udemy-go-microservices/broker-service/cmd/api/handlers.go

package main

import (
	"broker/cmd/api/event"
	"bytes"
	"encoding/json"
	"errors"
	"log"
	"net/http"
)

type RequestPayload struct {
	Action string      `string:"action"`
	Auth   AuthPayload `json:"auth,omitempty"`
	Log    LogPayload  `json:"log,omitempty"`
	Mail   MailPayload `json:"mail,omitempty"`
}

type AuthPayload struct {
	Email    string `json:"email"`
	Password string `json:"password"`
}

type LogPayload struct {
	Name string `json:"name"`
	Data string `json:"data"`
}

type MailPayload struct {
	From    string `json:"from"`
	To      string `json:"to"`
	Subject string `json:"subject"`
	Content string `json:"content"`
}

func (app *Config) Broker(w http.ResponseWriter, r *http.Request) {
	payload := jsonResponse{
		Error:   false,
		Message: "Hit the broker",
	}

	app.writeJSON(w, http.StatusOK, payload)
}

func (app *Config) HandleSubmission(w http.ResponseWriter, r *http.Request) {
	var requestPayload RequestPayload

	err := app.readJSON(w, r, &requestPayload)
	if err != nil {
		app.errorJSON(w, err, http.StatusBadRequest)
		return
	}

	switch requestPayload.Action {
	case "auth":
		app.authenticate(w, requestPayload.Auth)
	case "log":
		// app.LogItem(w, requestPayload.Log)
		app.logEventViaRabbit(w, requestPayload.Log)
	case "mail":
		app.SendMail(w, requestPayload.Mail)
	default:
		app.errorJSON(w, errors.New("unknown action"))
	}
}

func (app *Config) authenticate(w http.ResponseWriter, a AuthPayload) {
	authService := Microservice{
		Input: a,
		Addr:  "http://authentication-service/authenticate",
		ErrCode: statusError{
			ExpectedCode: http.StatusAccepted,
			ErrCode:      http.StatusUnauthorized,
			Err:          errors.New("invalid credentials"),
		},
		SuccessMsg: "Authenticated",
	}
	app.callService(w, authService)
}

func (app *Config) LogItem(w http.ResponseWriter, entry LogPayload) {
	log.Println(entry)
	loggerService := Microservice{
		Input: entry,
		Addr:  "http://logger-service/log",
		ErrCode: statusError{
			ExpectedCode: http.StatusAccepted,
			ErrCode:      http.StatusInternalServerError,
			Err:          errors.New("internal error"),
		},
		SuccessMsg: "Logged!",
	}
	app.callService(w, loggerService)
}

func (app *Config) SendMail(w http.ResponseWriter, entry MailPayload) {
	log.Println(entry)
	mailService := Microservice{
		Input: entry,
		Addr:  "http://mail-service/send-mail",
		ErrCode: statusError{
			ExpectedCode: http.StatusAccepted,
			ErrCode:      http.StatusInternalServerError,
			Err:          errors.New("internal error"),
		},
		SuccessMsg: "Mail sent!",
	}
	app.callService(w, mailService)
}

type statusError struct {
	ExpectedCode int
	ErrCode      int
	Err          error
}

type Microservice struct {
	Input      any
	Addr       string
	ErrCode    statusError
	SuccessMsg string
}

func (app *Config) callService(w http.ResponseWriter, ms Microservice) {
	// create some json we'll send to the microservice
	inputPayload, err := json.MarshalIndent(ms.Input, "", "\t")
	if err != nil {
		app.errorJSON(w, err, http.StatusBadRequest)
		return
	}
	log.Println(ms.Input)

	// call the service
	req, err := http.NewRequest(
		"POST",
		ms.Addr,
		bytes.NewBuffer(inputPayload),
	)
	if err != nil {
		app.errorJSON(w, err, http.StatusBadRequest)
		return
	}
	req.Header.Add("Content-Type", "application/json")
	client := &http.Client{}
	resp, err := client.Do(req)
	if err != nil {
		app.errorJSON(w, err, http.StatusInternalServerError)
		return
	}
	defer resp.Body.Close()

	log.Println(resp.Body)

	// make sure we get back the correct status code
	if resp.StatusCode != ms.ErrCode.ExpectedCode {
		app.errorJSON(w, ms.ErrCode.Err, ms.ErrCode.ErrCode)
		return
	}

	// create a variable we'll read resp.Body into
	var respPayload jsonResponse

	err = json.NewDecoder(resp.Body).Decode(&respPayload)
	if err != nil {
		app.errorJSON(w, err, http.StatusBadRequest)
		return
	}

	if respPayload.Error {
		app.errorJSON(w, errors.New(respPayload.Message))
		return
	}

	var payload jsonResponse
	payload.Error = false
	payload.Message = ms.SuccessMsg
	payload.Data = respPayload.Data

	app.writeJSON(w, http.StatusOK, payload)
}

func (app *Config) logEventViaRabbit(w http.ResponseWriter, l LogPayload) {
	err := app.pushToQueue(l.Name, l.Data)
	if err != nil {
		app.errorJSON(w, err)
		return
	}

	var payload jsonResponse
	payload.Error = false
	payload.Message = "logged via RabbitMQ"

	app.writeJSON(w, http.StatusOK, payload)
}

func (app *Config) pushToQueue(name, msg string) error {
	emitter, err := event.NewEmitter(app.Rabbit)
	if err != nil {
		return err
	}

	payload := LogPayload{
		Name: name,
		Data: msg,
	}

	j, _ := json.MarshalIndent(&payload, "", "\t")
	err = emitter.Push(string(j), "log.INFO")
	if err != nil {
		return err
	}

	return nil
}