package middleware

import (
	"net/http"
	"strings"
)

// ForwardedHeaders sets r.URL.Scheme and r.URL.Host from reverse-proxy headers so
// chi RedirectSlashes and other absolute redirects use https behind Cloudflare/nginx.
func ForwardedHeaders(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if proto := strings.TrimSpace(r.Header.Get("X-Forwarded-Proto")); proto != "" {
			if i := strings.IndexByte(proto, ','); i >= 0 {
				proto = strings.TrimSpace(proto[:i])
			}
			r.URL.Scheme = proto
		}
		if host := strings.TrimSpace(r.Header.Get("X-Forwarded-Host")); host != "" {
			if i := strings.IndexByte(host, ','); i >= 0 {
				host = strings.TrimSpace(host[:i])
			}
			r.URL.Host = host
		} else if r.Host != "" {
			r.URL.Host = r.Host
		}
		next.ServeHTTP(w, r)
	})
}