aduio mail

internal/email/email.go

@@ -0,0 +1,73 @@
+// Package email sends QSO recordings to correspondents via SMTP. Pure Go (no
+// CGO) using go-mail; supports implicit SSL (465), STARTTLS (587) or none.
+package email
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/wneessen/go-mail"
+)
+
+// Config is the user's SMTP configuration.
+type Config struct {
+	Host       string
+	Port       int
+	User       string
+	Password   string
+	From       string
+	Encryption string // "ssl" | "starttls" | "none"
+	Auth       bool   // SMTP requires authorization (send username/password)
+}
+
+func (c Config) opts() []mail.Option {
+	o := []mail.Option{mail.WithPort(c.Port), mail.WithTimeout(30 * time.Second)}
+	if c.Auth && c.User != "" {
+		// AutoDiscover negotiates whatever mechanism the server advertises
+		// (LOGIN, PLAIN, CRAM-MD5, …). OVH, for instance, rejects forced PLAIN.
+		o = append(o, mail.WithSMTPAuth(mail.SMTPAuthAutoDiscover), mail.WithUsername(c.User), mail.WithPassword(c.Password))
+	}
+	switch c.Encryption {
+	case "ssl":
+		o = append(o, mail.WithSSL())
+	case "none":
+		o = append(o, mail.WithTLSPolicy(mail.NoTLS))
+	default: // starttls
+		o = append(o, mail.WithTLSPolicy(mail.TLSMandatory))
+	}
+	return o
+}
+
+// Send delivers a plain-text email to `to`, optionally attaching a file.
+func Send(cfg Config, to, subject, body, attachPath string) error {
+	if cfg.Host == "" {
+		return fmt.Errorf("SMTP server not configured")
+	}
+	if to == "" {
+		return fmt.Errorf("no recipient e-mail")
+	}
+	from := cfg.From
+	if from == "" {
+		from = cfg.User
+	}
+	m := mail.NewMsg()
+	if err := m.From(from); err != nil {
+		return fmt.Errorf("bad sender %q: %w", from, err)
+	}
+	if err := m.To(to); err != nil {
+		return fmt.Errorf("bad recipient %q: %w", to, err)
+	}
+	m.Subject(subject)
+	m.SetBodyString(mail.TypeTextPlain, body)
+	if attachPath != "" {
+		m.AttachFile(attachPath)
+	}
+	client, err := mail.NewClient(cfg.Host, cfg.opts()...)
+	if err != nil {
+		return fmt.Errorf("smtp client: %w", err)
+	}
+	if err := client.DialAndSend(m); err != nil {
+		return fmt.Errorf("send: %w", err)
+	}
+	return nil
+}