package cif

import (
	"errors"
	"time"

	"git.fjla.uk/owlboard/timetable-mgr/log"
	"go.uber.org/zap"
)

// Fetches the day string for the provided date.
func getDayString(t time.Time) string {
	london, err := time.LoadLocation("Europe/London")
	if err != nil {
		log.Msg.Error("Unable to load time zone info", zap.Error(err))
	}

	timeNow := t.In(london)
	day := timeNow.Weekday()

	dayStrings := [...]string{"sun", "mon", "tue", "wed", "thu", "fri", "sat"}

	return dayStrings[day]
}

// Simply returns the correct URL for either a 'daily' or 'full' update.
func getUpdateUrl(updateType string) (string, error) {
	if updateType == "daily" {
		return dailyUpdateUrl, nil
	} else if updateType == "full" {
		return fullUpdateUrl, nil
	}
	err := errors.New("invalid update type provided, must be one of 'daily' or 'full'")
	return "", err
}

// Takes a time.Time as input and returns True if it is
// the same day as now, or false if it is not the same day as now
func isSameToday(t time.Time) bool {
	test := t.In(time.UTC)
	today := time.Now().In(time.UTC)
	return test.Year() == today.Year() && test.Month() == today.Month() && test.Day() == today.Day()
}

// Returns how many days ago `t` was compared to today
func howManyDaysAgo(t time.Time) int {
	today := time.Now().In(time.UTC).Truncate(24 * time.Hour)
	input := t.In(time.UTC).Truncate(24 * time.Hour)

	diff := today.Sub(input)
	days := int(diff.Hours() / 24)
	return days
}

// Generates a slice of time.Time values representing which days files need downloading
func generateUpdateDays(days int) []time.Time {
	var updateDays []time.Time

	for i := 0; i < days; i++ {
		day := time.Now().Add(-time.Duration(i) * 24 * time.Hour)
		updateDays = append(updateDays, day)
	}

	// Reverse slice to ensure chronological order
	for i, j := 0, len(updateDays)-1; i < j; i, j = i+1, j-1 {
		updateDays[i], updateDays[j] = updateDays[j], updateDays[i]
	}

	return updateDays
}

// Parses CIF Schedule Start/End Dates (YYYY-MM-DD) into time.Time types (00:00:00 for start, 23:59:59 for end)
func ParseCifDate(input, startOrEnd string) time.Time {
	layout := "2006-01-02" // Layout of input
	t, err := time.ParseInLocation(layout, input, londonTimezone)
	if err != nil {
		log.Msg.Error("Error parsing date string", zap.String("date string", input), zap.Error(err))
		return time.Time{}
	}

	if startOrEnd == "start" {
		t = time.Date(t.Year(), t.Month(), t.Day(), 0, 0, 0, 0, londonTimezone)
	} else if startOrEnd == "end" {
		t = time.Date(t.Year(), t.Month(), t.Day(), 23, 59, 59, 0, londonTimezone)
	} else {
		log.Msg.Error("Error parsing date string", zap.String("date string", input), zap.Error(err))
		return time.Time{}
	}

	return t
}

// Parses CIF days_run field and converts to array of day strings
func parseDaysRun(daysBinary string) []string {
	shortDays := []string{"m", "t", "w", "th", "f", "s", "su"}
	var result []string
	for i, digit := range daysBinary {
		if digit == '1' {
			result = append(result, shortDays[i])
		}
	}
	return result
}