Handlers

Create Campaign Post

• Analyze error after coding

r := chi.NewRouter()
campaignService := campaign.Service{}
hander := handler.Handler{CampaignService: campaignService}
r.Post("/campaigns", hander.CampaignPost)
http.ListenAndServe(":3000", r)

func (h *Handler) CampaignPost(w http.ResponseWriter, r *http.Request) {
	var request contract.NewCampaign
	render.DecodeJSON(r.Body, &request)

	id, err := h.CampaignService.Create(request)

	if err != nil {
		http.Error(w, err.Error(), 400)
	}

	render.Status(r, 202)
	render.JSON(w, r, map[string]string{"id": id})
}

Create memory database

• Show the post working
• Create a second handler to show all the campaigns sent

type CampaignRepository struct {
	Campaigns []campaign.Campaign
}

func (c *CampaignRepository) Save(campaign *campaign.Campaign) error {

	c.Campaigns = append(c.Campaigns, *campaign)

	return nil
}

func (c *CampaignRepository) Get() []campaign.Campaign {
	return c.Campaigns
}

Show custom erros

• Show what is shown when a error on database happens

func (c *CampaignRepository) Save(campaign *campaign.Campaign) error {

	c.Campaigns = append(c.Campaigns, *campaign)

	return errors.New("error to connect to database")
}

• Create a custom error

type ApplicationError struct {
	Err string
}

func (a *ApplicationError) Error() string {
	return a.Err
}

//On campaign_post.go
if err != nil {
	_, ok := err.(*domain.ApplicationError)
	if ok {
		http.Error(w, "internal server error", 500)
	} else {
		http.Error(w, err.Error(), 400)
	}
}

Midlewares

• Show how to create a midlewares
• Show the interface http.Handler
• Show what happens if the midleware gets on the end of route

func MyMidlewareCtx(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {

		println("before")		
		next.ServeHTTP(w, r)
		println("after")
	})
}

• Create a log to show the requests

func MyMidlewareCtx(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {

		println("Method ", r.Method, "URL", r.RequestURI)
		next.ServeHTTP(w, r)
		println("end")
	})
}

• Show the middlewares that Chi has done get github.com/go-chi/chi/middleware

Custom error

• Explain how to create a wrap handlerfunc
• Create a signature to a custom handler func go type HandlerFunc func(w http.ResponseWriter, r *http.Request) (any, int, error)

func errorHandler(handler handler.HandlerFunc) http.HandlerFunc {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		obj, status, err := handler(w, r)
		if err != nil {
			_, ok := err.(*domain.ApplicationError)
			if ok {
				http.Error(w, "internal server error", 500)

			} else {
				http.Error(w, err.Error(), 400)
			}
			return
		}
		render.Status(r, status)
		if obj != nil {
			render.JSON(w, r, obj)
		}

	})
}

func (h *Handler) CampaignPost(w http.ResponseWriter, r *http.Request) (any, int, error) {
	println("handler")
	var request contract.NewCampaign
	render.DecodeJSON(r.Body, &request)

	id, err := h.CampaignService.Create(request)

	if err != nil {
		return nil, 0, err
	}

	return map[string]string{"id": id}, 202, nil
}