From 54c465281496ec09030863d62e0a1b81eb8b1dbc Mon Sep 17 00:00:00 2001
From: "Arnaud (Arhuman) ASSAD" <arnaud.assad@epfl.ch>
Date: Tue, 10 Oct 2023 14:31:53 +0200
Subject: [PATCH] Add emailclient

---
 emailclient/emailclient.go | 199 +++++++++++++++++++++++++++++++++++++
 1 file changed, 199 insertions(+)
 create mode 100644 emailclient/emailclient.go

diff --git a/emailclient/emailclient.go b/emailclient/emailclient.go
new file mode 100644
index 0000000..b4c3b8c
--- /dev/null
+++ b/emailclient/emailclient.go
@@ -0,0 +1,199 @@
+package emailclient
+
+import (
+	"crypto/tls"
+	"errors"
+	"fmt"
+	"net"
+	"net/mail"
+	"net/smtp"
+
+	log "github.com/sirupsen/logrus"
+)
+
+// SMTPCredentials is a struc holding the information needed to connect to a SMTP server
+type SMTPCredentials struct {
+	Host     string
+	Email    string
+	Password string
+}
+
+// emailClient is a struct holding the information requiered to send with SMTP
+type emailClient struct {
+	client *smtp.Client
+}
+
+// EmailClient is the generic interface for all client sending emails
+type EmailClient interface {
+	SendMsg(headers map[string]string, body string)
+}
+
+// NewSMTPClient (host, user, password) returns a SMTPClient
+//
+//	host is the SMTP server used to connect
+//	port is the SMTP port used to connect
+//	user is usually the email address use to connect to SMTP
+//	password is the associated password
+func NewSMTPClient(host string, port string, user string, password string) (EmailClient, error) {
+	var ec emailClient
+
+	log.Infof("user: (%s) pass: (%s)", user, password)
+
+	auth := smtp.PlainAuth("", user, password, host)
+
+	// TLS config
+	tlsconfig := &tls.Config{
+		InsecureSkipVerify: false,
+		ServerName:         host,
+	}
+
+	// Here is the key, you need to call tls.Dial instead of smtp.Dial
+	// for smtp servers running on 465 that require an ssl connection
+	// from the very beginning (no starttls)
+	var conn *tls.Conn
+	var c *smtp.Client
+	var err error
+	if port == "465" {
+		conn, err = tls.Dial("tcp", host+":"+port, tlsconfig)
+		if err != nil {
+			log.Error("[sendMail] ERROR while dialing: " + err.Error())
+			return ec, err
+		}
+
+		c, err = smtp.NewClient(conn, host)
+		if err != nil {
+			log.Error("[sendMail] ERROR while NewClient: " + err.Error())
+			return ec, err
+		}
+	} else {
+		c, err = smtp.Dial(host + ":" + port)
+		if err != nil {
+			log.Error("[sendMail] ERROR while Dialing: " + err.Error())
+			return ec, err
+		}
+		err = c.StartTLS(tlsconfig)
+		if err != nil {
+			log.Error("[sendMail] ERROR while StartTLS: " + err.Error())
+			return ec, err
+		}
+	}
+	// defer c.Quit()
+	// defer c.Close()
+
+	ec.client = c
+
+	// Auth
+	if err = ec.client.Auth(auth); err != nil {
+		log.Error("[sendMail] ERROR while Auth: " + err.Error())
+		return ec, err
+	}
+
+	return ec, nil
+}
+
+// NewGmailClient returns a GmailClient
+func NewGmailClient(email, pass string) (EmailClient, error) {
+	var ec emailClient
+
+	// cred.Host = "smtp.gmail.com:587"
+	echost := "smtp.gmail.com:465"
+	if pass == "" {
+		log.Error("Email password missing")
+		return ec, errors.New("Email password missing")
+	}
+
+	host, _, _ := net.SplitHostPort(echost)
+	auth := smtp.PlainAuth("", email, pass, host)
+
+	// TLS config
+	tlsconfig := &tls.Config{
+		InsecureSkipVerify: true,
+		ServerName:         host,
+	}
+
+	// Cavehat, you need to call tls.Dial instead of smtp.Dial
+	// for smtp servers running on 465 that require an ssl connection
+	// from the very beginning (no starttls)
+	conn, err := tls.Dial("tcp", echost, tlsconfig)
+	if err != nil {
+		log.Error(fmt.Sprintf("Dial error: " + err.Error()))
+		return ec, err
+	}
+
+	client, err := smtp.NewClient(conn, host)
+	if err != nil {
+		log.Error(fmt.Sprintf("NewClient error: " + err.Error()))
+		return ec, err
+	}
+	ec.client = client
+
+	// Auth
+	if err = ec.client.Auth(auth); err != nil {
+		log.Error(fmt.Sprintf("Auth error: %s (%s)", err, host))
+		return ec, err
+	}
+
+	return ec, nil
+}
+
+// SendMsg send a message (email) to rcpt which is in the 'headers' parameter ('To' key) and whose content is the 'body' parameter.
+// Ohter keys of interest in headers are 'Subject' and 'MIME-version'
+func (ec emailClient) SendMsg(headers map[string]string, body string) {
+	from := mail.Address{Name: "", Address: headers["From"]}
+	to := mail.Address{Name: "", Address: headers["To"]}
+
+	// headers["To"] = to.String()
+	if _, ok := headers["Subject"]; ok {
+		headers["Subject"] = "Subject unknown"
+	}
+
+	log.Printf("from = %s", headers["From"])
+	log.Printf("to = %s", headers["To"])
+	log.Printf("subj = %s", headers["Subject"])
+
+	// Setup message
+	message := ""
+	for k, v := range headers {
+		message += fmt.Sprintf("%s: %s\r\n", k, v)
+	}
+	message += "\r\n" + body
+
+	c := ec.client
+
+	// To && From
+	if err := c.Mail(from.Address); err != nil {
+		log.Error("Can't set From: " + err.Error())
+		return
+	}
+
+	if err := c.Rcpt(to.Address); err != nil {
+		log.Error("Can't set To: " + err.Error())
+		return
+	}
+
+	// Data
+	w, err := c.Data()
+	if err != nil {
+		log.Error("Can't set Data: " + err.Error())
+		return
+	}
+
+	_, err = w.Write([]byte(message))
+	if err != nil {
+		log.Error("Can't write Data: " + err.Error())
+		return
+	}
+
+	err = w.Close()
+	if err != nil {
+		log.Error("Can't Close: " + err.Error())
+		return
+	}
+
+	err = c.Quit()
+	if err != nil {
+		log.Error("Can't Quit: " + err.Error())
+		return
+	}
+	c.Close()
+}