Spinner/internal/router/router.go

// Package router maps the hostname a client typed to a configured server.
package router

import (
	"sort"
	"strings"

	"git.veillax.com/Veillax/spinner/internal/config"
)

type Router struct {
	exact map[string]*config.Server
	wild  []wildcard
}

type wildcard struct {
	suffix string // ".example.com"
	srv    *config.Server
}

// Normalize lowercases a handshake host and strips the trailing dot and any
// Forge "\0FML\0" suffix.
func Normalize(host string) string {
	if i := strings.IndexByte(host, 0); i >= 0 {
		host = host[:i]
	}
	return strings.ToLower(strings.TrimRight(host, "."))
}

// New builds a router. Exact domains win; wildcards (*.example.com) match any
// depth of subdomain but not the apex, and longer suffixes win over shorter.
func New(cfg *config.Config) *Router {
	r := &Router{exact: map[string]*config.Server{}}
	for i := range cfg.Servers {
		s := &cfg.Servers[i]
		for _, d := range s.Domains {
			d = strings.ToLower(strings.TrimRight(d, "."))
			if rest, ok := strings.CutPrefix(d, "*."); ok {
				r.wild = append(r.wild, wildcard{"." + rest, s})
			} else if _, dup := r.exact[d]; !dup {
				r.exact[d] = s
			}
		}
	}
	sort.SliceStable(r.wild, func(i, j int) bool { return len(r.wild[i].suffix) > len(r.wild[j].suffix) })
	return r
}

func (r *Router) Match(host string) *config.Server {
	host = Normalize(host)
	if s, ok := r.exact[host]; ok {
		return s
	}
	for _, w := range r.wild {
		if strings.HasSuffix(host, w.suffix) && len(host) > len(w.suffix) {
			return w.srv
		}
	}
	return nil
}