package calendar

import (
	"fmt"
	"github.com/avast/retry-go"
	"github.com/dolanor/caldav-go/caldav"
	"github.com/dolanor/caldav-go/caldav/entities"
	"github.com/dolanor/caldav-go/icalendar/components"
	"go.uber.org/zap"
	"math"
	"net/http"
	"strings"
	"time"
)

type Caldav interface {
	QueryEvents(path string, query *entities.CalendarQuery) (events []*components.Event, oerr error)
}

type Calendar struct {
	Location             *time.Location
	cdav                 Caldav
	caldavPath           string
	caldavSummaryPattern string
}

func NewCaldav(caldavUrl, caldavPath string) (Caldav, error) {
	// create a reference to your CalDAV-compliant server
	server, _ := caldav.NewServer(caldavUrl)
	// create a CalDAV client to speak to the server
	var client = caldav.NewClient(server, http.DefaultClient)
	err := retry.Do(
		func() error {
			// start executing requests!
			err := client.ValidateServer(caldavPath)
			if err != nil {
				return fmt.Errorf("bad caldav configuration, unable to validate connexion: %w", err)
			}
			return nil
		},
		retry.OnRetry(
			func(n uint, err error) {
				zap.S().Errorf("unable to validate caldav connection on retry %d: %v", n, err)
			},
		),
		retry.Attempts(0), // Infinite attempts
		retry.DelayType(retry.BackOffDelay),
	)
	if err != nil {
		return nil, fmt.Errorf("unable to validate caldav connection: %w", err)
	}
	return client, nil
}

type Option func(calendar *Calendar)

func WithCaldav(cdav Caldav) Option {
	return func(calendar *Calendar) {
		calendar.cdav = cdav
	}
}

func WithCaldavSummaryPattern(caldavSummaryPattern string) Option {
	return func(calendar *Calendar) {
		calendar.caldavSummaryPattern = caldavSummaryPattern
	}
}

func WithCaldavPath(caldavPath string) Option {
	return func(calendar *Calendar) {
		calendar.caldavPath = caldavPath
	}
}

func New(location *time.Location, opts ...Option) *Calendar {
	c := &Calendar{
		location,
		nil,
		"",
		"",
	}

	for _, opt := range opts {
		opt(c)
	}
	return c
}

func (cal *Calendar) GetEasterDay(year int) time.Time {
	g := float64(year % 19.0)
	c := math.Floor(float64(year) / 100.0)
	c4 := math.Floor(c / 4.0)
	h := float64(int(19.0*g+c-c4-math.Floor((8.0*c+13)/25)+15) % 30.0)
	k := math.Floor(h / 28.0)
	i := (k*math.Floor(29./(h+1.))*math.Floor((21.-g)/11.)-1.)*k + h

	// jour de Pâques (0=dimanche, 1=lundi....)
	dayWeek := int(math.Floor(float64(year)/4.)+float64(year)+i+2+c4-c) % 7

	// Jour de Pâques en jours enpartant de 1 = 1er mars
	presJour := int(28 + int(i) - dayWeek)

	// mois (0 = janvier, ... 2 = mars, 3 = avril)
	month := 2
	if presJour > 31 {
		month = 3
	}

	// Mois dans l'année
	month += 1

	// jour du mois
	day := presJour - 31
	if month == 2 {
		day = presJour
	}

	return time.Date(year, 3, 31, 0, 0, 0, 0, cal.Location).AddDate(0, 0, day)
}

func (cal *Calendar) GetHolidays(year int) *[]time.Time {

	// Calcul du jour de pâques
	paques := cal.GetEasterDay(year)

	joursFeries := []time.Time{
		// Jour de l'an
		time.Date(year, time.January, 1, 0, 0, 0, 0, cal.Location),
		// Easter
		paques.AddDate(0, 0, 1),
		// 1 mai
		time.Date(year, time.May, 1, 0, 0, 0, 0, cal.Location),
		// 8 mai
		time.Date(year, time.May, 8, 0, 0, 0, 0, cal.Location),
		// Ascension
		paques.AddDate(0, 0, 39),
		// 14 juillet
		time.Date(year, time.July, 14, 0, 0, 0, 0, cal.Location),
		// 15 aout
		time.Date(year, time.August, 15, 0, 0, 0, 0, cal.Location),
		// Toussaint
		time.Date(year, time.November, 1, 0, 0, 0, 0, cal.Location),
		// 11 novembre
		time.Date(year, time.November, 11, 0, 0, 0, 0, cal.Location),
		// noël
		time.Date(year, time.December, 25, 0, 0, 0, 0, cal.Location),
	}

	return &joursFeries
}

func (cal *Calendar) GetHolidaysSet(year int) map[time.Time]bool {
	holidays := cal.GetHolidays(year)
	result := make(map[time.Time]bool, len(*holidays))
	for _, h := range *holidays {
		result[h] = true
	}
	return result
}

func (cal *Calendar) IsHoliday(date time.Time) bool {
	h := cal.GetHolidaysSet(date.Year())
	d := date.In(cal.Location)
	day := time.Date(d.Year(), d.Month(), d.Day(), 0, 0, 0, 0, cal.Location)
	caldavHolidays, err := cal.IsHolidaysFromCaldav(day)
	if err != nil {
		zap.S().Errorf("unable to check holidays from caldav: %v", err)
	}
	return h[day] || caldavHolidays
}

func (cal *Calendar) IsWorkingDay(date time.Time) bool {
	return !cal.IsHoliday(date) && date.Weekday() >= time.Monday && date.Weekday() <= time.Friday
}

func (cal *Calendar) IsWorkingDayToday() bool {
	return cal.IsWorkingDay(time.Now())
}

func (cal *Calendar) IsWeekDay(day time.Time) bool {
	return day.Weekday() >= time.Monday && day.Weekday() <= time.Friday
}

func (cal *Calendar) IsHolidaysFromCaldav(day time.Time) (bool, error) {
	if cal.cdav == nil {
		return false, nil
	}
	query, err := entities.NewEventRangeQuery(day.UTC(), day.UTC().Add(23*time.Hour+59*time.Minute))
	if err != nil {
		return false, fmt.Errorf("unable to build events range query: %v", err)
	}
	events, err := cal.cdav.QueryEvents(cal.caldavPath, query)
	if err != nil {
		return false, fmt.Errorf("unable list events from caldav: %v", err)
	}

	for _, evt := range events {
		if strings.Contains(evt.Summary, cal.caldavSummaryPattern) {
			return true, nil
		}
	}
	return false, nil
}