package sitemap

import (
	"net/http"
	"strconv"
	"time"
)

type ChangeFreq string

const (
	ChangeFreqAlways  ChangeFreq = "always"
	ChangeFreqNever   ChangeFreq = "never"
	ChangeFreqHourly  ChangeFreq = "hourly"
	ChangeFreqDaily   ChangeFreq = "daily"
	ChangeFreqWeekly  ChangeFreq = "weekly"
	ChangeFreqMonthly ChangeFreq = "monthly"
	ChangeFreqYearly  ChangeFreq = "yearly"
)

type URL struct {
	Loc        string
	ChangeFreq ChangeFreq
	Priority   float64
	LastMod    time.Time
}

type internalURL struct {
	Loc        string
	ChangeFreq ChangeFreq
	Priority   string
	// Date in ISO 8601 format.
	LastMod string
}

func convertURLs(urlset []URL) []internalURL {
	res := make([]internalURL, 0, len(urlset))

	for _, url := range urlset {
		res = append(res, internalURL{
			Loc:        url.Loc,
			ChangeFreq: url.ChangeFreq,
			Priority:   formatPriority(url.Priority),
			LastMod:    formatLastMod(url.LastMod),
		})
	}

	return res
}

func formatLastMod(lastMod time.Time) string {
	if lastMod.IsZero() {
		return ""
	}

	return lastMod.Format("2006-01-02")
}

func formatPriority(priority float64) string {
	if priority < 0.0 {
		priority = 0.0
	}

	if priority > 1.0 {
		priority = 1.0
	}

	return strconv.FormatFloat(priority, 'f', 1, 64)
}

func Execute(w http.ResponseWriter, urlset []URL) error {
	if parsingError != nil {
		return parsingError
	}

	w.Header().Set("Content-Type", "application/xml")

	internalURLSet := convertURLs(urlset)
	return parsedTemplate.Execute(w, internalURLSet)
}