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package alerts
import (
"crypto/tls"
"fmt"
"net/smtp"
"strings"
)
func sendMail(addr, user, pass, from string, to []string, subject, body string) error {
host := addr
for i, c := range addr {
if c == ':' {
host = addr[:i]
break
}
}
msg := fmt.Sprintf("From: %s\r\nTo: %s\r\nSubject: %s\r\nMIME-Version: 1.0\r\nContent-Type: text/plain; charset=UTF-8\r\n\r\n%s",
from, strings.Join(to, ", "), subject, body)
auth := newLoginAuth(user, pass)
c, err := smtp.Dial(addr)
if err != nil {
return fmt.Errorf("dial: %w", err)
}
defer c.Close()
if err := c.StartTLS(&tls.Config{ServerName: host}); err != nil {
return fmt.Errorf("starttls: %w", err)
}
if user != "" {
if err := c.Auth(auth); err != nil {
return fmt.Errorf("auth: %w", err)
}
}
if err := c.Mail(from); err != nil {
return fmt.Errorf("mail from: %w", err)
}
for _, addr := range to {
if err := c.Rcpt(addr); err != nil {
return fmt.Errorf("rcpt %s: %w", addr, err)
}
}
w, err := c.Data()
if err != nil {
return fmt.Errorf("data: %w", err)
}
if _, err := fmt.Fprint(w, msg); err != nil {
return fmt.Errorf("write: %w", err)
}
if err := w.Close(); err != nil {
return fmt.Errorf("close: %w", err)
}
return c.Quit()
}
type loginAuth struct {
user, pass string
}
func newLoginAuth(user, pass string) smtp.Auth {
return &loginAuth{user, pass}
}
func (a *loginAuth) Start(server *smtp.ServerInfo) (string, []byte, error) {
return "LOGIN", []byte(a.user), nil
}
func (a *loginAuth) Next(fromServer []byte, more bool) ([]byte, error) {
if more {
msg := string(fromServer)
switch {
case strings.EqualFold(msg, "Username:"):
return []byte(a.user), nil
case strings.EqualFold(msg, "Password:"):
return []byte(a.pass), nil
}
}
return nil, nil
}
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