[#149] Add host bucket router

Signed-off-by: Denis Kirillov <d.kirillov@yadro.com>

api/host_bucket_router.go

@@ -0,0 +1,71 @@
+package api
+
+import (
+	"net/http"
+	"strings"
+
+	"github.com/go-chi/chi/v5"
+)
+
+type HostBucketRouter struct {
+	routes        map[string]chi.Router
+	bktParam      string
+	defaultRouter chi.Router
+}
+
+func NewHostBucketRouter(bktParam string) HostBucketRouter {
+	return HostBucketRouter{
+		routes:   make(map[string]chi.Router),
+		bktParam: bktParam,
+	}
+}
+
+func (hr *HostBucketRouter) Default(router chi.Router) {
+	hr.defaultRouter = router
+}
+
+func (hr HostBucketRouter) Map(host string, h chi.Router) {
+	hr.routes[strings.ToLower(host)] = h
+}
+
+func (hr HostBucketRouter) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	bucket, domain := getBucketDomain(getHost(r))
+	router, ok := hr.routes[strings.ToLower(domain)]
+	if !ok {
+		router = hr.defaultRouter
+		if router == nil {
+			http.Error(w, http.StatusText(404), 404)
+			return
+		}
+	}
+
+	if rctx := chi.RouteContext(r.Context()); rctx != nil && bucket != "" {
+		rctx.URLParams.Add(hr.bktParam, bucket)
+	}
+
+	router.ServeHTTP(w, r)
+}
+
+func getBucketDomain(host string) (bucket string, domain string) {
+	parts := strings.Split(host, ".")
+	if len(parts) > 1 {
+		return parts[0], strings.Join(parts[1:], ".")
+	}
+	return "", host
+}
+
+// getHost tries its best to return the request host.
+// According to section 14.23 of RFC 2616 the Host header
+// can include the port number if the default value of 80 is not used.
+func getHost(r *http.Request) string {
+	host := r.Host
+	if r.URL.IsAbs() {
+		host = r.URL.Host
+	}
+
+	if i := strings.Index(host, ":"); i != -1 {
+		host = host[:i]
+	}
+
+	return host
+}