package sport

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

	"github.com/PuerkitoBio/goquery"
)

// @TODO: add tests
// @TODO: make it like a cron job to fetch the sport courses once a week
func FetchAndUpdateSportEvents(app *pocketbase.PocketBase) []model.Event {

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

	var earliestDate time.Time
	var latestDate time.Time

	// find earliest and latest date in events
	for _, event := range events {
		if event.Start.Time().Before(earliestDate) {
			earliestDate = event.Start.Time()
		}
		if event.End.Time().After(latestDate) {
			latestDate = event.End.Time()
		}
	}

	// get all events from database where name = Feiertage und lehrveranstaltungsfreie Tage
	holidays, err := db.GetAllModulesByNameAndDateRange(app, "Feiertage und lehrveranstaltungsfreie Tage", earliestDate, latestDate)
	if err != nil {
		return nil
	}

	// remove all events that have same year, month and day as items in holidays
	for _, holiday := range holidays {
		for i, event := range events {
			if event.Start.Time().Year() == holiday.Start.Time().Year() &&
				event.Start.Time().Month() == holiday.Start.Time().Month() &&
				event.Start.Time().Day() == holiday.Start.Time().Day() {
				events = append(events[:i], events[i+1:]...)
			}
		}
	}

	err = db.DeleteAllEventsForCourse(app, "Sport", functions.GetCurrentSemesterString())
	if err != nil {
		return nil
	}

	// save events to database
	savedEvents, err := db.SaveEvents(events, app)

	if err != nil {
		return nil
	}

	return savedEvents

}

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

	var events []model.Event

	for _, entry := range entries {
		eventStarts, eventEnds := getWeekEvents(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+entry.ID+entry.Details.Type)).String(),
				Day:       toGermanWeekdayString(entry.Details.DateRange.Start.Weekday()),
				Week:      strconv.Itoa(23),
				Start:     start,
				End:       end,
				Name:      entry.Title + " (" + entry.ID + ")",
				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 getDayInt(weekDay string) int {
	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
	}
	return weekDayInt
}

func toGermanWeekdayString(weekday time.Weekday) string {
	switch weekday {
	case time.Monday:
		return "Montag"
	case time.Tuesday:
		return "Dienstag"
	case time.Wednesday:
		return "Mittwoch"
	case time.Thursday:
		return "Donnerstag"
	case time.Friday:
		return "Freitag"
	case time.Saturday:
		return "Samstag"
	case time.Sunday:
		return "Sonntag"
	default:
		return ""
	}
}

func extractStartAndEndTime(cycle string) (int, int, int, int) {
	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])
	return startHour, startMinute, endHour, endMinute
}

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

	var weekEvents []model.SportDayStartEnd

	// split by regexp to get the cycle parts
	var cycleParts []string
	cycleParts = splitByCommaWithTime(cycle)

	for _, cyclePart := range cycleParts {

		//cut string at the first integer/number
		cyclePartWithDaysOnly := cyclePart[0:strings.IndexFunc(cyclePart, func(r rune) bool { return r >= '0' && r <= '9' })]

		// check if cycle has multiple days by checking if it has a plus sign
		if strings.Contains(cyclePartWithDaysOnly, "+") {
			// find all days in cycle part by regexp
			dayRegExp, _ := regexp.Compile("[A-Z][a-z]")
			days := dayRegExp.FindAllString(cyclePart, -1)
			startHour, startMinute, endHour, endMinute := extractStartAndEndTime(cyclePart)

			// creating a SportDayStartEnd for each day in the cycle
			for _, day := range days {
				weekEvents = append(weekEvents, model.SportDayStartEnd{
					Start: time.Date(start.Year(), start.Month(), start.Day(), startHour, startMinute, 0, 0, start.Location()),
					End:   time.Date(end.Year(), end.Month(), end.Day(), endHour, endMinute, 0, 0, end.Location()),
					Day:   time.Weekday(getDayInt(day)),
				})
			}

		}

		// check if cycle has multiple days by checking if it has a minus sign
		if strings.Contains(cyclePartWithDaysOnly, "-") {
			// find all days in cycle part by regexp
			dayRegExp, _ := regexp.Compile("[A-Z][a-z]")
			days := dayRegExp.FindAllString(cyclePart, 2)
			startHour, startMinute, endHour, endMinute := extractStartAndEndTime(cyclePart)

			//create a int array with all days from start to end day
			var daysBetween []int
			for i := getDayInt(days[0]); i <= getDayInt(days[1]); i++ {
				daysBetween = append(daysBetween, i)
			}

			// creating a SportDayStartEnd for each day in the cycle
			for _, day := range daysBetween {
				weekEvents = append(weekEvents, model.SportDayStartEnd{
					Start: time.Date(start.Year(), start.Month(), start.Day(), startHour, startMinute, 0, 0, start.Location()),
					End:   time.Date(end.Year(), end.Month(), end.Day(), endHour, endMinute, 0, 0, end.Location()),
					Day:   time.Weekday(day),
				})
			}
		}

		// check if cycle has only one day
		if !strings.Contains(cyclePartWithDaysOnly, "-") && !strings.Contains(cyclePartWithDaysOnly, "+") {
			// find all days in cycle part by regexp
			dayRegExp, _ := regexp.Compile("[A-Z][a-z]")
			days := dayRegExp.FindAllString(cyclePart, -1)
			startHour, startMinute, endHour, endMinute := extractStartAndEndTime(cyclePart)

			// creating a SportDayStartEnd for each day in the cycle
			for _, day := range days {
				weekEvents = append(weekEvents, model.SportDayStartEnd{
					Start: time.Date(start.Year(), start.Month(), start.Day(), startHour, startMinute, 0, 0, start.Location()),
					End:   time.Date(end.Year(), end.Month(), end.Day(), endHour, endMinute, 0, 0, end.Location()),
					Day:   time.Weekday(getDayInt(day)),
				})
			}
		}
	}

	var startDatesList []time.Time
	var endDatesList []time.Time

	for _, weekEvent := range weekEvents {
		startDates, endDates := createEventListFromStartToEndMatchingDay(weekEvent)
		startDatesList = append(startDatesList, startDates...)
		endDatesList = append(endDatesList, endDates...)
	}

	return startDatesList, endDatesList
}

func createEventListFromStartToEndMatchingDay(weekEvent model.SportDayStartEnd) ([]time.Time, []time.Time) {
	var startDates []time.Time
	var endDates []time.Time
	for d := weekEvent.Start; d.Before(weekEvent.End); d = d.AddDate(0, 0, 1) {
		if d.Weekday() == weekEvent.Day {
			startDates = append(startDates, time.Date(d.Year(), d.Month(), d.Day(), weekEvent.Start.Hour(), weekEvent.Start.Minute(), 0, 0, d.Location()))
			endDates = append(endDates, time.Date(d.Year(), d.Month(), d.Day(), weekEvent.End.Hour(), weekEvent.End.Minute(), 0, 0, d.Location()))
		}
	}
	return startDates, endDates
}

func splitByCommaWithTime(input string) []string {
	var result []string

	// Split by comma
	parts := strings.Split(input, ", ")

	// Regular expression to match a day with time
	regex := regexp.MustCompile(`([A-Za-z]{2,}(\+[A-Za-z]{2,})* \d{2}:\d{2}-\d{2}:\d{2})`)

	// Iterate over parts and combine when necessary
	var currentPart string
	for _, part := range parts {
		if regex.MatchString(part) {
			if currentPart != "" {
				currentPart += ", " + part
				result = append(result, currentPart)
				currentPart = ""
			} else {
				result = append(result, part)
			}
			// If the part contains a day with time, start a new currentPart

		} else {
			// If there's no currentPart, start a new one
			if currentPart != "" {
				currentPart += ", " + part
			} else {
				currentPart = part
			}
		}
	}

	// Add the last currentPart to the result
	if currentPart != "" {
		result = append(result, currentPart)
	}

	return result
}

// 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) []model.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 []model.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) {
	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
	}

	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) ([]model.SportEntry, error) {
	var events []model.SportEntry
	germanTime, _ := time.LoadLocation("Europe/Berlin")

	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 model.SportEntry
		var details model.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])
		}

		event.ID = parseEventID(fullTitle)

		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.ParseInLocation("02.01.2006", strings.TrimSpace(dates[0]), germanTime)
					endDate, _ := time.ParseInLocation("02.01.2006", strings.TrimSpace(dates[1]), germanTime)
					details.DateRange = model.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 = model.CourseLead{Name: formattedLeaders, Link: leaderLink}
			case "Ort":
				locationDetails := strings.Split(value, "(")
				if len(locationDetails) == 2 {
					details.Location = model.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 = model.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
}

// parseEventID from fulltitle
// the event id is a number in the fulltitle thats not a time like HH:MM and shoudl be found after Nr. or Nr:
func parseEventID(fulltitle string) string {
	var eventID string
	var numberRegExp = regexp.MustCompile("[0-9]{1,4}")
	var fulltitleParts = strings.Split(fulltitle, " ")
	for i, part := range fulltitleParts {
		if part == "Nr." || part == "Nr:" {
			eventID = fulltitleParts[i+1]
			break
		}
	}
	if eventID == "" {
		eventID = numberRegExp.FindString(fulltitle)
	}
	return eventID

}