<?php
// This file is part of the Studyplan plugin for Moodle
//
// 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 <https://www.gnu.org/licenses/>.
/**
 *
 * @package    local_treestudyplan
 * @copyright  2023 P.M. Kuipers
 * @license    https://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

namespace local_treestudyplan;
require_once($CFG->libdir.'/externallib.php');

use \grade_item;

// $gi->courseid, .
// $gi->itemmodule, .
// $gi->iteminstance.
class gradingscanner
{
    private static $mod_supported = [];
    private static $course_students = [];
    private $scanner = null;
    private $gi = null;
    private $pending_cache = [];

    public static function supported($mod) {
        if (!array_key_exists($mod, self::$mod_supported)) {
            self::$mod_supported[$mod] = class_exists("\local_treestudyplan\\local\\ungradedscanners\\{$mod}_scanner");
        }
        return self::$mod_supported[$mod];
    }

    public static function get_course_students($courseid) {
        global $CFG;
        if (!array_key_exists($courseid, self::$course_students)) {
            $students = [];
            $context = \context_course::instance($courseid);
            foreach (explode(', ', $CFG->gradebookroles) as $roleid) {
                $roleid = trim($roleid);
                $students = array_keys(get_role_users($roleid, $context, false, 'u.id', 'u.id ASC'));
            }
            self::$course_students[$courseid] = $students;
        }
        return self::$course_students[$courseid];
    }

    public function __construct(grade_item $gi) {
        $this->courseid = $gi->courseid;
        $this->gi = $gi;
        if (self::supported($gi->itemmodule)) {
            $scannerclass = "\local_treestudyplan\\local\ungradedscanners\\{$gi->itemmodule}_scanner";
            $this->scanner = new $scannerclass($gi);
        }
    }

    public function is_available() {
        return $this->scanner !== null;
    }

    public function pending($userid) {
        if (!array_key_exists($userid, $this->pending_cache)) {
            if ($this->scanner === null) {
                $this->pending_cache[$userid] = false;
            } else {
                $this->pending_cache[$userid] = $this->scanner->has_ungraded_submission($userid);;
            }
        }
        return $this->pending_cache[$userid];
    }

    public static function structure($value=VALUE_OPTIONAL) {
        return new \external_single_structure([
            "ungraded" => new \external_value(PARAM_INT, 'number of ungraded submissions'),
            "completed" => new \external_value(PARAM_INT, 'number of completed students'),
            "completed_pass" => new \external_value(PARAM_INT, 'number of completed-pass students'),
            "completed_fail" => new \external_value(PARAM_INT, 'number of completed-fail students'),
            "students" => new \external_value(PARAM_INT, 'number of students that should submit'),
        ], "details about gradable submissions", $value);
    }

    public function model() {
        // Upda.
        $students = self::get_course_students($this->courseid);
        $completed = 0;
        $ungraded = 0;
        $completed_pass = 0;
        $completed_fail = 0;
        foreach ($students as $userid) {
            if ($this->pending($userid)) {
                // First check if the completion needs grading.
                $ungraded++;
            } else {
                $grade = $this->gi->get_final($userid);
                if (!is_numeric($grade->finalgrade) && empty($grade->finalgrade)) {
                    //skip.
                } else
                {
                    //compare grade to minimum grade.
                    if ($this->grade_passed($grade)) {
                        $completed_pass++;
                    } else {
                        $completed_fail++;
                    }
                }
            }
        }

        return [
            'ungraded' => $ungraded,
            'completed' => $completed,
            'completed_pass' => $completed_pass,
            'completed_fail' => $completed_fail,
            'students' => count($students),
        ];

    }

    // Function copied from bistate aggregator to avoid reference mazes.
    private function grade_passed($grade) {
        global $DB;
        $table = "local_treestudyplan_gradecfg";
        // first determine if we have a grade_config for this scale or this maximum grade.
        $finalgrade = $grade->finalgrade;
        $scale = $this->gi->load_scale();
        if ( isset($scale)) {
            $gradecfg = $DB->get_record($table, ["scale_id"=>$scale->id]);
        } else if ($this->gi->grademin == 0) {
            $gradecfg = $DB->get_record($table, ["grade_points"=>$this->gi->grademax]);
        } else
        {
            $gradecfg = null;
        }

        // for point grades, a provided grade pass overrides the defaults in the gradeconfig.
        // for scales, the configuration in the gradeconfig is leading.

        if ($gradecfg && (isset($scale) || $this->gi->gradepass == 0)) {
            // if so, we need to know if the grade is .
            if ($finalgrade >= $gradecfg->min_completed) {
                return true;
            } else {
                return false;
            }
        } else if ($this->gi->gradepass > 0) {
            $range = floatval($this->gi->grademax - $this->gi->grademin);
            // if no gradeconfig and gradepass is set, use that one to determine config.
            if ($finalgrade >= $this->gi->gradepass) {
                return true;
            } else {
                return false;
            }
        } else {
            // Blind assumptions if nothing is provided.
            // over 55% of range is completed.
            // if range >= 3 and failed is enabled, assume that this means failed.
            $g = floatval($finalgrade - $this->gi->grademin);
            $range = floatval($this->gi->grademax - $this->gi->grademin);
            $score = $g / $range;

            if ($score > 0.55) {
                return true;
            } else {
                return false;
            }
        }
    }


}