<?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;
defined('MOODLE_INTERNAL') || die();

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

abstract class aggregator {
    private const FALLBACK = "bistate";
    private static $modsupported = [];

    public static function supported($mod) {
        if (!array_key_exists($mod, self::$modsupported)) {
            self::$modsupported[$mod] = class_exists(self::aggregator_name($mod));
        }
        return self::$modsupported[$mod];
    }

    private static function aggregator_name($mod) {
        return "\local_treestudyplan\\local\\aggregators\\{$mod}_aggregator";
    }

    public static function list() {
        // Static list, since we'd need to implement a lot of static data for new aggregation methods anyway.
        // And this is faster than any dynamic method.
        return [
            "core", // Use moodle core completion.
            "bistate",
            "tristate", // Deprecated.
        ];
    }

    public static function create($mod, $configstr) {
        if (self::supported($mod)) {
            $agclass = self::aggregator_name($mod);
            return new $agclass($configstr);
        } else {
            throw new \InvalidArgumentException("Cannot find aggregator '{$mod}'");
        }
    }

    public static function createOrDefault($mod, $configstr) {
        try {
            return self::create($mod, $configstr);
        } catch (\ValueError $x) {
            return self::create(self::FALLBACK, "");
        }
    }

    private function __construct($configstr) {
        $this->initialize($configstr);
    }

    protected function initialize($configstr) {
    }

    abstract public function needSelectGradables();
    abstract public function isDeprecated();
    abstract public function aggregate_course(courseinfo $courseinfo, studyitem $studyitem, $userid);
    abstract public function aggregate_junction(array $completion, studyitem $studyitem, $userid);

    abstract public function grade_completion(gradeinfo $gradeinfo, $userid);

    // Aggregation method makes use of "required grades" in a course/module.
    abstract public function useRequiredGrades();
    // Aggregation method makes use of .
    abstract public function useItemConditions();

    // Whether the aggregation method uses core_completion, or treestudyplan custom completion.
    public function usecorecompletioninfo() {
        return false;
    }

    // Parameter editing functions - override in child class to implement parameter config for aggregation.

    // Return the current configuration string.
    public function config_string() {
        return "";
    }

    public static function basic_structure($value=VALUE_REQUIRED) {
        return new \external_single_structure([
            "useRequiredGrades" => new \external_value(PARAM_BOOL, 'id of studyplan'),
            "useItemConditions" => new \external_value(PARAM_BOOL, 'name of studyplan'),
        ], "Aggregator requirements", $value);
    }

    public function basic_model() {
        return [
            "useRequiredGrades" => $this->useRequiredGrades(),
            "useItemConditions" => $this->useItemConditions(),
        ];
    }

    public static function list_structure($value=VALUE_REQUIRED) {
        return  new \external_multiple_structure(new \external_single_structure([
            "id" => new \external_value(PARAM_TEXT, 'id of aggregator'),
            "name" => new \external_value(PARAM_TEXT, 'name of agregator'),
            "deprecated" => new \external_value(PARAM_BOOL, 'if method is deprecated'),
            "defaultconfig" => new \external_value(PARAM_TEXT, 'default config of agregator'),

        ], "Available aggregators", $value));
    }

    public static function list_model() {

        $list = [];
        foreach (self::list() as $agid) {
            $a = self::create($agid, ""); // Create new one with empty config string.
            $list[] = [
                'id' => $agid,
                'name' => get_string("{$agid}_aggregator_title", "local_treestudyplan"),
                'deprecated' => $a->isDeprecated(),
                'defaultconfig' => $a->config_string(),
            ];
        }

        return $list;
    }
}