listmonk/internal/messenger/emailer.go

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package messenger
import (
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"errors"
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"fmt"
"math/rand"
"net/smtp"
"time"
"github.com/jaytaylor/html2text"
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"github.com/jordan-wright/email"
)
const emName = "email"
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// loginAuth is used for enabling SMTP "LOGIN" auth.
type loginAuth struct {
username string
password string
}
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// Server represents an SMTP server's credentials.
type Server struct {
Name string
Host string `koanf:"host"`
Port int `koanf:"port"`
AuthProtocol string `koanf:"auth_protocol"`
Username string `koanf:"username"`
Password string `koanf:"password"`
EmailFormat string `koanf:"email_format"`
HelloHostname string `koanf:"hello_hostname"`
SendTimeout time.Duration `koanf:"send_timeout"`
MaxConns int `koanf:"max_conns"`
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mailer *email.Pool
}
type emailer struct {
servers map[string]*Server
serverNames []string
numServers int
}
// NewEmailer creates and returns an e-mail Messenger backend.
// It takes multiple SMTP configurations.
func NewEmailer(srv ...Server) (Messenger, error) {
e := &emailer{
servers: make(map[string]*Server),
}
for _, server := range srv {
s := server
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var auth smtp.Auth
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switch s.AuthProtocol {
case "cram":
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auth = smtp.CRAMMD5Auth(s.Username, s.Password)
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case "plain":
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auth = smtp.PlainAuth("", s.Username, s.Password, s.Host)
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case "login":
auth = &loginAuth{username: s.Username, password: s.Password}
case "":
default:
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return nil, fmt.Errorf("unknown SMTP auth type '%s'", s.AuthProtocol)
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}
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pool, err := email.NewPool(fmt.Sprintf("%s:%d", s.Host, s.Port), s.MaxConns, auth)
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if err != nil {
return nil, err
}
// Optional SMTP HELLO hostname.
if server.HelloHostname != "" {
pool.SetHelloHostname(server.HelloHostname)
}
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s.mailer = pool
e.servers[s.Name] = &s
e.serverNames = append(e.serverNames, s.Name)
}
e.numServers = len(e.serverNames)
return e, nil
}
// Name returns the Server's name.
func (e *emailer) Name() string {
return emName
}
// Push pushes a message to the server.
func (e *emailer) Push(fromAddr string, toAddr []string, subject string, m []byte, atts []*Attachment) error {
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var key string
// If there are more than one SMTP servers, send to a random
// one from the list.
if e.numServers > 1 {
key = e.serverNames[rand.Intn(e.numServers)]
} else {
key = e.serverNames[0]
}
// Are there attachments?
var files []*email.Attachment
if atts != nil {
files = make([]*email.Attachment, 0, len(atts))
for _, f := range atts {
a := &email.Attachment{
Filename: f.Name,
Header: f.Header,
Content: make([]byte, len(f.Content)),
}
copy(a.Content, f.Content)
files = append(files, a)
}
}
mtext, err := html2text.FromString(string(m), html2text.Options{PrettyTables: true})
if err != nil {
return err
}
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srv := e.servers[key]
em := &email.Email{
From: fromAddr,
To: toAddr,
Subject: subject,
Attachments: files,
}
switch srv.EmailFormat {
case "html":
em.HTML = m
case "plain":
em.Text = []byte(mtext)
default:
em.HTML = m
em.Text = []byte(mtext)
}
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return srv.mailer.Send(em, srv.SendTimeout)
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}
// Flush flushes the message queue to the server.
func (e *emailer) Flush() error {
return nil
}
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// https://gist.github.com/andelf/5118732
// Adds support for SMTP LOGIN auth.
func (a *loginAuth) Start(server *smtp.ServerInfo) (string, []byte, error) {
return "LOGIN", []byte{}, nil
}
func (a *loginAuth) Next(fromServer []byte, more bool) ([]byte, error) {
if more {
switch string(fromServer) {
case "Username:":
return []byte(a.username), nil
case "Password:":
return []byte(a.password), nil
default:
return nil, errors.New("unkown SMTP fromServer")
}
}
return nil, nil
}