cmd/sendemail: command line interface to send an email

The sendemail command is proof of concept on how to use lib/email and
lib/smtp to write and send email through SMTP.

3 files changed, 193 insertions, 0 deletions

diff --git a/cmd/sendemail/body.html b/cmd/sendemail/body.html
new file mode 100644
index 00000000..107d9acf
--- /dev/null
+++ b/cmd/sendemail/body.html
@@ -0,0 +1 @@
+Hello, this is email body as <b>text/html</b>.
diff --git a/cmd/sendemail/body.txt b/cmd/sendemail/body.txt
new file mode 100644
index 00000000..a0bc3536
--- /dev/null
+++ b/cmd/sendemail/body.txt
@@ -0,0 +1 @@
+Hello, this is email body as text/plain.
diff --git a/cmd/sendemail/main.go b/cmd/sendemail/main.go
new file mode 100644
index 00000000..3289b7d0
--- /dev/null
+++ b/cmd/sendemail/main.go
@@ -0,0 +1,191 @@
+// Program sendemail is command line interface that use lib/email and lib/smtp
+// to send email.
+package main
+
+import (
+	"flag"
+	"fmt"
+	"log"
+	"os"
+
+	"github.com/shuLhan/share/lib/email"
+	"github.com/shuLhan/share/lib/smtp"
+)
+
+const (
+	envSmtpUsername = "SMTP_USERNAME"
+	envSmtpPassword = "SMTP_PASSWORD"
+)
+
+func main() {
+	var (
+		smtpc      *smtp.Client
+		smtpRes    *smtp.Response
+		mailtx     *smtp.MailTx
+		clientOpts smtp.ClientOptions
+		msg        email.Message
+		err        error
+
+		from         string
+		to           string
+		subject      string
+		fileBodyText string
+		fileBodyHtml string
+		serverUrl    string
+
+		content []byte
+		mailb   []byte
+
+		isHelp bool
+	)
+
+	log.SetFlags(0)
+	log.SetPrefix("sendemail: ")
+
+	flag.BoolVar(&isHelp, "help", false, "Print the command usage and flags.")
+	flag.StringVar(&from, "from", "", "Set the sender address.")
+	flag.StringVar(&to, "to", "", "Set the recipients.")
+	flag.StringVar(&subject, "subject", "", "Set the subject.")
+	flag.StringVar(&fileBodyText, "bodytext", "", "Set the text body from content of file.")
+	flag.StringVar(&fileBodyHtml, "bodyhtml", "", "Set the HTML body from content of file.")
+	flag.Usage = usage
+	flag.Parse()
+
+	if isHelp {
+		usage()
+		os.Exit(1)
+	}
+
+	serverUrl = flag.Arg(0)
+	if len(serverUrl) == 0 {
+		log.Printf("missing server URL")
+		os.Exit(1)
+	}
+
+	if len(from) == 0 {
+		log.Printf("missing -from flag")
+		os.Exit(1)
+	}
+	err = msg.SetFrom(from)
+	if err != nil {
+		log.Println(err)
+		os.Exit(1)
+	}
+
+	if len(to) == 0 {
+		log.Printf("missing -to flag")
+		os.Exit(1)
+	}
+	err = msg.SetTo(to)
+	if err != nil {
+		log.Println(err)
+		os.Exit(1)
+	}
+
+	if len(subject) == 0 {
+		log.Printf("missing -subject flag")
+		os.Exit(1)
+	}
+	msg.SetSubject(subject)
+
+	if len(fileBodyText) == 0 && len(fileBodyHtml) == 0 {
+		log.Printf("missing -bodytext or -bodyhtml")
+		os.Exit(1)
+	}
+
+	if len(fileBodyText) > 0 {
+		content, err = os.ReadFile(fileBodyText)
+		if err != nil {
+			log.Println(err)
+		}
+		_ = msg.SetBodyText(content)
+	}
+
+	if len(fileBodyHtml) > 0 {
+		content, err = os.ReadFile(fileBodyHtml)
+		if err != nil {
+			log.Println(err)
+		}
+		_ = msg.SetBodyHtml(content)
+	}
+
+	mailb, err = msg.Pack()
+	if err != nil {
+		log.Println(err)
+		os.Exit(1)
+	}
+
+	fmt.Printf("mail data:\n%s\n", mailb)
+
+	mailtx = smtp.NewMailTx(from, []string{to}, mailb)
+
+	clientOpts = smtp.ClientOptions{
+		ServerUrl:     serverUrl,
+		AuthUser:      os.Getenv(envSmtpUsername),
+		AuthPass:      os.Getenv(envSmtpPassword),
+		AuthMechanism: smtp.SaslMechanismPlain,
+	}
+
+	smtpc, err = smtp.NewClient(clientOpts)
+	if err != nil {
+		log.Println(err)
+		os.Exit(1)
+	}
+
+	smtpRes, err = smtpc.MailTx(mailtx)
+	if err != nil {
+		log.Println(err)
+		os.Exit(1)
+	}
+
+	fmt.Printf("SMTP response: %+v\n", smtpRes)
+}
+
+func usage() {
+	fmt.Println(`
+sendemail - command line interface to send an email using SMTP.
+
+== SYNOPSIS
+
+	sendemail <FLAGS> <SERVER_URL>
+
+== FLAGS
+
+Unless otherwise noted, all of the flags below are required.`)
+
+	fmt.Println()
+	flag.PrintDefaults()
+
+	fmt.Println(`
+The 'from' and 'to' flags are set using mailbox format, for example
+"John <john@domain.tld>, Jane <jane@domain.tld>"
+
+Only one of 'bodytext' and 'bodyhtml' is required.
+
+== SERVER_URL
+
+The SERVER_URL argument define the SMTP server where the email will be submitted.
+Its use the following URL format,
+
+	<scheme://><ip_address / domain>[:port]
+
+The scheme can be 'smtps' for SMTP with implicit TLS (port 465) or
+'smtp+starttls' for SMTP with STARTTLS (port 587).
+
+The following environment variables are read for authentication with SMTP,
+
+* SMTP_USERNAME: for SMTP user
+* SMTP_PASSWORD: for SMTP password
+
+== EXAMPLES
+
+Send an email with message body set and read from HTML file,
+
+	$ SMTP_USERNAME=myuser
+	$ SMTP_PASSWORD=mypass
+	$ sendemail -from="my@email.tld" \
+		-to="John <john@example.com>, Jane <jane@example.com>" \
+		-subject="Happy new years!" \
+		-bodytext=/path/to/message.html \
+		smtps://mail.myserver.com`)
+}