package main

import (
	"context"
	"flag"
	"fmt"
	"os"
	"time"

	mailgun "github.com/mailgun/mailgun-go/v3"

	_ "github.com/joho/godotenv/autoload"
)

func main() {
	/*
	  MAILGUN_API_KEY=key-xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
	  MAILGUN_DOMAIN=mail.example.com
	  MAILGUN_FROM="Rob the Robot <rob.the.robot@mail.example.com>"
	*/

	to := flag.String("to", "", "message recipient in the format of 'John Doe <john@example.com>'")
	replyTo := flag.String("reply-to", "", "reply-to in the format of 'John Doe <john@example.com>'")
	subject := flag.String("subject", "Test Subject", "the utf8-encoded subject of the email")
	text := flag.String(
		"text",
		"Testing some Mailgun awesomeness!",
		"the body of the email as utf8-encoded plain-text format",
	)
	flag.Parse()

	if 0 == len(*to) {
		flag.Usage()
		os.Exit(1)
	}

	domain := os.Getenv("MAILGUN_DOMAIN")
	apiKey := os.Getenv("MAILGUN_API_KEY")
	from := os.Getenv("MAILGUN_FROM")

	if 0 == len(*text) {
		*text = "Testing some Mailgun awesomeness!"
	}

	msgId, err := SendSimpleMessage(domain, apiKey, *to, from, *subject, *text, *replyTo)
	if nil != err {
		panic(err)
	}
	fmt.Printf("Queued with Message ID %q\n", msgId)
}

func SendSimpleMessage(domain, apiKey, to, from, subject, text, replyTo string) (string, error) {
	mg := mailgun.NewMailgun(domain, apiKey)
	m := mg.NewMessage(from, subject, text, to)
	if 0 != len(replyTo) {
		// mailgun's required "h:" prefix is added by the library
		m.AddHeader("Reply-To", replyTo)
	}

	ctx, cancel := context.WithTimeout(context.Background(), time.Second*30)
	defer cancel()

	_, id, err := mg.Send(ctx, m)
	return id, err
}