowed to play games, if not reply and exit now
        if (!$this->isTimekeeperOperable()) {
            return;
        }

        if (!$this->checkPlayTime()) {
            return;
        }

        // If a game is being played then update the statistics database
        if ($this->charging()) {
            $this->playTimeStatistics();
        }
    }

    /**
     * Is this request supposed to use up a minute of play time?
     */
    private function charging() {
        return $this->game !== '' && !$this->peek;
    }

    private function getSettings() {
        $this->debug(__FUNCTION__);
        $this->settings = $this->sql->retrieve('timekeeper', '*', 'username="' . $this->q($this->user) . '"');
    }

    /**
     * Should the timekeeper be operable for this user right now?
     *
     * @return boolean
     */
    private function isTimekeeperOperable() {
        $this->debug(__FUNCTION__);

        if (is_array($this->settings) && isset($this->settings['enabled'])) {
            // timekeeper switched off for this user: no limit. The reply is a large number
            // (the Java client treats the number literally and warns at exactly 30 minutes).
            if (!$this->settings['enabled']) {
                echo 1440;
                return false;
            }
        } else {
            // Only people with an e107 account get a settings row.
            if ($this->sql->count('user', '(*)', 'user_loginname="' . $this->q($this->user) . '"') < 1) {
                echo 'Unknown user.';
                return false;
            }

            $query = ['username' => $this->user, 'enabled' => 1, 'freeMins' => 10, 'enableTime' => 10.00, 'disableTime' => 22.00, 'minQuestionCount' => 100, 'usedMinutes' => 0, 'lastDate' => 0, 'maxDailyPlayTime' => 1440];
            $this->sql->insert('timekeeper', $query);

            echo $this->user . ' added to timekeepers database.';
            // exit here as the class variable would not be setup for the user.
            exit;
        }

        // Check if user is within allowed play times
        if (!$this->playTimeWindow()) {
            echo 'You are not within allowed play times.';
            return false;
        }

        // Check has the user answered enough questions today.
        if (!$this->minimumQuestionsMet()) {
            if ($this->settings['freeMins'] >= 1) {
                return true;
            }
            echo 'You have not answered enough questions to play.';
            return false;
        }

        return true;
    }

    /**
     * Is the time of day within the play window?
     *
     * @return boolean
     */
    private function playTimeWindow() {
        $this->debug(__FUNCTION__);

        if (isset($this->settings['enableTime']) && isset($this->settings['disableTime'])) {
            // Disable time is less than enable time consider it the next day
            if ((double) date('H.i') <= (double) $this->settings['disableTime'] && (double) $this->settings['disableTime'] <= (double) $this->settings['enableTime']) {
                return true;
            }
            // Check if the enable time has been met, return false if not
            if ((double) date('H.i') <= (double) $this->settings['enableTime']) {
                return false;
            }
            // Check if the disable time has been exceeded (not when disable < enable)
            if ((double) date('H.i') >= (double) $this->settings['disableTime'] && !((double) $this->settings['disableTime'] <= (double) $this->settings['enableTime'])) {
                return false;
            }
        }

        return true;
    }

    /**
     * Has the user answered at least minQuestionCount questions today?
     *
     * @return boolean
     */
    private function minimumQuestionsMet() {
        $this->debug(__FUNCTION__);

        if (isset($this->settings['minQuestionCount'])) {
            $answered = (int) $this->sql->retrieve('tkReport', 'COUNT(id)', 'username="' . $this->q($this->user) . '" '
                    . 'AND answereddatestamp >= ' . (int) mktime(0, 0, 0, date('n'), date('j')) . ' '
                    . 'AND answereddatestamp <= ' . (int) mktime(23, 59, 59, date('n'), date('j')));

            if ($answered < (int) $this->settings['minQuestionCount']) {
                return false;
            }
        }

        return true;
    }

    /**
     * Work out the minutes remaining, and (unless peeking) use one up.
     *
     * Free minutes (freeMins minus today's usedMinutes) are used first; once
     * they are gone the minutes earned from answering questions are used.
     *
     * @return boolean False when the user may not play now (reply already sent).
     */
    private function checkPlayTime() {
        $this->debug(__FUNCTION__);

        $s = $this->settings;
        if (!isset($s['freeMins']) || !isset($s['usedMinutes']) || !isset($s['lastDate']) || !isset($s['maxDailyPlayTime'])) {
            return true;
        }

        // New day: today's counter starts again from zero.
        $isToday = ((int) $s['lastDate'] > 0) && date('Ymd', (int) $s['lastDate']) === date('Ymd');
        $used = $isToday ? (int) $s['usedMinutes'] : 0;

        if ($used >= (int) $s['maxDailyPlayTime']) {
            echo 'Max play time exceeded.';
            return false;
        }

        $free = (int) $s['freeMins'] - $used;

        if ($free > 0) {
            // Free play time left: use it before earned minutes.
            $this->useMinute($isToday, false);
            echo $free;
            return true;
        }

        // Free time is gone, so the questions-answered rule applies.
        if (!$this->minimumQuestionsMet()) {
            echo 'You have not answered enough questions to play.';
            return false;
        }

        $earned = (int) $this->sql->retrieve('timekeeperScore', 'timekeeper_minutes', 'timekeeper_username="' . $this->q($this->user) . '"');
        if ($earned <= 0) {
            echo 0;
            return false;
        }

        $this->useMinute($isToday, true);
        echo $earned;
        return true;
    }

    /**
     * Use up one minute of play time (no-op when peeking or no game given).
     *
     * @param boolean $isToday   Whether the stored counter belongs to today.
     * @param boolean $fromScore Also take the minute off the earned minutes.
     */
    private function useMinute($isToday, $fromScore) {
        if (!$this->charging()) {
            return;
        }

        $u = $this->q($this->user);

        if ($isToday) {
            $this->sql->gen("UPDATE `" . MPREFIX . "timekeeper` SET `usedMinutes` = `usedMinutes` + 1 WHERE `username` = '{$u}'");
        } else {
            $this->sql->gen("UPDATE `" . MPREFIX . "timekeeper` SET `lastDate` = " . (int) time() . ", `usedMinutes` = 1 WHERE `username` = '{$u}'");
        }

        if ($fromScore) {
            $this->sql->gen("UPDATE `" . MPREFIX . "timekeeperScore` SET `timekeeper_minutes` = `timekeeper_minutes` - 1 WHERE `timekeeper_username` = '{$u}' AND `timekeeper_minutes` > 0");
        }
    }

    /**
     * Update the statistics for games played and for how long.
     */
    private function playTimeStatistics() {
        $this->debug(__FUNCTION__);

        $where = 'userName="' . $this->q($this->user) . '" AND gameName="' . $this->q($this->game) . '" AND playDate="' . (int) mktime(12, 0, 0, date('n'), date('j')) . '"';
        $playMinutes = (int) $this->sql->retrieve('timekeeperStatistics', 'minutesPlayed', $where);

        if ($playMinutes === 0) {
            $this->sql->insert('timekeeperStatistics', ['uniqueId' => 0, 'minutesPlayed' => 1, 'userName' => $this->user, 'gameName' => $this->game, 'playDate' => mktime(12, 0, 0, date('n'), date('j'))]);
        } else {
            $this->sql->update('timekeeperStatistics', ['minutesPlayed' => ($playMinutes + 1), 'WHERE' => $where]);
        }
    }

}

//run the timer class as standalone
$timerClass = new timer();
$timerClass->main();