learning_go/testing/go-code-samples/go-rest-demo/cmd/standardlib/main.go

package main

import (
	"encoding/json"
	"net/http"
	"regexp"

	"github.com/gosimple/slug"
	"github.com/xNok/go-rest-demo/pkg/recipes"
)

var (
	RecipeRe       = regexp.MustCompile(`^/recipes/*$`)
	RecipeReWithID = regexp.MustCompile(`^/recipes/([a-z0-9]+(?:-[a-z0-9]+)+)$`)
)

func main() {

	// create the Store and Recipe Handler
	store := recipes.NewMemStore()
	recipesHandler := NewRecipesHandler(store)

	// Create a new request multiplexer
	// Takes incoming requests and dispatch them to the matching handlers
	mux := http.NewServeMux()

	// Register the routes and handlers
	mux.Handle("/", &homeHandler{})
	mux.Handle("/recipes", recipesHandler)
	mux.Handle("/recipes/", recipesHandler)

	// Run the server
	http.ListenAndServe(":8080", mux)
}

type homeHandler struct{}

func (h *homeHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	w.Write([]byte("This is my home page"))
}

func InternalServerErrorHandler(w http.ResponseWriter, r *http.Request) {
	w.WriteHeader(http.StatusInternalServerError)
	w.Write([]byte("500 Internal Server Error"))
}

func NotFoundHandler(w http.ResponseWriter, r *http.Request) {
	w.WriteHeader(http.StatusNotFound)
	w.Write([]byte("404 Not Found"))
}

// recipeStore represent a data storage containing recipes
type recipeStore interface {
	Add(name string, recipe recipes.Recipe) error
	Get(name string) (recipes.Recipe, error)
	List() (map[string]recipes.Recipe, error)
	Update(name string, recipe recipes.Recipe) error
	Remove(name string) error
}

// RecipesHandler implements http.Handler and dispatch request to the store
type RecipesHandler struct {
	store recipeStore
}

func NewRecipesHandler(s recipeStore) *RecipesHandler {
	return &RecipesHandler{
		store: s,
	}
}

func (h *RecipesHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	switch {
	case r.Method == http.MethodPost && RecipeRe.MatchString(r.URL.Path):
		h.CreateRecipe(w, r)
		return
	case r.Method == http.MethodGet && RecipeRe.MatchString(r.URL.Path):
		h.ListRecipes(w, r)
		return
	case r.Method == http.MethodGet && RecipeReWithID.MatchString(r.URL.Path):
		h.GetRecipe(w, r)
		return
	case r.Method == http.MethodPut && RecipeReWithID.MatchString(r.URL.Path):
		h.UpdateRecipe(w, r)
		return
	case r.Method == http.MethodDelete && RecipeReWithID.MatchString(r.URL.Path):
		h.DeleteRecipe(w, r)
		return
	default:
		NotFoundHandler(w, r)
		return
	}
}

func (h *RecipesHandler) CreateRecipe(w http.ResponseWriter, r *http.Request) {
	// Recipe object that will be populated from json payload
	var recipe recipes.Recipe

	if err := json.NewDecoder(r.Body).Decode(&recipe); err != nil {
		InternalServerErrorHandler(w, r)
		return
	}

	resourceID := slug.Make(recipe.Name)

	if err := h.store.Add(resourceID, recipe); err != nil {
		InternalServerErrorHandler(w, r)
		return
	}

	w.WriteHeader(http.StatusOK)
}

func (h *RecipesHandler) ListRecipes(w http.ResponseWriter, r *http.Request) {
	recipesList, err := h.store.List()

	jsonBytes, err := json.Marshal(recipesList)
	if err != nil {
		InternalServerErrorHandler(w, r)
		return
	}

	w.WriteHeader(http.StatusOK)
	w.Write(jsonBytes)
}

func (h *RecipesHandler) GetRecipe(w http.ResponseWriter, r *http.Request) {
	matches := RecipeReWithID.FindStringSubmatch(r.URL.Path)
	if len(matches) < 2 {
		InternalServerErrorHandler(w, r)
		return
	}

	recipe, err := h.store.Get(matches[1])
	if err != nil {
		if err == recipes.NotFoundErr {
			NotFoundHandler(w, r)
			return
		}

		InternalServerErrorHandler(w, r)
		return
	}

	jsonBytes, err := json.Marshal(recipe)
	if err != nil {
		InternalServerErrorHandler(w, r)
		return
	}

	w.WriteHeader(http.StatusOK)
	w.Write(jsonBytes)
}

func (h *RecipesHandler) UpdateRecipe(w http.ResponseWriter, r *http.Request) {
	matches := RecipeReWithID.FindStringSubmatch(r.URL.Path)
	if len(matches) < 2 {
		InternalServerErrorHandler(w, r)
		return
	}

	// Recipe object that will be populated from JSON payload
	var recipe recipes.Recipe
	if err := json.NewDecoder(r.Body).Decode(&recipe); err != nil {
		InternalServerErrorHandler(w, r)
		return
	}

	if err := h.store.Update(matches[1], recipe); err != nil {
		if err == recipes.NotFoundErr {
			NotFoundHandler(w, r)
			return
		}
		InternalServerErrorHandler(w, r)
		return
	}

	w.WriteHeader(http.StatusOK)
}

func (h *RecipesHandler) DeleteRecipe(w http.ResponseWriter, r *http.Request) {
	matches := RecipeReWithID.FindStringSubmatch(r.URL.Path)
	if len(matches) < 2 {
		InternalServerErrorHandler(w, r)
		return
	}

	if err := h.store.Remove(matches[1]); err != nil {
		InternalServerErrorHandler(w, r)
		return
	}

	w.WriteHeader(http.StatusOK)
}