Added adminmailer program

.gitignore

@@ -9,3 +9,5 @@ cinera/cinera.conf
 annotations/
 /hmn
 deploy.conf
+adminmailer/config.go
+adminmailer/adminmailer

adminmailer/config.go.example

@@ -0,0 +1,9 @@
+package main
+
+const RecvAddress = "admin@example.com"
+const RecvName = "Admin"
+const FromName = "From Name"
+const FromAddress = "from@address.com"
+const FromAddressPassword = "password"
+const ServerAddress = "server.address"
+const ServerPort = 587

adminmailer/main.go

@@ -0,0 +1,83 @@
+package main
+
+import (
+	"fmt"
+	"mime"
+	"mime/quotedprintable"
+	"net/smtp"
+	"os"
+	"strings"
+	"time"
+)
+
+func main() {
+	if len(os.Args) == 1 {
+		fmt.Printf(`The source code for this program can be found at git.handmade.network/hmn/hmn/adminmailer
+The config data is compiled into the program. If you need to change the config,
+find the adminmailer package in the hmn repo, modify config.go, and recompile.`)
+		fmt.Printf("\n\nUsage:\n")
+		fmt.Printf("%s [subject] [message]\n\n", os.Args[0])
+		os.Exit(1)
+	}
+	if len(os.Args) < 3 {
+		fmt.Printf("You must provide a subject and message to send\n\n")
+		fmt.Printf("%s [subject] [message]\n\n", os.Args[0])
+		os.Exit(1)
+	}
+
+	subject := os.Args[1]
+	message := strings.Join(os.Args[2:], " ")
+
+	err := sendMail(RecvAddress, RecvName, subject, message)
+	if err != nil {
+		fmt.Printf("Failed to send email:\n%v\n\n", err)
+		os.Exit(1)
+	}
+}
+
+func sendMail(toAddress, toName, subject, contentHtml string) error {
+	contents := prepMailContents(
+		makeHeaderAddress(toAddress, toName),
+		makeHeaderAddress(FromAddress, FromName),
+		subject,
+		contentHtml,
+	)
+	return smtp.SendMail(
+		fmt.Sprintf("%s:%d", ServerAddress, ServerPort),
+		smtp.PlainAuth("", FromAddress, FromAddressPassword, ServerAddress),
+		FromAddress,
+		[]string{toAddress},
+		contents,
+	)
+}
+
+func makeHeaderAddress(email, fullname string) string {
+	if fullname != "" {
+		encoded := mime.BEncoding.Encode("utf-8", fullname)
+		if encoded == fullname {
+			encoded = strings.ReplaceAll(encoded, `"`, `\"`)
+			encoded = fmt.Sprintf("\"%s\"", encoded)
+		}
+		return fmt.Sprintf("%s <%s>", encoded, email)
+	} else {
+		return email
+	}
+}
+
+func prepMailContents(toLine string, fromLine string, subject string, contentHtml string) []byte {
+	var builder strings.Builder
+
+	builder.WriteString(fmt.Sprintf("To: %s\r\n", toLine))
+	builder.WriteString(fmt.Sprintf("From: %s\r\n", fromLine))
+	builder.WriteString(fmt.Sprintf("Date: %s\r\n", time.Now().UTC().Format(time.RFC1123Z)))
+	builder.WriteString(fmt.Sprintf("Subject: %s\r\n", mime.QEncoding.Encode("utf-8", subject)))
+	builder.WriteString("Content-Type: text/html; charset=UTF-8\r\n")
+	builder.WriteString("Content-Transfer-Encoding: quoted-printable\r\n")
+	builder.WriteString("\r\n")
+	writer := quotedprintable.NewWriter(&builder)
+	writer.Write([]byte(contentHtml))
+	writer.Close()
+	builder.WriteString("\r\n")
+
+	return []byte(builder.String())
+}