Add option to have no header encoding (#104)

* Thread through HeaderEncoding value

* Use separate enum for header encodings

This is necessary as we support a separate set of encodings for headers

* Add support for HeaderEncodingNone

* Add tests for None encoding for headers

email.go

@@ -18,20 +18,21 @@ import (
 
 // Email represents an email message.
 type Email struct {
-	from        string
-	sender      string
-	replyTo     string
-	returnPath  string
-	recipients  []string
-	headers     textproto.MIMEHeader
-	parts       []part
-	attachments []*File
-	inlines     []*File
-	Charset     string
-	Encoding    encoding
-	Error       error
-	SMTPServer  *smtpClient
-	DkimMsg     string
+	from           string
+	sender         string
+	replyTo        string
+	returnPath     string
+	recipients     []string
+	headers        textproto.MIMEHeader
+	parts          []part
+	attachments    []*File
+	inlines        []*File
+	Charset        string
+	Encoding       encoding
+	HeaderEncoding headerEncoding
+	Error          error
+	SMTPServer     *smtpClient
+	DkimMsg        string
 
 	// UseProvidedAddress if set to true will disable any parsing and
 	// validation of addresses and uses the address provided by the user
@@ -110,6 +111,23 @@ func (encryption Encryption) String() string {
 	return encryptionTypes[encryption]
 }
 
+type headerEncoding int
+
+const (
+	// HeaderEncodingNone turns off encoding on the message headers
+	// https://www.rfc-editor.org/rfc/rfc6530#section-7.1
+	HeaderEncodingNone headerEncoding = iota
+
+	// TODO: Add Base64 encoding
+	// HeaderEncodingBase64 sets the message header encoding to base64
+	// https://www.rfc-editor.org/rfc/rfc2045#section-6.8
+	// HeaderEncodingBase64
+
+	// HeaderEncodingQ sets the message header encoding to Q encoding
+	// https://www.rfc-editor.org/rfc/rfc2047#section-4.2
+	HeaderEncodingQ
+)
+
 type encoding int
 
 const (
@@ -205,9 +223,10 @@ func (dsn DSN) String() string {
 // NewMSG creates a new email. It uses UTF-8 by default. All charsets: http://webcheatsheet.com/HTML/character_sets_list.php
 func NewMSG() *Email {
 	email := &Email{
-		headers:  make(textproto.MIMEHeader),
-		Charset:  "UTF-8",
-		Encoding: EncodingQuotedPrintable,
+		headers:        make(textproto.MIMEHeader),
+		Charset:        "UTF-8",
+		Encoding:       EncodingQuotedPrintable,
+		HeaderEncoding: HeaderEncodingQ,
 	}
 
 	email.AddHeader("MIME-Version", "1.0")

header.go

@@ -15,19 +15,21 @@ import (
 type encoder struct {
 	w         *bufio.Writer
 	charset   string
+	encoding  headerEncoding
 	usedChars int
 }
 
 // newEncoder returns a new mime header encoder that writes to w. The c
 // parameter specifies the name of the character set of the text that will be
 // encoded. The u parameter indicates how many characters have been used
 // already.
-func newEncoder(w io.Writer, c string, u int) *encoder {
-	return &encoder{bufio.NewWriter(w), strings.ToUpper(c), u}
+func newEncoder(w io.Writer, c string, encoding headerEncoding, u int) *encoder {
+	return &encoder{bufio.NewWriter(w), strings.ToUpper(c), encoding, u}
 }
 
-// encode encodes p using the "Q" encoding and writes it to the underlying
-// io.Writer. It limits line length to 75 characters.
+// encode encodes p using the encoding scheme specified in e
+// If all chars are printable ascii chars, no encoding is performed.
+// Limits line length to 75 characters and folds lines as necessary.
 func (e *encoder) encode(p []byte) (n int, err error) {
 	var output bytes.Buffer
 	allPrintable := true
@@ -48,7 +50,7 @@ func (e *encoder) encode(p []byte) (n int, err error) {
 	}
 
 	// all characters are printable. just do line folding
-	if allPrintable {
+	if allPrintable || e.encoding == HeaderEncodingNone {
 		text := string(p)
 		words := strings.Split(text, " ")
 
@@ -57,18 +59,14 @@ func (e *encoder) encode(p []byte) (n int, err error) {
 
 		// split the line where necessary
 		for _, word := range words {
-			/*fmt.Println("Current Line:",lineBuffer)
-			fmt.Println("Here: Max:", maxLineLength ,"Buffer Length:", len(lineBuffer), "Used Chars:", e.usedChars, "Length Encoded Char:",len(word))
-			fmt.Println("----------")*/
-
 			newWord := ""
 			if !firstWord {
 				newWord += " "
 			}
 			newWord += word
 
 			// check line length
-			if (e.usedChars+len(lineBuffer)+len(newWord) /*+len(" ")+len(word)*/) > maxLineLength && (lineBuffer != "" || e.usedChars != 0) {
+			if (e.usedChars+len(lineBuffer)+len(newWord)) > maxLineLength && (lineBuffer != "" || e.usedChars != 0) {
 				output.WriteString(lineBuffer + "\r\n")
 
 				// first word on newline needs a space in front
@@ -78,29 +76,17 @@ func (e *encoder) encode(p []byte) (n int, err error) {
 					lineBuffer = " "
 				}
 
-				//firstLine = false
-				//firstWord = true
 				// reset since not on the first line anymore
 				e.usedChars = 0
 			}
 
-			/*if !firstWord {
-				lineBuffer += " "
-			}*/
-
 			lineBuffer += newWord /*word*/
-
 			firstWord = false
-
-			// reset since not on the first line anymore
-			/*if !firstLine {
-				e.usedChars = 0
-			}*/
 		}
 
 		output.WriteString(lineBuffer)
-
 	} else {
+		// else block can only be HeaderEncodingQ as of now
 		firstLine := true
 
 		// A single encoded word can not be longer than 75 characters
@@ -117,10 +103,6 @@ func (e *encoder) encode(p []byte) (n int, err error) {
 			// encode the character
 			encodedChar, runeLength := encode(p, i)
 
-			/*fmt.Println("Current Line:",lineBuffer)
-			fmt.Println("Here: Max:", maxLineLength ,"Buffer Length:", len(lineBuffer), "Used Chars:", e.usedChars, "Length Encoded Char:",len(encodedChar))
-			fmt.Println("----------")*/
-
 			// Check line length
 			if len(lineBuffer)+e.usedChars+len(encodedChar) > (maxLineLength - len(wordEnd)) {
 				output.WriteString(lineBuffer + wordEnd + "\r\n")