package remind

import (
	"fmt"
	"strings"
	"time"
	"unicode"
)

func formatWhen(timestamp time.Time, loc *time.Location) string {
	day := "più tardi"
	_, todaym, todayd := time.Now().Date()
	_, targetm, targetd := timestamp.Date()
	if todaym != targetm || todayd != targetd {
		day = "il " + timestamp.In(loc).Format("2/1")
	}

	return fmt.Sprintf("%s alle %s", day, timestamp.In(loc).Format("15:04:05"))
}

func isSscanfValid(n int, err error) bool {
	return err == nil
}

func scanMixedDelay(str string) (bool, time.Time, error) {
	remaining := str
	now := time.Now()
	num := 0
	sep := ' '
	for len(remaining) > 1 {
		_, err := fmt.Sscanf(remaining, "%d%c", &num, &sep)
		if err != nil {
			return false, now, err
		}
		dur := time.Duration(num)
		switch unicode.ToLower(sep) {
		case 's':
			dur *= time.Second
		case 'm':
			dur *= time.Minute
		case 'h':
			dur *= time.Hour
		case 'd':
			dur *= time.Hour * 24
		default:
			return true, now, fmt.Errorf("La durata ha una unità che non conosco, usa una di queste: s (secondi) m (minuti) h (ore) d (giorni)")
		}
		now = now.Add(dur)
		nextIndex := strings.IndexRune(remaining, sep)
		remaining = remaining[nextIndex+1:]
	}
	fmt.Printf("tot: %s", now.Sub(time.Now()))
	return true, now, nil
}

func parseDuration(date string, loc *time.Location) (time.Time, error) {
	now := time.Now().In(loc)
	hour := now.Hour()
	min := now.Minute()
	sec := now.Second()
	day := now.Day()
	month := now.Month()
	year := now.Year()
	dayunspecified := false
	isDurationFmt, duration, err := scanMixedDelay(date)
	switch {
	case isSscanfValid(fmt.Sscanf(date, "%d/%d/%d-%d:%d:%d", &day, &month, &year, &hour, &min, &sec)):
	case isSscanfValid(fmt.Sscanf(date, "%d/%d/%d-%d:%d", &day, &month, &year, &hour, &min)):
		sec = 0
	case isSscanfValid(fmt.Sscanf(date, "%d/%d/%d", &day, &month, &year)):
		hour = now.Hour()
		min = now.Minute()
		sec = now.Second()
	case isSscanfValid(fmt.Sscanf(date, "%d:%d:%d", &hour, &min, &sec)):
		day = now.Day()
		month = now.Month()
		year = now.Year()
		dayunspecified = true
	case isSscanfValid(fmt.Sscanf(date, "%d:%d", &hour, &min)):
		day = now.Day()
		month = now.Month()
		year = now.Year()
		sec = 0
		dayunspecified = true
	case isDurationFmt:
		return duration, err
	default:
		return now, fmt.Errorf("Non capisco quando dovrei ricordartelo!")
	}
	targetDate := time.Date(year, month, day, hour, min, sec, 0, loc)
	if targetDate.Before(now) {
		// If day was not specified assume tomorrow
		if dayunspecified {
			targetDate = targetDate.Add(time.Hour * 24)
		} else {
			return now, fmt.Errorf("Non posso ricordarti cose nel passato!")
		}
	}
	if targetDate.After(now.Add(reminderMaxDuration)) {
		return now, fmt.Errorf("Non credo riuscirei a ricordarmi qualcosa per così tanto")
	}
	return targetDate, nil
}