Added new ServeHTTP end point for fetching dispatcher set (#5)

main.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"context"
+	"encoding/json"
 	"flag"
 	"fmt"
 	"io"
@@ -156,7 +157,7 @@ func (s *dispatcherSets) maintain(ctx context.Context) error {
 	return ctx.Err()
 }
 
-// ServeHTTP offers a web service by which clients may validate membership of an IP address within a dispatcher set
+// ServeHTTP offers a web service by which clients may validate membership of an IP address within a dispatcher set or fetch a dispatcher set
 func (s *dispatcherSets) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	// Handle requests for /check/<setID>/<ip address> to validate membership of an IP to a dispatcher set
 	if strings.HasPrefix(r.URL.Path, "/check/") {
@@ -176,6 +177,27 @@ func (s *dispatcherSets) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		}
 		w.WriteHeader(http.StatusNotFound)
 		return
+	} else if strings.HasPrefix(r.URL.Path, "/dispatcher/") { // Handle requests for /dispatcher/<setID> to fetch a dispatcher set
+		pieces := strings.Split(strings.TrimPrefix(r.URL.Path, "/dispatcher/"), "/")
+		if len(pieces) != 1 {
+			w.WriteHeader(http.StatusBadRequest)
+			return
+		}
+		setID, err := strconv.Atoi(pieces[0])
+		if err != nil {
+			w.WriteHeader(http.StatusBadRequest)
+			return
+		}
+		selectedSet := s.getDispatcherSet(setID)
+		if selectedSet != nil {
+			js, err := json.Marshal(selectedSet)
+			if err != nil {
+				w.WriteHeader(http.StatusInternalServerError)
+				return
+			}
+			w.Write(js) //If WriteHeader has not yet been called, Write calls WriteHeader(http.StatusOK) before writing the data
+			return
+		}
 	}
 
 	w.WriteHeader(http.StatusNotFound)
@@ -189,6 +211,14 @@ func (s *dispatcherSets) validateSetMember(id int, addr string) bool {
 	return selectedSet.Validate(addr)
 }
 
+func (s *dispatcherSets) getDispatcherSet(id int) sets.DispatcherSet {
+	selectedSet, ok := s.sets[id]
+	if !ok {
+		return nil
+	}
+	return selectedSet
+}
+
 // notify signals to kamailio to reload its dispatcher list
 func (s *dispatcherSets) notify() error {
 	return binrpc.InvokeMethod("dispatcher.reload", s.rpcHost, s.rpcPort)
@@ -268,7 +298,7 @@ func run() error {
 		}
 	})
 
-	// Run a web service to offer IP checks for each member of the dispatcher set
+	// Run a web service to offer IP checks for each member of the dispatcher set and fetch a dispatcher set
 	if apiAddr != "" {
 		var srv http.Server
 		srv.Addr = apiAddr