package api

import (
	"net/http"

	"git.golem15.com/golem15/sm-seo-plugin/classes"
)

// Robots serves GET /robots.txt (D-22, D-25, P-23) as text/plain. In
// production it is the stored rules, a Disallow group for every
// switched-off AI bot and the Sitemap lines; outside production it is
// "User-agent: *" / "Disallow: /" with X-Robots-Tag: noindex, nofollow,
// whatever is stored, and no admin setting can change that. It never
// answers a 5xx: when the stored file cannot be read it serves the last
// body it served, else an allow-all file, and logs the error.
func Robots(service func() *classes.Service) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		svc := service()
		body := classes.FallbackRobots
		staging := false
		if svc == nil {
			log.Error("golem15.seo: robots.txt served before boot")
		} else {
			staging = svc.Staging()
			served, err := svc.ServedFile(r.Context(), !staging)
			switch {
			case err == nil:
				body = served
			case svc.LastServedRobots() != "":
				log.Error("golem15.seo: robots.txt, serving the last good file", "error", err)
				body = svc.LastServedRobots()
			default:
				log.Error("golem15.seo: robots.txt, serving the allow-all fallback", "error", err)
			}
		}
		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
		if staging {
			w.Header().Set("X-Robots-Tag", "noindex, nofollow")
		}
		w.WriteHeader(http.StatusOK)
		_, _ = w.Write([]byte(body))
	}
}