package main

import (
	"errors"
	"github.com/google/uuid"
	"github.com/pocketbase/pocketbase/tools/types"
	"htwkalender/model"
	"net/http"
	"regexp"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/PuerkitoBio/goquery"
)

// @TODO: fix bug where cycle contains multiple days (e.g. "Mo + Mi 18:00-20:00")
// @TODO: add tests
// @TODO: add it to the service
// @TODO: make it like a cron job to fetch the sport courses once a week
func main() {

	var sportCourseLinks = fetchAllAvailableSportCourses()
	sportEntries := fetchHTWKSportCourses(sportCourseLinks)

	for _, event := range sportEntries {
		println(event.Title)
	}

	events := formatEntriesToEvents(sportEntries)

	for _, event := range events {
		println(event.Name)
	}
}

func formatEntriesToEvents(entries []SportEntry) []model.Event {

	var events []model.Event

	for i, entry := range entries {

		eventStarts, eventEnds := calculateEventStarts(entry.Details.DateRange.Start, entry.Details.DateRange.End, entry.Details.Cycle)

		for j := range eventStarts {

			start, _ := types.ParseDateTime(eventStarts[j].In(time.UTC))
			end, _ := types.ParseDateTime(eventEnds[j].In(time.UTC))

			var event = model.Event{
				UUID:      uuid.NewSHA1(uuid.NameSpaceDNS, []byte(entry.Title+strconv.FormatInt(int64(i), 10))).String(),
				Day:       entry.Details.DateRange.Start.Weekday().String(),
				Week:      strconv.Itoa(23),
				Start:     start,
				End:       end,
				Name:      entry.Title,
				EventType: entry.Details.Type,
				Prof:      entry.Details.CourseLead.Name,
				Rooms:     entry.Details.Location.Name,
				Notes:     entry.AdditionalNote,
				BookedAt:  "",
				Course:    "Sport",
				Semester:  checkSemester(entry.Details.DateRange.Start),
			}
			events = append(events, event)
		}

	}
	return events
}

func calculateEventStarts(start time.Time, end time.Time, cycle string) ([]time.Time, []time.Time) {

	// start is the begin of the cycle e.g. 01.04.2020
	// end is the end of the cycle e.g. 30.09.2020
	// cycle is the day and timespan (e.g. "Mo 18:00-20:00")

	// check if start is before end
	if start.After(end) {
		return nil, nil
	}

	// check if cycle is valid
	if !checkCycle(cycle) {
		return nil, nil
	}

	var weekDay = cycle[0:2]
	// match weekday to time.Weekday (e.g. "Mo" -> time.Monday)
	var weekDayInt int

	switch weekDay {
	case "Mo":
		weekDayInt = 1
	case "Di":
		weekDayInt = 2
	case "Mi":
		weekDayInt = 3
	case "Do":
		weekDayInt = 4
	case "Fr":
		weekDayInt = 5
	case "Sa":
		weekDayInt = 6
	case "So":
		weekDayInt = 0
	}

	// get every date matching the weekday in the cycle between start and end
	var eventDates []time.Time
	for d := start; d.Before(end); d = d.AddDate(0, 0, 1) {
		if d.Weekday() == time.Weekday(weekDayInt) {
			eventDates = append(eventDates, d)
		}
	}

	// add hours and minutes to the dates in eventDates
	// array of tuple of start and end times
	var eventStartsWithTime []time.Time
	var eventEndWithTime []time.Time

	for _, eventStart := range eventDates {
		timeRegExp, _ := regexp.Compile("[0-9]{2}:[0-9]{2}")
		times := timeRegExp.FindAllString(cycle, 2)
		startHour, _ := strconv.Atoi(times[0][0:2])
		startMinute, _ := strconv.Atoi(times[0][3:5])

		endHour, _ := strconv.Atoi(times[1][0:2])
		endMinute, _ := strconv.Atoi(times[1][3:5])
		eventStartsWithTime = append(eventStartsWithTime, time.Date(eventStart.Year(), eventStart.Month(), eventStart.Day(), startHour, startMinute, 0, 0, eventStart.Location()))
		eventEndWithTime = append(eventEndWithTime, time.Date(eventStart.Year(), eventStart.Month(), eventStart.Day(), endHour, endMinute, 0, 0, eventStart.Location()))
	}

	return eventStartsWithTime, eventEndWithTime
}

func checkCycle(cycle string) bool {

	// check if cycle is valid
	if len(cycle) < 12 {
		return false
	}

	// check if cycle has a weekday
	weekDay := cycle[0:2]
	if weekDay != "Mo" && weekDay != "Di" && weekDay != "Mi" && weekDay != "Do" && weekDay != "Fr" && weekDay != "Sa" && weekDay != "So" {
		return false
	}

	// check if cycle has a timespan
	timeSpan := cycle[3:12]
	if len(timeSpan) != 9 {
		return false
	}

	// check if timespan has a start and end time
	startTime := timeSpan[0:5]
	endTime := timeSpan[6:9]
	if len(startTime) != 5 || len(endTime) != 3 {
		return false
	}

	// check if start time is before end time
	if startTime > endTime {
		return false
	}

	return true

}

// check if ws or ss
func checkSemester(date time.Time) string {
	if date.Month() >= 4 && date.Month() <= 9 {
		return "ss"
	} else {
		return "ws"
	}
}

// fetch the main page where all sport courses are listed and extract all links to the sport courses
func fetchAllAvailableSportCourses() []string {
	var url = "https://sport.htwk-leipzig.de/sportangebote"

	var doc, err = htmlRequest(url)

	if err != nil {
		return nil
	}

	// link list of all sport courses
	var links []string

	// find all links to sport courses with regex https://sport.htwk-leipzig.de/sportangebote/detail/sport/ + [0-9]{1,4}
	doc.Find("a[href]").Each(func(i int, s *goquery.Selection) {
		link, _ := s.Attr("href")
		if strings.HasPrefix(link, "/sportangebote/detail/sport/") {
			links = append(links, link)
		}
	})

	return links
}

// fetchAllHTWKSportCourses fetches all sport courses from the given links.
// to speed up the process, it uses multithreading.

func fetchHTWKSportCourses(links []string) []SportEntry {

	//multithreaded webpage requests to speed up the process

	var maxThreads = 10
	var htmlPageArray = make([]*goquery.Document, len(links))
	var hostUrl = "https://sport.htwk-leipzig.de"

	var wg sync.WaitGroup
	wg.Add(maxThreads)
	for i := 0; i < maxThreads; i++ {
		go func(i int) {
			for j := i; j < len(links); j += maxThreads {
				doc, err := htmlRequest(hostUrl + links[j])
				if err == nil {
					htmlPageArray[j] = doc
				}
			}
			wg.Done()
		}(i)
	}
	wg.Wait()

	var events []SportEntry

	for _, doc := range htmlPageArray {
		if doc != nil {
			event, err := fetchHtwkSportCourse(doc)
			if err == nil {
				events = append(events, event...)
			}
		}
	}
	return events
}

func htmlRequest(url string) (*goquery.Document, error) {
	println("fetching " + url)

	resp, err := http.Get(url)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	doc, err := goquery.NewDocumentFromReader(resp.Body)
	if err != nil {
		return nil, err
	}

	println("finished fetching " + url)
	return doc, nil
}

// fetchHtwkSportCourse fetches the sport course from the given url and id.
// If the sport course does not exist, it will return an error.
// If the sport course exists, it will return the sport course.
// goquery is used to parse the html. The html structure is not very consistent, so it is hard to parse.
// May be improved in the future.
func fetchHtwkSportCourse(doc *goquery.Document) ([]SportEntry, error) {
	var events []SportEntry

	if doc.Find("h1").Text() == "Aktuelle Sportangebote" {
		return nil, errors.New("not a sport course page")
	}

	doc.Find(".eventHead").Each(func(i int, s *goquery.Selection) {
		var event SportEntry
		var details EventDetails

		fullTitle := strings.TrimSpace(s.Find("h3").Text())
		titleParts := strings.Split(fullTitle, "-")
		if len(titleParts) > 0 {
			event.Title = strings.TrimSpace(titleParts[0])
		}

		if len(titleParts) > 2 {
			details.Type = strings.TrimSpace(titleParts[len(titleParts)-1])
		}

		s.NextFiltered("table.eventDetails").Find("tr").Each(func(i int, s *goquery.Selection) {
			key := strings.TrimSpace(s.Find("td").First().Text())
			value := strings.TrimSpace(s.Find("td").Last().Text())

			switch key {
			case "Zeitraum":
				dates := strings.Split(value, "-")
				if len(dates) == 2 {
					startDate, _ := time.Parse("02.01.2006", strings.TrimSpace(dates[0]))
					endDate, _ := time.Parse("02.01.2006", strings.TrimSpace(dates[1]))
					details.DateRange = DateRange{Start: startDate, End: endDate}
				}
			case "Zyklus":
				details.Cycle = value
			case "Geschlecht":
				details.Gender = value
			case "Leiter":
				leaderName := strings.TrimSpace(s.Find("td a").Text())
				leadersSlice := strings.Split(leaderName, "\n")
				for i, leader := range leadersSlice {
					leadersSlice[i] = strings.TrimSpace(leader)
				}
				formattedLeaders := strings.Join(leadersSlice, ", ")
				leaderLink, _ := s.Find("td a").Attr("href")
				details.CourseLead = CourseLead{Name: formattedLeaders, Link: leaderLink}
			case "Ort":
				locationDetails := strings.Split(value, "(")
				if len(locationDetails) == 2 {
					details.Location = Location{
						Name:    strings.TrimSpace(locationDetails[0]),
						Address: strings.TrimRight(strings.TrimSpace(locationDetails[1]), ")"),
					}
				}
			case "Teilnehmer":
				parts := strings.Split(value, "/")
				if len(parts) >= 3 {
					bookings, _ := strconv.Atoi(strings.TrimSpace(parts[0]))
					totalPlaces, _ := strconv.Atoi(strings.TrimSpace(parts[1]))
					waitList, _ := strconv.Atoi(strings.TrimSpace(parts[2]))
					details.Participants = Participants{Bookings: bookings, TotalPlaces: totalPlaces, WaitList: waitList}
				}
			case "Kosten":
				details.Cost = value // makes no sense since you need to be logged in to see the price
			case "Hinweis":
				var allNotes []string

				s.Find("td").Last().Contents().Each(func(i int, s *goquery.Selection) {
					if s.Is("h4.eventAdvice") || goquery.NodeName(s) == "#text" {
						note := strings.TrimSpace(s.Text())
						if note != "" {
							allNotes = append(allNotes, note)
						}
					}
				})

				event.AdditionalNote = strings.Join(allNotes, " ")
			}
		})

		event.Details = details
		events = append(events, event)
	})

	return events, nil
}