init work of uptime

internal/alert/email.go

@@ -0,0 +1,34 @@
+package alert
+
+import (
+	"fmt"
+	"net/smtp"
+	"strings"
+
+	"arclineit/arcline-uptime/internal/config"
+)
+
+type EmailAlerter struct {
+	cfg config.AlertConfig
+}
+
+func NewEmailAlerter(cfg config.AlertConfig) *EmailAlerter {
+	return &EmailAlerter{cfg: cfg}
+}
+
+// Send delivers an email via STARTTLS on the configured SMTP server.
+// Port 587 with STARTTLS is expected; port 465 (SMTPS) is not supported.
+func (e *EmailAlerter) Send(subject, body string) error {
+	if len(e.cfg.To) == 0 {
+		return fmt.Errorf("email alerter: no recipients configured")
+	}
+
+	auth := smtp.PlainAuth("", e.cfg.Username, e.cfg.Password, e.cfg.SMTPHost)
+	toHeader := strings.Join(e.cfg.To, ", ")
+	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",
+		e.cfg.From, toHeader, subject, body,
+	)
+	addr := fmt.Sprintf("%s:%d", e.cfg.SMTPHost, e.cfg.SMTPPort)
+	return smtp.SendMail(addr, auth, e.cfg.From, []string(e.cfg.To), []byte(msg))
+}