130 lines
3.5 KiB
Go
130 lines
3.5 KiB
Go
// Copyright (C) 2019 Storj Labs, Inc.
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// See LICENSE for copying information
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package post
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import (
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"bytes"
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"fmt"
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"io"
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"mime"
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"mime/multipart"
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"mime/quotedprintable"
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"net/textproto"
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"time"
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"github.com/zeebo/errs"
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)
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// Message is RFC compliant email message.
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type Message struct {
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From Address
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To []Address
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Subject string
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ID string
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Date time.Time
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ReceiptTo []string
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PlainText string
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Parts []Part
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}
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// Part represent one part of multipart message.
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type Part struct {
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Type string
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Encoding string
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Disposition string
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Content string
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}
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// Error is the default message errs class.
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var Error = errs.Class("Email message error")
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// Bytes builds message and returns result as bytes.
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func (msg *Message) Bytes() (data []byte, err error) {
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// always returns nil error on read and write, so most of the errors can be ignored
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var body bytes.Buffer
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// write headers
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fmt.Fprintf(&body, "MIME-Version: 1.0\r\n")
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fmt.Fprintf(&body, "Subject: %v\r\n", mime.QEncoding.Encode("utf-8", msg.Subject))
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fmt.Fprintf(&body, "From: %s\r\n", &msg.From)
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for _, to := range msg.To {
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fmt.Fprintf(&body, "To: %s\r\n", &to) // nolint:scopelint
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}
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for _, recipient := range msg.ReceiptTo {
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fmt.Fprintf(&body, "Disposition-Notification-To: <%v>\r\n", mime.QEncoding.Encode("utf-8", recipient))
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}
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// date and id are optional as they can be set by server itself
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if !msg.Date.IsZero() {
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fmt.Fprintf(&body, "Date: %v\r\n", msg.Date)
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}
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if msg.ID != "" {
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fmt.Fprintf(&body, "Message-ID: <%v>\r\n", mime.QEncoding.Encode("utf-8", msg.ID))
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}
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switch {
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// multipart upload
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case len(msg.Parts) > 0:
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wr := multipart.NewWriter(&body)
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defer func() { err = errs.Combine(err, wr.Close()) }()
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fmt.Fprintf(&body, "Content-Type: multipart/alternative;")
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fmt.Fprintf(&body, "\tboundary=\"%v\"\r\n", wr.Boundary())
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fmt.Fprintf(&body, "\r\n")
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var sub io.Writer
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if len(msg.PlainText) > 0 {
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sub, err := wr.CreatePart(textproto.MIMEHeader{
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"Content-Type": []string{"text/plain; charset=UTF-8; format=flowed"},
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"Content-Transfer-Encoding": []string{"quoted-printable"},
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})
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if err != nil {
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return nil, Error.Wrap(err)
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}
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enc := quotedprintable.NewWriter(sub)
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defer func() { err = errs.Combine(err, enc.Close()) }()
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_, err = enc.Write([]byte(msg.PlainText))
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if err != nil {
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return nil, Error.Wrap(err)
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}
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}
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for _, part := range msg.Parts {
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header := textproto.MIMEHeader{"Content-Type": []string{mime.QEncoding.Encode("utf-8", part.Type)}}
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if part.Encoding != "" {
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header["Content-Transfer-Encoding"] = []string{mime.QEncoding.Encode("utf-8", part.Encoding)}
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}
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if part.Disposition != "" {
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header["Content-Disposition"] = []string{mime.QEncoding.Encode("utf-8", part.Disposition)}
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}
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sub, _ = wr.CreatePart(header)
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fmt.Fprint(sub, part.Content)
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}
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// fallback if there are no parts, write PlainText with appropriate Content-Type
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default:
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fmt.Fprintf(&body, "Content-Type: text/plain; charset=UTF-8; format=flowed\r\n")
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fmt.Fprintf(&body, "Content-Transfer-Encoding: quoted-printable\r\n\r\n")
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enc := quotedprintable.NewWriter(&body)
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defer func() { err = errs.Combine(err, enc.Close()) }()
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if _, err := enc.Write([]byte(msg.PlainText)); err != nil {
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return nil, Error.Wrap(err)
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}
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}
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return tocrlf(body.Bytes()), nil
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}
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func tocrlf(data []byte) []byte {
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lf := bytes.ReplaceAll(data, []byte("\r\n"), []byte("\n"))
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crlf := bytes.ReplaceAll(lf, []byte("\n"), []byte("\r\n"))
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return crlf
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}
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