package email

import (
	"bytes"
	"crypto/sha256"
	"fmt"
	"mime"
	"mime/multipart"
	"mime/quotedprintable"
	"net/mail"
	"net/textproto"
	"strings"
	"time"

	"git.sendico.io/tech/sxchnge/notifications/model"
	merrors "git.sendico.io/tech/sxchnge/shared/errors"
)

func smtpMessage(s smtpSettings, key string, email model.Email) ([]byte, error) {
	if !ValidAddress(email.Address) || strings.ContainsAny(email.Subject, "\r\n") || (email.Text == "" && email.HTML == "") {
		return nil, merrors.InvalidArgument("invalid email content")
	}
	var body bytes.Buffer
	parts := multipart.NewWriter(&body)
	for _, part := range []struct{ kind, value string }{{"text/plain", email.Text}, {"text/html", email.HTML}} {
		if part.value == "" {
			continue
		}
		writer, err := parts.CreatePart(textproto.MIMEHeader{"Content-Type": {part.kind + "; charset=utf-8"}, "Content-Transfer-Encoding": {"quoted-printable"}})
		if err != nil {
			return nil, merrors.InternalWrap(err, "create email MIME part")
		}
		encoded := quotedprintable.NewWriter(writer)
		if _, err = encoded.Write([]byte(part.value)); err != nil {
			return nil, merrors.InternalWrap(err, "encode email MIME part")
		}
		if err = encoded.Close(); err != nil {
			return nil, merrors.InternalWrap(err, "finish email MIME part")
		}
	}
	if err := parts.Close(); err != nil {
		return nil, merrors.InternalWrap(err, "finish email MIME body")
	}
	from := (&mail.Address{Name: s.SenderName, Address: s.SenderAddress}).String()
	to := (&mail.Address{Address: email.Address}).String()
	domain := s.SenderAddress[strings.LastIndex(s.SenderAddress, "@")+1:]
	headers := fmt.Sprintf("From: %s\r\nTo: %s\r\nSubject: %s\r\nDate: %s\r\nMessage-ID: <%x@%s>\r\nMIME-Version: 1.0\r\nContent-Type: multipart/alternative; boundary=%q\r\n\r\n", from, to, mime.QEncoding.Encode("utf-8", email.Subject), time.Now().UTC().Format(time.RFC1123Z), sha256.Sum256([]byte(key)), domain, parts.Boundary())
	return append([]byte(headers), body.Bytes()...), nil
}