first commit

pkg/mailer/mailer.go

@@ -0,0 +1,123 @@
+package mailer
+
+import (
+	"crypto/tls"
+	"fmt"
+	"net/smtp"
+	"os"
+	"strconv"
+	"strings"
+)
+
+func envBool(key string) bool {
+	v, err := strconv.ParseBool(strings.TrimSpace(os.Getenv(key)))
+	if err != nil {
+		return false
+	}
+	return v
+}
+
+func Send(to, subject, body string) error {
+	host := strings.TrimSpace(os.Getenv("EMAIL_HOST"))
+	port := strings.TrimSpace(os.Getenv("EMAIL_PORT"))
+	from := strings.TrimSpace(os.Getenv("EMAIL_FROM"))
+	username := strings.TrimSpace(os.Getenv("EMAIL_HOST_USER"))
+	password := strings.TrimSpace(os.Getenv("EMAIL_HOST_PASSWORD"))
+
+	if host == "" || port == "" || from == "" {
+		return fmt.Errorf("email configuration is incomplete")
+	}
+
+	addr := host + ":" + port
+	msg := strings.Join([]string{
+		"From: " + from,
+		"To: " + to,
+		"Subject: " + subject,
+		"MIME-Version: 1.0",
+		"Content-Type: text/plain; charset=UTF-8",
+		"",
+		body,
+	}, "\r\n")
+
+	var auth smtp.Auth
+	if username != "" {
+		auth = smtp.PlainAuth("", username, password, host)
+	}
+
+	useSSL := envBool("EMAIL_USE_SSL")
+	useTLS := envBool("EMAIL_USE_TLS")
+
+	if useSSL {
+		conn, err := tls.Dial("tcp", addr, &tls.Config{ServerName: host})
+		if err != nil {
+			return err
+		}
+		defer conn.Close()
+
+		client, err := smtp.NewClient(conn, host)
+		if err != nil {
+			return err
+		}
+		defer client.Quit()
+
+		if auth != nil {
+			if err := client.Auth(auth); err != nil {
+				return err
+			}
+		}
+
+		if err := client.Mail(from); err != nil {
+			return err
+		}
+		if err := client.Rcpt(to); err != nil {
+			return err
+		}
+
+		w, err := client.Data()
+		if err != nil {
+			return err
+		}
+		if _, err := w.Write([]byte(msg)); err != nil {
+			_ = w.Close()
+			return err
+		}
+		return w.Close()
+	}
+
+	if !useTLS {
+		return smtp.SendMail(addr, auth, from, []string{to}, []byte(msg))
+	}
+
+	client, err := smtp.Dial(addr)
+	if err != nil {
+		return err
+	}
+	defer client.Quit()
+
+	if err := client.StartTLS(&tls.Config{ServerName: host}); err != nil {
+		return err
+	}
+
+	if auth != nil {
+		if err := client.Auth(auth); err != nil {
+			return err
+		}
+	}
+
+	if err := client.Mail(from); err != nil {
+		return err
+	}
+	if err := client.Rcpt(to); err != nil {
+		return err
+	}
+
+	w, err := client.Data()
+	if err != nil {
+		return err
+	}
+	if _, err := w.Write([]byte(msg)); err != nil {
+		_ = w.Close()
+		return err
+	}
+	return w.Close()
+}