main.go

package main

import (
	"encoding/json"
	"log"
	"net/http"
	"os"
	"strconv"
	"strings"

	"github.com/gorilla/mux"
	"github.com/spf13/cobra"
	"github.com/urfave/negroni"
	"github.com/xyproto/simpleredis/v2"
)

var (
	redisEnabled bool
	masterPool   *simpleredis.ConnectionPool
	replicaPool  *simpleredis.ConnectionPool

	// in-memory guestbook
	guestbookEntries = make([]string, 0)
)

func ListRangeHandler(rw http.ResponseWriter, req *http.Request) {
	key := mux.Vars(req)["key"]
	var membersJSON []byte
	if redisEnabled {
		list := simpleredis.NewList(replicaPool, key)
		members := HandleError(list.GetAll()).([]string)
		membersJSON = HandleError(json.MarshalIndent(members, "", "  ")).([]byte)
	} else {
		membersJSON = HandleError(json.MarshalIndent(guestbookEntries, "", "  ")).([]byte)
	}
	_, _ = rw.Write(membersJSON)
}

func ListPushHandler(rw http.ResponseWriter, req *http.Request) {
	key := mux.Vars(req)["key"]
	value := mux.Vars(req)["value"]
	if redisEnabled {
		list := simpleredis.NewList(masterPool, key)
		HandleError(nil, list.Add(value))
	} else {
		guestbookEntries = append(guestbookEntries, value)
	}
	ListRangeHandler(rw, req)
}

func InfoHandler(rw http.ResponseWriter, req *http.Request) {
	var info []byte
	if redisEnabled {
		info = HandleError(masterPool.Get(0).Do("INFO")).([]byte)
	} else {
		info = []byte(`redis not enabled`)
	}
	rw.Write(info)
}

func EnvHandler(rw http.ResponseWriter, req *http.Request) {
	environment := make(map[string]string)
	for _, item := range os.Environ() {
		splits := strings.Split(item, "=")
		key := splits[0]
		val := strings.Join(splits[1:], "=")
		environment[key] = val
	}

	envJSON := HandleError(json.MarshalIndent(environment, "", "  ")).([]byte)
	rw.Write(envJSON)
}

func HandleError(result interface{}, err error) (r interface{}) {
	if err != nil {
		panic(err)
	}
	return result
}

func NewRootCommand() *cobra.Command {
	var (
		port         int64
		redisMaster  string
		redisReplica string
	)

	var rootCmd = &cobra.Command{
		Use:   "guestbook",
		Short: "Guestbook is a simple web application that allows users to leave messages.",
		Run: func(cmd *cobra.Command, args []string) {
			redisEnabled = redisMaster != "" && redisReplica != ""
			if redisEnabled {
				masterPool = simpleredis.NewConnectionPoolHost(redisMaster)
				defer masterPool.Close()
				replicaPool = simpleredis.NewConnectionPoolHost("redis-replica:6379")
				defer replicaPool.Close()
			}

			r := mux.NewRouter()
			r.Path("/lrange/{key}").Methods("GET").HandlerFunc(ListRangeHandler)
			r.Path("/rpush/{key}/{value}").Methods("GET").HandlerFunc(ListPushHandler)
			r.Path("/info").Methods("GET").HandlerFunc(InfoHandler)
			r.Path("/env").Methods("GET").HandlerFunc(EnvHandler)

			n := negroni.Classic()
			n.UseHandler(r)
			n.Run(":" + strconv.FormatInt(port, 10))
		},
	}
	rootCmd.Flags().StringVar(&redisMaster, "redis-master", "", "Redis master (e.g. redis-master:6379)")
	rootCmd.Flags().StringVar(&redisReplica, "redis-replica", "", "Redis replica (e.g. redis-replica:6379)")
	rootCmd.Flags().Int64Var(&port, "port", 3000, "Listening port")
	return rootCmd
}

func main() {
	cmd := NewRootCommand()
	if err := cmd.Execute(); err != nil {
		log.Fatal(err)
	}
}