package main

import (
	"crypto/tls"
	"fmt"
	"net/smtp"
	"strings"
)

type Emailer struct {
	From     string
	SMTP     string
	POP3     string
	Password string
}

func (e *Emailer) Send(to, subj, msg string) error {
	headers := e.headers(to, e.From, subj)
	body := e.body(headers, msg)
	smtp, err := e.smtp()
	if err != nil {
		return err
	}
	defer smtp.Quit()
	if err := smtp.Mail(e.From); err != nil {
		return err
	}
	if err := smtp.Rcpt(to); err != nil {
		return err
	}
	w, err := smtp.Data()
	if err != nil {
		return err
	}
	if _, err := w.Write([]byte(body)); err != nil {
		return err
	}
	return w.Close()
}

func (e *Emailer) headers(to, from, subj string) map[string]string {
	return map[string]string{
		"To":      to,
		"From":    from,
		"Subject": subj,
	}
}

func (e *Emailer) body(headers map[string]string, body string) string {
	b := ""
	for k, v := range headers {
		b += fmt.Sprintf("%s: %s\r\n", k, v)
	}
	return b + "\r\n" + body
}

func (e *Emailer) smtp() (*smtp.Client, error) {
	host := strings.Split(e.SMTP, ":")[0]
	auth := smtp.PlainAuth("", e.From, e.Password, host)
	tlsconfig := &tls.Config{ServerName: host}
	conn, err := tls.Dial("tcp", e.SMTP, tlsconfig)
	if err != nil {
		return nil, fmt.Errorf("cannot dial %v: %v", e.SMTP, err)
	}
	smtp, err := smtp.NewClient(conn, host)
	if err != nil {
		return nil, fmt.Errorf("cannot new client %v: %v", host, err)
	}
	if err := smtp.Auth(auth); err != nil {
		return nil, fmt.Errorf("cannot auth client: %v", err)
	}
	return smtp, nil
}