package auth

import (
	"encoding/json"
	"io"
	"net/http"
	"strings"
	"sync"
	"time"
)

const defaultFrontierTemplate = "https://launcher.finalfantasyxiv.com/v740/index.html?rc_lang={0}&time={1}"

var (
	templateOnce sync.Once
	frontierTpl  string
)

// frontierReferer builds the Referer header value SE's login page expects,
// e.g. https://launcher.finalfantasyxiv.com/v740/index.html?rc_lang=en_us&time=2026-10-10-12-34
func frontierReferer() string {
	templateOnce.Do(func() {
		frontierTpl = fetchFrontierTemplate()
	})

	tpl := strings.ReplaceAll(frontierTpl, "{0}", "en_us")
	return strings.ReplaceAll(tpl, "{1}", time.Now().UTC().Format("2006-01-02-15-04"))
}

func fetchFrontierTemplate() string {
	client := &http.Client{Timeout: 5 * time.Second}
	resp, err := client.Get("https://kamori.goats.dev/Launcher/GetLauncherClientConfig")
	if err != nil {
		return defaultFrontierTemplate
	}
	defer resp.Body.Close()
	var cfg struct {
		FrontierUrl string `json:"frontierUrl"`
	}
	body, _ := io.ReadAll(resp.Body)
	if err := json.Unmarshal(body, &cfg); err != nil || cfg.FrontierUrl == "" {
		return defaultFrontierTemplate
	}
	return cfg.FrontierUrl
}