GoServiceGenerator/templates/app.tmpl

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"net/http"
	"os"
	"os/signal"
	"strconv"
	"strings"
	"syscall"
	"time"
  "{{.URL}}/{{.Name}}/data"
  
	_ "github.com/lib/pq"
	"github.com/nats-io/go-nats"
)

type AppError struct {
  error
  Action string
  Data   string
}

type EventMessage struct {
  Status    string
  DataType  string
  Data      interface{}
}

type response struct {
	Message string `json:"message"`
}

func initializeNats() (*nats.EncodedConn, error) {
	nc, err := nats.Connect(nats.DefaultURL)
	if err != nil {
		return nil, err
	}
	c, err := nats.NewEncodedConn(nc, nats.JSON_ENCODER)
	if err != nil {
		return nil, err
	}
	return c, nil
}

func contextualize(timeout time.Duration) func(next http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		fn := func(w http.ResponseWriter, r *http.Request) {
			ctx, cancel := context.WithTimeout(r.Context(), timeout)
			defer func() {
				cancel()
				if ctx.Err() == context.DeadlineExceeded {
					w.WriteHeader(http.StatusGatewayTimeout)
				}
			}()
			r = r.WithContext(ctx)
			next.ServeHTTP(w, r)
		}
		return http.HandlerFunc(fn)
	}
}

type chanRet struct {
	result []byte
	err    error
  status int
}

func (app *application) runner(w http.ResponseWriter, r *http.Request, task func() *chanRet) {
	fin := make(chan *chanRet, 1)
	go func() {
		fin <- task()
	}()
	select {
	case <-r.Context().Done():
    close(fin)
		return
	case res := <-fin:
		if res.err != nil {
			fmt.Fprint(os.Stderr, res.err)
      app.Publish("error", res.err)
		} 
		w.WriteHeader(res.status)
		w.Write(res.result)
	}
}

type application struct {
	db *db.DB
	events *nats.EncodedConn
}

func (a *application) Publish(action string, v interface{}) {
	subject := strings.ToLower("{{.Name}}.") + action + "." + strconv.Itoa(int(time.Now().Unix()))
  a.events.Flush()
	a.events.Publish(subject, v) 
}

func execByVerb(r *http.Request, post func(body []byte) ([]byte, error), get func(key string) ([]byte, error), delete func(key string) error) *chanRet {
	var result []byte
	var err error
	switch r.Method {
	case http.MethodGet:
		key := r.URL.Query().Get("key")
		result, err = get(key)
	case http.MethodPut:
	case http.MethodPost:
		defer r.Body.Close()
		body, bodyReadErr := ioutil.ReadAll(r.Body)
		if bodyReadErr != nil {
			err = bodyReadErr
		} else {
		  result, err = post(body)
    }
  case http.MethodDelete:
		key := r.URL.Query().Get("key")
	  err = delete(key)
    result = []byte{'o', 'k'}
	}
  status := http.StatusOK
  if err != nil {
    status = http.StatusInternalServerError
  } else if err == nil && result == nil {
    status = http.StatusNotFound
  }
	return &chanRet{result, err, status}
}

func (app *application) root(w http.ResponseWriter, r *http.Request) {
	app.runner(w, r, func() *chanRet {
		return execByVerb(r,
			func(body []byte) ([]byte, error) {
				return nil, nil
			},
			func(key string) ([]byte, error) {
				return json.Marshal(&response{Message: "{{.Name}}"})
			},
			func(key string) error {
				return nil
			})
	})
}

{{.GetRoutes}}

func main() {
	newDb, err := db.NewDB()
	if err != nil {
		panic(err)
	}
	nEvents, err := initializeNats()
	if err != nil {
		panic(err)
	}
	app := &application{
		db:     newDb,
		events: nEvents,
	}
	mux := http.NewServeMux()

	mux.Handle("/", contextualize(time.Second*1)(http.HandlerFunc(app.root)))
  {{.MuxHandlers}}
	server := &http.Server{
		Addr: fmt.Sprintf(
			"%s:%d",
			"0.0.0.0",
			9111,
		),
		Handler: mux,
	}
	serverStartup := make(chan error, 1)

	go func() {
		serverStartup <- server.ListenAndServe()
	}()
	osSignals := make(chan os.Signal, 1)
	signal.Notify(
		osSignals,
		syscall.SIGINT,
		syscall.SIGTERM,
		syscall.SIGKILL,
		syscall.SIGQUIT,
	)
	select {
	case sig := <-osSignals:
		fmt.Printf(sig.String())
	case err := <-serverStartup:
		fmt.Printf(err.Error())
	}
	fmt.Printf("\n\nADIOS! TOT ZIENS! HASTA LUEGO!\n")
}