package api

import (
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"net/http"
	"strconv"
)

// handleRemoteConfig serves one app-scoped, immutable-at-runtime document. It is public
// for the same reason the update verdict is public: a fresh install and a signed-out TV
// must be able to warm the next launch. No viewer or session data belongs in this answer.
func (s *Server) handleRemoteConfig(w http.ResponseWriter, r *http.Request) {
	body, err := json.Marshal(s.cfg.RemoteConfig)
	if err != nil {
		// Config is validated during start-up, so this is defensive rather than an expected
		// operational failure.
		writeError(w, http.StatusInternalServerError, "remote configuration unavailable")
		return
	}
	digest := sha256.Sum256(body)
	etag := `"rc-` + hex.EncodeToString(digest[:12]) + `"`
	w.Header().Set("Cache-Control", "no-cache")
	w.Header().Set("ETag", etag)
	w.Header().Set("X-Memby-Config-Version", configVersionHeader(s.cfg.RemoteConfig.ConfigVersion))
	if r.Header.Get("If-None-Match") == etag {
		w.WriteHeader(http.StatusNotModified)
		return
	}
	writeRaw(w, http.StatusOK, body)
}

func configVersionHeader(version int64) string {
	return strconv.FormatInt(version, 10)
}