email.go

package main

import (
	"gopkg.in/mail.v2"
	"log"
	"os"
	"time"
)

var emailChan chan *mail.Message

func init() {
	emailChan = make(chan *mail.Message)

	go func() {
		d := mail.NewDialer(
			os.Getenv("SMARTALARM_EMAILHOST"),
			587,
			os.Getenv("SMARTALARM_EMAILADDR"),
			os.Getenv("SMARTALARM_EMAILPASS"),
		)
		d.StartTLSPolicy = mail.MandatoryStartTLS

		var s mail.SendCloser
		var err error
		open := false
		for {
			select {
			case m, ok := <-emailChan:
				log.Println("Sending email", m)
				if !ok {
					return
				}
				if !open {
					if s, err = d.Dial(); err != nil {
						panic(err)
					}
					open = true
				}
				if err := mail.Send(s, m); err != nil {
					log.Println(err)
					return
				}

				// Increment "use" counter in DB
				go func(emails []string) {
					if len(emails) != 1 {
						log.Println("Wrong number of emails, not updating DB")
						return
					}

					_, err := db.Exec("UPDATE smartalarm_emails SET uses=uses+1 WHERE email=?", emails[0])
					if err != nil {
						log.Println(err)
					}
				}(m.GetHeader("To"))
			// Close the connection to the SMTP server if no email was sent in
			// the last 5 seconds.
			case <-time.After(5 * time.Second):
				if open {
					log.Println("Closing SMTP connection")
					if err := s.Close(); err != nil {
						log.Println(err)
					}
					open = false
				}
			}
		}
	}()
}