http.go

package main

import (
	"context"
	"encoding/json"
	"log"
	"net/http"
	"strconv"
	"strings"
)

func (s *dispatcherSets) startHTTP(ctx context.Context, addr string) {
	http.HandleFunc("/check/", s.handleIPCheckRequest)
	http.HandleFunc("/dispatcher/", s.handleListSetRequest)
	http.HandleFunc("/dispatchers/", s.handleListSetRequest)

	log.Fatalln(http.ListenAndServe(addr, nil))
}

// Check IP address for membership in a dispatcher set.
// URL:  /check/<setID>/<ip>
func (s *dispatcherSets) handleIPCheckRequest(w http.ResponseWriter, r *http.Request) {
	pieces := strings.Split(strings.TrimPrefix(r.URL.Path, "/check/"), "/")
	if len(pieces) != 2 {
		w.WriteHeader(http.StatusBadRequest)
		return
	}

	setID, err := strconv.Atoi(pieces[0])
	if err != nil {
		w.WriteHeader(http.StatusBadRequest)
		return
	}

	if s.validateSetMember(setID, pieces[1]) {
		w.WriteHeader(http.StatusOK)
		return
	}

	w.WriteHeader(http.StatusNotFound)
}

// Return a given dispatcher set
// URL:  /dispatcher/<setID>
func (s *dispatcherSets) handleListSetRequest(w http.ResponseWriter, r *http.Request) {
	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 {
		w.Header().Add("Content-Type", "application/json")

		if err = json.NewEncoder(w).Encode(selectedSet.Hosts()); err != nil {
			w.WriteHeader(http.StatusInternalServerError)
		}
		return
	}

	w.WriteHeader(http.StatusNotFound)
}