package webmiddleware

import (
	"fmt"
	"net/http"

	"git.mstar.dev/mstar/linstrom/config"
)

func AddUpgradeHeader(h http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		switch r.ProtoMajor {
		case 1:
			// Always offer upgrade to http2
			headerText := fmt.Sprintf(
				"h2=\":%d\"; ma=3600",
				config.GlobalConfig.General.GetFinalPublicPort(),
			)
			// Offer upgrade to http3 if enabled
			if config.GlobalConfig.Experimental.Http3Support && config.GlobalConfig.SSL.HandleSSL {
				headerText = fmt.Sprintf(
					"h3=\":%d\"; ma=3600, %s",
					config.GlobalConfig.General.GetFinalPublicPort(),
					headerText,
				)
			}
			w.Header().Add("Alt-Svc", headerText)
		case 2:
			// Offer upgrade to http3 if enabled
			if config.GlobalConfig.Experimental.Http3Support && config.GlobalConfig.SSL.HandleSSL {
				headerText := fmt.Sprintf(
					"h3=\":%d\"; ma=3600",
					config.GlobalConfig.General.GetFinalPublicPort(),
				)
				w.Header().Add("Alt-Svc", headerText)
			}
		}
		h.ServeHTTP(w, r)
	})
}