htwkalender-pwa/backend/service/fetch/fetchSeminarEventService.go

package fetch

import (
	"fmt"
	"github.com/labstack/echo/v5"
	"github.com/pocketbase/pocketbase"
	"github.com/pocketbase/pocketbase/apis"
	"golang.org/x/net/html"
	"htwk-planner/model"
	"htwk-planner/service/date"
	"htwk-planner/service/db"
	"io"
	"net/http"
	"regexp"
	"strconv"
	"strings"
	"time"
)

func GetSeminarEvents(c echo.Context, app *pocketbase.PocketBase) error {

	seminarGroupsLabel := db.GetAllCourses(app)

	seminarGroups := GetSeminarGroupsEventsFromHTML(seminarGroupsLabel)

	collection, dbError := db.FindCollection(app, "events")
	if dbError != nil {
		return apis.NewNotFoundError("Collection not found", dbError)
	}

	seminarGroups = clearEmptySeminarGroups(seminarGroups)

	savedRecords, dbError := db.SaveEvents(seminarGroups, collection, app)

	if dbError != nil {
		return apis.NewNotFoundError("Events could not be saved", dbError)
	}

	return c.JSON(http.StatusOK, savedRecords)
}

func clearEmptySeminarGroups(seminarGroups []model.SeminarGroup) []model.SeminarGroup {
	var newSeminarGroups []model.SeminarGroup
	for _, seminarGroup := range seminarGroups {
		if len(seminarGroup.Events) > 0 && seminarGroup.Course != "" {
			newSeminarGroups = append(newSeminarGroups, seminarGroup)
		}
	}
	return newSeminarGroups
}

func GetSeminarGroupsEventsFromHTML(seminarGroupsLabel []string) []model.SeminarGroup {
	var seminarGroups []model.SeminarGroup
	for _, seminarGroupLabel := range seminarGroupsLabel {

		result, getError := getPlanHTML("ss", seminarGroupLabel)
		if getError == nil {
			seminarGroup := parseSeminarGroup(result)
			seminarGroups = append(seminarGroups, seminarGroup)
		}

		result, getError = getPlanHTML("ws", seminarGroupLabel)
		if getError == nil {
			seminarGroup := parseSeminarGroup(result)
			seminarGroups = append(seminarGroups, seminarGroup)
		}
	}
	return seminarGroups
}

func parseSeminarGroup(result string) model.SeminarGroup {
	doc, err := html.Parse(strings.NewReader(result))
	if err != nil {
		fmt.Printf("Error occurred while parsing the HTML document: %s\n", err.Error())
		return model.SeminarGroup{}
	}

	table := findFirstTable(doc)
	eventTables := getEventTables(doc)
	allDayLabels := getAllDayLabels(doc)

	if eventTables == nil || allDayLabels == nil {
		return model.SeminarGroup{}
	}

	eventsWithCombinedWeeks := toEvents(eventTables, allDayLabels)
	splitEventsByWeekVal := splitEventsByWeek(eventsWithCombinedWeeks)
	events := splitEventsBySingleWeek(splitEventsByWeekVal)
	semesterString := findFirstSpanWithClass(table, "header-0-2-0").FirstChild.Data
	semester, year := extractSemesterAndYear(semesterString)
	events = convertWeeksToDates(events, semester, year)
	var seminarGroup = model.SeminarGroup{
		University: findFirstSpanWithClass(table, "header-1-0-0").FirstChild.Data,
		Course:     findFirstSpanWithClass(table, "header-2-0-1").FirstChild.Data,
		Events:     events,
	}
	return seminarGroup
}

func convertWeeksToDates(events []model.Event, semester string, year string) []model.Event {
	var newEvents []model.Event
	eventYear, _ := strconv.Atoi(year)

	// for each event we need to calculate the start and end date based on the week and the year
	for _, event := range events {
		eventWeek, _ := strconv.Atoi(event.Week)
		eventDay, _ := date.GetDateFromWeekNumber(eventYear, eventWeek, event.Day)
		start := addTimeToDate(eventDay, event.Start)
		end := addTimeToDate(eventDay, event.End)
		newEvent := event
		newEvent.Start = start.String()
		newEvent.End = end.String()
		newEvent.Semester = semester
		newEvents = append(newEvents, newEvent)
	}
	return newEvents
}

func addTimeToDate(date time.Time, timeString string) time.Time {
	//convert time string to time
	timeParts := strings.Split(timeString, ":")
	hour, _ := strconv.Atoi(timeParts[0])
	minute, _ := strconv.Atoi(timeParts[1])

	return time.Date(date.Year(), date.Month(), date.Day(), hour, minute, 0, 0, time.UTC)
}

func extractSemesterAndYear(semesterString string) (string, string) {
	winterPattern := "Wintersemester"
	summerPattern := "Sommersemester"

	winterMatch := strings.Contains(semesterString, winterPattern)
	summerMatch := strings.Contains(semesterString, summerPattern)

	semester := ""
	semesterShortcut := ""

	if winterMatch {
		semester = "Wintersemester"
		semesterShortcut = "ws"
	} else if summerMatch {
		semester = "Sommersemester"
		semesterShortcut = "ss"
	} else {
		return "", ""
	}

	yearPattern := `\d{4}`
	combinedPattern := semester + `\s` + yearPattern
	re := regexp.MustCompile(combinedPattern)
	match := re.FindString(semesterString)
	year := ""

	if match != "" {
		reYear := regexp.MustCompile(yearPattern)
		year = reYear.FindString(match)
	}
	return semesterShortcut, year
}

func toEvents(tables [][]*html.Node, days []string) []model.Event {
	var events []model.Event

	for table := range tables {
		for row := range tables[table] {

			tableData := findTableData(tables[table][row])
			if len(tableData) > 0 {
				events = append(events, model.Event{
					Day:       days[table],
					Week:      getTextContent(tableData[0]),
					Start:     getTextContent(tableData[1]),
					End:       getTextContent(tableData[2]),
					Name:      getTextContent(tableData[3]),
					EventType: getTextContent(tableData[4]),
					Prof:      getTextContent(tableData[5]),
					Rooms:     getTextContent(tableData[6]),
					Notes:     getTextContent(tableData[7]),
					BookedAt:  getTextContent(tableData[8]),
				})
			}
		}

	}

	return events
}

func splitEventsByWeek(events []model.Event) []model.Event {
	var newEvents []model.Event

	for _, event := range events {
		weeks := strings.Split(event.Week, ",")
		for _, week := range weeks {
			newEvent := event
			newEvent.Week = strings.TrimSpace(week)
			newEvents = append(newEvents, newEvent)
		}
	}
	return newEvents
}

func splitEventsBySingleWeek(events []model.Event) []model.Event {
	var newEvents []model.Event

	for _, event := range events {
		if strings.Contains(event.Week, "-") {
			weeks := splitWeekRange(event.Week)
			for _, week := range weeks {
				newEvent := event
				newEvent.Week = week
				newEvents = append(newEvents, newEvent)
			}
		} else {
			newEvents = append(newEvents, event)
		}
	}
	return newEvents
}

func splitWeekRange(weekRange string) []string {
	parts := strings.Split(weekRange, "-")
	if len(parts) != 2 {
		return nil // Invalid format
	}

	start, errStart := strconv.Atoi(strings.TrimSpace(parts[0]))
	end, errEnd := strconv.Atoi(strings.TrimSpace(parts[1]))

	if errStart != nil || errEnd != nil {
		return nil // Error converting to integers
	}

	var weeks []string
	for i := start; i <= end; i++ {
		weeks = append(weeks, strconv.Itoa(i))
	}

	return weeks
}

func toUtf8(iso88591Buf []byte) string {
	buf := make([]rune, len(iso88591Buf))
	for i, b := range iso88591Buf {
		buf[i] = rune(b)
	}
	return string(buf)
}

// getPlanHTML Get the HTML document from the specified URL
func getPlanHTML(semester string, matrikel string) (string, error) {
	url := "https://stundenplan.htwk-leipzig.de/" + string(semester) + "/Berichte/Text-Listen;Studenten-Sets;name;" + matrikel + "?template=sws_semgrp&weeks=1-65"

	// 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 toUtf8(body), err

}