first-golang-simpleServer.go

first-golang-simpleServer.go

package main

import (
	"encoding/json"
	"fmt"
	"net/http"
	"net/url"
	"strconv"
	"strings"
)

type UserDetail struct {
	Username string
	Password string
	Email    string
}
type User struct {
	Id   int        `json:"id"`
	User UserDetail `json:"user"`
}

var firstUserDetail = UserDetail{
	Username: "Daniel",
	Password: "12345",
	Email:    "[email protected]",
}
var secondUserDetail = UserDetail{
	Username: "Daniel2",
	Password: "67890",
	Email:    "[email protected]",
}
var Users []User
var usersCount = 0

func addUser(count int, detail UserDetail) {
	var newUser = User{count, detail}
	Users = append(Users, newUser)
	usersCount++
}

func init() {
	fmt.Println("Initializing server...")
	addUser(usersCount, firstUserDetail)
	addUser(usersCount, secondUserDetail)
	fmt.Println("Initial Users :", Users)
}

func handler(w http.ResponseWriter, request *http.Request) {
	u, err := url.Parse(request.RequestURI)
	if err != nil {
		panic(err)
	}
	if request.Method == "GET" {
		var id = strings.Split(u.Path, "/")
		if len(id) < 3 { //No Id
			js, err := json.Marshal(Users)
			if err != nil {
				http.Error(w, err.Error(), http.StatusInternalServerError)
				return
			}
			w.Header().Set("Content-Type", "application/json")
			w.WriteHeader(http.StatusOK)
			w.Write(js)
			return
		} else if len(id) == 3 {
			requestedId, convError := strconv.Atoi(id[2])
			if convError != nil {
				http.Error(w, convError.Error(), http.StatusInternalServerError)
				return
			}
			for i := 0; i < len(Users); i++ {
				if Users[i].Id == requestedId {
					js, err := json.Marshal(Users[i])
					if err != nil {
						http.Error(w, err.Error(), http.StatusInternalServerError)
						return
					}
					w.Header().Set("Content-Type", "application/json")
					w.WriteHeader(http.StatusOK)
					w.Write(js)
					return
				}
			}

			fmt.Println("ID ", requestedId, "Not Found")
			w.WriteHeader(http.StatusNotFound)
			return
		}
		return
	}

	if request.Method == "POST" {
		decoder := json.NewDecoder(request.Body)
		var u UserDetail
		err = decoder.Decode(&u)
		if err != nil {
			panic(err)
		}
		addUser(usersCount, u)
		w.WriteHeader(http.StatusCreated)
		return
	}

	if request.Method == "PATCH" {
		var id = strings.Split(u.Path, "/")

		if len(id) < 3 { //No Id
			fmt.Println("Update without ID not implemented.")
			w.WriteHeader(http.StatusNotImplemented)
			return
		} else if len(id) == 3 {
			requestedId, convError := strconv.Atoi(id[2])
			if convError != nil {
				http.Error(w, convError.Error(), http.StatusInternalServerError)
				return
			}
			for i := 0; i < len(Users); i++ {
				if Users[i].Id == requestedId {
					decoder := json.NewDecoder(request.Body)
					var u UserDetail
					err = decoder.Decode(&u)
					if err != nil {
						panic(err)
					}
					newUser := User{requestedId, u}
					// update array
					leftSide := append(Users[:i], newUser)
					Users = append(leftSide, Users[i+1:]...)

					fmt.Println("Successful Update, ID:", requestedId)
					// send the deleted element
					w.WriteHeader(http.StatusAccepted)
					return
				}
			}

			//no match
			fmt.Println("Update Failed: ID", requestedId, "Not Found")
			w.WriteHeader(http.StatusNotFound)
			return
		}
		return
	}

	if request.Method == "DELETE" {
		var id = strings.Split(u.Path, "/")

		if len(id) < 3 { //No Id
			fmt.Println("Delete without ID not implemented.")
			w.WriteHeader(http.StatusNotImplemented)
			return
		} else if len(id) == 3 {
			requestedId, convError := strconv.Atoi(id[2])
			if convError != nil {
				http.Error(w, convError.Error(), http.StatusInternalServerError)
				return
			}
			for i := 0; i < len(Users); i++ {
				if Users[i].Id == requestedId {
					js, err := json.Marshal(Users[i])
					if err != nil {
						http.Error(w, err.Error(), http.StatusInternalServerError)
						return
					}
					Users = append(Users[:i], Users[i+1:]...)
					fmt.Println("Successful Delete, ID:", requestedId)
					w.WriteHeader(http.StatusAccepted)
					w.Write(js)
					return
				}
			}
			fmt.Println("Delete Failed: ID ", requestedId, "Not Found")
			w.WriteHeader(http.StatusNotFound)
			return
		}
	}
}

func main() {
	mux := http.NewServeMux()
	mux.HandleFunc("/", handler)
	fmt.Println("Listening...")
	fmt.Println("Users...", Users)
	http.ListenAndServe(":8000", mux)
}

I think I could use advice on the following: (resources/examples appreciated)

• 12-32 removing globals
• idiomatic ways to:
  • (34) move manipulation of my Users slice into functions, for update/delete
  • (111) check if a url param exists
  • add statuscodes
  • encode/decode JSON
  • do error checking
• Using an interface for the following:
  • adding add/update/delete methods for Users
  • when UPDATE receives incomplete details for a user, the server will fail. I'd like to only updating specific fields
  • 2-3 other things?
• any packages/patterns I should be using
• anything else you can think of!