lib.php

<?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/>.


/**
 * Functions used by gradebook plugins and reports.
 *
 * @package   moodlecore
 * @copyright 2009 Petr Skoda and Nicolas Connault
 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

require_once $CFG->libdir.'/gradelib.php';

/**
 * This class iterates over all users that are graded in a course.
 * Returns detailed info about users and their grades.
 *
 * @author Petr Skoda <skodak@moodle.org>
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class graded_users_iterator {
    public $course;
    public $grade_items;
    public $groupid;
    public $users_rs;
    public $grades_rs;
    public $gradestack;
    public $sortfield1;
    public $sortorder1;
    public $sortfield2;
    public $sortorder2;

    /**
     * Constructor
     *
     * @param object $course A course object
     * @param array  $grade_items array of grade items, if not specified only user info returned
     * @param int    $groupid iterate only group users if present
     * @param string $sortfield1 The first field of the users table by which the array of users will be sorted
     * @param string $sortorder1 The order in which the first sorting field will be sorted (ASC or DESC)
     * @param string $sortfield2 The second field of the users table by which the array of users will be sorted
     * @param string $sortorder2 The order in which the second sorting field will be sorted (ASC or DESC)
     */
    public function graded_users_iterator($course, $grade_items=null, $groupid=0,
                                          $sortfield1='lastname', $sortorder1='ASC',
                                          $sortfield2='firstname', $sortorder2='ASC') {
        $this->course      = $course;
        $this->grade_items = $grade_items;
        $this->groupid     = $groupid;
        $this->sortfield1  = $sortfield1;
        $this->sortorder1  = $sortorder1;
        $this->sortfield2  = $sortfield2;
        $this->sortorder2  = $sortorder2;

        $this->gradestack  = array();
    }

    /**
     * Initialise the iterator
     * @return boolean success
     */
    public function init() {
        global $CFG, $DB;

        $this->close();

        grade_regrade_final_grades($this->course->id);
        $course_item = grade_item::fetch_course_item($this->course->id);
        if ($course_item->needsupdate) {
            // can not calculate all final grades - sorry
            return false;
        }

        list($gradebookroles_sql, $params) =
            $DB->get_in_or_equal(explode(',', $CFG->gradebookroles), SQL_PARAMS_NAMED, 'grbr0');

        $relatedcontexts = get_related_contexts_string(get_context_instance(CONTEXT_COURSE, $this->course->id));

        if ($this->groupid) {
            $groupsql = "INNER JOIN {groups_members} gm ON gm.userid = u.id";
            $groupwheresql = "AND gm.groupid = :groupid";
            // $params contents: gradebookroles
            $params['groupid'] = $this->groupid;
        } else {
            $groupsql = "";
            $groupwheresql = "";
        }

        if (empty($this->sortfield1)) {
            // we must do some sorting even if not specified
            $ofields = ", u.id AS usrt";
            $order   = "usrt ASC";

        } else {
            $ofields = ", u.$this->sortfield1 AS usrt1";
            $order   = "usrt1 $this->sortorder1";
            if (!empty($this->sortfield2)) {
                $ofields .= ", u.$this->sortfield2 AS usrt2";
                $order   .= ", usrt2 $this->sortorder2";
            }
            if ($this->sortfield1 != 'id' and $this->sortfield2 != 'id') {
                // user order MUST be the same in both queries,
                // must include the only unique user->id if not already present
                $ofields .= ", u.id AS usrt";
                $order   .= ", usrt ASC";
            }
        }

        // $params contents: gradebookroles and groupid (for $groupwheresql)
        $users_sql = "SELECT u.* $ofields
                        FROM {user} u
                             INNER JOIN {role_assignments} ra ON u.id = ra.userid
                             $groupsql
                       WHERE ra.roleid $gradebookroles_sql
                             AND ra.contextid $relatedcontexts
                             $groupwheresql
                    ORDER BY $order";

        $this->users_rs = $DB->get_recordset_sql($users_sql, $params);

        if (!empty($this->grade_items)) {
            $itemids = array_keys($this->grade_items);
            list($itemidsql, $grades_params) = $DB->get_in_or_equal($itemids, SQL_PARAMS_NAMED, 'items0');
            $params = array_merge($params, $grades_params);

            // $params contents: gradebookroles, groupid (for $groupwheresql) and itemids
            $grades_sql = "SELECT g.* $ofields
                             FROM {grade_grades} g
                                  INNER JOIN {user} u ON g.userid = u.id
                                  INNER JOIN {role_assignments} ra ON u.id = ra.userid
                                  $groupsql
                            WHERE ra.roleid $gradebookroles_sql
                                  AND ra.contextid $relatedcontexts
                                  $groupwheresql
                                  AND g.itemid $itemidsql
                         ORDER BY $order, g.itemid ASC";
            $this->grades_rs = $DB->get_recordset_sql($grades_sql, $params);
        } else {
            $this->grades_rs = false;
        }

        return true;
    }

    /**
     * Returns information about the next user
     * @return mixed array of user info, all grades and feedback or null when no more users found
     */
    function next_user() {
        if (!$this->users_rs) {
            return false; // no users present
        }

        if (!$this->users_rs->valid()) {
            if ($current = $this->_pop()) {
                // this is not good - user or grades updated between the two reads above :-(
            }

            return false; // no more users
        } else {
            $user = $this->users_rs->current();
            $this->users_rs->next();
        }

        // find grades of this user
        $grade_records = array();
        while (true) {
            if (!$current = $this->_pop()) {
                break; // no more grades
            }

            if (empty($current->userid)) {
                break;
            }

            if ($current->userid != $user->id) {
                // grade of the next user, we have all for this user
                $this->_push($current);
                break;
            }

            $grade_records[$current->itemid] = $current;
        }

        $grades = array();
        $feedbacks = array();

        if (!empty($this->grade_items)) {
            foreach ($this->grade_items as $grade_item) {
                if (array_key_exists($grade_item->id, $grade_records)) {
                    $feedbacks[$grade_item->id]->feedback       = $grade_records[$grade_item->id]->feedback;
                    $feedbacks[$grade_item->id]->feedbackformat = $grade_records[$grade_item->id]->feedbackformat;
                    unset($grade_records[$grade_item->id]->feedback);
                    unset($grade_records[$grade_item->id]->feedbackformat);
                    $grades[$grade_item->id] = new grade_grade($grade_records[$grade_item->id], false);
                } else {
                    $feedbacks[$grade_item->id]->feedback       = '';
                    $feedbacks[$grade_item->id]->feedbackformat = FORMAT_MOODLE;
                    $grades[$grade_item->id] =
                        new grade_grade(array('userid'=>$user->id, 'itemid'=>$grade_item->id), false);
                }
            }
        }

        $result = new object();
        $result->user      = $user;
        $result->grades    = $grades;
        $result->feedbacks = $feedbacks;

        return $result;
    }

    /**
     * Close the iterator, do not forget to call this function.
     * @return void
     */
    function close() {
        if ($this->users_rs) {
            $this->users_rs->close();
            $this->users_rs = null;
        }
        if ($this->grades_rs) {
            $this->grades_rs->close();
            $this->grades_rs = null;
        }
        $this->gradestack = array();
    }


    /**
     * _push
     *
     * @param grade_grade $grade Grade object
     *
     * @return void
     */
    function _push($grade) {
        array_push($this->gradestack, $grade);
    }


    /**
     * _pop
     *
     * @return void
     */
    function _pop() {
        global $DB;
        if (empty($this->gradestack)) {
            if (!$this->grades_rs) {
                return null; // no grades present
            }

            if ($this->grades_rs->next()) {
                return null; // no more grades
            }

            return $this->grades_rs->current();
        } else {
            return array_pop($this->gradestack);
        }
    }
}

/**
 * Print a selection popup form of the graded users in a course.
 *
 * @param int    $course id of the course
 * @param string $actionpage The page receiving the data from the popoup form
 * @param int    $userid   id of the currently selected user (or 'all' if they are all selected)
 * @param int    $groupid id of requested group, 0 means all
 * @param int    $includeall bool include all option
 * @param bool   $return If true, will return the HTML, otherwise, will print directly
 * @return null
 */
function print_graded_users_selector($course, $actionpage, $userid=0, $groupid=0, $includeall=true, $return=false) {
    global $CFG, $USER;

    if (is_null($userid)) {
        $userid = $USER->id;
    }

    $context = get_context_instance(CONTEXT_COURSE, $course->id);

    $menu = array(); // Will be a list of userid => user name

    $gui = new graded_users_iterator($course, null, $groupid);
    $gui->init();


    $label = get_string('selectauser', 'grades');
    if ($includeall) {
        $menu[0] = get_string('allusers', 'grades');
        $label = get_string('selectalloroneuser', 'grades');
    }

    $nextuser = $gui->next_user();

    while ($userdata = $gui->next_user()) {
        $user = $userdata->user;
        $menu[$user->id] = fullname($user);
    }

    $gui->close();

    if ($includeall) {
        $menu[0] .= " (" . (count($menu) - 1) . ")";
    }

    return popup_form($CFG->wwwroot.'/grade/' . $actionpage . '&amp;userid=',
                      $menu, 'choosegradeduser', $userid, null, '', '',
                      $return, 'self', $label);
}

/**
 * Print grading plugin selection popup form.
 *
 * @param array   $plugin_info An array of plugins containing information for the selector
 * @param boolean $return return as string
 *
 * @return nothing or string if $return true
 */
function print_grade_plugin_selector($plugin_info, $return=false) {
    global $CFG;

    $menu = array();
    $count = 0;
    $active = '';

    foreach ($plugin_info as $plugin_type => $plugins) {
        if ($plugin_type == 'strings') {
            continue;
        }

        $first_plugin = reset($plugins);

        $menu[$first_plugin->link.'&amp;'] = '--'.$plugin_info['strings'][$plugin_type];

        if (empty($plugins->id)) {
            foreach ($plugins as $plugin) {
                $menu[$plugin->link] = $plugin->string;
                $count++;
            }
        }
    }

    // finally print/return the popup form
    if ($count > 1) {
        $select = popup_form('', $menu, 'choosepluginreport', '',
                             get_string('chooseaction', 'grades'), '', '', true, 'self');
        if ($return) {
            return $select;
        } else {
            echo $select;
        }
    } else {
        // only one option - no plugin selector needed
        return '';
    }
}

/**
 * Print grading plugin selection tab-based navigation.
 *
 * @param string  $active_type type of plugin on current page - import, export, report or edit
 * @param string  $active_plugin active plugin type - grader, user, cvs, ...
 * @param array   $plugin_info Array of plugins
 * @param boolean $return return as string
 *
 * @return nothing or string if $return true
 */
function grade_print_tabs($active_type, $active_plugin, $plugin_info, $return=false) {
    global $CFG, $COURSE;
    
    if (!isset($currenttab)) {
        $currenttab = '';
    }

    $tabs = array();
    $top_row  = array();
    $bottom_row = array();
    $inactive = array($active_plugin);
    $activated = array();

    $count = 0;
    $active = '';

    foreach ($plugin_info as $plugin_type => $plugins) {
        if ($plugin_type == 'strings') {
            continue;
        }

        // If $plugins is actually the definition of a child-less parent link:
        if (!empty($plugins->id)) {
            $string = $plugins->string;
            if (!empty($plugin_info[$active_type]->parent)) {
                $string = $plugin_info[$active_type]->parent->string;
            }

            $top_row[] = new tabobject($plugin_type, $plugins->link, $string);
            continue;
        }

        $first_plugin = reset($plugins);
        $url = $first_plugin->link;

        if ($plugin_type == 'report') {
            $url = $CFG->wwwroot.'/grade/report/index.php?id='.$COURSE->id;
        }

        $top_row[] = new tabobject($plugin_type, $url, $plugin_info['strings'][$plugin_type]);

        if ($active_type == $plugin_type) {
            foreach ($plugins as $plugin) {
                $bottom_row[] = new tabobject($plugin->id, $plugin->link, $plugin->string);
                if ($plugin->id == $active_plugin) {
                    $inactive = array($plugin->id);
                }
            }
        }
    }

    $tabs[] = $top_row;
    $tabs[] = $bottom_row;

    if ($return) {
        return print_tabs($tabs, $active_type, $inactive, $activated, true);
    } else {
        print_tabs($tabs, $active_type, $inactive, $activated);
    }
}

/**
 * grade_get_plugin_info
 *
 * @param int    $courseid The course id
 * @param string $active_type type of plugin on current page - import, export, report or edit
 * @param string $active_plugin active plugin type - grader, user, cvs, ...
 *
 * @return array
 */
function grade_get_plugin_info($courseid, $active_type, $active_plugin) {
    global $CFG;

    $context = get_context_instance(CONTEXT_COURSE, $courseid);

    $plugin_info = array();
    $count = 0;
    $active = '';
    $url_prefix = $CFG->wwwroot . '/grade/';

    // Language strings
    $plugin_info['strings'] = array(
        'report' => get_string('view'),
        'edittree' => get_string('edittree', 'grades'),
        'scale' => get_string('scales'),
        'outcome' => get_string('outcomes', 'grades'),
        'letter' => get_string('letters', 'grades'),
        'export' => get_string('export', 'grades'),
        'import' => get_string('import'),
        'preferences' => get_string('mypreferences', 'grades'),
        'settings' => get_string('settings'));

    // Settings tab first
    if (has_capability('moodle/course:update', $context)) {
        $url = $url_prefix.'edit/settings/index.php?id='.$courseid;

        if ($active_type == 'settings' and $active_plugin == 'course') {
            $active = $url;
        }

        $plugin_info['settings'] = array();
        $plugin_info['settings']['course'] =
                new grade_plugin_info('coursesettings', $url, get_string('course'));
        $count++;
    }


    // report plugins with its special structure

    // Get all installed reports
    if ($reports = get_plugin_list('gradereport')) {

        // Remove ones we can't see
        foreach ($reports as $plugin => $unused) {
            if (!has_capability('gradereport/'.$plugin.':view', $context)) {
                unset($reports[$key]);
            }
        }
    }

    $reportnames = array();

    if (!empty($reports)) {
        foreach ($reports as $plugin => $plugindir) {
            $pluginstr = get_string('modulename', 'gradereport_'.$plugin);
            $url = $url_prefix.'report/'.$plugin.'/index.php?id='.$courseid;
            if ($active_type == 'report' and $active_plugin == $plugin ) {
                $active = $url;
            }
            $reportnames[$plugin] = new grade_plugin_info($plugin, $url, $pluginstr);

            // Add link to preferences tab if such a page exists
            if (file_exists($plugindir.'/preferences.php')) {
                $pref_url = $url_prefix.'report/'.$plugin.'/preferences.php?id='.$courseid;
                $plugin_info['preferences'][$plugin] = new grade_plugin_info($plugin, $pref_url, $pluginstr);
            }

            $count++;
        }
        asort($reportnames);
    }
    if (!empty($reportnames)) {
        $plugin_info['report']=$reportnames;
    }

    // editing scripts - not real plugins
    if (has_capability('moodle/grade:manage', $context)
      or has_capability('moodle/grade:manageletters', $context)
      or has_capability('moodle/course:managescales', $context)
      or has_capability('moodle/course:update', $context)) {

        if (has_capability('moodle/grade:manage', $context)) {
            $url = $url_prefix.'edit/tree/index.php?sesskey='.sesskey().
                    '&amp;showadvanced=0&amp;id='.$courseid;
            $url_adv = $url_prefix.'edit/tree/index.php?sesskey='.sesskey().
                    '&amp;showadvanced=1&amp;id='.$courseid;

            if ($active_type == 'edittree' and $active_plugin == 'simpleview') {
                $active = $url;
            } else if ($active_type == 'edittree' and $active_plugin == 'fullview') {
                $active = $url_adv;
            }

            $plugin_info['edittree'] = array();
            $plugin_info['edittree']['simpleview'] =
                    new grade_plugin_info('simpleview', $url, get_string('simpleview', 'grades'));
            $plugin_info['edittree']['fullview'] =
                    new grade_plugin_info('fullview', $url_adv, get_string('fullview', 'grades'));
            $count++;
        }

        if (has_capability('moodle/course:managescales', $context)) {
            $url = $url_prefix.'edit/scale/index.php?id='.$courseid;

            if ($active_type == 'scale' and is_null($active_plugin)) {
                $active = $url;
            }

            $plugin_info['scale'] = array();

            if ($active_type == 'scale' and $active_plugin == 'edit') {
                $edit_url = $url_prefix.'edit/scale/edit.php?courseid='.$courseid.
                        '&amp;id='.optional_param('id', 0, PARAM_INT);
                $active = $edit_url;
                $parent = new grade_plugin_info('scale', $url, get_string('scales'));
                $plugin_info['scale']['view'] =
                        new grade_plugin_info('edit', $edit_url, get_string('edit'), $parent);
            } else {
                $plugin_info['scale']['view'] =
                        new grade_plugin_info('scale', $url, get_string('view'));
            }

            $count++;
        }

        if (!empty($CFG->enableoutcomes) && (has_capability('moodle/grade:manage', $context) or
                                             has_capability('moodle/course:update', $context))) {

            $url_course = $url_prefix.'edit/outcome/course.php?id='.$courseid;
            $url_edit = $url_prefix.'edit/outcome/index.php?id='.$courseid;

            $plugin_info['outcome'] = array();

            if (has_capability('moodle/course:update', $context)) {  // Default to course assignment
                $plugin_info['outcome']['course'] =
                        new grade_plugin_info('course', $url_course, get_string('outcomescourse', 'grades'));
                $plugin_info['outcome']['edit'] =
                        new grade_plugin_info('edit', $url_edit, get_string('editoutcomes', 'grades'));
            } else {
                $plugin_info['outcome'] =
                        new grade_plugin_info('edit', $url_course, get_string('outcomescourse', 'grades'));
            }

            if ($active_type == 'outcome' and is_null($active_plugin)) {
                $active = $url_edit;
            } else if ($active_type == 'outcome' and $active_plugin == 'course' ) {
                $active = $url_course;
            } else if ($active_type == 'outcome' and $active_plugin == 'edit' ) {
                $active = $url_edit;
            } else if ($active_type == 'outcome' and $active_plugin == 'import') {
                $plugin_info['outcome']['import'] =
                        new grade_plugin_info('import', null, get_string('importoutcomes', 'grades'));
            }

            $count++;
        }

        if (has_capability('moodle/grade:manage', $context) or
                    has_capability('moodle/grade:manageletters', $context)) {
            $course_context = get_context_instance(CONTEXT_COURSE, $courseid);
            $url = $url_prefix.'edit/letter/index.php?id='.$courseid;
            $url_edit = $url_prefix.'edit/letter/edit.php?id='.$course_context->id;

            if ($active_type == 'letter' and $active_plugin == 'view' ) {
                $active = $url;
            } else if ($active_type == 'letter' and $active_plugin == 'edit' ) {
                $active = $url_edit;
            }

            $plugin_info['letter'] = array();
            $plugin_info['letter']['view'] = new grade_plugin_info('view', $url, get_string('view'));
            $plugin_info['letter']['edit'] = new grade_plugin_info('edit', $url_edit, get_string('edit'));
            $count++;
        }
    }

    // standard import plugins
    if ($imports = get_plugin_list('gradeimport')) { // Get all installed import plugins
        foreach ($imports as $plugin => $plugindir) { // Remove ones we can't see
            if (!has_capability('gradeimport/'.$plugin.':view', $context)) {
                unset($imports[$key]);
            }
        }
    }
    $importnames = array();
    if (!empty($imports)) {
        foreach ($imports as $plugin) {
            $pluginstr = get_string('modulename', 'gradeimport_'.$plugin);
            $url = $url_prefix.'import/'.$plugin.'/index.php?id='.$courseid;
            if ($active_type == 'import' and $active_plugin == $plugin ) {
                $active = $url;
            }
            $importnames[$plugin] = new grade_plugin_info($plugin, $url, $pluginstr);
            $count++;
        }
        asort($importnames);
    }
    if (!empty($importnames)) {
        $plugin_info['import']=$importnames;
    }

    // standard export plugins
    if ($exports = get_plugin_list('gradeexport')) { // Get all installed export plugins
        foreach ($exports as $key => $plugin) { // Remove ones we can't see
            if (!has_capability('gradeexport/'.$plugin.':view', $context)) {
                unset($exports[$key]);
            }
        }
    }
    $exportnames = array();
    if (!empty($exports)) {
        foreach ($exports as $plugin => $plugindir) {
            $pluginstr = get_string('modulename', 'gradeexport_'.$plugin);
            $url = $url_prefix.'export/'.$plugin.'/index.php?id='.$courseid;
            if ($active_type == 'export' and $active_plugin == $plugin ) {
                $active = $url;
            }
            $exportnames[$plugin] = new grade_plugin_info($plugin, $url, $pluginstr);
            $count++;
        }
        asort($exportnames);
    }

    if (!empty($exportnames)) {
        $plugin_info['export']=$exportnames;
    }

    // Key managers
    if ($CFG->gradepublishing) {
        $keymanager_url = $url_prefix.'export/keymanager.php?id='.$courseid;
        $plugin_info['export']['keymanager'] =
                new grade_plugin_info('keymanager', $keymanager_url, get_string('keymanager', 'grades'));
        if ($active_type == 'export' and $active_plugin == 'keymanager' ) {
            $active = $keymanager_url;
        }
        $count++;

        $keymanager_url = $url_prefix.'import/keymanager.php?id='.$courseid;
        $plugin_info['import']['keymanager'] =
                new grade_plugin_info('keymanager', $keymanager_url, get_string('keymanager', 'grades'));
        if ($active_type == 'import' and $active_plugin == 'keymanager' ) {
            $active = $keymanager_url;
        }
        $count++;
    }


    foreach ($plugin_info as $plugin_type => $plugins) {
        if (!empty($plugins->id) && $active_plugin == $plugins->id) {
            $plugin_info['strings']['active_plugin_str'] = $plugins->string;
            break;
        }
        foreach ($plugins as $plugin) {
            if (is_a($plugin, 'grade_plugin_info')) {
                if ($active_plugin == $plugin->id) {
                    $plugin_info['strings']['active_plugin_str'] = $plugin->string;
                }
            }
        }
    }

    // Put settings last
    if (!empty($plugin_info['settings'])) {
        $settings = $plugin_info['settings'];
        unset($plugin_info['settings']);
        $plugin_info['settings'] = $settings;
    }

    // Put preferences last
    if (!empty($plugin_info['preferences'])) {
        $prefs = $plugin_info['preferences'];
        unset($plugin_info['preferences']);
        $plugin_info['preferences'] = $prefs;
    }

    // Check import and export caps
    if (!has_capability('moodle/grade:export', $context)) {
        unset($plugin_info['export']);
    }
    if (!has_capability('moodle/grade:import', $context)) {
        unset($plugin_info['import']);
    }
    return $plugin_info;
}

/**
 * A simple class containing info about grade plugins.
 * Can be subclassed for special rules
 *
 * @package moodlecore
 * @copyright 2009 Nicolas Connault
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class grade_plugin_info {
    /**
     * A unique id for this plugin
     *
     * @var mixed
     */
    public $id;
    /**
     * A URL to access this plugin
     *
     * @var mixed
     */
    public $link;
    /**
     * The name of this plugin
     *
     * @var mixed
     */
    public $string;
    /**
     * Another grade_plugin_info object, parent of the current one
     *
     * @var mixed
     */
    public $parent;

    /**
     * Constructor
     *
     * @param int $id A unique id for this plugin
     * @param string $link A URL to access this plugin
     * @param string $string The name of this plugin
     * @param object $parent Another grade_plugin_info object, parent of the current one
     *
     * @return void
     */
    public function __construct($id, $link, $string, $parent=null) {
        $this->id = $id;
        $this->link = $link;
        $this->string = $string;
        $this->parent = $parent;
    }
}

/**
 * Prints the page headers, breadcrumb trail, page heading, (optional) dropdown navigation menu and
 * (optional) navigation tabs for any gradebook page. All gradebook pages MUST use these functions
 * in favour of the usual print_header(), print_header_simple(), print_heading() etc.
 * !IMPORTANT! Use of tabs.php file in gradebook pages is forbidden unless tabs are switched off at
 * the site level for the gradebook ($CFG->grade_navmethod = GRADE_NAVMETHOD_DROPDOWN).
 *
 * @param int     $courseid Course id
 * @param string  $active_type The type of the current page (report, settings,
 *                             import, export, scales, outcomes, letters)
 * @param string  $active_plugin The plugin of the current page (grader, fullview etc...)
 * @param string  $heading The heading of the page. Tries to guess if none is given
 * @param boolean $return Whether to return (true) or echo (false) the HTML generated by this function
 * @param string  $bodytags Additional attributes that will be added to the <body> tag
 * @param string  $buttons Additional buttons to display on the page
 * @param array   $extracss An array of additional stylesheets to load (relative paths)
 *
 * @return string HTML code or nothing if $return == false
 */
function print_grade_page_head($courseid, $active_type, $active_plugin=null,
                               $heading = false, $return=false,
                               $buttons=false, $extracss=array()) {
    global $CFG, $COURSE;
    $strgrades = get_string('grades');
    $plugin_info = grade_get_plugin_info($courseid, $active_type, $active_plugin);
    
    // Determine the string of the active plugin
    $stractive_plugin = ($active_plugin) ? $plugin_info['strings']['active_plugin_str'] : $heading;
    $stractive_type = $plugin_info['strings'][$active_type];

    $navlinks = array();
    $first_link = '';

    if ($active_type == 'settings' && $active_plugin != 'coursesettings') {
        $first_link = $plugin_info['report'][$active_plugin]->link;
    } else if ($active_type != 'report') {
        $first_link = $CFG->wwwroot.'/grade/index.php?id='.$COURSE->id;
    }

    if ($active_type == 'preferences') {
        $CFG->stylesheets[] = $CFG->wwwroot . '/grade/report/styles.css';
    }

    foreach ($extracss as $css_url) {
        $CFG->stylesheets[] = $css_url;
    }

    $navlinks[] = array('name' => $strgrades,
                        'link' => $first_link,
                        'type' => 'misc');

    $active_type_link = '';

    if (!empty($plugin_info[$active_type]->link) && $plugin_info[$active_type]->link != qualified_me()) {
        $active_type_link = $plugin_info[$active_type]->link;
    }

    if (!empty($plugin_info[$active_type]->parent->link)) {
        $active_type_link = $plugin_info[$active_type]->parent->link;
        $navlinks[] = array('name' => $stractive_type, 'link' => $active_type_link, 'type' => 'misc');
    }

    if (empty($plugin_info[$active_type]->id)) {
        $navlinks[] = array('name' => $stractive_type, 'link' => $active_type_link, 'type' => 'misc');
    }

    $navlinks[] = array('name' => $stractive_plugin, 'link' => null, 'type' => 'misc');

    $navigation = build_navigation($navlinks);

    $title = ': ' . $stractive_plugin;
    if (empty($plugin_info[$active_type]->id) || !empty($plugin_info[$active_type]->parent)) {
        $title = ': ' . $stractive_type . ': ' . $stractive_plugin;
    }

    $returnval = print_header_simple($strgrades . ': ' . $stractive_type, $title, $navigation, '',
            '', true, $buttons, navmenu($COURSE), false, '', $return);

    // Guess heading if not given explicitly
    if (!$heading) {
        $heading = $stractive_plugin;
    }

    if ($CFG->grade_navmethod == GRADE_NAVMETHOD_COMBO || $CFG->grade_navmethod == GRADE_NAVMETHOD_DROPDOWN) {
        $returnval .= print_grade_plugin_selector($plugin_info, $return);
    }
    $returnval .= print_heading($heading);

    if ($CFG->grade_navmethod == GRADE_NAVMETHOD_COMBO || $CFG->grade_navmethod == GRADE_NAVMETHOD_TABS) {
        $returnval .= grade_print_tabs($active_type, $active_plugin, $plugin_info, $return);
    }

    if ($return) {
        return $returnval;
    }
}

/**
 * Utility class used for return tracking when using edit and other forms in grade plugins
 *
 * @package moodlecore
 * @copyright 2009 Nicolas Connault
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class grade_plugin_return {
    public $type;
    public $plugin;
    public $courseid;
    public $userid;
    public $page;

    /**
     * Constructor
     *
     * @param array $params - associative array with return parameters, if null parameter are taken from _GET or _POST
     */
    public function grade_plugin_return($params = null) {
        if (empty($params)) {
            $this->type     = optional_param('gpr_type', null, PARAM_SAFEDIR);
            $this->plugin   = optional_param('gpr_plugin', null, PARAM_SAFEDIR);
            $this->courseid = optional_param('gpr_courseid', null, PARAM_INT);
            $this->userid   = optional_param('gpr_userid', null, PARAM_INT);
            $this->page     = optional_param('gpr_page', null, PARAM_INT);

        } else {
            foreach ($params as $key=>$value) {
                if (array_key_exists($key, $this)) {
                    $this->$key = $value;
                }
            }
        }
    }

    /**
     * Returns return parameters as options array suitable for buttons.
     * @return array options
     */
    public function get_options() {
        if (empty($this->type)) {
            return array();
        }

        $params = array();

        if (!empty($this->plugin)) {
            $params['plugin'] = $this->plugin;
        }

        if (!empty($this->courseid)) {
            $params['id'] = $this->courseid;
        }

        if (!empty($this->userid)) {
            $params['userid'] = $this->userid;
        }

        if (!empty($this->page)) {
            $params['page'] = $this->page;
        }

        return $params;
    }

    /**
     * Returns return url
     *
     * @param string $default default url when params not set
     * @param array  $extras Extra URL parameters
     *
     * @return string url
     */
    public function get_return_url($default, $extras=null) {
        global $CFG;

        if (empty($this->type) or empty($this->plugin)) {
            return $default;
        }

        $url = $CFG->wwwroot.'/grade/'.$this->type.'/'.$this->plugin.'/index.php';
        $glue = '?';

        if (!empty($this->courseid)) {
            $url .= $glue.'id='.$this->courseid;
            $glue = '&amp;';
        }

        if (!empty($this->userid)) {
            $url .= $glue.'userid='.$this->userid;
            $glue = '&amp;';
        }

        if (!empty($this->page)) {
            $url .= $glue.'page='.$this->page;
            $glue = '&amp;';
        }

        if (!empty($extras)) {
            foreach ($extras as $key=>$value) {
                $url .= $glue.$key.'='.$value;
                $glue = '&amp;';
            }
        }

        return $url;
    }

    /**