<?php // $Id$
/**
 * File containing the grade_report class.
 * @package gradebook
 */

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

/**
 * An abstract class containing variables and methods used by all or most reports.
 * @abstract
 * @package gradebook
 */
class grade_report {
    /**
     * The courseid.
     * @var int $courseid
     */
    var $courseid;

    /** Grade plugin return tracking object.
    var $gpr;

    /**
     * The context.
     * @var int $context
     */
    var $context;

    /**
     * The grade_tree object.
     * @var object $gtree
     */
    var $gtree;

    /**
     * User preferences related to this report.
     * @var array $prefs
     */
    var $prefs = array();

    /**
     * The roles for this report.
     * @var string $gradebookroles
     */
    var $gradebookroles;

    /**
     * base url for sorting by first/last name.
     * @var string $baseurl
     */
    var $baseurl;

    /**
     * base url for paging.
     * @var string $pbarurl
     */
    var $pbarurl;

    /**
     * Current page (for paging).
     * @var int $page
     */
    var $page;

    /**
     * Array of cached language strings (using get_string() all the time takes a long time!).
     * @var array $lang_strings
     */
    var $lang_strings = array();

//// GROUP VARIABLES (including SQL)

    /**
     * The current group being displayed.
     * @var int $currentgroup
     */
    var $currentgroup;

    /**
     * A HTML select element used to select the current group.
     * @var string $group_selector
     */
    var $group_selector;

    /**
     * An SQL fragment used to add linking information to the group tables.
     * @var string $groupsql
     */
    var $groupsql;

    /**
     * An SQL constraint to append to the queries used by this object to build the report.
     * @var string $groupwheresql
     */
    var $groupwheresql;


    /**
     * Constructor. Sets local copies of user preferences and initialises grade_tree.
     * @param int $courseid
     * @param object $gpr grade plugin return tracking object
     * @param string $context
     * @param int $page The current page being viewed (when report is paged)
     */
    function grade_report($courseid, $gpr, $context, $page=null) {
        global $CFG;

        $this->courseid  = $courseid;
        $this->gpr       = $gpr;
        $this->context   = $context;
        $this->page      = $page;

        // roles to be displayed in the gradebook
        $this->gradebookroles = $CFG->gradebookroles;

        // init gtree in child class
    }

    /**
     * Given the name of a user preference (without grade_report_ prefix), locally saves then returns
     * the value of that preference. If the preference has already been fetched before,
     * the saved value is returned. If the preference is not set at the User level, the $CFG equivalent
     * is given (site default).
     * @static (Can be called statically, but then doesn't benefit from caching)
     * @param string $pref The name of the preference (do not include the grade_report_ prefix)
     * @param int $objectid An optional itemid or categoryid to check for a more fine-grained preference
     * @return mixed The value of the preference
     */
    function get_pref($pref, $objectid=null) {
        global $CFG;
        $fullprefname = 'grade_report_' . $pref;

        $retval = null;

        if (!isset($this) OR get_class($this) != 'grade_report') {
            if (!empty($objectid)) {
                $retval = get_user_preferences($fullprefname . $objectid, grade_report::get_pref($pref));
            } else {
                $retval = get_user_preferences($fullprefname, $CFG->$fullprefname);
            }
        } else {
            if (empty($this->prefs[$pref.$objectid])) {

                if (!empty($objectid)) {
                    $retval = get_user_preferences($fullprefname . $objectid);
                    if (empty($retval)) {
                        // No item pref found, we are returning the global preference
                        $retval = $this->get_pref($pref);
                        $objectid = null;
                    }
                } else {
                    $retval = get_user_preferences($fullprefname, $CFG->$fullprefname);
                }
                $this->prefs[$pref.$objectid] = $retval;
            } else {
                $retval = $this->prefs[$pref.$objectid];
            }
        }

        return $retval;
    }

    /**
     * Uses set_user_preferences() to update the value of a user preference. If 'default' is given as the value,
     * the preference will be removed in favour of a higher-level preference.
     * @static
     * @param string $pref_name The name of the preference.
     * @param mixed $pref_value The value of the preference.
     * @param int $itemid An optional itemid to which the preference will be assigned
     * @return bool Success or failure.
     * TODO print visual feedback
     */
    function set_pref($pref, $pref_value='default', $itemid=null) {
        $fullprefname = 'grade_report_' . $pref;
        if ($pref_value == 'default') {
            return unset_user_preference($fullprefname.$itemid);
        } else {
            return set_user_preference($fullprefname.$itemid, $pref_value);
        }
    }

    /**
     * Handles form data sent by this report for this report. Abstract method to implement in all children.
     * @abstract
     * @param array $data
     * @return mixed True or array of errors
     */
    function process_data($data) {
        // Implement in children classes
    }

    /**
     * Processes a single action against a category, grade_item or grade.
     * @param string $target Sortorder
     * @param string $action Which action to take (edit, delete etc...)
     * @return
     */
    function process_action($target, $action) {
        //implement if needed
    }

    /**
     * First checks the cached language strings, then returns match if found, or uses get_string()
     * to get it from the DB, caches it then returns it.
     * @param string $strcode
     * @param string $section Optional language section
     * @return string
     */
    function get_lang_string($strcode, $section=null) {
        if (empty($this->lang_strings[$strcode])) {
            $this->lang_strings[$strcode] = get_string($strcode, $section);
        }
        return $this->lang_strings[$strcode];
    }

    /**
     * Computes then returns the percentage value of the grade value within the given range.
     * @param float $gradeval
     * @param float $grademin
     * @param float $grademx
     * @return float $percentage
     */
    function grade_to_percentage($gradeval, $grademin, $grademax) {
        if ($grademin >= $grademax) {
            debugging("The minimum grade ($grademin) was higher than or equal to the maximum grade ($grademax)!!! Cannot proceed with computation.");
        }
        $offset_value = $gradeval - $grademin;
        $offset_max = $grademax - $grademin;
        $factor = 100 / $offset_max;
        $percentage = $offset_value * $factor;
        return $percentage;
    }

    /**
     * Fetches and returns an array of grade letters indexed by their grade boundaries, as stored in preferences.
     * @return array
     */
    function get_grade_letters() {
        $letters = array();
        for ($i = 1; $i <= 10; $i++) {
            $boundary = grade_report::get_pref('gradeboundary' . $i);
            $letter = grade_report::get_pref('gradeletter' . $i);
            if (!is_null($boundary) && $boundary != -1 && !empty($letter)) {
                $letters[$boundary] = $letter;
            }
        }
        return $letters;
    }

    /**
     * Fetches and returns a count of all the users that will be shown on this page.
     * @return int Count of users
     */
    function get_numusers() {
        global $CFG;

        $countsql = "SELECT COUNT(DISTINCT u.id)
                    FROM {$CFG->prefix}grade_grades g RIGHT OUTER JOIN
                         {$CFG->prefix}user u ON u.id = g.userid
                         LEFT JOIN {$CFG->prefix}role_assignments ra ON u.id = ra.userid
                         $this->groupsql
                    WHERE ra.roleid in ($this->gradebookroles)
                         $this->groupwheresql
                    AND ra.contextid ".get_related_contexts_string($this->context);
        return count_records_sql($countsql);
    }

    /**
     * Sets up this object's group variables, mainly to restrict the selection of users to display.
     */
    function setup_groups() {
        global $CFG;

        /// find out current groups mode
        $course = get_record('course', 'id', $this->courseid);
        $groupmode = $course->groupmode;
        ob_start();
        $this->currentgroup = setup_and_print_groups($course, $groupmode, $this->pbarurl);
        $this->group_selector = ob_get_clean();

        // update paging after group
        $this->baseurl .= 'group='.$this->currentgroup;
        $this->pbarurl .= 'group='.$this->currentgroup;

        if ($this->currentgroup) {
            $this->groupsql = " LEFT JOIN {$CFG->prefix}groups_members gm ON gm.userid = u.id ";
            $this->groupwheresql = " AND gm.groupid = $this->currentgroup ";
        }
    }

    /**
     * Returns an arrow icon inside an <a> tag, for the purpose of sorting a column.
     * @param string $direction
     * @param string $sort_link
     * @param string HTML
     */
    function get_sort_arrow($direction='move', $sort_link=null) {
        $matrix = array('up' => 'asc', 'down' => 'desc', 'move' => 'desc');
        $strsort = $this->get_lang_string('sort' . $matrix[$direction]);
        $arrow = print_arrow($direction, $strsort, true);
        $html = '<a href="'.$sort_link .'">' . $arrow . '</a>';
        return $html;
    }

    /**
     * Builds and returns a HTML link to the grade or view page of the module given.
     * If no itemmodule is given, only the name of the category/item is returned, no link.
     * @param string $modulename The shortname of the module, will become the visible header
     * @param string $itemmodule The name of the module type (e.g. assignment, quiz...)
     * @param int $iteminstance The instance number of the module
     * @return string HTML
     */
    function get_module_link($modulename, $itemmodule=null, $iteminstance=null) {
        global $CFG, $COURSE;

        $link = null;
        if (!is_null($itemmodule) AND !is_null($iteminstance)) {
            // Add module icon if toggle is enabled
            if ($this->get_pref('showactivityicons')) {
                $modulename = '<img src="' . $CFG->modpixpath . '/' . $itemmodule
                            . '/icon.gif" class="icon activity" alt="' . $modulename . '" />' . $modulename;
            }

            $coursemodule = get_coursemodule_from_instance($itemmodule, $iteminstance, $COURSE->id);

            $dir = $CFG->dirroot . "/mod/$itemmodule/";
            $url = $CFG->wwwroot . "/mod/$itemmodule/";

            if (file_exists($dir . 'grade.php')) {
                $url .= 'grade.php';
            } else {
                $url .= 'view.php';
            }

            $url .= "?id=$coursemodule->id";
            return '<a href="' . $url . '">' . $modulename . '</a>';
        }

        return $modulename;
    }
}
?>
