Implemented MIME multipart handling for alternative content

README.md

@@ -6,6 +6,9 @@ The main idea of this library was to provide a simple interface to sending mails
 my [JS-Mailer](https://github.com/wneessen/js-mailer) project. It quickly evolved into a 
 full-fledged mail library.
 
+Parts (especially the msgWriter) of this library have been ported from the [GoMail](https://github.com/go-mail/mail)
+which seems to not be maintained anymore.
+
 **This library is "WIP" an should not be considered "production ready", yet.**
 
 go-mail follows idiomatic Go style and best practice. It's only dependency is the Go Standard Library.

client.go

@@ -298,16 +298,10 @@ func (c *Client) Send(ml ...*Msg) error {
 				return fmt.Errorf("sending RCPT TO command failed: %w", err)
 			}
 		}
-		w := os.Stderr
-
-		/*
-			w, err := c.sc.Data()
-			if err != nil {
-				return fmt.Errorf("sending DATA command failed: %w", err)
-			}
-
-		*/
-
+		w, err := c.sc.Data()
+		if err != nil {
+			return fmt.Errorf("sending DATA command failed: %w", err)
+		}
 		_, err = m.Write(w)
 		if err != nil {
 			return fmt.Errorf("sending mail content failed: %w", err)

cmd/main.go

@@ -3,6 +3,7 @@ package main
 import (
 	"fmt"
 	"github.com/wneessen/go-mail"
+	"io"
 	"os"
 )
 
@@ -12,8 +13,6 @@ func main() {
 		fmt.Printf("$TEST_HOST env variable cannot be empty\n")
 		os.Exit(1)
 	}
-	tu := os.Getenv("TEST_USER")
-	tp := os.Getenv("TEST_PASS")
 
 	fa := "Winni Neessen <[email protected]>"
 	toa := "Winfried Neessen <[email protected]>"
@@ -37,6 +36,15 @@ func main() {
 	m.SetDate()
 	m.SetBulk()
 
+	m.SetBodyWriter(mail.TypeTextPlain, func(fw io.Writer) error {
+		_, err := io.WriteString(fw, "This is a writer test")
+		return err
+	})
+	m.AddAlternativeString(mail.TypeTextHTML, "This is HTML content")
+	//m.Write(os.Stdout)
+
+	tu := os.Getenv("TEST_USER")
+	tp := os.Getenv("TEST_PASS")
 	c, err := mail.NewClient(th, mail.WithTLSPolicy(mail.TLSMandatory),
 		mail.WithSMTPAuth(mail.SMTPAuthLogin), mail.WithUsername(tu),
 		mail.WithPassword(tp))
@@ -48,4 +56,5 @@ func main() {
 		fmt.Printf("failed to dial: %s\n", err)
 		os.Exit(1)
 	}
+
 }

encoding.go

@@ -1,10 +1,19 @@
 package mail
 
+// Charset represents a character set for the encoding
+type Charset string
+
+// ContentType represents a content type for the Msg
+type ContentType string
+
 // Encoding represents a MIME encoding scheme like quoted-printable or Base64.
 type Encoding string
 
-// Charset represents a character set for the encodingA
-type Charset string
+// MIMEVersion represents the MIME version for the mail
+type MIMEVersion string
+
+// MIMEType represents the MIME type for the mail
+type MIMEType string
 
 // List of supported encodings
 const (
@@ -117,6 +126,26 @@ const (
 	CharsetGBK Charset = "GBK"
 )
 
+// List of MIME versions
+const (
+	//Mime10 is the MIME Version 1.0
+	Mime10 MIMEVersion = "1.0"
+)
+
+// List of common content types
+const (
+	TypeTextPlain      ContentType = "text/plain"
+	TypeTextHTML       ContentType = "text/html"
+	TypeAppOctetStream ContentType = "application/octet-stream"
+)
+
+// List of MIMETypes
+const (
+	MIMEAlternative MIMEType = "alternative"
+	MIMEMixed       MIMEType = "mixed"
+	MIMERelated     MIMEType = "related"
+)
+
 // String is a standard method to convert an Encoding into a printable format
 func (e Encoding) String() string {
 	return string(e)

go.mod

@@ -1,3 +1,10 @@
 module github.com/wneessen/go-mail
 
 go 1.17
+
+require github.com/go-mail/mail/v2 v2.3.0
+
+require (
+	gopkg.in/alexcesaro/quotedprintable.v3 v3.0.0-20150716171945-2caba252f4dc // indirect
+	gopkg.in/mail.v2 v2.3.1 // indirect
+)

go.sum

@@ -0,0 +1,6 @@
+github.com/go-mail/mail/v2 v2.3.0 h1:wha99yf2v3cpUzD1V9ujP404Jbw2uEvs+rBJybkdYcw=
+github.com/go-mail/mail/v2 v2.3.0/go.mod h1:oE2UK8qebZAjjV1ZYUpY7FPnbi/kIU53l1dmqPRb4go=
+gopkg.in/alexcesaro/quotedprintable.v3 v3.0.0-20150716171945-2caba252f4dc h1:2gGKlE2+asNV9m7xrywl36YYNnBG5ZQ0r/BOOxqPpmk=
+gopkg.in/alexcesaro/quotedprintable.v3 v3.0.0-20150716171945-2caba252f4dc/go.mod h1:m7x9LTH6d71AHyAX77c9yqWCCa3UKHcVEj9y7hAtKDk=
+gopkg.in/mail.v2 v2.3.1 h1:WYFn/oANrAGP2C0dcV6/pbkPzv8yGzqTjPmTeO7qoXk=
+gopkg.in/mail.v2 v2.3.1/go.mod h1:htwXN1Qh09vZJ1NVKxQqHPBaCBbzKhp5GzuJEA4VJWw=

header.go

@@ -8,9 +8,15 @@ type AddrHeader string
 
 // List of common generic header field names
 const (
+	// HeaderContentDisposition is the "Content-Disposition" header
+	HeaderContentDisposition Header = "Content-Disposition"
+
 	// HeaderContentLang is the "Content-Language" header
 	HeaderContentLang Header = "Content-Language"
 
+	// HeaderContentTransferEnc is the "Content-Transfer-Encoding" header
+	HeaderContentTransferEnc Header = "Content-Transfer-Encoding"
+
 	// HeaderContentType is the "Content-Type" header
 	HeaderContentType Header = "Content-Type"
 

msg.go

@@ -1,6 +1,7 @@
 package mail
 
 import (
+	"bytes"
 	"errors"
 	"fmt"
 	"io"
@@ -21,6 +22,12 @@ var (
 
 // Msg is the mail message struct
 type Msg struct {
+	// addrHeader is a slice of strings that the different mail AddrHeader fields
+	addrHeader map[AddrHeader][]*mail.Address
+
+	// boundary is the MIME content boundary
+	boundary string
+
 	// charset represents the charset of the mail (defaults to UTF-8)
 	charset Charset
 
@@ -33,20 +40,35 @@ type Msg struct {
 	// genHeader is a slice of strings that the different generic mail Header fields
 	genHeader map[Header][]string
 
-	// addrHeader is a slice of strings that the different mail AddrHeader fields
-	addrHeader map[AddrHeader][]*mail.Address
+	// mimever represents the MIME version
+	mimever MIMEVersion
+
+	// parts represent the different parts of the Msg
+	parts []*Part
 }
 
+// Part is a part of the Msg
+type Part struct {
+	w     func(io.Writer) error
+	x     io.Writer
+	ctype ContentType
+	enc   Encoding
+}
+
+// PartOption returns a function that can be used for grouping Part options
+type PartOption func(*Part)
+
 // MsgOption returns a function that can be used for grouping Msg options
 type MsgOption func(*Msg)
 
 // NewMsg returns a new Msg pointer
 func NewMsg(o ...MsgOption) *Msg {
 	m := &Msg{
-		encoding:   EncodingQP,
+		addrHeader: make(map[AddrHeader][]*mail.Address),
 		charset:    CharsetUTF8,
+		encoding:   EncodingQP,
 		genHeader:  make(map[Header][]string),
-		addrHeader: make(map[AddrHeader][]*mail.Address),
+		mimever:    Mime10,
 	}
 
 	// Override defaults with optionally provided MsgOption functions
@@ -77,6 +99,13 @@ func WithEncoding(e Encoding) MsgOption {
 	}
 }
 
+// WithMIMEVersion overrides the default MIME version
+func WithMIMEVersion(mv MIMEVersion) MsgOption {
+	return func(m *Msg) {
+		m.mimever = mv
+	}
+}
+
 // SetCharset sets the encoding charset of the Msg
 func (m *Msg) SetCharset(c Charset) {
 	m.charset = c
@@ -87,6 +116,16 @@ func (m *Msg) SetEncoding(e Encoding) {
 	m.encoding = e
 }
 
+// SetBoundary sets the boundary of the Msg
+func (m *Msg) SetBoundary(b string) {
+	m.boundary = b
+}
+
+// SetMIMEVersion sets the MIME version of the Msg
+func (m *Msg) SetMIMEVersion(mv MIMEVersion) {
+	m.mimever = mv
+}
+
 // Encoding returns the currently set encoding of the Msg
 func (m *Msg) Encoding() string {
 	return m.encoding.String()
@@ -294,22 +333,91 @@ func (m *Msg) GetRecipients() ([]string, error) {
 	return rl, nil
 }
 
+// SetBodyString sets the body of the message.
+func (m *Msg) SetBodyString(ct ContentType, b string, o ...PartOption) {
+	buf := bytes.NewBufferString(b)
+	w := func(w io.Writer) error {
+		_, err := io.Copy(w, buf)
+		return err
+	}
+	m.SetBodyWriter(ct, w, o...)
+}
+
+// SetBodyWriter sets the body of the message.
+func (m *Msg) SetBodyWriter(ct ContentType, w func(io.Writer) error, o ...PartOption) {
+	p := m.NewPart(ct, o...)
+	p.w = w
+	m.parts = []*Part{p}
+}
+
+// AddAlternativeString sets the alternative body of the message.
+func (m *Msg) AddAlternativeString(ct ContentType, b string, o ...PartOption) {
+	buf := bytes.NewBufferString(b)
+	w := func(w io.Writer) error {
+		_, err := io.Copy(w, buf)
+		return err
+	}
+	m.AddAlternativeWriter(ct, w, o...)
+}
+
+// AddAlternativeWriter sets the body of the message.
+func (m *Msg) AddAlternativeWriter(ct ContentType, w func(io.Writer) error, o ...PartOption) {
+	p := m.NewPart(ct, o...)
+	p.w = w
+	m.parts = append(m.parts, p)
+}
+
 // Write writes the formated Msg into a give io.Writer
 func (m *Msg) Write(w io.Writer) (int64, error) {
 	mw := &msgWriter{w: w}
 	mw.writeMsg(m)
 	return mw.n, mw.err
 }
 
+// NewPart returns a new Part for the Msg
+func (m *Msg) NewPart(ct ContentType, o ...PartOption) *Part {
+	p := &Part{
+		ctype: ct,
+		enc:   m.encoding,
+	}
+
+	// Override defaults with optionally provided MsgOption functions
+	for _, co := range o {
+		if co == nil {
+			continue
+		}
+		co(p)
+	}
+
+	return p
+}
+
+// WithPartEncoding overrides the default Part encoding
+func WithPartEncoding(e Encoding) PartOption {
+	return func(p *Part) {
+		p.enc = e
+	}
+}
+
+// SetEncoding creates a new mime.WordEncoder based on the encoding setting of the message
+func (p *Part) SetEncoding(e Encoding) {
+	p.enc = e
+}
+
 // setEncoder creates a new mime.WordEncoder based on the encoding setting of the message
 func (m *Msg) setEncoder() {
-	switch m.encoding {
+	m.encoder = getEncoder(m.encoding)
+}
+
+// getEncoder creates a new mime.WordEncoder based on the encoding setting of the message
+func getEncoder(e Encoding) mime.WordEncoder {
+	switch e {
 	case EncodingQP:
-		m.encoder = mime.QEncoding
+		return mime.QEncoding
 	case EncodingB64:
-		m.encoder = mime.BEncoding
+		return mime.BEncoding
 	default:
-		m.encoder = mime.QEncoding
+		return mime.QEncoding
 	}
 }
 
@@ -318,3 +426,8 @@ func (m *Msg) setEncoder() {
 func (m *Msg) encodeString(s string) string {
 	return m.encoder.Encode(string(m.charset), s)
 }
+
+// hasAlt returns true if the Msg has more than one part
+func (m *Msg) hasAlt() bool {
+	return len(m.parts) > 1
+}