package web

import (
	"bytes"
	"encoding/binary"
	"fmt"
	"html/template"
	"log/slog"
	"net/http"
	"strings"
	"time"

	"tug/internal/transport/web/text"
)

const (
	flashCookie = "__Host-authsvc_flash"
	flashTTL    = 60 * time.Second
)

func (k *Kit) SetFlash(w http.ResponseWriter, key text.Key, v Ident) error {
	if !key.IsFlash() {
		return fmt.Errorf("web: %q is not a flash key", key)
	}
	if _, err := lookup(key); err != nil {
		return err
	}
	setCookie(w, flashCookie, k.sealFlash(key, v, k.now()), int(flashTTL/time.Second))
	return nil
}

func (k *Kit) sealFlash(key text.Key, v Ident, now time.Time) string {
	payload := binary.BigEndian.AppendUint64(nil, uint64(now.Add(flashTTL).Unix()))
	payload = append(payload, key...)
	payload = append(payload, 0)
	payload = append(payload, v...)
	return seal(k.keys.flash, payload)
}

func (k *Kit) takeFlash(w http.ResponseWriter, r *http.Request) template.HTML {
	c, err := r.Cookie(flashCookie)
	if err != nil {
		return ""
	}
	setCookie(w, flashCookie, "", -1)
	payload, err := unseal(k.keys.flash, c.Value)
	if err != nil || len(payload) < 9 || k.now().Unix() > int64(binary.BigEndian.Uint64(payload[:8])) {
		return ""
	}
	key, v, _ := bytes.Cut(payload[8:], []byte{0})
	fk := text.Key(key)
	if !fk.IsFlash() {
		return ""
	}
	s, err := lookup(fk)
	if err != nil {
		return ""
	}
	if !strings.Contains(s, identMarker) {
		return template.HTML(template.HTMLEscapeString(s))
	}
	out, err := translate(fk, Ident(v))
	if err != nil || len(v) == 0 {
		slog.Warn("flash not shown", "key", string(fk))
		return ""
	}
	return out
}