//Calendar implementation for the HTWK Leipzig timetable. Evaluation and display of the individual dates in iCal format.
//Copyright (C) 2024 HTWKalender support@htwkalender.de

//This program is free software: you can redistribute it and/or modify
//it under the terms of the GNU Affero General Public License as published by
//the Free Software Foundation, either version 3 of the License, or
//(at your option) any later version.

//This program 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 Affero General Public License for more details.

//You should have received a copy of the GNU Affero General Public License
//along with this program.  If not, see <https://www.gnu.org/licenses/>.

package v1

import (
	"encoding/xml"
	"fmt"
	"github.com/pocketbase/pocketbase"
	"github.com/pocketbase/pocketbase/models"
	"htwkalender/model"
	"htwkalender/service/db"
	"io"
	"log/slog"
	"net/http"
)

func getSeminarHTML(semester string) (string, error) {
	url := "https://stundenplan.htwk-leipzig.de/stundenplan/xml/public/semgrp_" + semester + ".xml"

	// Send GET request
	response, err := http.Get(url)
	if err != nil {
		fmt.Printf("Error occurred while making the request: %s\n", err.Error())
		return "", err
	}
	defer func(Body io.ReadCloser) {
		err := Body.Close()
		if err != nil {
			return
		}
	}(response.Body)

	// Read the response body
	body, err := io.ReadAll(response.Body)

	if err != nil {
		fmt.Printf("Error occurred while reading the response: %s\n", err.Error())
		return "", err
	}

	return string(body), err

}

func FetchSeminarGroups(app *pocketbase.PocketBase) ([]*models.Record, error) {
	var groups []model.SeminarGroup

	resultSummer, err := getSeminarHTML("ss")

	if err != nil {
		slog.Error("Error while fetching seminar groups for winter semester", err)
		return nil, err
	}

	resultWinter, _ := getSeminarHTML("ws")

	if err != nil {
		slog.Error("Error while fetching seminar groups for summer semester", err)
		return nil, err
	}

	groups = parseSeminarGroups(resultSummer, "ss")
	groups = append(groups, parseSeminarGroups(resultWinter, "ws")...)

	// filter duplicates
	groups = removeDuplicates(groups)

	collection, dbError := db.FindCollection(app, "groups")
	if dbError != nil {
		slog.Error("Error while searching collection groups", dbError)
		return nil, err
	}
	var insertedGroups []*models.Record

	insertedGroups, dbError = db.SaveGroups(groups, collection, app)
	if dbError != nil {
		slog.Error("Error while saving groups", dbError)
		return nil, err
	}

	return insertedGroups, nil
}

func removeDuplicates(groups []model.SeminarGroup) []model.SeminarGroup {
	var uniqueGroups []model.SeminarGroup
	for _, group := range groups {
		if !contains(uniqueGroups, group) {
			uniqueGroups = append(uniqueGroups, group)
		}
	}
	return uniqueGroups
}

func contains(groups []model.SeminarGroup, group model.SeminarGroup) bool {
	for _, a := range groups {
		if (a.Course == group.Course) && (a.Semester == group.Semester) {
			return true
		}
	}
	return false
}

func parseSeminarGroups(result string, semester string) []model.SeminarGroup {

	var studium model.Studium
	err := xml.Unmarshal([]byte(result), &studium)
	if err != nil {
		return nil
	}

	var seminarGroups []model.SeminarGroup
	for _, faculty := range studium.Faculty {
		for _, Studiengang := range faculty.Studiengang {
			for _, Studienrichtung := range Studiengang.Semgrp {
				seminarGroup := model.SeminarGroup{
					University:    "HTWK-Leipzig",
					GroupShortcut: Studiengang.Name,
					GroupId:       Studiengang.ID,
					Course:        Studienrichtung.Name,
					Faculty:       faculty.Name,
					FacultyId:     faculty.ID,
					Semester:      semester,
				}
				seminarGroups = append(seminarGroups, seminarGroup)
			}
		}
	}
	return seminarGroups
}