simple_std_go_api.go

package main

import (
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"regexp"
)

type User struct {
	Id          string `json:"Id"`
	FirstName   string `json:"first_name"`
	LastName    string `json:"last_name"`
	DOB         string `json:"date_of_birth"`
	Email       string `json:"email"`
	PhoneNumber string `json:"phone_number"`
}

type Response struct {
	Status   int `json:"status"`
	Response any `json:"response"`
}

// Index let's declare a global Index array
// that we can then populate in our main function
// to simulate a database
var Index = make(map[string]User)
var (
	getUserRe    = regexp.MustCompile(`^\/users\/(\d+)$`)
	createUserRe = regexp.MustCompile(`^\/users[\/]*$`)
)

func homePage(w http.ResponseWriter, r *http.Request) {
	fmt.Println("Endpoint Hit: homePage")
	response := Response{Status: http.StatusOK, Response: "Welcome to the Simple API!"}
	json.NewEncoder(w).Encode(response)
}

func userHandler(w http.ResponseWriter, r *http.Request) {
	fmt.Println("Endpoint Hit: returnUser")
	switch {
	case r.Method == http.MethodGet && getUserRe.MatchString(r.URL.Path):
		if len(Index) == 0 {
      // if Index is empty, i.e,. no users
			w.WriteHeader(http.StatusNotFound)
			json.NewEncoder(w).Encode(Response{Status: http.StatusNotFound, Response: "Empty database"})
		} else {
			matches := getUserRe.FindStringSubmatch(r.URL.Path)
			user, ok := Index[matches[1]] // check if Index has user.
			if len(matches) < 2 {
        // if url in not in the format `/users/1`
				w.WriteHeader(http.StatusNotFound)
				json.NewEncoder(w).Encode(Response{Status: http.StatusNotFound, Response: "User not found."})
			} else if ok {
        // if Index has the user
				w.WriteHeader(http.StatusOK)
				json.NewEncoder(w).Encode(Response{Status: http.StatusOK, Response: user})
			} else {
        // if Index don't have any user
				w.WriteHeader(http.StatusNotFound)
				json.NewEncoder(w).Encode(Response{Status: http.StatusNotFound, Response: "User not found."})
			}
		}
	case r.Method == http.MethodPost && createUserRe.MatchString(r.URL.Path):
    // case to handle adding a User; IDK if it works 
		var u User
		if err := json.NewDecoder(r.Body).Decode(&u); err != nil {
			w.WriteHeader(http.StatusInternalServerError)
			json.NewEncoder(w).Encode(Response{Status: http.StatusInternalServerError, Response: "Internal Server Error."})
			return
		}
		Index[u.Id] = u
    w.WriteHeader(http.StatusCreated)
    json.NewEncoder(w).Encode(Response{Status: http.StatusCreated, Response: "User added"})
	}

}

func returnAllUsers(w http.ResponseWriter, r *http.Request) {
	fmt.Println("Endpoint Hit: returnAllUsers")
	json.NewEncoder(w).Encode(Index)
}

func handleRequests() {
	http.HandleFunc("/", homePage)
	http.HandleFunc("/users", returnAllUsers)
	http.HandleFunc("/users/", userHandler)

	log.Fatal(http.ListenAndServe(":8080", nil))
}

func main() {
	handleRequests()
}