impl sender watcher and queue

services/sender.go

@@ -3,33 +3,45 @@ package services
 import (
 	cfg "mailsrv/config"
 	"mailsrv/mail"
+	"mailsrv/runtime"
+	"os"
+	"path"
+	"strings"
+	"time"
 
 	"github.com/go-kit/kit/log"
 	"github.com/go-kit/kit/log/level"
 	"net/smtp"
 )
 
+const (
+	TickerInterval time.Duration = 10 * time.Second
+	JSONSuffix     string        = ".json"
+)
+
 type Sender struct {
-	SMTPConfig cfg.SMTPConfig
+	smtpConfig cfg.SMTPConfig
 	logger     log.Logger
 	// fetch this directory to collect `.json` e-mail format
-	OutboxPath string
+	outboxPath string
+	queue      *runtime.Queue
 }
 
 func NewSender(logger log.Logger, config cfg.SMTPConfig, outboxPath string) Sender {
 	logger = log.With(logger, "actor", "sender")
 	return Sender{
-		SMTPConfig: config,
+		smtpConfig: config,
 		logger:     logger,
-		OutboxPath: outboxPath,
+		outboxPath: outboxPath,
+		queue:      runtime.NewQueue(),
 	}
 }
 
 func (s Sender) SendMail(email mail.Email) error {
-	auth := smtp.PlainAuth("", s.SMTPConfig.User, s.SMTPConfig.Password, s.SMTPConfig.Url)
+	auth := smtp.PlainAuth("", s.smtpConfig.User, s.smtpConfig.Password, s.smtpConfig.Url)
 	s.logger.Log("action", "authentication succeed")
 
-	if err := smtp.SendMail(s.SMTPConfig.GetFullUrl(), auth, email.Sender, email.Receivers, email.Generate()); err != nil {
+	if err := smtp.SendMail(s.smtpConfig.GetFullUrl(), auth, email.Sender, email.Receivers, email.Generate()); err != nil {
 		level.Error(s.logger).Log("msg", "error while sending email", "err", err)
 		return err
 	}
@@ -37,3 +49,65 @@ func (s Sender) SendMail(email mail.Email) error {
 	s.logger.Log("msg", "mail send successfully")
 	return nil
 }
+
+// every `TickerInterval` reads the `outbox` directory and put JSON format e-mail in the queue
+func (s Sender) watchOutbox() {
+	ticker := time.NewTicker(TickerInterval)
+	go func() {
+		for _ = range ticker.C {
+			s.logger.Log("action", "retrieving json e-mail format...", "path", s.outboxPath)
+
+			files, err := os.ReadDir(s.outboxPath)
+			if err != nil && !os.IsExist(err) {
+				level.Error(s.logger).Log("msg", "outbox directory does not exist", "err", err)
+				s.queue.Shutdown()
+			}
+
+			for _, file := range files {
+				filename := file.Name()
+				if strings.HasSuffix(filename, JSONSuffix) {
+					s.queue.Add(path.Join(s.outboxPath, filename))
+					continue
+				}
+				level.Warn(s.logger).Log("msg", "incorrect suffix", "filename", filename)
+			}
+		}
+	}()
+}
+
+// loops over the queue and send email
+func (s Sender) processNextMail() bool {
+	item, quit := s.queue.Get()
+	if quit {
+		return false
+	}
+	defer s.queue.Done(item)
+
+	path, ok := item.(string)
+	if !ok {
+		level.Error(s.logger).Log("msg", "unable to cast queue item into mail.Email")
+		return true
+	}
+
+	email, err := mail.FromJSON(path)
+	if err != nil {
+		level.Error(s.logger).Log("msg", "unable to parse JSON email", "err", err)
+		return true
+	}
+
+	s.SendMail(email)
+
+	if err := os.Remove(path); err != nil {
+		level.Error(s.logger).Log("msg", "unable to remove the JSON email", "path", path, "err", err)
+	}
+
+	return true
+}
+
+func (s Sender) Run() {
+	s.logger.Log("msg", "sender service is running")
+
+	s.watchOutbox()
+	for s.processNextMail() {
+	}
+}